ROTORCRAFT FLYING HANDBOOK (2000)

Confusing attitude changes for altitude changes,

more pedal pressure as the helicopter turns to the cross-

which result in improper use of the controls.

wind position. This is because the wind is striking the

tail surface and tail rotor area, making it more difficult

Hovering too high, creating a hazardous flight

for the tail to turn into the wind. As pedal pressures

condition.

increase due to crosswind forces, you must increase the

cyclic pressure into the wind to maintain position. Use

Hovering too low, resulting in occasional touch-

the collective with the throttle to maintain a constant

down.

altitude and r.p.m. [Figure 9-2]

HOVERING TURN

After the 90° portion of the turn, you need to decrease

A hovering turn is a maneuver performed at hovering

pedal pressure slightly to maintain the same rate of

altitude in which the nose of the helicopter is rotated

turn. Approaching the 180°, or downwind, portion,

either left or right while maintaining position over a

you need to anticipate opposite pedal pressure due to

reference point on the surface. The maneuver requires

the tail moving from an upwind position to a down-

the coordination of all flight controls and demands pre-

wind position. At this point, the rate of turn has a ten-

cise control near the surface. You should maintain a

dency to increase at a rapid rate due to the

constant altitude, rate of turn, and r.p.m.

weathervaning tendency of the tail surfaces. Because

of the tailwind condition, you need to hold rearward

TECHNIQUE

cyclic pressure to keep the helicopter over the same

Initiate the turn in either direction by applying anti-

spot.

torque pedal pressure toward the desired direction. It

should be noted that during a turn to the left, you need

Because of the helicopter’s tendency to weathervane,

to add more power because left pedal pressure

maintaining the same rate of turn from the 180° posi-

increases the pitch angle of the tail rotor, which, in turn,

tion actually requires some pedal pressure opposite the

requires additional power from the engine. A turn to the

direction of turn. If you do not apply opposite pedal

right requires less power. (On helicopters with a clock-

pressure, the helicopter tends to turn at a faster rate.

wise rotating main rotor, right pedal increases the pitch

The amount of pedal pressure and cyclic deflection

angle and, therefore, requires more power.)

throughout the turn depends on the wind velocity. As

you finish the turn on the upwind heading, apply

As the turn begins, use the cyclic as necessary (usually

opposite pedal pressure to stop the turn. Gradually

into the wind) to keep the helicopter over the desired

apply forward cyclic pressure to keep the helicopter

spot. To continue the turn, you need to add more and

from drifting.

WIND

Cyclic - Forward

Cyclic - Right

Cyclic - Rearward

Cyclic - Left

Cyclic - Forward

Pedal - Some left in

Pedal - Most left

Pedal - Changing from

Pedal - Most right pedal

Pedal - Some right to

hover, more left to start

pressure in turn.

left to right pressure.

pressure in turn.

stop turn, then left to

turn to left.

maintain heading.

Collective -Most power

Collective - Power

Collective - Least power

Collective - Power

in turn.

reducing.

in turn.

Collective - Increasing

required to hover at

as left pedal applied.

desired height.

Throttle - As necessary

to maintain r.p.m.

Throttle - As necessary

to maintain r.p.m.

Figure 9-2. Left turns in helicopters with a counterclockwise rotating main rotor are more difficult to execute because the tail

rotor demands more power. This requires that you compensate with additional collective pitch and increased throttle. You

might want to refer to this graphic throughout the remainder of the discussion on a hovering turn to the left.

9-6

Control pressures and direction of application change

continuously throughout the turn. The most dramatic

change is the pedal pressure (and corresponding power

requirement) necessary to control the rate of turn as the

helicopter moves through the downwind portion of the

maneuver.

Turns can be made in either direction; however, in a

high wind condition, the tail rotor may not be able to

produce enough thrust, which means you will not be

able to control a turn to the right in a counterclockwise

Reference

rotor system. Therefore, if control is ever question-

Points

able, you should first attempt to make a 90° turn to the

left. If sufficient tail rotor thrust exists to turn the

helicopter crosswind in a left turn, a right turn can

be successfully controlled. The opposite applies to

helicopters with clockwise rotor systems. In this

case, you should start your turn to the right.

Hovering turns should be avoided in winds strong

enough to preclude sufficient aft cyclic control to

Figure 9-3. To maintain a straight ground track, use two refer-

maintain the helicopter on the selected surface

ence points in line and at some distance in front of the helicopter.

reference point when headed downwind. Check

the flight manual for the manufacturer’s recom-

mendations for this limitation.

pedals, altitude with the collective, and the proper

r.p.m. with the throttle.

COMMON ERRORS

Failing to maintain a slow, constant rate of turn.

To stop the forward movement, apply reward cyclic

Failing to maintain position over the reference

pressure until the helicopter stops. As forward motion

point.

stops, return the cyclic to the neutral position to pre-

vent rearward movement. Forward movement can also

Failing to maintain r.p.m. within normal range.

be stopped by simply applying rearward pressure to

level the helicopter and let it drift to a stop.

Failing to maintain constant altitude.

COMMON ERRORS

Failing to use the antitorque pedals properly.

Exaggerated movement of the cyclic, resulting in

erratic movement over the surface.

HOVERING-FORWARD FLIGHT

Failure to use the antitorque pedals properly,

You normally use forward hovering flight to move a

resulting is excessive heading changes.

helicopter to a specific location, and it is usually begun

from a stationary hover. During the maneuver, constant

Failure to maintain desired hovering altitude.

groundspeed, altitude, and heading should be maintained.

Failure to maintain proper r.p.m.

TECHNIQUE

HOVERING-SIDEWARD FLIGHT

Before starting, pick out two references directly in

Sideward hovering flight may be necessary to move

front and in line with the helicopter. These reference

the helicopter to a specific area when conditions make

points should be kept in line throughout the maneuver.

it impossible to use forward flight. During the maneu-

[Figure 9-3]

ver, a constant groundspeed, altitude, and heading

should be maintained.

Begin the maneuver from a normal hovering altitude by

applying forward pressure on the cyclic. As movement

begins, return the cyclic toward the neutral position to

TECHNIQUE

keep the groundspeed at a slow rate-no faster than a

Before starting sideward hovering flight, make sure the

brisk walk. Throughout the maneuver, maintain a

area you are going to hover into is clear. Then pick two

constant groundspeed and path over the ground with

points of reference in a line in the direction of sideward

the cyclic, a constant heading with the antitorque

hovering flight to help you maintain the proper ground

9-7

track. These reference points should be kept in line

Failure to maintain proper r.p.m.

throughout the maneuver. [Figure 9-4]

Failure to make sure the area is clear prior to

starting the maneuver.

HOVERING-REARWARD FLIGHT

Rearward hovering flight may be necessary to move the

helicopter to a specific area when the situation is such

that forward or sideward hovering flight cannot be used.

During the maneuver, maintain a constant groundspeed,

altitude, and heading. Due to the limited visibility

behind a helicopter, it is important that you make sure

Reference

that the area behind the helicopter is cleared before

Points

beginning the maneuver. Use of ground personnel is rec-

ommended.

TECHNIQUE

Before starting rearward hovering flight, pick out two

reference points in front of, and in line with the heli-

copter just like you would if you were hovering for-

ward. [Figure 9-3] The movement of the helicopter

should be such that these points remain in line.

Figure 9-4. The key to hovering sideward is establishing at

least two reference points that help you maintain a straight

track over the ground while keeping a constant heading.

Begin the maneuver from a normal hovering altitude by

applying rearward pressure on the cyclic. After the

movement has begun, position the cyclic to maintain a

slow groundspeed (no faster than a brisk walk).

Begin the maneuver from a normal hovering altitude

Throughout the maneuver, maintain constant ground-

by applying cyclic toward the side in which the

speed and ground track with the cyclic, a constant

movement is desired. As the movement begins, return

heading with the antitorque pedals, constant altitude

the cyclic toward the neutral position to keep the

with the collective, and the proper r.p.m. with the throttle.

groundspeed at a slow rate-no faster than a brisk

walk. Throughout the maneuver, maintain a constant

To stop the rearward movement, apply forward cyclic

groundspeed and ground track with cyclic. Maintain

and hold it until the helicopter stops. As the motion

heading, which in this maneuver is perpendicular to

stops, return the cyclic to the neutral position. Also, as

the ground track, with the antitorque pedals, and a

in the case of forward and sideward hovering flight,

constant altitude with the collective. Use the throttle

opposite cyclic can be used to level the helicopter and

to maintain the proper operating r.p.m.

let it drift to a stop.

To stop the sideward movement, apply cyclic pres-

COMMON ERRORS

sure in the direction opposite to that of movement

Exaggerated movement of the cyclic resulting in

and hold it until the helicopter stops. As motion

overcontrolling and an uneven movement over

stops, return the cyclic to the neutral position to

the surface.

prevent movement in the opposite direction.

Applying sufficient opposite cyclic pressure to

Failure to use the antitorque pedals properly,

level the helicopter may also stop sideward move-

resulting in excessive heading change.

ment. The helicopter then drifts to a stop.

Failure to maintain desired hovering altitude.

COMMON ERRORS

Failure to maintain proper r.p.m.

Exaggerated movement of the cyclic, resulting in

overcontrolling and erratic movement over the

Failure to make sure the area is clear prior to

surface.

starting the maneuver.

Failure to use proper antitorque pedal control,

TAXIING

resulting in excessive heading change.

Taxiing refers to operations on, or near the surface of

taxiways or other prescribed routes. In helicopters,

Failure to maintain desired hovering altitude.

there are three different types of taxiing.

9-8

HOVER TAXI

r.p.m. with the throttle. Throughout the maneuver,

A "hover taxi" is used when operating below 25 feet

maintain a desired groundspeed and ground track with

AGL. [Figure 9-5] Since hover taxi is just like forward,

the cyclic, a constant heading with antitorque pedals,

sideward, or rearward hovering flight, the technique to

the desired altitude with the collective, and proper

perform it will not be presented here.

operating r.p.m. with the throttle.

To stop the forward movement, apply aft cyclic pressure

to reduce forward speed. Simultaneously lower the col-

Hover Taxi

(25 Feet or Less)

lective to initiate a descent to hover altitude. As

forward motion stops, return the cyclic to the neutral posi-

tion to prevent rearward movement. When at the proper

hover altitude, increase the collective as necessary.

COMMON ERRORS

Erratic movement of the cyclic, resulting in

improper airspeed control and erratic movement

Poor Surface Conditions or Skid Type Helicopters

over the surface.

Failure to use antitorque pedals properly, result-

Figure 9-5. Hover taxi.

ing in excessive heading changes.

Failure to maintain desired altitude.

AIR TAXI

An "air taxi" is preferred when movements require

Failure to maintain proper r.p.m.

greater distances within an airport or heliport bound-

Overflying parked aircraft causing possible dam-

ary. [Figure 9-6] In this case, you basically fly to your

age from rotor downwash.

new location; however, you are expected to remain

below 100 feet AGL, and to avoid overflight of other

Flying in the cross-hatched or shaded area of the

aircraft, vehicles, and personnel.

height-velocity diagram.

Flying in a crosswind that could lead to loss of

Air Taxi

tail rotor effectiveness.

(100 Feet or Less)

SURFACE TAXI

A "surface taxi," for those helicopters with wheels, is

used whenever you wish to minimize the effects of

rotor downwash. [Figure 9-7]

Faster Travel

Surface Taxi

Figure 9-6. Air taxi.

TECHNIQUE

Before starting, determine the appropriate airspeed and

altitude combination to remain out of the cross-hatched

Less Rotor Downwash

or shaded areas of the height-velocity diagram.

Additionally, be aware of crosswind conditions that

Figure 9-7. Surface taxi.

could lead to loss of tail rotor effectiveness. Pick out

two references directly in front of the helicopter for the

ground path desired. These reference points should be

TECHNIQUE

kept in line throughout the maneuver.

The helicopter should be in a stationary position on the

surface with the collective full down and the r.p.m. the

Begin the maneuver from a normal hovering altitude

same as that used for a hover. This r.p.m. should be

by applying forward pressure on the cyclic. As move-

maintained throughout the maneuver. Then, move the

ment begins, attain the desired airspeed with the cyclic.

cyclic slightly forward and apply gradual upward pres-

Control the desired altitude with the collective, and

sure on the collective to move the helicopter forward

9-9

along the surface. Use the antitorque pedals to maintain

hover. Wind will necessitate some cyclic deflection,

heading and the cyclic to maintain ground track. The

but there should not be an extreme deviation from

collective controls starting, stopping, and speed while

neutral. Flight controls must move freely, and the hel-

taxiing. The higher the collective pitch, the faster the

icopter should respond normally. Then visually clear

taxi speed; however, you should not taxi faster than a

the area all around.

brisk walk. If your helicopter is equipped with brakes,

use them to help you slow down. Do not use the cyclic

Start the helicopter moving by smoothly and slowly eas-

to control groundspeed.

ing the cyclic forward (position 2). As the helicopter

starts to move forward, increase the collective, as nec-

During a crosswind taxi, hold the cyclic into the wind a

essary, to prevent the helicopter from sinking and adjust

sufficient amount to eliminate any drifting movement.

the throttle to maintain r.p.m. The increase in power

requires an increase in the proper antitorque pedal to

COMMON ERRORS

maintain heading. Maintain a straight takeoff path

Improper use of cyclic.

throughout the takeoff. As you accelerate through effec-

tive translational lift (position 3), the helicopter begins

Failure to use antitorque pedals for heading

to climb and the nose tends to rise due to increased lift.

control.

At this point adjust the collective to obtain normal climb

Improper use of the controls during crosswind

power and apply enough forward cyclic to overcome

operations.

the tendency of the nose to rise. At position 4, hold an

attitude that allows a smooth acceleration toward climb-

Failure to maintain proper r.p.m.

ing airspeed and a commensurate gain in altitude so that

the takeoff profile does not take you through any of the

NORMAL TAKEOFF FROM A HOVER

cross-hatched or shaded areas of the height-velocity

A normal takeoff from a hover is an orderly transition

diagram. As airspeed increases (position 5), the stream-

to forward flight and is executed to increase altitude

lining of the fuselage reduces engine torque effect,

safely and expeditiously. During the takeoff, fly a pro-

requiring a gradual reduction of antitorque pedal

file that avoids the cross-hatched or shaded areas of the

pressure. As the helicopter continues to climb and accel-

height-velocity diagram.

erate to best rate of climb, apply aft cyclic pressure to

raise the nose smoothly to the normal climb attitude.

TECHNIQUE

Refer to figure 9-8 (position 1). Bring the helicopter to

COMMON ERRORS

a hover and make a performance check, which

Failing to use sufficient collective pitch to pre-

includes power, balance, and flight controls. The power

vent loss of altitude prior to attaining transla-

check should include an evaluation of the amount of

tional lift.

excess power available; that is, the difference between

the power being used to hover and the power available

Adding power too rapidly at the beginning of the

at the existing altitude and temperature conditions. The

transition from hovering to forward flight without

balance condition of the helicopter is indicated by the

forward cyclic compensation, causing the helicopter

position of the cyclic when maintaining a stationary

to gain excessive altitude before acquiring airspeed.

Figure 9-8. The helicopter takes several positions during a normal takeoff from a hover. The numbered positions in the text refer

to the numbers in this illustration.

9-10

Assuming an extreme nose-down attitude near

the maneuver. [Figure 9-9] The cyclic is held into the

the surface in the transition from hovering to

wind a sufficient amount to maintain the desired

forward flight.

ground track for the takeoff. The heading is maintained

with the use of the antitorque pedals. In other words,

Failing to maintain a straight flight path over the

the rotor is tilted into the wind so that the sideward

surface (ground track).

movement of the helicopter is just enough to counter-

act the crosswind effect. To prevent the nose from

Failing to maintain proper airspeed during the

turning in the direction of the rotor tilt, it is necessary

climb.

to increase the antitorque pedal pressure on the side

opposite the rotor tilt.

Failing to adjust the throttle to maintain proper

r.p.m.

NORMAL TAKEOFF FROM THE

SURFACE

Normal takeoff from the surface is used to move the

helicopter from a position on the surface into effective

translational lift and a normal climb using a minimum

amount of power. If the surface is dusty or covered with

Helicopter

Wind

loose snow, this technique provides the most favorable

Side Movement

Movement

visibility conditions and reduces the possibility of

debris being ingested by the engine.

TECHNIQUE

Figure 9-9. During a slip, the rotor disc is tilted into the wind.

Place the helicopter in a stationary position on the sur-

face. Lower the collective to the full down position,

and reduce the r.p.m. below operating r.p.m. Visually

After approximately 50 feet of altitude is gained, make

clear the area and select terrain features, or other

a coordinated turn into the wind to maintain the desired

objects, to aid in maintaining the desired track during

ground track. This is called crabbing into the wind. The

takeoff and climb out. Increase the throttle to the

stronger the crosswind, the more you have to turn the

proper r.p.m. and raise the collective slowly until the

helicopter into the wind to maintain the desired ground

helicopter is light on the skids. Hesitate momentarily

track. [Figure 9-10]

and adjust the cyclic and antitorque pedals, as neces-

sary, to prevent any surface movement. Continue to

apply upward collective and, as the helicopter breaks

ground, use the cyclic, as necessary, to begin forward

Helicopter Ground

Track

movement as altitude is gained. Continue to acceler-

Helicopter

Heading

ate, and as effective translational lift is attained, the

helicopter begins to climb. Adjust attitude and power,

if necessary, to climb in the same manner as a takeoff

from a hover.

Wind

COMMOM ERRORS

Movement

Departing the surface in an attitude that is too

nose-low. This situation requires the use of exces-

sive power to initiate a climb.

Using excessive power combined with a level

attitude, which causes a vertical climb.

Too abrupt application of the collective when

departing the surface, causing r.p.m. and heading

control errors.

CROSSWIND CONSIDERATIONS

DURING TAKEOFFS

If the takeoff is made during crosswind conditions, the

Figure 9-10. To compensate for wind drift at altitude, crab the

helicopter is flown in a slip during the early stages of

helicopter into the wind.

9-11

cyclic to neutral slightly before the desired attitude is

STRAIGHT-AND-LEVEL FLIGHT

reached. This principal holds true for any cyclic input.

Straight-and-level flight is flight in which a constant

altitude and heading are maintained. The attitude of the

Since helicopters are inherently unstable, if a gust or

helicopter determines the airspeed and is controlled by

turbulence causes the nose to drop, the nose tends to

the cyclic. Altitude is primarily controlled by use of the

continue to drop instead of returning to a straight-and-

collective.

level attitude as would a fixed-wing aircraft.

Therefore, you must remain alert and FLY the helicop-

TECHNIQUE

ter at all times.

To maintain forward flight, the rotor tip-path plane must

be tilted forward to obtain the necessary horizontal

COMMON ERRORS

thrust component from the main rotor. This generally

Failure to properly trim the helicopter, tending to

results in a nose-low attitude. The lower the nose, the

hold antitorque pedal pressure and opposite

greater the power required to maintain altitude, and the

cyclic. This is commonly called cross-controlling.

higher the resulting airspeed. Conversely, the greater

the power used, the lower the nose must be to maintain

Failure to maintain desired airspeed.

altitude. [Figure 9-11]

Failure to hold proper control position to main-

Tip-Path Plane

tain desired ground track.

TURNS

A turn is a maneuver used to change the heading of the

helicopter. The aerodynamics of a turn were previously

discussed in Chapter 3-Aerodynamics of Flight.

Figure 9-11. You can maintain a straight-and-level attitude by

TECHNIQUE

keeping the tip-path plane parallel to and a constant distance

Before beginning any turn, the area in the direction of

above or below the natural horizon. For any given airspeed,

this distance remains the same as long as you sit in the same

the turn must be cleared not only at the helicopter’s alti-

position in the same type of aircraft.

tude, but also above and below. To enter a turn from

straight-and-level flight, apply sideward pressure on

When in straight-and-level flight, any increase in the

the cyclic in the direction the turn is to be made. This is

collective, while holding airspeed constant, causes the

the only control movement needed to start the turn. Do

helicopter to climb. A decrease in the collective, while

not use the pedals to assist the turn. Use the pedals only

holding airspeed constant, causes the helicopter to

to compensate for torque to keep the helicopter in lon-

descend. A change in the collective requires a coordi-

gitudinal trim. [Figure 9-12]

nated change of the throttle to maintain a constant

r.p.m. Additionally, the antitorque pedals need to be

How fast the helicopter banks depends on how much

adjusted to maintain heading and to keep the helicopter

lateral cyclic pressure you apply. How far the helicop-

in longitudinal trim.

ter banks (the steepness of the bank) depends on how

long you displace the cyclic. After establishing the

To increase airspeed in straight-and-level flight, apply

proper bank angle, return the cyclic toward the neutral

forward pressure on the cyclic and raise the collective

position. Increase the collective and throttle to main-

as necessary to maintain altitude. To decrease airspeed,

apply rearward pressure on the cyclic and lower the

collective, as necessary, to maintain altitude.

Although the cyclic is sensitive, there is a slight delay

in control reaction, and it will be necessary to antici-

pate actual movement of the helicopter. When making

cyclic inputs to control the altitude or airspeed of a hel-

icopter, take care not to overcontrol. If the nose of the

helicopter rises above the level-flight attitude, apply

forward pressure to the cyclic to bring the nose down.

If this correction is held too long, the nose drops too

low. Since the helicopter continues to change attitude

Figure 9-12. During a level, coordinated turn, the rate of turn

momentarily after the controls reach neutral, return the

is commensurate with the angle of bank used, and inertia and

horizontal component of lift (HCL) are equal.

9-12

tain altitude and r.p.m. As the torque increases, increase

opposite the turn in relation to the amount of power

the proper antitorque pedal pressure to maintain longi-

used. If the helicopter is forced to turn faster with

tudinal trim. Depending on the degree of bank, addi-

increased pedal pressure instead of by increasing the

tional forward cyclic pressure may be required to

degree of the bank, it skids sideways away from the

maintain airspeed.

center of the turn instead of flying in its normal curved

pattern.

Rolling out of the turn to straight-and-level flight is the

same as the entry into the turn except that pressure on

In summary, a skid occurs when the rate of turn is too

the cyclic is applied in the opposite direction. Since the

fast for the amount of bank being used, and a slip occurs

helicopter continues to turn as long as there is any bank,

when the rate of turn is too slow for the amount of bank

start the rollout before reaching the desired heading.

being used.

The discussion on level turns is equally applicable to

making turns while climbing or descending. The only

Skid

difference being that the helicopter is in a climbing or

descending attitude rather than that of level flight. If a

simultaneous entry is desired, merely combine the

techniques of both maneuvers-climb or descent

entry and turn entry. When recovering from a climbing

or descending turn, the desired heading and altitude are

HCL

Inertia

rarely reached at the same time. If the heading is

reached first, stop the turn and maintain the climb or

descent until reaching the desired altitude. On the

other hand, if the altitude is reached first, establish the

level flight attitude and continue the turn to the

Figure 9-14. During a skid, the rate of turn is too fast for the

desired heading.

angle of bank used, and inertia exceeds the horizontal com-

ponent of lift (HCL).

SLIPS

A slip occurs when the helicopter slides sideways

COMMON ERRORS

toward the center of the turn. [Figure 9-13] It is caused

Using antitorque pedal pressures for turns. This is

by an insufficient amount of antitorque pedal in the

usually not necessary for small helicopters.

direction of the turn, or too much in the direction oppo-

site the turn, in relation to the amount of power used. In

Slipping or skidding in the turn.

other words, if you hold improper antitorque pedal pres-

sure, which keeps the nose from following the turn, the

helicopter slips sideways toward the center of the turn.

NORMAL CLIMB

The entry into a climb from a hover has already been

discussed under “Normal Takeoff from a Hover;” there-

Slip

fore, this discussion is limited to a climb entry from

cruising flight.

TECHNIQUE

To enter a climb from cruising flight, apply aft cyclic to

obtain the approximate climb attitude. Simultaneously

HCL

Inertia

increase the collective and throttle to obtain climb

power and maintain r.p.m. In a counterclockwise rotor

system, increase the left antitorque pedal pressure to

compensate for the increased torque. As the airspeed

approaches normal climb airspeed, adjust the cyclic to

Figure 9-13. During a slip, the rate of turn is too slow for the

hold this airspeed. Throughout the maneuver, maintain

angle of bank used, and the horizontal component of lift

(HCL) exceeds inertia.

climb attitude, heading, and airspeed with the cyclic;

climb power and r.p.m. with the collective and throttle;

and longitudinal trim with the antitorque pedals.

SKIDS

A skid occurs when the helicopter slides sideways

To level off from a climb, start adjusting the attitude to the

away from the center of the turn. [Figure 9-14] It is

level flight attitude a few feet prior to reaching the desired

caused by too much antitorque pedal pressure in the

altitude. The amount of lead depends on the rate of climb

direction of the turn, or by too little in the direction

at the time of level-off (the higher the rate of climb, the

9-13

more the lead). Generally, the lead is 10 percent of the

Failure to lead the level-off sufficiently, which

climb rate. For example, if your climb rate is 500 feet per

results in recovery below the desired altitude.

minute, you should lead the level-off by 50 feet.

Failure to adjust antitorque pedal pressures for

changes in power.

To begin the level-off, apply forward cyclic to adjust

and maintain a level flight attitude, which is slightly

GROUND REFERENCE MANEUVERS

nose low. You should maintain climb power until the

airspeed approaches the desired cruising airspeed, then

Ground reference maneuvers are training exercises

lower the collective to obtain cruising power and adjust

flown to help you develop a division of attention

the throttle to obtain and maintain cruising r.p.m.

between the flight path and ground references, while

Throughout the level-off, maintain longitudinal trim

controlling the helicopter and watching for other air-

and heading with the antitorque pedals.

craft in the vicinity. Prior to each maneuver, a clearing

turn should be accomplished to ensure the practice area

COMMON ERRORS

is free of conflicting traffic.

Failure to maintain proper power and airspeed.

RECTANGULAR COURSE

Holding too much or too little antitorque pedal.

The rectangular course is a training maneuver in which

the ground track of the helicopter is equidistant from

In the level-off, decreasing power before lower-

all sides of a selected rectangular area on the ground.

ing the nose to cruising attitude.

While performing the maneuver, the altitude and air-

speed should be held constant. The rectangular course

helps you to develop a recognition of a drift toward or

NORMAL DESCENT

away from a line parallel to the intended ground track.

A normal descent is a maneuver in which the helicop-

This is helpful in recognizing drift toward or from an

ter loses altitude at a controlled rate in a controlled

airport runway during the various legs of the airport

attitude.

traffic pattern.

TECHNIQUE

For this maneuver, pick a square or rectangular field,

To establish a normal descent from straight-and-level

or an area bounded on four sides by section lines or

flight at cruising airspeed, lower the collective to obtain

roads, where the sides are approximately a mile in

proper power, adjust the throttle to maintain r.p.m., and

length. The area selected should be well away from

increase right antitorque pedal pressure to maintain

other air traffic. Fly the maneuver approximately 600

heading in a counterclockwise rotor system, or left

to 1,000 feet above the ground, which is the altitude

pedal pressure in a clockwise system. If cruising

usually required for an airport traffic pattern. You

airspeed is the same as, or slightly above descending air-

should fly the helicopter parallel to and at a uniform

speed, simultaneously apply the necessary cyclic

distance, about one-fourth to one-half mile, from the

pressure to obtain the approximate descending attitude.

field boundaries, not above the boundaries. For best

If cruising speed is well above descending airspeed, you

results, position your flight path outside the field

can maintain a level flight attitude until the airspeed

boundaries just far enough away that they may be

approaches the descending airspeed, then lower the

easily observed from either pilot seat by looking out

nose to the descending attitude. Throughout the maneu-

the side of the helicopter. If an attempt is made to fly

ver, maintain descending attitude and airspeed with the

directly above the edges of the field, you will have

cyclic; descending power and r.p.m. with the collective

no usable reference points to start and complete the

and throttle; and heading with the antitorque pedals.

turns. In addition, the closer the track of the helicop-

ter is to the field boundaries, the steeper the bank

To level off from the descent, lead the desired altitude by

necessary at the turning points. Also, you should be

approximately 10 percent of the rate of descent. For exam-

able to see the edges of the selected field while seated

ple, a 500 feet per minute rate of descent would require a

in a normal position and looking out the side of the

50 foot lead. At this point, increase the collective to obtain

helicopter during either a left-hand or right-hand

cruising power, adjust the throttle to maintain r.p.m., and

course. The distance of the ground track from the

increase left antitorque pedal pressure to maintain heading

edges of the field should be the same regardless of

(right pedal pressure in a clockwise rotor system). Adjust

whether the course is flown to the left or right. All

the cyclic to obtain cruising airspeed and a level flight atti-

turns should be started when your helicopter is abeam

tude as the desired altitude is reached.

the corners of the field boundaries. The bank nor-

mally should not exceed 30°.

COMMON ERRORS

Failure to maintain constant angle of decent dur-

Although the rectangular course may be entered from

ing training.

any direction, this discussion assumes entry on a

9-14

Enter

Start Turn

Pattern

No Crab

At Boundary

Turn More Than

Complete Turn

90°-Roll Out

At Boundary

With Crab Established

Turn More

Complete Turn

Than 90°

At Boundary

Start Turn

At Boundary

Crab Into

WIND

Wind

Turn less Than

Start Turn

90°-Roll Out

At Boundary

With Crab Established

Complete Turn

Turn Less

At Boundary

Than 90°

Start Turn

At Boundary

Complete Turn

At Boundary

No Crab

Figure 9-15. Rectangular course. The numbered positions in the text refer to the numbers in this illustration.

downwind heading. [Figure 9-15] As you approach the

necessary, to maintain a uniform distance from the field

field boundary on the downwind leg, you should begin

boundary (position 4).

planning for your turn to the crosswind leg. Since you

have a tailwind on the downwind leg, the helicopter's

As the next field boundary is being approached (posi-

groundspeed is increased (position 1). During the turn

tion 5), plan the turn onto the upwind leg. Since a wind

onto the crosswind leg, which is the equivalent of the

correction angle is being held into the wind and toward

base leg in a traffic pattern, the wind causes the heli-

the field while on the crosswind leg, this next turn

copter to drift away from the field. To counteract this

requires a turn of less than 90°. Since the crosswind

effect, the roll-in should be made at a fairly fast rate

becomes a headwind, causing the groundspeed to

with a relatively steep bank (position 2).

decrease during this turn, the bank initially must be

medium and progressively decreased as the turn pro-

As the turn progresses, the tailwind component

ceeds. To complete the turn, time the rollout so that the

decreases, which decreases the groundspeed.

helicopter becomes level at a point aligned with the

Consequently, the bank angle and rate of turn must be

corner of the field just as the longitudinal axis of the

reduced gradually to ensure that upon completion of

helicopter again becomes parallel to the field boundary

the turn, the crosswind ground track continues to be the

(position 6). The distance from the field boundary

same distance from the edge of the field. Upon comple-

should be the same as on the other sides of the field.

tion of the turn, the helicopter should be level and

aligned with the downwind corner of the field.

On the upwind leg, the wind is a headwind, which

However, since the crosswind is now pushing you

results in an decreased groundspeed (position

7).

away from the field, you must establish the proper drift

Consequently, enter the turn onto the next leg with a

correction by flying slightly into the wind. Therefore,

fairly slow rate of roll-in, and a relatively shallow bank

the turn to crosswind should be greater than a 90°

(position 8). As the turn progresses, gradually increase

change in heading (position 3). If the turn has been

the bank angle because the headwind component is

made properly, the field boundary again appears to be

diminishing, resulting in an increasing groundspeed.

one-fourth to one-half mile away. While on the cross-

During and after the turn onto this leg, the wind tends

wind leg, the wind correction should be adjusted, as

to drift the helicopter toward the field boundary. To

9-15

compensate for the drift, the amount of turn must be

less than 90° (position 9).

Points of

Again, the rollout from this turn must be such that as

WIND

Shallowest Bank

the helicopter becomes level, the nose of the helicopter

is turned slightly away the field and into the wind to

correct for drift. The helicopter should again be the

same distance from the field boundary and at the same

altitude, as on other legs. Continue the crosswind leg

until the downwind leg boundary is approached (posi-

tion 10). Once more you should anticipate drift and

Points of

turning radius. Since drift correction was held on the

Steepest Bank

crosswind leg, it is necessary to turn greater than 90° to

align the helicopter parallel to the downwind leg

Figure 9-16. S-turns across a road.

boundary. Start this turn with a medium bank angle,

gradually increasing it to a steeper bank as the turn pro-

highest. Gradually reduce the bank, as necessary, to

gresses. Time the rollout to assure paralleling the

describe a ground track of a half circle. Time the turn

boundary of the field as the helicopter becomes level

so that as the rollout is completed, the helicopter is

(position 11).

crossing the reference line perpendicular to it and head-

If you have a direct headwind or tailwind on the

ing directly upwind. Immediately enter a bank in the

upwind and downwind leg, drift should not be encoun-

opposite direction to begin the second half of the “S.”

tered. However, it may be difficult to find a situation

Since the helicopter is now on an upwind heading, this

where the wind is blowing exactly parallel to the field

bank (and the one just completed before crossing the

boundaries. This makes it necessary to use a slight

reference line) is the shallowest in the maneuver.

wind correction angle on all the legs. It is important to

Gradually increase the bank, as necessary, to describe a

anticipate the turns to compensate for groundspeed,

ground track that is a half circle identical in size to the

drift, and turning radius. When the wind is behind the

one previously completed on the other side of the refer-

helicopter, the turn is faster and steeper; when it is

ence line. The steepest bank in this turn should be

ahead of the helicopter, the turn is slower and

attained just prior to rollout when the helicopter is

shallower. These same techniques apply while flying in

approaching the reference line nearest the downwind

an airport traffic pattern.

heading. Time the turn so that as the rollout is com-

plete, the helicopter is perpendicular to the reference

S-TURNS

line and is again heading directly downwind.

Another training maneuver you might use is the S-turn,

which helps you correct for wind drift in turns. This

In summary, the angle of bank required at any given

maneuver requires turns to the left and right. The refer-

point in the maneuver is dependent on the ground-

ence line used, whether a road, railroad, or fence, should

speed. The faster the groundspeed, the steeper the

be straight for a considerable distance and should

bank; the slower the groundspeed, the shallower

extend as nearly perpendicular to the wind as possible.

the bank. To express it another way, the more nearly

the helicopter is to a downwind heading, the steeper the

The object of S-turns is to fly a pattern of two half cir-

bank; the more nearly it is to an upwind heading,

cles of equal size on opposite sides of the reference line.

the shallower the bank. In addition to varying the angle

[Figure 9-16] The maneuver should be performed at a

of bank to correct for drift in order to maintain the

constant altitude between 600 and 1,000 feet above the

proper radius of turn, the helicopter must also be flown

terrain. S-turns may be started at any point; however,

with a drift correction angle (crab) in relation to its

during early training it may be beneficial to start on a

ground track; except of course, when it is on direct

downwind heading. Entering downwind permits the

upwind or downwind headings or there is no wind. One

immediate selection of the steepest bank that is desired

would normally think of the fore and aft axis of the heli-

throughout the maneuver. The discussion that follows is

copter as being tangent to the ground track pattern at

based on choosing a reference line that is perpendicular

each point. However, this is not the case. During the turn

to the wind and starting the maneuver on a downwind

on the upwind side of the reference line (side from

heading.

which the wind is blowing), crab the nose of the heli-

copter toward the outside of the circle. During the turn

As the helicopter crosses the reference line, immedi-

on the downwind side of the reference line (side of the

ately establish a bank. This initial bank is the steepest

reference line opposite to the direction from which the

used throughout the maneuver since the helicopter is

wind is blowing), crab the nose of the helicopter toward

headed directly downwind and the groundspeed is at its

the inside of the circle. In either case, it is obvious that

9-16

the helicopter is being crabbed into the wind just as it is

greatest, the steeper the bank, and the faster the rate

when trying to maintain a straight ground track. The

of turn required to establish the proper wind correc-

amount of crab depends upon the wind velocity and

tion angle. The more nearly it is to a direct upwind

how nearly the helicopter is to a crosswind position.

heading where the groundspeed is least, the shallower

The stronger the wind, the greater the crab angle at any

the bank, and the slower the rate of turn required to

given position for a turn of a given radius. The more

establish the proper wind correction angle. It follows,

nearly the helicopter is to a crosswind position, the

then, that throughout the maneuver, the bank and rate

greater the crab angle. The maximum crab angle should

of turn must be gradually varied in proportion to the

be at the point of each half circle farthest from the

groundspeed.

reference line.

The point selected for turns around a point should be

Astandard radius for S-turns cannot be specified, since

prominent and easily distinguishable, yet small enough

the radius depends on the airspeed of the helicopter,

to present a precise reference. Isolated trees, crossroads,

the velocity of the wind, and the initial bank chosen

or other similar small landmarks are usually suitable.

for entry.

The point should be in an area away from communities,

livestock, or groups of people on the ground to prevent

TURNS AROUND A POINT

possible annoyance or hazard to others. Since the

This training maneuver requires you to fly constant

maneuver is performed between 600 and 1,000 feet

radius turns around a preselected point on the ground

AGL, the area selected should also afford an opportu-

using a bank of approximately 30°, while maintaining

nity for a safe emergency autorotation in the event it

a constant altitude. [Figure 9-17] Your objective, as in

becomes necessary.

other ground reference maneuvers, is to develop the

ability to subconsciously control the helicopter while

To enter turns around a point, fly the helicopter on a

dividing attention between the flight path and ground

downwind heading to one side of the selected point

references, while still watching for other air traffic in

at a distance equal to the desired radius of turn. When

the vicinity.

any significant wind exists, it is necessary to roll into

the initial bank at a rapid rate so that the steepest

bank is attained abeam the point when the helicopter

WIND

is headed directly downwind. By entering the maneu-

ver while heading directly downwind, the steepest

Steeper

bank can be attained immediately. Thus, if a bank of

Bank

30° is desired, the initial bank is 30° if the helicopter

is at the correct distance from the point. Thereafter,

the bank is gradually shallowed until the point is

reached where the helicopter is headed directly

upwind. At this point, the bank is gradually steepened

until the steepest bank is again attained when head-

Shallowest

Steepest

ing downwind at the initial point of entry.

Bank

Just as S-turns require that the helicopter be turned

into the wind in addition to varying the bank, so do

turns around a point. During the downwind half of the

circle, the helicopter’s nose must be progressively

turned toward the inside of the circle; during the

Shallower

upwind half, the nose must be progressively turned

Bank

toward the outside. The downwind half of the turn

around the point may be compared to the downwind

Figure 9-17. Turns around a point.

side of the S-turn, while the upwind half of the turn

around a point may be compared to the upwind side

of the S-turn.

The factors and principles of drift correction that are

involved in S-turns are also applicable in this maneu-

As you become experienced in performing turns

ver. As in other ground track maneuvers, a constant

around a point and have a good understanding of the

radius around a point will, if any wind exists, require

effects of wind drift and varying of the bank angle

a constantly changing angle of bank and angles of

and wind correction angle as required, entry into the

wind correction. The closer the helicopter is to a

maneuver may be from any point. When entering

direct downwind heading where the groundspeed is

this maneuver at any point, the radius of the turn

9-17

must be carefully selected, taking into account the

wind velocity and groundspeed so that an excessive

Downwind Leg

bank is not required later on to maintain the proper

ground track.

COMMON ERRORS DURING GROUND

REFERENCE MANEUVERS

Faulty entry technique.

Poor planning, orientation, or division of

Final Approach

Takeoff Leg

attention.

Leg

(Upwind)

Uncoordinated flight control application.

Improper correction for wind drift.

Figure 9-18. A standard traffic pattern has turns to left and

five designated legs.

An unsymmetrical ground track during S-Turns

Across a Road.

Failure to maintain selected altitude or airspeed.

flow of traffic when obstacles or highly populated areas

make the use of a left-hand pattern undesirable.

Selection of a ground reference where there is no

suitable emergency landing area within gliding

When approaching an airport with an operating control

distance.

tower in a helicopter, it is possible to expedite traffic by

stating your intentions, for example:

TRAFFIC PATTERNS

A traffic pattern is useful to control the flow of traffic, par-

(Call sign of helicopter) Robinson 8340J.

ticularly at airports without operating control towers. It

affords a measure of safety, separation, protection, and

(Position) 10 miles west.

administrative control over arriving, departing, and

circling aircraft. Due to specialized operating character-

(Request) for landing and hover to...

istics, airplanes and helicopters do not mix well in the

same traffic environment. At multiple-use airports,

In order to avoid the flow of fixed-wing traffic, the

you routinely must avoid the flow of fixed-wing traf-

tower will often clear you direct to an approach point

fic. To do this, you need to be familiar with the

or to a particular runway intersection nearest your

patterns typically flown by airplanes. In addition, you

destination point. At uncontrolled airports, if at all

should learn how to fly these patterns in case air traf-

possible, you should adhere to standard practices

fic control (ATC) requests that you fly a fixed-wing

and patterns.

traffic pattern.

Traffic pattern entry procedures at airports with an

A normal traffic pattern is rectangular, has five named

operating control tower are specified by the controller.

legs, and a designated altitude, usually 600 to 1,000

At uncontrolled airports, traffic pattern altitudes and

feet AGL. A pattern in which all turns are to the left is

entry procedures may vary according to established

called a standard pattern. [Figure 9-18] The takeoff leg

local procedures. The general procedure is for you to

(item 1) normally consists of the aircraft’s flight path

enter the pattern at a 45° angle to the downwind leg

after takeoff. This leg is also called the upwind leg. You

abeam the midpoint of the runway. For information

should turn to the crosswind leg (item 2), after passing

concerning traffic pattern and landing direction, you

the departure end of the runway when you are at a safe

should utilize airport advisory service or UNICOM,

altitude. Fly the downwind leg (item 3) parallel to the

when available.

runway at the designated traffic pattern altitude and

distance from the runway. Begin the base leg (item 4)

at a point selected according to other traffic and wind

The standard departure procedure when using the

conditions. If the wind is very strong, begin the turn

fixed-wing traffic pattern is usually straight-out, down-

sooner than normal. If the wind is light, delay the turn

wind, or a right-hand departure. When a control tower

to base. The final approach (item 5) is the path the air-

is in operation, you can request the type of departure

craft flies immediately prior to touchdown.

you desire. In most cases, helicopter departures are

made into the wind unless obstacles or traffic dictate

You may find variations at different localities and at

otherwise. At airports without an operating control

airports with operating control towers. For example, a

tower, you must comply with the departure procedures

right-hand pattern may be designated to expedite the

established for that airport.

9-18

APPROACHES

An approach is the transition from traffic pattern alti-

tude to either a hover or to the surface. The approach

should terminate at the hover altitude with the rate of

descent and groundspeed reaching zero at the same

time. Approaches are categorized according to the angle

of descent as normal, steep, or shallow. In this chapter

Imaginary

we will concentrate on the normal approach. Steep and

Centerline

shallow approaches are discussed in the next chapter.

You should use the type of approach best suited to the

existing conditions. These conditions may include

obstacles, size and surface of the landing area, density

altitude, wind direction and speed, and weight.

Regardless of the type of approach, it should always

be made to a specific, predetermined landing spot.

NORMAL APPROACH TO A HOVER

A normal approach uses a descent profile of between

8° and 12° starting at approximately 300 feet AGL.

TECHNIQUE

On final approach, at the recommended approach

airspeed and at approximately 300 feet AGL, align the

helicopter with the point of intended touchdown.

[Figure 9-19] After intercepting an approach angle of 8°

Figure 9-19. Plan the turn to final so the helicopter rolls out

to 12°, begin the approach by lowering the collective

on an imaginary extension of the centerline for the final

sufficiently to get the helicopter decelerating and

approach path. This path should neither angle to the land-

descending down the approach angle. With the decrease

ing area, as shown by the helicopter on the left, nor require

in the collective, the nose tends to pitch down, requiring

an S-turn, as shown by the helicopter on the right.

aft cyclic to maintain the recommended approach air-

speed attitude. Adjust antitorque pedals, as necessary, to

maintain longitudinal trim. You can determine the proper

As the helicopter approaches the recommended hover

approach angle by relating the point of intended

altitude, you need to increase the collective sufficiently

touchdown to a point on the helicopter windshield. The

to maintain the hover. At the same time you need to

collective controls the angle of approach. If the touch-

apply aft cyclic to stop any forward movement, while

down point seems to be moving up on the windshield, the

controlling the heading with antitorque pedals.

angle is becoming shallower, necessitating a slight

increase in collective. If the touchdown point moves

COMMON ERRORS

down on the windshield, the approach angle is becoming

Failing to maintain proper r.p.m. during the entire

steeper, requiring a slight decrease in collective. Use the

approach.

cyclic to control the rate of closure or how fast your are

moving toward the touchdown point. Maintain entry

Improper use of the collective in controlling the

airspeed until the apparent groundspeed and rate of

angle of descent.

closure appear to be increasing. At this point, slowly

begin decelerating with slight aft cyclic, and smoothly

Failing to make antitorque pedal corrections to

lower the collective to maintain approach angle. Use the

compensate for collective changes during the

cyclic to maintain a rate of closure equivalent to a

approach.

brisk walk.

Failing to simultaneously arrive at hovering alti-

At approximately 25 to 40 feet AGL, depending on wind,

tude and attitude with zero groundspeed.

the helicopter begins to lose effective translational lift. To

compensate for loss of effective translational lift, you

Low r.p.m. in transition to the hover at the end of

must increase the collective to maintain the approach

the approach.

angle, while maintaining the proper r.p.m. The increase

of collective pitch tends to make the nose rise, requiring

Using too much aft cyclic close to the surface,

forward cyclic to maintain the proper rate of closure.

which may result in tail rotor strikes.

9-19

NORMAL APPROACH TO THE SURFACE

A good rule of thumb to use during an approach is to

A normal approach to the surface or a no-hover landing is

make a go-around if the helicopter is in a position from

used if loose snow or dusty surface conditions exist.

which it is not safe to continue the approach. Anytime

These situations could cause severely restricted visibility,

you feel an approach is uncomfortable, incorrect, or

or the engine could possibly ingest debris when the heli-

potentially dangerous, abandon the approach. The deci-

copter comes to a hover. The approach is the same as the

sion to make a go-around should be positive and initiated

normal approach to a hover; however, instead of termi-

before a critical situation develops. When the decision is

nating at a hover, continue the approach to touchdown.

made, carry it out without hesitation. In most cases, when

Touchdown should occur with the skids level, zero

you initiate the go-around, power is at a low setting.

groundspeed, and a rate of descent approaching zero.

Therefore, your first response is to increase collective to

takeoff power. This movement is coordinated with the

TECHNIQUE:

throttle to maintain r.p.m., and the proper antitorque pedal

As the helicopter nears the surface, increase the collec-

to control heading. Then, establish a climb attitude and

tive, as necessary, to cushion the landing on the sur-

maintain climb speed to go around for another approach.

face, terminate in a skids-level attitude with no forward

movement.

AFTER LANDING AND SECURING

When the flight is terminated, park the helicopter

COMMON ERRORS

where it will not interfere with other aircraft and not

Terminating at a hover, then making a vertical

be a hazard to people during shutdown. Rotor down-

landing.

wash can cause damage to other aircraft in close

proximity, and spectators may not realize the danger

Touching down with forward movement.

or see the rotors turning. Passengers should remain in

the helicopter with their seats belts secured until the

Approaching too slow, requiring the use of exces-

rotors have stopped turning. During the shutdown

sive power during the termination.

and postflight inspection, follow the manufacturer’s

checklist. Any discrepancies found should be noted

Approaching too fast, causing a hard landing.

and, if necessary, reported to maintenance personnel.

CROSSWIND DURING APPROACHES

NOISE ABATEMENT PROCEDURES

During a crosswind approach, you should crab into the

The FAA, in conjunction with airport operators and

wind. At approximately 50 feet of altitude, use a slip to

community leaders, is now using noise abatement

align the fuselage with the ground track. The rotor is

procedures to reduce the level of noise generated by

tilted into the wind with cyclic pressure so that the

aircraft departing over neighborhoods that are near

sideward movement of the helicopter and wind drift

airports. The airport authority may simply request that

counteract each other. Maintain the heading and ground

you use a designated runway, wind permitting. You

track with the antitorque pedals. This technique should

also may be asked to restrict some of your operations,

be used on any type of crosswind approach, whether it is

such as practicing landings, during certain time peri-

a shallow, normal, or steep approach.

ods. There are three ways to determine the noise abate-

ment procedure at an airport. First, if there is a control

GO-AROUND

tower on the field, they will assign the preferred noise

A go-around is a procedure for remaining airborne after

abatement runway or takeoff direction to you. Second,

an intended landing is discontinued. A go-around may

you can check the Airport/Facility Directory for infor-

be necessary when:

mation on local procedures. Third, there may be infor-

mation for you to read in the pilot’s lounge, or even

•

Instructed by the control tower.

signs posted next to a runway that will advise you on

•

Traffic conflict occurs.

local procedures.

9-20

The maneuvers presented in this chapter require more

and small crevices. If everything is alright, you can

finesse and understanding of the helicopter and the

complete the approach to a landing. However, you must

surrounding environment. When performing these

make the decision to land or go-around before effective

maneuvers, you will probably be taking your helicopter

translational lift is lost.

to the edge of the safe operating envelope. Therefore, if

you are ever in doubt about the outcome of the maneuver,

If a decision is made to complete the approach, termi-

you should abort the mission entirely or wait for more

nate it in a hover, so you can carefully check the

favorable conditions.

landing point before lowering the helicopter to the

surface. Under certain conditions, it may be desirable

to continue the approach to the surface. Once the heli-

RECONNAISSANCE PROCEDURES

copter is on the ground, maintain operating r.p.m. until

Anytime you are planning to land or takeoff at an unfa-

you have checked the stability of the helicopter to be

miliar site, you should gather as much information as

sure it is in a secure and safe position.

you can about the area. Reconnaissance techniques are

ways of gathering this information.

GROUND RECONNAISSANCE

Prior to departing an unfamiliar location, make a

HIGH RECONNAISSANCE

detailed analysis of the area. There are several factors

The purpose of a high reconnaissance is to determine

to consider during this evaluation. Besides determining

the wind direction and speed, a point for touchdown,

the best departure path, you must select a route that will

the suitability of the landing area, the approach and

get your helicopter from its present position to the take-

departure axes, obstacles and their effect on wind pat-

off point.

terns, and the most suitable flight paths into and out of

the area. When conducting a high reconnaissance, give

Some things to consider while formulating a takeoff

particular consideration to forced landing areas in case

plan are the aircraft load, height of obstacles, the shape

of an emergency.

of the area, and direction of the wind. If the helicopter is

heavily loaded, you must determine if there is sufficient

Altitude, airspeed, and flight pattern for a high recon-

power to clear the obstacles. Sometimes it is better to

naissance are governed by wind and terrain features.

pick a path over shorter obstacles than to take off

You must strike a balance between a reconnaissance

directly into the wind. You should also evaluate the

conducted too high and one too low. It should not be

shape of the area so that you can pick a path that will

flown so low that you have to divide your attention

give you the most room to maneuver and abort the take-

between studying the area and avoiding obstructions to

off if necessary. Wind analysis also helps determine the

flight. A high reconnaissance should be flown at an alti-

route of takeoff. The prevailing wind can be altered by

tude of 300 to 500 feet above the surface. A general rule

obstructions on the departure path, and can significantly

to follow is to ensure that sufficient altitude is available

affect aircraft performance. One way to determine the

at all times to land into the wind in case of engine fail-

wind direction is to drop some dust or grass, and

ure. In addition, a 45° angle of observation generally

observe which way it is blowing. Keep in mind that if

allows the best estimate of the height of barriers, the

the main rotor is turning, you will need to be a sufficient

presence of obstacles, the size of the area, and the slope

distance from the helicopter to ensure that the down-

of the terrain. Always maintain safe altitudes and air-

wash of the blades does not give you a false indication.

speeds, and keep a forced landing area within reach

whenever possible.

If possible, you should walk the route from the helicop-

ter to the takeoff position. Evaluate obstacles that could

LOW RECONNAISSANCE

be hazardous and ensure that you will have adequate

A low reconnaissance is accomplished during the

rotor clearance. Once at the downwind end of the avail-

approach to the landing area. When flying the

able area, mark a position for takeoff so that the tail and

approach, verify what was observed in the high recon-

main rotors have sufficient clearance from any obstruc-

naissance, and check for anything new that may have

tions behind the helicopter. Use a sturdy marker, such

been missed at a higher altitude, such as wires, slopes,

as a heavy stone or log, so it does not blow away.

10-1

path to maintain ground track. You should also consider

MAXIMUM PERFORMANCE TAKEOFF

alternate routes in case you are not able to complete the

A maximum performance takeoff is used to climb at a

maneuver. [Figure 10-1]

steep angle to clear barriers in the flight path. It can be

used when taking off from small areas surrounded by

Begin the takeoff by getting the helicopter light on the

high obstacles. Before attempting a maximum

skids (position 1). Pause and neutralize all aircraft move-

performance takeoff, you must know thoroughly the

ment. Slowly increase the collective and position the

capabilities and limitations of your equipment. You

cyclic so as to break ground in a 40 knot attitude. This is

must also consider the wind velocity, temperature, alti-

approximately the same attitude as when the helicopter is

tude, gross weight, center-of-gravity location, and

light on the skids. Continue to slowly increase the collec-

other factors affecting your technique and the perform-

tive until the maximum power available is reached. This

ance of the helicopter.

large collective movement requires a substantial increase

in pedal pressure to maintain heading (position 2). Use the

To safely accomplish this type of takeoff, there must be

cyclic, as necessary, to control movement toward the

enough power to hover, in order to prevent the helicop-

desired flight path and, therefore, climb angle during the

ter from sinking back to the surface after becoming

maneuver (position 3). Maintain rotor r.p.m. at its maxi-

airborne. This hover power check can be used to deter-

mum, and do not allow it to decrease since you would

mine if there is sufficient power available to accomplish

probably have to lower the collective to regain it. Maintain

this maneuver.

these inputs until the helicopter clears the obstacle, or until

The angle of climb for a maximum performance take-

reaching 50 feet for demonstration purposes (position 4).

off depends on existing conditions. The more critical

Then, establish a normal climb attitude and reduce power

the conditions, such as high density altitudes, calm

(position 5). As in any maximum performance maneuver,

winds, and high gross weights, the shallower the angle

the techniques you use affect the actual results. Smooth,

of climb. In light or no wind conditions, it might be

coordinated inputs coupled with precise control allow the

necessary to operate in the crosshatched or shaded

helicopter to attain its maximum performance.

areas of the height/velocity diagram during the begin-

COMMON ERRORS

ning of this maneuver. Therefore, be aware of the

calculated risk when operating in these areas. An

Failure to consider performance data, including

engine failure at a low altitude and airspeed could place

height/velocity diagram.

the helicopter in a dangerous position, requiring a high

Nose too low initially, causing horizontal flight

degree of skill in making a safe autorotative landing.

rather than more vertical flight.

TECHNIQUE

Failure to maintain maximum permissible r.p.m.

Before attempting a maximum performance takeoff,

Abrupt control movements.

bring the helicopter to a hover, and determine the

Failure to resume normal climb power and air-

excess power available by noting the difference

speed after clearing the obstacle.

between the power available and that required to hover.

You should also perform a balance and flight control

RUNNING/ROLLING TAKEOFF

check and note the position of the cyclic. Then position

A running takeoff in a skid-type helicopter or a rolling

the helicopter into the wind and return the helicopter to

takeoff in a wheeled helicopter is sometimes used when

the surface. Normally, this maneuver is initiated from

conditions of load and/or density altitude prevent a sus-

the surface. After checking the area for obstacles and

tained hover at normal hovering altitude. However, you

other aircraft, select reference points along the takeoff

should not attempt this maneuver if you do not have

sufficient power to hover, at least momentarily. If the

helicopter cannot be hovered, its performance is unpre-

dictable. If the helicopter cannot be raised off the

surface at all, sufficient power might not be available

to safely accomplish the maneuver. If you cannot

momentarily hover the helicopter, you must wait for

conditions to improve or off-load some of the weight.

To accomplish a safe running or rolling takeoff, the sur-

face area must be of sufficient length and smoothness,

and there cannot be any barriers in the flight path to

interfere with a shallow climb.

For wheeled helicopters, a rolling takeoff is sometimes

used to minimize the downwash created during a take-

Figure 10-1. Maximum performance takeoff.

off from a hover.

10-2

TECHNIQUE

Attempting to become airborne before obtaining

Refer to figure 10-2. To begin the maneuver, first align

effective translational lift.

the helicopter to the takeoff path. Next, increase the

Using too much forward cyclic during the surface

throttle to obtain takeoff r.p.m., and increase the collec-

run.

tive smoothly until the helicopter becomes light on the

Lowering the nose too much after becoming air-

skids or landing gear (position 1). Then, move the

borne, resulting in the helicopter settling back to

cyclic slightly forward of the neutral hovering position,

the surface.

and apply additional collective to start the forward

movement (position 2). To simulate a reduced power

Failing to remain below the recommended altitude

condition during practice, use one to two inches less

until airspeed approaches normal climb speed.

manifold pressure, or three to five percent less torque,

than that required to hover.

RAPID DECELERATION (QUICK STOP)

In normal operations, use the rapid deceleration or quick

stop maneuver to slow the helicopter rapidly and bring

it to a stationary hover. The maneuver requires a high

degree of coordination of all controls. It is practiced at

an altitude that permits a safe clearance between the tail

rotor and the surface throughout the maneuver, espe-

cially at the point where the pitch attitude is highest.

The altitude at completion should be no higher than the

maximum safe hovering altitude prescribed by the man-

Figure 10-2. Running/rolling takeoff.

ufacturer. In selecting an altitude at which to begin the

maneuver, you should take into account the overall

length of the helicopter and the height/velocity diagram.

Even though the maneuver is called a rapid deceleration

or quick stop, it is performed slowly and smoothly with

Maintain a straight ground track with lateral cyclic and

the primary emphasis on coordination.

heading with antitorque pedals until a climb is established.

As effective translational lift is gained, the helicopter

TECHNIQUE

becomes airborne in a fairly level attitude with little or no

During training always perform this maneuver into the

pitching (position 3). Maintain an altitude to take advan-

wind. [Figure 10-3, position 1] After leveling off at an

tage of ground effect, and allow the airspeed to increase

altitude between 25 and 40 feet, depending on the man-

toward normal climb speed. Then, follow a climb profile

ufacturer’s recommendations, accelerate to the desired

that takes you through the clear area of the height/velocity

entry speed, which is approximately 45 knots for most

diagram (position 4). During practice maneuvers, after

training helicopters (position 2). The altitude you

you have climbed to an altitude of 50 feet, establish the

choose should be high enough to avoid danger to the

normal climb power setting and attitude.

tail rotor during the flare, but low enough to stay out of

the crosshatched or shaded areas of the height/velocity

COMMON ERRORS

diagram throughout the maneuver. In addition, this

Failing to align heading and ground track to keep

altitude should be low enough that you can bring the

surface friction to a minimum.

helicopter to a hover during the recovery.

Figure 10-3. Rapid deceleration or quick stop.

10-3

At position 3, initiate the deceleration by applying aft

most confined areas and is sometimes used to avoid

cyclic to reduce forward speed. Simultaneously, lower

areas of turbulence around a pinnacle. An approach

the collective, as necessary, to counteract any climbing

angle of approximately 15° is considered a steep

tendency. The timing must be exact. If you apply too

approach. [Figure 10-4]

little down collective for the amount of aft cyclic

applied, a climb results. If you apply too much down

collective, a descent results. A rapid application of aft

cyclic requires an equally rapid application of down

collective. As collective pitch is lowered, apply proper

15° Descent

antitorque pedal pressure to maintain heading, and

adjust the throttle to maintain r.p.m.

After attaining the desired speed (position 4), initiate

the recovery by lowering the nose and allowing the hel-

icopter to descend to a normal hovering altitude in level

flight and zero groundspeed (position 5). During the

recovery, increase collective pitch, as necessary, to stop

the helicopter at normal hovering altitude, adjust the

throttle to maintain r.p.m., and apply proper pedal pres-

sure, as necessary, to maintain heading.

Figure 10-4. Steep approach to a hover.

COMMON ERRORS

Initiating the maneuver by applying down

collective.

TECHNIQUE

Initially applying aft cyclic stick too rapidly,

On final approach, head your helicopter into the wind

causing the helicopter to balloon.

and align it with the intended touchdown point at the

recommended approach airspeed (position 1). When

Failing to effectively control the rate of decelera-

you intercept an approach angle of 15°, begin the

tion to accomplish the desired results.

approach by lowering the collective sufficiently to

Allowing the helicopter to stop forward motion

start the helicopter descending down the approach

in a tail-low attitude.

path and decelerating (position 2). Use the proper

antitorque pedal for trim. Since this angle is steeper

Failing to maintain proper r.p.m.

than a normal approach angle, you need to reduce the

collective more than that required for a normal

Waiting too long to apply collective pitch (power)

approach. Continue to decelerate with slight aft

during the recovery, resulting in excessive mani-

cyclic, and smoothly lower the collective to maintain

fold pressure or an over-torque situation when

the approach angle. As in a normal approach,

collective pitch is applied rapidly.

reference the touchdown point on the windshield to

Failing to maintain a safe clearance over the

determine changes in approach angle. This point is in

terrain.

a lower position than a normal approach. Aft cyclic is

required to decelerate sooner than a normal approach,

Improper use of antitorque pedals resulting in

and the rate of closure becomes apparent at a higher

erratic heading changes.

altitude. Maintain the approach angle and rate of

descent with the collective, rate of closure with the

cyclic, and trim with antitorque pedals. Use a crab

above 50 feet and a slip below 50 feet for any cross-

STEEP APPROACH TO A HOVER

wind that might be present.

A steep approach is used primarily when there are

obstacles in the approach path that are too high to allow

Loss of effective translational lift occurs higher in a

a normal approach. A steep approach permits entry into

steep approach (position 3), requiring an increase in the

collective to prevent settling, and more forward cyclic

to achieve the proper rate of closure. Terminate the

approach at hovering altitude above the intended land-

ing point with zero groundspeed (position 4). If power

has been properly applied during the final portion of

the approach, very little additional power is required in

Balloon-Gaining an excessive amount of altitude as a result of an

abrupt flare.

the hover.

10-4

COMMON ERRORS

As you lower the collective, maintain heading with

proper antitorque pedal pressure, and r.p.m. with the

Failing to maintain proper r.p.m. during the entire

throttle. Maintain approach airspeed until the apparent

approach.

rate of closure appears to be increasing. Then, begin to

Improper use of collective in maintaining the

slow the helicopter with aft cyclic (position 2).

selected angle of descent.

As in normal and steep approaches, the primary control

Failing to make antitorque pedal corrections to

for the angle and rate of descent is the collective, while

compensate for collective pitch changes during

the cyclic primarily controls the groundspeed.

the approach.

However, there must be a coordination of all the con-

Slowing airspeed excessively in order to remain

trols for the maneuver to be accomplished successfully.

on the proper angle of descent.

The helicopter should arrive at the point of touchdown

at or slightly above effective translational lift. Since

Inability to determine when effective transla-

translational lift diminishes rapidly at slow airspeeds,

tional lift is lost.

the deceleration must be smoothly coordinated, at the

Failing to arrive at hovering altitude and attitude,

same time keeping enough lift to prevent the helicopter

and zero groundspeed almost simultaneously.

from settling abruptly.

Low r.p.m. in transition to the hover at the end of

Just prior to touchdown, place the helicopter in a level

the approach.

attitude with the cyclic, and maintain heading with the

Using too much aft cyclic close to the surface,

antitorque pedals. Use the cyclic to keep the heading

which may result in the tail rotor striking the sur-

and ground track identical (position 3). Allow the

face.

helicopter to descend gently to the surface in a straight-

and-level attitude, cushioning the landing with the

SHALLOW APPROACH AND

collective. After surface contact, move the cyclic

slightly forward to ensure clearance between the

RUNNING/ROLL-ON LANDING

tailboom and the rotor disc. You should also use the

Use a shallow approach and running landing when a

cyclic to maintain the surface track. (position 4). You

high-density altitude or a high gross weight condition,

normally hold the collective stationary until the heli-

or some combination thereof, is such that a normal or

copter stops; however, if you want more braking action,

steep approach cannot be made because of insufficient

you can lower the collective slightly. Keep in mind that

power to hover. [Figure 10-5] To compensate for this

due to the increased ground friction when you lower the

lack of power, a shallow approach and running landing

collective, the helicopter’s nose might pitch forward.

makes use of translational lift until surface contact is

Exercise caution not to correct this pitching movement

made. If flying a wheeled helicopter, you can also use a

with aft cyclic since this movement could result in the

roll-on landing to minimize the effect of downwash.

rotor making contact with the tailboom. During the

The glide angle for a shallow approach is approxi-

landing, maintain normal r.p.m. with the throttle and

mately 5°. Since the helicopter will be sliding or rolling

directional control with the antitorque pedals.

to a stop during this maneuver, the landing area must

be smooth and long enough to accomplish this task.

For wheeled helicopters, use the same technique except

after landing, lower the collective, neutralize the

controls, and apply the brakes, as necessary, to slow the

5° Descent

helicopter. Do not use aft cyclic when bringing the

helicopter to a stop.

COMMON ERRORS

Assuming excessive nose-high attitude to slow

the helicopter near the surface.

Figure 10-5. Shallow approach and running landing.

Insufficient collective and throttle to cushion

landing.

Failing to add proper antitorque pedal as collec-

TECHNIQUE

tive is added to cushion landing, resulting in a

A shallow approach is initiated in the same manner as

touchdown while the helicopter is moving side-

the normal approach except that a shallower angle of

ward.

descent is maintained. The power reduction to initiate

the desired angle of descent is less than that for a normal

Failing to maintain a speed that takes advantage

approach since the angle of descent is less (position 1).

of effective translational lift.

10-5

Touching down at an excessive groundspeed for

can hold the helicopter against it with the cyclic during

the existing conditions. (Some helicopters have

the entire landing. A slope of 5° is considered maxi-

maximum touchdown groundspeeds.)

mum for normal operation of most helicopters.

Failing to touch down in a level attitude.

You should be aware of any abnormal vibration or mast

Failing to maintain proper r.p.m. during and after

bumping that signals maximum cyclic deflection. If

touchdown.

this occurs, abandon the landing because the slope is

too steep. In most helicopters with a counterclockwise

Poor directional control during touchdown.

rotor system, landings can be made on steeper slopes

when you are holding the cyclic to the right. When

SLOPE OPERATIONS

landing on slopes using left cyclic, some cyclic input

Prior to conducting any slope operations, you should

must be used to overcome the translating tendency. If

be thoroughly familiar with the characteristics of

wind is not a factor, you should consider the drifting

dynamic rollover and mast bumping, which are dis-

tendency when determining landing direction.

cussed in Chapter 11-Helicopter Emergencies. The

approach to a slope is similar to the approach to any

After the downslope skid is on the surface, reduce the

other landing area. During slope operations, make

collective to full down, and neutralize the cyclic and

allowances for wind, barriers, and forced landing sites

pedals (frame 4). Normal operating r.p.m. should be

in case of engine failure. Since the slope may constitute

maintained until the full weight of the helicopter is on

an obstruction to wind passage, you should anticipate

the landing gear. This ensures adequate r.p.m. for

turbulence and downdrafts.

immediate takeoff in case the helicopter starts sliding

down the slope. Use antitorque pedals as necessary

SLOPE LANDING

throughout the landing for heading control. Before

You usually land a helicopter across the slope rather

reducing the r.p.m., move the cyclic control as neces-

than with the slope. Landing with the helicopter facing

sary to check that the helicopter is firmly on the

down the slope or downhill is not recommended

ground.

because of the possibility of striking the tail rotor on

the surface.

COMMON ERRORS

TECHNIQUE

Failure to consider wind effects during the

Refer to figure 10-6. At the termination of the

approach and landing.

approach, move the helicopter slowly toward the slope,

Failure to maintain proper r.p.m. throughout the

being careful not to turn the tail upslope. Position the

entire maneuver.

helicopter across the slope at a stabilized hover headed

into the wind over the spot of intended landing

Turning the tail of the helicopter into the slope.

(frame 1). Downward pressure on the collective starts

Lowering the downslope skid or wheel too rapidly.

the helicopter descending. As the upslope skid touches

the ground, hesitate momentarily in a level attitude,

Applying excessive cyclic control into the slope,

then apply lateral cyclic in the direction of the slope

causing mast bumping.

(frame 2). This holds the skid against the slope while

you continue lowering the downslope skid with the col-

SLOPE TAKEOFF

lective. As you lower the collective, continue to move

A slope takeoff is basically the reverse of a slope land-

the cyclic toward the slope to maintain a fixed position

ing. [Figure 10-7] Conditions that may be associated

(frame 3). The slope must be shallow enough so you

with the slope, such as turbulence and obstacles, must

Figure 10-6. Slope landing.

10-6

Figure 10-7. Slope takeoff.

be considered during the takeoff. Planning should

There are several things to consider when operating in

include suitable forced landing areas.

confined areas. One of the most important is maintaining

a clearance between the rotors and obstacles forming the

TECHNIQUE

confined area. The tail rotor deserves special considera-

Begin the takeoff by increasing r.p.m. to the normal

tion because, in some helicopters, you cannot always see

range with the collective full down. Then, move the

it from the cabin. This not only applies while making the

cyclic toward the slope (frame 1). Holding cyclic

approach, but while hovering as well. Another consider-

toward the slope causes the downslope skid to rise as

ation is that wires are especially difficult to see;

you slowly raise the collective (frame 2). As the skid

however, their supporting devices, such as poles or

comes up, move the cyclic toward the neutral position.

towers, serve as an indication of their presence and

If properly coordinated, the helicopter should attain a

approximate height. If any wind is present, you should

level attitude as the cyclic reaches the neutral position.

also expect some turbulence. [Figure 10-8]

At the same time, use antitorque pedal pressure to

maintain heading and throttle to maintain r.p.m. With

the helicopter level and the cyclic centered, pause

momentarily to verify everything is correct, and then

Wind

gradually raise the collective to complete the liftoff

(frame 3).

After reaching a hover, take care to avoid hitting the

ground with the tail rotor. If an upslope wind exists,

execute a crosswind takeoff and then make a turn into

the wind after clearing the ground with the tail rotor.

COMMON ERRORS

Figure 10-8. If the wind velocity is 10 knots or greater, you

should expect updrafts on the windward side and downdrafts

Failure to adjust cyclic control to keep the heli-

on the lee side of obstacles. You should plan the approach

copter from sliding downslope.

with these factors in mind, but be ready to alter your plans if

the wind speed or direction changes.

Failure to maintain proper r.p.m.

Holding excessive cyclic into the slope as the

Something else for you to consider is the availability of

downslope skid is raised.

forced landing areas during the planned approach. You

Turning the tail of the helicopter into the slope

should think about the possibility of flying from one

during takeoff.

alternate landing area to another throughout the

approach, while avoiding unfavorable areas. Always

CONFINED AREA OPERATIONS

leave yourself a way out in case the landing cannot be

A confined area is an area where the flight of the heli-

completed or a go-around is necessary.

copter is limited in some direction by terrain or the

presence of obstructions, natural or manmade. For

APPROACH

example, a clearing in the woods, a city street, a road, a

A high reconnaissance should be completed before ini-

building roof, etc., can each be regarded as a confined

tiating the confined area approach. Start the approach

area. Generally, takeoffs and landings should be made

phase using the wind and speed to the best possible

into the wind to obtain maximum airspeed with mini-

advantage. Keep in mind areas suitable for forced land-

mum groundspeed.

ing. It may be necessary to choose between an

10-7

approach that is crosswind, but over an open area, and

flight is required to reach the takeoff position, place

one directly into the wind, but over heavily wooded or

reference markers in front of the helicopter in such a

extremely rough terrain where a safe forced landing

way that a ground track can be safely followed to the

would be impossible. If these conditions exist, consider

takeoff position. In addition, the takeoff marker should

the possibility of making the initial phase of the

be located so that it can be seen without hovering

approach crosswind over the open area and then turn-

beyond it.

ing into the wind for the final portion of the approach.

When planning the takeoff, consider the direction of

Always operate the helicopter as close to its normal

the wind, obstructions, and forced landing areas. To

capabilities as possible, taking into consideration the

help you fly up and over an obstacle, you should form

situation at hand. In all confined area operations, with

an imaginary line from a point on the leading edge of

the exception of the pinnacle operation, the angle of

the helicopter to the highest obstacle to be cleared. Fly

descent should be no steeper than necessary to clear

this line of ascent with enough power to clear the

any barrier in the approach path and still land on the

obstacle by a safe distance. After clearing the obstacle,

selected spot. The angle of climb on takeoff should be

maintain the power setting and accelerate to the normal

normal, or not steeper than necessary to clear any bar-

climb speed. Then, reduce power to the normal climb

rier. Clearing a barrier by a few feet and maintaining

power setting.

normal operating r.p.m., with perhaps a reserve of

power, is better than clearing a barrier by a wide mar-

COMMON ERRORS

gin but with a dangerously low r.p.m. and no power

Failure to perform, or improper performance of, a

reserve.

high or low reconnaissance.

Flying the approach angle at too steep or too shal-

Always make the landing to a specific point and not to

low an approach for the existing conditions.

some general area. This point should be located well

forward, away from the approach end of the area. The

Failing to maintain proper r.p.m.

more confined the area, the more essential it is that you

Failure to consider emergency landing areas.

land the helicopter precisely at a definite point. Keep

Failure to select a specific landing spot.

this point in sight during the entire final approach.

Failure to consider how wind and turbulence

When flying a helicopter near obstructions, always

could affect the approach.

consider the tail rotor. A safe angle of descent over bar-

Improper takeoff and climb technique for exist-

riers must be established to ensure tail rotor clearance

ing conditions.

of all obstructions. After coming to a hover, take care

to avoid turning the tail into obstructions.

PINNACLE AND RIDGELINE

OPERATIONS

TAKEOFF

A pinnacle is an area from which the surface drops

A confined area takeoff is considered an altitude over

away steeply on all sides. A ridgeline is a long area

airspeed maneuver. Before takeoff, make a ground

from which the surface drops away steeply on one or

reconnaissance to determine the type of takeoff to be

two sides, such as a bluff or precipice. The absence of

performed, to determine the point from which the take-

obstacles does not necessarily lessen the difficulty of

off should be initiated to ensure the maximum amount

pinnacle or ridgeline operations. Updrafts, downdrafts,

of available area, and finally, how to best maneuver the

and turbulence, together with unsuitable terrain in

helicopter from the landing point to the proposed take-

which to make a forced landing, may still present

off position.

extreme hazards.

If wind conditions and available area permit, the heli-

copter should be brought to a hover, turned around, and

APPROACH AND LANDING

hovered forward from the landing position to the take-

If you need to climb to a pinnacle or ridgeline, do it on

off position. Under certain conditions, sideward flight

the upwind side, when practicable, to take advantage of

to the takeoff position may be necessary. If rearward

any updrafts. The approach flight path should be paral-

lel to the ridgeline and into the wind as much as possi-

ble. [Figure 10-9]

Load, altitude, wind conditions, and terrain features

determine the angle to use in the final part of an

approach. As a general rule, the greater the winds, the

Altitude over Airspeed-In this type of maneuver, it is more important

to gain altitude than airspeed. However, unless operational considera-

steeper the approach needs to be to avoid turbulent air

tions dictate otherwise, the crosshatched or shaded areas of the

height/velocity diagram should be avoided.

and downdrafts. Groundspeed during the approach is

10-8

made in the forward portion of the area. Always per-

form a stability check, prior to reducing r.p.m., to

ensure the landing gear is on firm terrain that can safely

support the weight of the helicopter.

TAKEOFF

A pinnacle takeoff is an airspeed over altitude maneu-

ver made from the ground or from a hover. Since

pinnacles and ridgelines are generally higher than the

immediate surrounding terrain, gaining airspeed on the

takeoff is more important than gaining altitude. The

higher the airspeed, the more rapid the departure from

slopes of the pinnacle. In addition to covering unfavor-

able terrain rapidly, a higher airspeed affords a more

favorable glide angle and thus contributes to the

chances of reaching a safe area in the event of a forced

landing. If a suitable forced landing area is not avail-

Figure 10-9. When flying an approach to a pinnacle or ridge-

able, a higher airspeed also permits a more effective

line, avoid the areas where downdrafts are present, espe-

flare prior to making an autorotative landing.

cially when excess power is limited. If you encounter

downdrafts, it may become necessary to make an immediate

On takeoff, as the helicopter moves out of ground

turn away from the pinnacle to avoid being forced into the

effect, maintain altitude and accelerate to normal climb

rising terrain.

airspeed. When normal climb speed is attained, estab-

lish a normal climb attitude. Never dive the helicopter

more difficult to judge because visual references are

down the slope after clearing the pinnacle.

farther away than during approaches over trees or flat

terrain. If a crosswind exists, remain clear of down-

COMMON ERRORS

drafts on the leeward or downwind side of the

ridgeline. If the wind velocity makes the crosswind

Failure to perform, or improper performance of, a

landing hazardous, you may be able to make a low,

high or low reconnaissance.

coordinated turn into the wind just prior to terminating

Flying the approach angle at too steep or too shal-

the approach. When making an approach to a pinnacle,

low an approach for the existing conditions.

avoid leeward turbulence and keep the helicopter

within reach of a forced landing area as long as

Failure to maintain proper r.p.m.

possible.

Failure to consider emergency landing areas.

On landing, take advantage of the long axis of the area

Failure to consider how wind and turbulence

when wind conditions permit. Touchdown should be

could affect the approach and takeoff.

Airspeed over Altitude-This means that in this maneuver, obstacles

are not a factor, and it is more important to gain airspeed than altitude.

10-9

Today helicopters are quite reliable. However

airspeed increases beyond that which gives minimum

emergencies do occur, whether a result of mechanical

rate of descent, the rate of descent increases again.

failure or pilot error. By having a thorough knowledge

of the helicopter and its systems, you will be able to

When landing from an autorotation, the energy stored

more readily handle the situation. In addition, by

in the rotating blades is used to decrease the rate of

knowing the conditions that can lead to an

descent and make a soft landing. A greater amount of

emergency, many potential accidents can be avoided.

rotor energy is required to stop a helicopter with a high

rate of descent than is required to stop a helicopter that

AUTOROTATION

is descending more slowly. Therefore, autorotative

In a helicopter, an autorotation is a descending maneu-

descents at very low or very high airspeeds are more

ver where the engine is disengaged from the main rotor

critical than those performed at the minimum rate of

system and the rotor blades are driven solely by the

descent airspeed.

upward flow of air through the rotor. In other words, the

engine is no longer supplying power to the main rotor.

Each type of helicopter has a specific airspeed at which

a power-off glide is most efficient. The best airspeed is

The most common reason for an autorotation is an

the one which combines the greatest glide range with

engine failure, but autorotations can also be performed

the slowest rate of descent. The specific airspeed is

in the event of a complete tail rotor failure, since there

somewhat different for each type of helicopter, yet

is virtually no torque produced in an autorotation. If

certain factors affect all configurations in the same

altitude permits, they can also be used to recover from

manner. For specific autorotation airspeeds for a partic-

settling with power. If the engine fails, the freewheel-

ular helicopter, refer to the FAA-approved rotorcraft

ing unit automatically disengages the engine from the

flight manual.

main rotor allowing the main rotor to rotate freely.

Essentially, the freewheeling unit disengages anytime

The specific airspeed for autorotations is established

the engine r.p.m. is less than the rotor r.p.m.

for each type of helicopter on the basis of average

weather and wind conditions and normal loading.

At the instant of engine failure, the main rotor blades

When the helicopter is operated with heavy loads in

are producing lift and thrust from their angle of attack

high density altitude or gusty wind conditions, best

and velocity. By immediately lowering collective pitch,

performance is achieved from a slightly increased air-

which must be done in case of an engine failure, lift and

speed in the descent. For autorotations at low density

drag are reduced, and the helicopter begins an immedi-

altitude and light loading, best performance is achieved

ate descent, thus producing an upward flow of air

from a slight decrease in normal airspeed. Following

through the rotor system. This upward flow of air

this general procedure of fitting airspeed to existing

through the rotor provides sufficient thrust to maintain

conditions, you can achieve approximately the same

rotor r.p.m. throughout the descent. Since the tail rotor

glide angle in any set of circumstances and estimate the

is driven by the main rotor transmission during autoro-

touchdown point.

tation, heading control is maintained as in normal flight.

When making turns during an autorotation, generally

Several factors affect the rate of descent in autorota-

use cyclic control only. Use of antitorque pedals to

tion; density altitude, gross weight, rotor r.p.m., and

assist or speed the turn causes loss of airspeed and

airspeed. Your primary control of the rate of descent is

downward pitching of the nose. When an autorotation

airspeed. Higher or lower airspeeds are obtained with

is initiated, sufficient antitorque pedal pressure should

the cyclic pitch control just as in normal flight.

be used to maintain straight flight and prevent yawing.

In theory, you have a choice in the angle of descent

This pressure should not be changed to assist the turn.

varying from a vertical descent to maximum range,

which is the minimum angle of descent. Rate of descent

is high at zero airspeed and decreases to a minimum at

Use collective pitch control to manage rotor r.p.m. If

approximately 50 to 60 knots, depending upon the par-

rotor r.p.m. builds too high during an autorotation, raise

ticular helicopter and the factors just mentioned. As the

the collective sufficiently to decrease r.p.m. back to the

11-1

normal operating range. If the r.p.m. begins decreasing,

you have to again lower the collective. Always keep

the rotor r.p.m. within the established range for your

helicopter. During a turn, rotor r.p.m. increases due to

the increased back cyclic control pressure, which

induces a greater airflow through the rotor system. The

r.p.m. builds rapidly and can easily exceed the maxi-

mum limit if not controlled by use of collective. The

tighter the turn and the heavier the gross weight, the

higher the r.p.m.

To initiate an autorotation, other than in a low hover,

lower the collective pitch control. This holds true

whether performing a practice autorotation or in the

event of an in-flight engine failure. This reduces the

pitch of the main rotor blades and allows them to

continue turning at normal r.p.m. During practice

autorotations, maintain the r.p.m. in the green arc

with the throttle while lowering collective. Once the

collective is fully lowered, reduce engine r.p.m. by

Figure 11-1. Straight-in autorotation.

decreasing the throttle. This causes a split of the

engine and rotor r.p.m. needles.

and leads to “chasing the r.p.m.” Avoid looking straight

STRAIGHT-IN AUTOROTATION

down in front of the aircraft. Continually cross-check

A straight-in autorotation implies an autorotation from

attitude, trim, rotor r.p.m., and airspeed.

altitude with no turns. The speed at touchdown and the

resulting ground run depends on the rate and amount of

At approximately 40 to 100 feet above the surface, or

flare. The greater the degree of flare and the longer it is

at the altitude recommended by the manufacturer (posi-

held, the slower the touchdown speed and the shorter

tion 3), begin the flare with aft cyclic control to reduce

the ground run. The slower the speed desired at touch-

forward airspeed and decrease the rate of descent.

down, the more accurate the timing and speed of the

Maintain heading with the antitorque pedals. Care must

flare must be, especially in helicopters with low inertia

be taken in the execution of the flare so that the cyclic

rotor systems.

control is not moved rearward so abruptly as to cause

the helicopter to climb, nor should it be moved so

TECHNIQUE

slowly as to not arrest the descent, which may allow

Refer to figure 11-1 (position 1). From level flight at

the helicopter to settle so rapidly that the tail rotor

the manufacturer’s recommended airspeed, between

strikes the ground. When forward motion decreases to

500 to 700 feet AGL, and heading into the wind,

the desired groundspeed, which is usually the slowest

smoothly, but firmly lower the collective pitch control

possible speed (position 4), move the cyclic control

to the full down position, maintaining r.p.m. in the

forward to place the helicopter in the proper attitude

green arc with throttle. Coordinate the collective move-

for landing.

ment with proper antitorque pedal for trim, and apply

aft cyclic control to maintain proper airspeed. Once the

The altitude at this time should be approximately 8 to

collective is fully lowered, decrease throttle to ensure a

15 feet AGL, depending on the altitude recommended

clean split of the needles. After splitting the needles,

by the manufacturer. Extreme caution should be used

readjust the throttle to keep engine r.p.m. above

to avoid an excessive nose high and tail low attitude

normal idling speed, but not high enough to cause

below 10 feet. At this point, if a full touchdown landing

rejoining of the needles. The manufacturer often

is to be made, allow the helicopter to descend vertically

recommends the proper r.p.m.

(position 5). Increase collective pitch, as necessary, to

check the descent and cushion the landing. Additional

At position 2, adjust attitude with cyclic control to

antitorque pedal is required to maintain heading as col-

obtain the manufacturer’s recommended autorotation

lective pitch is raised due to the reduction in rotor

or best gliding speed. Adjust collective pitch control, as

r.p.m. and the resulting reduced effect of the tail rotor.

necessary, to maintain rotor r.p.m. in the green arc. Aft

Touch down in a level flight attitude.

cyclic movements cause an increase in rotor r.p.m.,

which is then controlled by a small increase in collec-

A power recovery can be made during training in lieu

tive pitch control. Avoid a large collective pitch

of a full touchdown landing. Refer to the section on

increase, which results in a rapid decay of rotor r.p.m.,

power recoveries for the correct technique.

11-2

After touchdown and after the helicopter has come to a

COMMON ERRORS

complete stop, lower the collective pitch to the full-

Initiating recovery too late, requiring a rapid appli-

down position. Do not try to stop the forward ground

cation of controls, resulting in overcontrolling.

run with aft cyclic, as the main rotor blades can strike

the tail boom. Rather, by lowering the collective

Failing to obtain and maintain a level attitude

slightly during the ground run, more weight is placed

near the surface.

on the undercarriage, slowing the helicopter.

Failing to coordinate throttle and collective pitch

COMMON ERRORS

properly, resulting in either an engine overspeed

or a loss of r.p.m.

Failing to use sufficient antitorque pedal when

power is reduced.

Failing to coordinate proper antitorque pedal with

the increase in power

Lowering the nose too abruptly when power is

reduced, thus placing the helicopter in a dive.

AUTOROTATIONS WITH TURNS

A turn, or a series of turns, can be made during an

Failing to maintain proper rotor r.p.m. during

autorotation in order to land into the wind or avoid

the descent.

obstacles. The turn is usually made early so that the

Application of up-collective pitch at an excessive

remainder of the autorotation is the same as a straight

altitude resulting in a hard landing, loss of

in autorotation. The most common types are 90° and

heading control, and possible damage to the tail

180° autorotations. The technique below describes a

rotor and to the main rotor blade stops.

180° autorotation.

Failing to level the helicopter.

TECHNIQUE

Establish the aircraft on downwind at recommended

POWER RECOVERY FROM PRACTICE

airspeed at 700 feet AGL, parallel to the touchdown area.

AUTOROTATION

In a no wind or headwind condition, establish the ground

A power recovery is used to terminate practice

track approximately 200 feet away from the touchdown

autorotations at a point prior to actual touchdown.

point. If a strong crosswind exists, it will be necessary to

After the power recovery, a landing can be made or a

move your downwind leg closer or farther out. When

go-around initiated.

abeam the intended touchdown point, reduce

collective, and then split the needles. Apply proper

TECHNIQUE

antitorque pedal and cyclic to maintain proper attitude.

At approximately 8 to 15 feet above the ground,

Cross check attitude, trim, rotor r.p.m., and airspeed.

depending upon the helicopter being used, begin to

level the helicopter with forward cyclic control. Avoid

After the descent and airspeed is established, roll into a

excessive nose high, tail low attitude below 10 feet.

180° turn. For training, you should initially roll into a

Just prior to achieving level attitude, with the nose still

bank of a least 30°, but no more than 40°. Check your

slightly up, coordinate upward collective pitch control

airspeed and rotor r.p.m. Throughout the turn, it is

with an increase in the throttle to join the needles at

important to maintain the proper airspeed and keep the

operating r.p.m. The throttle and collective pitch must

aircraft in trim. Changes in the aircraft’s attitude and

be coordinated properly. If the throttle is increased too

the angle of bank cause a corresponding change in rotor

fast or too much, an engine overspeed can occur; if

r.p.m. Adjust the collective, as necessary, in the turn to

throttle is increased too slowly or too little in propor-

maintain rotor r.p.m. in the green arc.

tion to the increase in collective pitch, a loss of rotor

r.p.m. results. Use sufficient collective pitch to stop the

At the 90° point, check the progress of your turn by

descent and coordinate proper antitorque pedal

glancing toward your landing area. Plan the second

pressure to maintain heading. When a landing is to be

90 degrees of turn to roll out on the centerline. If you are

made following the power recovery, bring the helicop-

too close, decrease the bank angle; if too far out, increase

ter to a hover at normal hovering altitude and then

the bank angle. Keep the helicopter in trim with anti-

descend to a landing.

torque pedals.

If a go-around is to be made, the cyclic control should

The turn should be completed and the helicopter

be moved forward to resume forward flight. In transi-

aligned with the intended touchdown area prior to pass-

tioning from a practice autorotation to a go-around,

ing through 100 feet AGL. If the collective pitch was

exercise care to avoid an altitude-airspeed combination

increased to control the r.p.m., it may have to be

that would place the helicopter in an unsafe area of its

lowered on roll out to prevent a decay in r.p.m. Make

height-velocity diagram.

an immediate power recovery if the aircraft is not

11-3

aligned with the touchdown point, and if the rotor

When the weight of the helicopter is entirely on the

r.p.m. and/or airspeed is not within proper limits.

skids, cease the application of upward collective. When

the helicopter has come to a complete stop, lower the

From this point, complete the procedure as if it were a

collective pitch to the full down position.

straight-in autorotation.

The timing of the collective pitch is a most important

POWER FAILURE IN A HOVER

consideration. If it is applied too soon, the remaining

Power failures in a hover, also called hovering autoro-

r.p.m. may not be sufficient to make a soft landing. On

tations, are practiced so that you automatically make

the other hand, if collective pitch control is applied too

the correct response when confronted with engine

late, surface contact may be made before sufficient

stoppage or certain other emergencies while hovering.

blade pitch is available to cushion the landing.

The techniques discussed in this section refer to heli-

copters with a counter-clockwise rotor system and an

COMMON ERRORS

antitorque rotor.

Failing to use sufficient proper antitorque pedal

TECHNIQUE

when power is reduced.

To practice hovering autorotations, establish a normal

hovering altitude for the particular helicopter being

Failing to stop all sideward or backward move-

used, considering load and atmospheric conditions.

ment prior to touchdown.

Keep the helicopter headed into the wind and hold

maximum allowable r.p.m.

Failing to apply up-collective pitch properly,

resulting in a hard touchdown.

To simulate a power failure, firmly roll the throttle into

the spring loaded override position, if applicable. This

Failing to touch down in a level attitude.

disengages the driving force of the engine from the

rotor, thus eliminating torque effect. As the throttle is

Not rolling the throttle completely to idle.

closed, apply proper antitorque pedal to maintain head-

ing. Usually, a slight amount of right cyclic control is

HEIGHT/VELOCITY DIAGRAM

necessary to keep the helicopter from drifting to the

A height/velocity (H/V) diagram, published by the

left, to compensate for the loss of tail rotor thrust.

manufacturer for each model of helicopter, depicts the

However, use cyclic control, as required, to ensure a

critical combinations of airspeed and altitude should an

vertical descent and a level attitude. Leave the collec-

engine failure occur. Operating at the altitudes and air-

tive pitch where it is on entry.

speeds shown within the crosshatched or shaded areas

of the H/V diagram may not allow enough time for the

Helicopters with low inertia rotor systems will begin to

critical transition from powered flight to autorotation.

settle immediately. Keep a level attitude and ensure a

[Figure 11-2]

vertical descent with cyclic control while maintaining

heading with the pedals. At approximately 1 foot above

An engine failure in a climb after takeoff occurring in

the surface, apply upward collective pitch control, as

section A of the diagram is most critical. During a

necessary, to slow the descent and cushion the landing.

climb, a helicopter is operating at higher power settings

Usually the full amount of collective pitch is required.

and blade angle of attack. An engine failure at this point

As upward collective pitch control is applied, the throt-

causes a rapid rotor r.p.m. decay because the upward

tle has to be held in the closed position to prevent the

movement of the helicopter must be stopped, then a

rotor from re-engaging.

descent established in order to drive the rotor. Time is

also needed to stabilize, then increase the r.p.m. to the

Helicopters with high inertia rotor systems will maintain

normal operating range. The rate of descent must reach

altitude momentarily after the throttle is closed. Then, as

a value that is normal for the airspeed at the moment.

the rotor r.p.m. decreases, the helicopter starts to settle.

Since altitude is insufficient for this sequence, you end

When the helicopter has settled to approximately 1 foot

up with decaying r.p.m., an increasing sink rate, no

above the surface, apply upward collective pitch control

deceleration lift, little translational lift, and little

while holding the throttle in the closed position to slow

response to the application of collective pitch to cush-

the descent and cushion the landing. The timing of col-

ion the landing.

lective pitch control application, and the rate at which it

is applied, depends upon the particular helicopter being

It should be noted that, once a steady state autorotation

used, its gross weight, and the existing atmospheric con-

has been established, the H/V diagram no longer

ditions. Cyclic control is used to maintain a level attitude

applies. An engine failure while descending through

and to ensure a vertical descent. Maintain heading with

section A of the diagram, is less critical, provided a safe

antitorque pedals.

landing area is available.

11-4

500

can be made. The time required, and therefore, altitude

necessary to attain a steady state autorotative descent,

450

is dependent on the weight of the helicopter and the

density altitude. For this reason, the H/V diagram for

400

some helicopter models is valid only when the helicop-

Smooth Hard Surface.

ter is operated in accordance with the gross weight vs.

350

Avoid Operation in

density altitude chart. Where appropriate, this chart is

Shaded Areas.

found in the rotorcraft flight manual for the particular

300

helicopter. [Figure 11-3]

250

7,000

200

150

6,000

100

5,000

50 60

90 100 110 120

INDICATED AIRSPEED KNOTS

(CORRECTED FOR INSTRUMENT ERROR)

4,000

Figure

11-2. By carefully studying the height/velocity

diagram, you will be able to avoid the combinations of alti-

tude and airspeed that may not allow you sufficient time or

3,000

altitude to enter a stabilized autorotative descent. You might

1,500

1,600

1,700

1,800

1,900

want to refer to this diagram during the remainder of the

GROSS WEIGHT - POUNDS

discussion on the height/velocity diagram.

Figure 11-3. Assuming a density altitude of 5,500 feet, the

height/velocity diagram in figure 11-2 would be valid up to a

gross weight of approximately 1,700 pounds. This is found by

You should avoid the low altitude, high airspeed portion

entering the graph at a density altitude of 5,500 feet (point A),

of the diagram (section B), because your recognition of an

then moving horizontally to the solid line (point B). Moving ver-

engine failure will most likely coincide with, or shortly

tically to the bottom of the graph (point C), you find that with the

occur after, ground contact. Even if you detect an engine

existing density altitude, the maximum gross weight under

failure, there may not be sufficient time to rotate the

which the height/velocity diagram is applicable is 1,700 pounds.

helicopter from a nose low, high airspeed attitude to one

suitable for slowing, then landing. Additionally, the

The gross weight vs. density altitude chart is not

altitude loss that occurs during recognition of engine fail-

intended as a restriction to gross weight, but as an advi-

ure and rotation to a landing attitude, may not leave

sory to the autorotative capability of the helicopter

enough altitude to prevent the tail skid from hitting the

during takeoff and climb. You must realize, however,

ground during the landing maneuver.

that at gross weights above those recommended by the

gross weight vs. density altitude chart, the H/V diagram

Basically, if the helicopter represented by this H/V dia-

is not restrictive enough.

gram is above 445 feet AGL, you have enough time and

altitude to enter a steady state autorotation, regardless

VORTEX RING STATE (SETTLING WITH

of your airspeed. If the helicopter is hovering at 5 feet

POWER)

AGL (or less) in normal conditions and the engine fails,

Vortex ring state describes an aerodynamic condition

a safe hovering autorotation can be made. Between

where a helicopter may be in a vertical descent with up

approximately 5 feet and 445 feet AGL, however, the

to maximum power applied, and little or no cyclic

transition to autorotation depends on the altitude and

authority. The term “settling with power” comes from

airspeed of the helicopter. Therefore, you should

the fact that helicopter keeps settling even though full

always be familiar with the height/velocity diagram for

engine power is applied.

the particular model of helicopter you are flying.

In a normal out-of-ground-effect hover, the helicopter

THE EFFECT OF WEIGHT VERSUS

is able to remain stationary by propelling a large mass

DENSITY ALTITUDE

of air down through the main rotor. Some of the air is

The height/velocity diagram depicts altitude and air-

recirculated near the tips of the blades, curling up from

speed situations from which a successful autorotation

the bottom of the rotor system and rejoining the air

11-5

entering the rotor from the top. This phenomenon is

A vertical or nearly vertical descent of at least

common to all airfoils and is known as tip vortices. Tip

300 feet per minute. (Actual critical rate depends

vortices consume engine power but produce no useful

on the gross weight, r.p.m., density altitude, and

lift. As long as the tip vortices are small, their only

other pertinent factors.)

effect is a small loss in rotor efficiency. However, when

the helicopter begins to descend vertically, it settles

The rotor system must be using some of the avail-

into its own downwash, which greatly enlarges the tip

able engine power (from 20 to 100 percent).

vortices. In this vortex ring state, most of the power

developed by the engine is wasted in accelerating the

The horizontal velocity must be slower than

air in a doughnut pattern around the rotor.

effective translational lift.

In addition, the helicopter may descend at a rate that

Some of the situations that are conducive to a settling

exceeds the normal downward induced-flow rate of the

with power condition are: attempting to hover out of

inner blade sections. As a result, the airflow of the inner

ground effect at altitudes above the hovering ceiling of

blade sections is upward relative to the disc. This pro-

the helicopter; attempting to hover out of ground effect

duces a secondary vortex ring in addition to the normal

without maintaining precise altitude control; or down-

tip-vortices. The secondary vortex ring is generated

wind and steep power approaches in which airspeed is

about the point on the blade where the airflow changes

permitted to drop to nearly zero.

from up to down. The result is an unsteady turbulent

flow over a large area of the disc. Rotor efficiency is

When recovering from a settling with power condition,

lost even though power is still being supplied from the

the tendency on the part of the pilot is to first try to stop

engine. [Figure 11-4]

the descent by increasing collective pitch. However,

this only results in increasing the stalled area of the

rotor, thus increasing the rate of descent. Since inboard

portions of the blades are stalled, cyclic control is

limited. Recovery is accomplished by increasing

forward speed, and/or partially lowering collective

pitch. In a fully developed vortex ring state, the only

recovery may be to enter autorotation to break the

vortex ring state. When cyclic authority is regained,

you can then increase forward airspeed.

For settling with power demonstrations and training in

recognition of vortex ring state conditions, all maneu-

vers should be performed at an elevation of at least

1,500 feet AGL.

To enter the maneuver, reduce power below hover

power. Hold altitude with aft cyclic until the

airspeed approaches 20 knots. Then allow the sink

Figure 11-4. Vortex ring state.

rate to increase to 300 feet per minute or more as the

attitude is adjusted to obtain an airspeed of less than

10 knots. When the aircraft begins to shudder, the

A fully developed vortex ring state is characterized by

application of additional up collective increases the

an unstable condition where the helicopter experiences

vibration and sink rate.

uncommanded pitch and roll oscillations, has little or

no cyclic authority, and achieves a descent rate, which,

Recovery should be initiated at the first sign of vor-

if allowed to develop, may approach 6,000 feet per

tex ring state by applying forward cyclic to increase

minute. It is accompanied by increased levels of

airspeed and simultaneously reducing collective.

vibration.

The recovery is complete when the aircraft passes

through effective translational lift and a normal

A vortex ring state may be entered during any maneu-

climb is established.

ver that places the main rotor in a condition of high

upflow and low forward airspeed. This condition is

RETREATING BLADE STALL

sometimes seen during quick-stop type maneuvers or

In forward flight, the relative airflow through the

during recoveries from autorotations. The following

main rotor disc is different on the advancing and

combination of conditions are likely to cause settling in

retreating side. The relative airflow over the advanc-

a vortex ring state:

ing side is higher due to the forward speed of the

11-6

helicopter, while the relative airflow on the retreat-

ing side is lower. This dissymmetry of lift increases

as forward speed increases.

To generate the same amount of lift across the rotor

disc, the advancing blade flaps up while the retreat-

122°

ing blade flaps down. This causes the angle of attack

to decrease on the advancing blade, which reduces

lift, and increase on the retreating blade, which

increases lift. As the forward speed increases, at

122°

116°

some point the low blade speed on the retreating

blade, together with its high angle of attack, causes a

loss of lift (stall).

Retreating blade stall is a major factor in limiting a

helicopter’s top forward speed (V_NE) and can be felt

developing by a low frequency vibration, pitching

up of the nose, and a roll in the direction of the

Figure 11-5. Hard contact with the ground can send a shock

retreating blade. High weight, low rotor r.p.m., high

wave to the main rotor head, resulting in the blades of a

density altitude, turbulence and/or steep, abrupt

three-bladed rotor system moving from their normal 120°

turns are all conducive to retreating blade stall at

relationship to each other. This could result in something like

high forward airspeeds. As altitude is increased,

122°, 122°, and 116° between blades. When one of the other

higher blade angles are required to maintain lift at a

landing gear strikes the surface, the unbalanced condition

could be further aggravated.

given airspeed. Thus, retreating blade stall is

encountered at a lower forward airspeed at altitude.

If the r.p.m. is low, the corrective action to stop ground

Most manufacturers publish charts and graphs show-

resonance is to close the throttle immediately and fully

ing a V_NE decrease with altitude.

lower the collective to place the blades in low pitch. If the

r.p.m. is in the normal operating range, you should fly the

When recovering from a retreating blade stall condi-

helicopter off the ground, and allow the blades to auto-

tion, moving the cyclic aft only worsens the stall

matically realign themselves. You can then make a normal

as aft cyclic produces a flare effect, thus increasing

touchdown. If you lift off and allow the helicopter to

angles of attack. Pushing forward on the cyclic

firmly re-contact the surface before the blades are

also deepens the stall as the angle of attack on the

realigned, a second shock could move the blades again

retreating blade is increased. Correct recovery from

and aggravate the already unbalanced condition. This

retreating blade stall requires the collective to be

could lead to a violent, uncontrollable oscillation.

lowered first, which reduces blade angles and thus

angle of attack. Aft cyclic can then be used to slow

This situation does not occur in rigid or semirigid rotor

the helicopter.

systems, because there is no drag hinge. In addition,

skid type landing gear are not as prone to ground

GROUND RESONANCE

resonance as wheel type gear.

Ground resonance is an aerodynamic phenomenon

associated with fully-articulated rotor systems. It

DYNAMIC ROLLOVER

develops when the rotor blades move out of phase

A helicopter is susceptible to a lateral rolling tendency,

with each other and cause the rotor disc to become

called dynamic rollover, when lifting off the surface.

unbalanced. This condition can cause a helicopter to

For dynamic rollover to occur, some factor has to first

self-destruct in a matter of seconds. However, for

cause the helicopter to roll or pivot around a skid, or

this condition to occur, the helicopter must be in

landing gear wheel, until its critical rollover angle is

contact with the ground.

reached. Then, beyond this point, main rotor thrust con-

tinues the roll and recovery is impossible. If the critical

If you allow your helicopter to touch down firmly on

rollover angle is exceeded, the helicopter rolls on its

one corner (wheel type landing gear is most

side regardless of the cyclic corrections made.

conducive for this) the shock is transmitted to the

main rotor system. This may cause the blades to

Dynamic rollover begins when the helicopter starts to

move out of their normal relationship with each

pivot around its skid or wheel. This can occur for a

other. This movement occurs along the drag hinge.

variety of reasons, including the failure to remove a

[Figure 11-5]

tiedown or skid securing device, or if the skid or wheel

11-7

contacts a fixed object while hovering sideward, or if

crosswinds from the left.

the gear is stuck in ice, soft asphalt, or mud. Dynamic

left yaw inputs.

rollover may also occur if you do not use the proper

landing or takeoff technique or while performing slope

For helicopters with clockwise rotor rotation, the oppo-

operations. Whatever the cause, if the gear or skid

site would be true.

becomes a pivot point, dynamic rollover is possible if

you do not use the proper corrective technique.

CYCLIC TRIM

When maneuvering with one skid or wheel on the

Once started, dynamic rollover cannot be stopped by

ground, care must be taken to keep the helicopter cyclic

application of opposite cyclic control alone. For exam-

control properly trimmed. For example, if a slow take-

ple, the right skid contacts an object and becomes the

off is attempted and the cyclic is not positioned and

pivot point while the helicopter starts rolling to the

trimmed to account for translating tendency, the critical

right. Even with full left cyclic applied, the main rotor

recovery angle may be exceeded in less than two sec-

thrust vector and its moment follows the aircraft as it

onds. Control can be maintained if you maintain proper

continues rolling to the right. Quickly applying down

cyclic position and trim, and not allow the helicopter’s

collective is the most effective way to stop dynamic

roll and pitch rates to become too great. You should fly

rollover from developing. Dynamic rollover can occur

your helicopter into the air smoothly while keeping

in both skid and wheel equipped helicopters, and all

movements of pitch, roll, and yaw small, and not allow

types of rotor systems.

any untrimmed cyclic pressures.

CRITICAL CONDITIONS

NORMAL TAKEOFFS AND LANDINGS

Certain conditions reduce the critical rollover angle,

Dynamic rollover is possible even during normal take-

thus increasing the possibility for dynamic rollover and

offs and landings on relative level ground, if one wheel

reducing the chance for recovery. The rate of rolling

or skid is on the ground and thrust (lift) is approxi-

motion is also a consideration, because as the roll rate

mately equal to the weight of the helicopter. If the

increases, the critical rollover angle at which recovery

takeoff or landing is not performed properly, a roll rate

is still possible, is reduced. Other critical conditions

could develop around the wheel or skid that is on the

include operating at high gross weights with thrust (lift)

ground. When taking off or landing, perform the

approximately equal to the weight.

maneuver smoothly and trim the cyclic so that no pitch

or roll movement rates build up, especially the roll rate.

Refer to figure 11-6. The following conditions are

If the bank angle starts to increase to an angle of

most critical for helicopters with counter-clockwise

approximately 5 to 8°, and full corrective cyclic does

rotor rotation:

not reduce the angle, the collective should be reduced

to diminish the unstable rolling condition.

right side skid/wheel down, since translating ten-

dency adds to the rollover force.

SLOPE TAKEOFFS AND LANDINGS

right lateral center of gravity.

During slope operations, excessive application of cyclic

control into the slope, together with excessive collective

Main

pitch control, can result in the downslope skid rising

Rotor

sufficiently to exceed lateral cyclic control limits, and an

Thrust

upslope rolling motion can occur. [Figure 11-7]

Full Opposite Cyclic Limit

to Prevent Rolling Motion

Crosswind

Pivot Point

Bank Angle

Horizontal

Weight

Figure 11-6. Forces acting on a helicopter with right skid on

the ground.

Figure 11-7. Upslope rolling motion.

11-8

When performing slope takeoff and landing maneu-

develops a roll rate with one skid/wheel on the ground,

vers, follow the published procedures and keep the roll

the helicopter can roll over on its side.

rates small. Slowly raise the downslope skid or wheel

to bring the helicopter level, and then lift off. During

PRECAUTIONS

landing, first touch down on the upslope skid or wheel,

then slowly lower the downslope skid or wheel using

The following lists several areas to help you avoid

combined movements of cyclic and collective. If the

dynamic rollover.

helicopter rolls approximately 5 to 8° to the upslope

side, decrease collective to correct the bank angle and

Always practice hovering autorotations into the

return to level attitude, then start the landing procedure

wind, but never when the wind is gusty or over

again.

10 knots.

When hovering close to fences, sprinklers,

USE OF COLLECTIVE

bushes, runway/taxi lights, or other obstacles that

The collective is more effective in controlling the rolling

could catch a skid, use extreme caution.

motion than lateral cyclic, because it reduces the main

rotor thrust (lift). A smooth, moderate collective reduc-

Always use a two-step liftoff. Pull in just enough

tion, at a rate less than approximately full up to full down

collective pitch control to be light on the skids

in two seconds, is adequate to stop the rolling motion.

and feel for equilibrium, then gently lift the

Take care, however, not to dump collective at too high a

helicopter into the air.

rate, as this may cause a main rotor blade to strike the

fuselage. Additionally, if the helicopter is on a slope and

When practicing hovering maneuvers close to

the roll starts to the upslope side, reducing collective too

the ground, make sure you hover high enough to

fast may create a high roll rate in the opposite direction.

have adequate skid clearance with any obsta-

When the upslope skid/wheel hits the ground, the

cles, especially when practicing sideways or

dynamics of the motion can cause the helicopter to

rearward flight.

bounce off the upslope skid/wheel, and the inertia can

cause the helicopter to roll about the downslope ground

When the wind is coming from the upslope direc-

contact point and over on its side. [Figure 11-8]

tion, less lateral cyclic control will be available.

Tailwind conditions should be avoided when

Full Opposite Cyclic Limit

conducting slope operations.

to Prevent Rolling Motion

When the left skid/wheel is upslope, less lateral

cyclic control is available due to the translating

tendency of the tail rotor. (This is true for

counter-rotating rotor systems)

If passengers or cargo are loaded or unloaded, the

lateral cyclic requirement changes.

If the helicopter utilizes interconnecting fuel lines

that allow fuel to automatically transfer from one

Horizontal

side of the helicopter to the other, the gravitational

flow of fuel to the downslope tank could change

the center of gravity, resulting in a different

amount of cyclic control application to obtain the

same lateral result.

Figure 11-8. Downslope rolling motion.

10.

Do not allow the cyclic limits to be reached. If the

cyclic control limit is reached, further lowering of

the collective may cause mast bumping. If this

The collective should not be pulled suddenly to get air-

occurs, return to a hover and select a landing point

borne, as a large and abrupt rolling moment in the

with a lesser degree of slope.

opposite direction could occur. Excessive application

of collective can result in the upslope skid rising suffi-

11.

During a takeoff from a slope, if the upslope

ciently to exceed lateral cyclic control limits. This

skid/wheel starts to leave the ground before the

movement may be uncontrollable. If the helicopter

downslope skid/wheel, smoothly and gently

11-9

lower the collective and check to see if the

turbulence, slow your forward airspeed and make small

downslope skid/wheel is caught on something.

control inputs. If turbulence becomes excessive,

Under these conditions vertical ascent is the only

consider making a precautionary landing. To help pre-

acceptable method of liftoff.

vent turbulence induced inputs, make sure your cyclic

arm is properly supported. One way to accomplish this

12. During flight operations on a floating platform, if

is to brace your arm against your leg. Even if you are

the platform is pitching/rolling while attempting to

not in turbulent conditions, you should avoid abrupt

land or takeoff, the result could be dynamic rollover.

movement of the cyclic and collective.

If you do find yourself in a low G condition, which

LOW G CONDITIONS AND MAST

can be recognized by a feeling of weightlessness

BUMPING

and an uncontrolled roll to the right, you should imme-

For cyclic control, small helicopters depend primarily

diately and smoothly apply aft cyclic. Do not attempt

on tilting the main rotor thrust vector to produce

to correct the rolling action with lateral cyclic. By

control moments about the aircraft center of gravity

applying aft cyclic, you will load the rotor system,

(CG), causing the helicopter to roll or pitch in the

which in turn produces thrust. Once thrust is restored,

desired direction. Pushing the cyclic control forward

left cyclic control becomes effective, and you can roll

abruptly from either straight-and-level flight or after a

the helicopter to a level attitude.

climb can put the helicopter into a low G (weightless)

flight condition. In forward flight, when a push-over is

LOW ROTOR RPM AND BLADE STALL

performed, the angle of attack and thrust of the rotor is

As mentioned earlier, low rotor r.p.m. during an

reduced, causing a low G or weightless flight condi-

autorotation might result in a less than successful

tion. During the low G condition, the lateral cyclic has

maneuver. However, if you let rotor r.p.m. decay to the

little, if any, effect because the rotor thrust has been

point where all the rotor blades stall, the result is usu-

reduced. Also, in a counter-clockwise rotor system (a

ally fatal, especially when it occurs at altitude. The

clockwise system would be the reverse), there is no

danger of low rotor r.p.m. and blade stall is greatest in

main rotor thrust component to the left to counteract

small helicopters with low blade inertia. It can occur

the tail rotor thrust to the right, and since the tail rotor

in a number of ways, such as simply rolling the throt-

is above the CG, the tail rotor thrust causes the helicop-

tle the wrong way, pulling more collective pitch than

ter to roll rapidly to the right, If you attempt to stop the

power available, or when operating at a high density

right roll by applying full left cyclic before regaining

altitude.

main rotor thrust, the rotor can exceed its flapping

limits and cause structural failure of the rotor shaft due

to mast bumping, or it may allow a blade to contact the

When the rotor r.p.m. drops, the blades try to maintain

airframe. [Figure 11-9]

the same amount of lift by increasing pitch. As the

pitch increases, drag increases, which requires more

power to keep the blades turning at the proper r.p.m.

When power is no longer available to maintain r.p.m.,

and therefore lift, the helicopter begins to descend.

This changes the relative wind and further increases

the angle of attack. At some point the blades will stall

unless r.p.m. is restored. If all blades stall, it is almost

impossible to get smooth air flowing across the

blades.

Even though there is a safety factor built into most hel-

icopters, anytime your rotor r.p.m. falls below the green

Figure 11-9. In a low G condition, improper corrective action

arc, and you have power, simultaneously add throttle

could lead to the main rotor hub contacting the rotor mast.

The contact with the mast becomes more violent with each

and lower the collective. If you are in forward flight,

successive flapping motion. This, in turn, creates a greater

gently applying aft cyclic loads up the rotor system and

flapping displacement. The result could be a severely

helps increase rotor r.p.m. If you are without power,

damaged rotor mast, or the main rotor system could sepa-

immediately lower the collective and apply aft cyclic.

rate from the helicopter.

RECOVERY FROM LOW ROTOR RPM

Since a low G condition could have disastrous results,

Under certain conditions of high weight, high tempera-

the best way to prevent it from happening is to avoid the

ture, or high density altitude, you might get into a

conditions where it might occur. This means avoiding

situation where the r.p.m. is low even though you are

turbulence as much as possible. If you do encounter

using maximum throttle. This is usually the result of

11-10

the main rotor blades having an angle of attack that has

results in a severe yawing to the right. At low power

created so much drag that engine power is not suffi-

settings and high airspeeds, the yaw is less severe. High

cient to maintain or attain normal operating r.p.m.

airspeeds tend to streamline the helicopter and keep it

from spinning.

If you are in a low r.p.m. situation, the lifting power of

the main rotor blades can be greatly diminished. As soon

If a tail rotor failure occurs, power has to be reduced in

order to reduce main rotor torque. The techniques

as you detect a low r.p.m. condition, immediately apply

differ depending on whether the helicopter is in flight

additional throttle, if available, while slightly lowering

or in a hover, but will ultimately require an autorotation.

the collective. This reduces main rotor pitch and drag. As

If a complete tail rotor failure occurs while hovering,

the helicopter begins to settle, smoothly raise the collec-

enter a hovering autorotation by rolling off the

tive to stop the descent. At hovering altitude you may

throttle. If the failure occurs in forward flight,

have to repeat this technique several times to regain nor-

enter a normal autorotation by lowering the collective

mal operating r.p.m. This technique is sometimes called

and rolling off the throttle. If the helicopter has

“milking the collective.” When operating at altitude, the

enough forward airspeed (close to cruising speed) when

collective may have to be lowered only once to regain

the failure occurs, and depending on the helicopter

rotor speed. The amount the collective can be lowered

design, the vertical stabilizer may provide enough direc-

depends on altitude. When hovering near the surface,

tional control to allow you to maneuver the helicopter to

make sure the helicopter does not contact the ground as

a more desirable landing sight. Some of the yaw may be

the collective is lowered.

compensated for by applying slight cyclic control oppo-

site the direction of yaw. This helps in directional

Since the tail rotor is geared to the main rotor, low main

control, but also increases drag. Care must be taken not

rotor r.p.m. may prevent the tail rotor from producing

to lose too much forward airspeed because the stream-

enough thrust to maintain directional control. If pedal

lining effect diminishes as airspeed is reduced. Also,

control is lost and the altitude is low enough that a

more altitude is required to accelerate to the

landing can be accomplished before the turning rate

correct airspeed if an autorotation is entered into at a

increases dangerously, slowly decrease collective pitch,

low airspeed.

maintain a level attitude with cyclic control, and land.

A mechanical control failure limits or prevents con-

SYSTEM MALFUNCTIONS

trol of tail rotor thrust and is usually caused by a

The reliability and dependability record of modern

stuck or broken control rod or cable. While the tail

helicopters is very impressive. By following the

rotor is still producing antitorque thrust, it cannot be

manufacturer’s recommendations regarding periodic

controlled by the pilot. The amount of antitorque

maintenance and inspections, you can eliminate most

depends on the position where the controls jam or

systems and equipment failures. Most malfunctions or

fail. Once again, the techniques differ depending on

failures can be traced to some error on the part of the

the amount of tail rotor thrust, but an autorotation is

pilot; therefore, most emergencies can be averted before

generally not required.

they happen. An actual emergency is a rare occurrence.

LANDING-STUCK LEFT PEDAL

ANTITORQUE SYSTEM FAILURE

Be sure to follow the procedures and techniques

Antitorque failures usually fall into two categories.

outlined in the FAA-approved rotorcraft flight man-

One focuses on failure of the power drive portion of the

ual for the helicopter you are flying. A stuck left

tail rotor system resulting in a complete loss of anti-

pedal, such as might be experienced during takeoff or

torque. The other category covers mechanical control

climb conditions, results in the helicopter’s nose

failures where the pilot is unable to change or control

yawing to the left when power is reduced. Rolling off

tail rotor thrust even though the tail rotor may still be

the throttle and entering an autorotation only makes

providing antitorque thrust.

matters worse. The landing profile for a stuck left

pedal is best described as a normal approach to a

Tail rotor drive system failures include driveshaft fail-

momentary hover at three to four feet above the

ures, tail rotor gearbox failures, or a complete loss of

surface. Following an analysis, make the landing. If

the tail rotor itself. In any of these cases, the loss of

the helicopter is not turning, simply lower the

antitorque normally results in an immediate yawing of

helicopter to the surface. If the helicopter is turning

the helicopter’s nose. The helicopter yaws to the right

to the right, roll the throttle toward flight idle the

in a counter-clockwise rotor system and to the left in a

amount necessary to stop the turn as you land. If the

clockwise system. This discussion assumes a

helicopter is beginning to turn left, you should be

helicopter with a counter-clockwise rotor system. The

able to make the landing prior to the turn rate

severity of the yaw is proportionate to the amount of

becoming excessive. However, if the turn rate

power being used and the airspeed. An antitorque

becomes excessive prior to the landing, simply

failure with a high power setting at a low airspeed

execute a takeoff and return for another landing.

11-11

LANDING-STUCK NEUTRAL OR RIGHT PEDAL

have identified three relative wind azimuth regions that

The landing profile for a stuck neutral or a stuck right

can either singularly, or in combination, create an LTE

pedal is a low power approach or descent with a

conducive environment. These regions can overlap,

running or roll-on landing. The approach profile can

and thrust variations may be more pronounced. Also,

best be described as a steep approach with a flare at the

flight testing has determined that the tail rotor does not

bottom to slow the helicopter. The power should be low

actually stall during the period. When operating in

enough to establish a left yaw during the descent. The

these areas at less than 30 knots, pilot workload

left yaw allows a margin of safety due to the fact that

increases dramatically.

the helicopter will turn to the right when power is

applied. This allows the momentary use of power at the

MAIN ROTOR DISC INTERFERENCE

(285-315°)

bottom of the approach. As you apply power, the heli-

Refer to figure 11-10. Winds at velocities of 10 to 30

copter rotates to the right and becomes aligned with the

knots from the left front cause the main rotor

landing area. At this point, roll the throttle to flight idle

vortex to be blown into the tail rotor by the relative

and make the landing. The momentary use of power

wind. The effect of this main rotor disc vortex causes

helps stop the descent and allows additional time for

the tail rotor to operated in an extremely turbulent envi-

you to level the helicopter prior to closing the throttle.

ronment. During a right turn, the tail rotor experiences

a reduction of thrust as it comes into the area of the

If the helicopter is not yawed to the left at the conclusion

main rotor disc vortex. The reduction in tail rotor thrust

of the flare, roll the throttle to flight idle and use the

comes from the airflow changes experienced at the tail

collective to cushion the touchdown. As with any

rotor as the main rotor disc vortex moves across the tail

running or roll-on landing, use the cyclic to maintain the

rotor disc. The effect of the main rotor disc vortex

ground track. This technique results in a longer ground

initially increases the angle of attack of the tail rotor

run or roll than if the helicopter was yawed to the left.

blades, thus increasing tail rotor thrust. The increase in

the angle of attack requires that right pedal pressure be

UNANTICIPATED YAW / LOSS OF TAIL

ROTOR EFFECTIVENESS (LTE)

added to reduce tail rotor thrust in order to maintain the

Unanticipated yaw is the occurrence of an uncom-

same rate of turn. As the main rotor vortex passes the

manded yaw rate that does not subside of its own

tail rotor, the tail rotor angle of attack is reduced. The

accord and, which, if not corrected, can result in the

reduction in the angle of attack causes a reduction in

loss of helicopter control. This uncommanded yaw rate

thrust and a right yaw acceleration begins. This accel-

is referred to as loss of tail rotor effectiveness (LTE)

eration can be surprising, since you were previously

and occurs to the right in helicopters with a counter-

adding right pedal to maintain the right turn rate. This

clockwise rotating main rotor and to the left in helicop-

thrust reduction occurs suddenly, and if uncorrected,

ters with a clockwise main rotor rotation. Again, this

develops into an uncontrollable rapid rotation about the

discussion covers a helicopter with a counter-clockwise

mast. When operating within this region, be aware that

rotor system and an antitorque rotor.

the reduction in tail rotor thrust can happen quite

suddenly, and be prepared to react quickly to counter

LTE is not related to an equipment or maintenance mal-

this reduction with additional left pedal input.

function and may occur in all single-rotor helicopters

Region of Disc

at airspeeds less than 30 knots. It is the result of the tail

Vortex Interference

360°

rotor not providing adequate thrust to maintain direc-

0°

tional control, and is usually caused by either certain

315°

330°

30°

wind azimuths (directions) while hovering, or by an

insufficient tail rotor thrust for a given power setting at

60°

300°

higher altitudes.

285°

270°

90°

For any given main rotor torque setting in perfectly

steady air, there is an exact amount of tail rotor thrust

10 Knots

required to prevent the helicopter from yawing either

240°

120°

left or right. This is known as tail rotor trim thrust. In

15 Knots

order to maintain a constant heading while hovering,

you should maintain tail rotor thrust equal to trim thrust.

210°

150°

20 Knots

The required tail rotor thrust is modified by the effects

of the wind. The wind can cause an uncommanded yaw

by changing tail rotor effective thrust. Certain relative

wind directions are more likely to cause tail rotor thrust

variations than others. Flight and wind tunnel tests

Figure 11-10. Main rotor disc vortex interference.

11-12

WEATHERCOCK STABILITY

accelerates the right turn rate. Pilot workload during a

(120-240°)

tail rotor vortex ring state is high. Do not allow a right

In this region, the helicopter attempts to weathervane

yaw rate to increase.

its nose into the relative wind. [Figure 11-11] Unless a

360°

resisting pedal input is made, the helicopter starts a

0°

17 Knots

slow, uncommanded turn either to the right or left

330°

30°

15 Knots

depending upon the wind direction. If the pilot allows a

right yaw rate to develop and the tail of the helicopter

moves into this region, the yaw rate can accelerate

300°

10 Knots

60°

rapidly. In order to avoid the onset of LTE in this

downwind condition, it is imperative to maintain posi-

5 Knots

Region of

tive control of the yaw rate and devote full attention to

Roughness

flying the helicopter.

270°

90°

Due toTail

Rotor Vortex

360°

Ring State

0°

17 Knots

330°

30°

15 Knots

240°

120°

10 Knots

300°

60°

150°

210°

180°

5 Knots

270°

90°

Figure 11-12. Tail rotor vortex ring state.

LTE AT ALTITUDE

At higher altitudes, where the air is thinner, tail rotor

240°

120°

thrust and efficiency is reduced. When operating at

high altitudes and high gross weights, especially while

hovering, the tail rotor thrust may not be sufficient to

210°

150°

maintain directional control and LTE can occur. In this

180°

case, the hovering ceiling is limited by tail rotor thrust

Region Where Weathercock

and not necessarily power available. In these condi-

Stability Can Introduce Yaw Rates

tions gross weights need to be reduced and/or

Figure 11-11. Weathercock stability.

operations need to be limited to lower density altitudes.

TAIL ROTOR VORTEX RING STATE

REDUCING THE ONSET OF LTE

(210-330°)

To help reduce the onset of loss of tail rotor effective-

Winds within this region cause a tail rotor vortex ring

ness, there are some steps you can follow.

state to develop. [Figure 11-12] The result is a non-uni-

form, unsteady flow into the tail rotor. The vortex ring

Maintain maximum power-on rotor r.p.m. If the

state causes tail rotor thrust variations, which result in

main rotor r.p.m. is allowed to decrease, the anti-

yaw deviations. The net effect of the unsteady flow is

torque thrust available is decreased proportionally.

an oscillation of tail rotor thrust. Rapid and continuous

pedal movements are necessary to compensate for the

Avoid tailwinds below an airspeed of 30 knots. If

rapid changes in tail rotor thrust when hovering in a left

loss of translational lift occurs, it results in an

crosswind. Maintaining a precise heading in this region

increased power demand and additional anti-

is difficult, but this characteristic presents no signifi-

torque pressures.

cant problem unless corrective action is delayed.

However, high pedal workload, lack of concentration

Avoid out of ground effect (OGE) operations and

and overcontrolling can all lead to LTE.

high power demand situations below an airspeed

of 30 knots.

When the tail rotor thrust being generated is less than

the thrust required, the helicopter yaws to the right.

Be especially aware of wind direction and velocity

When hovering in left crosswinds, you must concen-

when hovering in winds of about 8-12 knots. There

trated on smooth pedal coordination and not allow an

are no strong indicators that translational lift has

uncontrolled right yaw to develop. If a right yaw rate

been reduced. A loss of translational lift results in

is allowed to build, the helicopter can rotate into the

an unexpected high power demand and an

wind azimuth region where weathercock stability then

increased antitorque requirement.

11-13

Be aware that if a considerable amount of left

although it is left on under normal conditions. A

pedal is being maintained, a sufficient amount of

pressure indicator in the cockpit may be installed to

left pedal may not be available to counteract an

monitor the system.

unanticipated right yaw.

An impending hydraulic failure can be recognized by a

Be alert to changing wind conditions, which may

grinding or howling noise from the pump or actuators,

be experienced when flying along ridge lines and

increased control forces and feedback, and limited

around buildings.

control movement. The corrective action required is

stated in detail in the appropriate rotorcraft flight

RECOVERY TECHNIQUE

manual. However, in most cases, airspeed needs to be

If a sudden unanticipated right yaw occurs, the follow-

reduced in order to reduce control forces. The hydraulic

ing recovery technique should be performed. Apply full

switch and circuit breaker should be checked and

left pedal while simultaneously moving cyclic control

recycled. If hydraulic power is not restored, make a

forward to increase speed. If altitude permits, reduce

shallow approach to a running or roll-on landing. This

power. As recovery is effected, adjust controls for

technique is used because it requires less control force

normal forward flight.

and pilot workload. Additionally, the hydraulic system

should be disabled, by either pulling the circuit breaker

Collective pitch reduction aids in arresting the yaw rate

and/or placing the switch in the off position. The

but may cause an excessive rate of descent. Any large,

reason for this is to prevent an inadvertent restoration

rapid increase in collective to prevent ground or

of hydraulic power, which may lead to overcontrolling

obstacle contact may further increase the yaw rate and

near the ground.

decrease rotor r.p.m. The decision to reduce collective

must be based on your assessment of the altitude

In those helicopters where the control forces are so

available for recovery.

high that they cannot be moved without hydraulic

assistance, two or more independent hydraulic systems

If the rotation cannot be stopped and ground contact is

may be installed. Some helicopters use hydraulic accu-

imminent, an autorotation may be the best course of

mulators to store pressure that can be used for a short

action. Maintain full left pedal until the rotation stops,

time while in an emergency if the hydraulic pump fails.

then adjust to maintain heading.

This gives you enough time to land the helicopter with

normal control.

MAIN DRIVE SHAFT FAILURE

The main drive shaft, located between the engine and

GOVERNOR FAILURE

the main rotor gearbox, transmits engine power to the

Governors automatically adjust engine power to main-

main rotor gearbox. In some helicopters, particularly

tain rotor r.p.m. when the collective pitch is changed. If

those with piston engines, a drive belt is used instead of

the governor fails, any change in collective pitch

a drive shaft. A failure of the drive shaft or belt has the

requires you to manually adjust the throttle to maintain

same effect as an engine failure, because power is no

correct r.p.m. In the event of a high side governor

longer provided to the main rotor, and an autorotation

failure, the engine and rotor r.p.m. try to increase above

has to be initiated. There are a few differences,

the normal range. If the r.p.m. cannot be reduced and

however, that need to be taken into consideration. If the

controlled with the throttle, close the throttle and enter

drive shaft or belt breaks, the lack of any load on the

an autorotation. If the governor fails on the low side,

engine results in an overspeed. In this case, the throttle

normal r.p.m. may not be attainable, even if the throttle

must be closed in order to prevent any further damage.

is manually controlled. In this case, the collective has

In some helicopters, the tail rotor drive system

to be lowered to maintain r.p.m. A running or roll-on

continues to be powered by the engine even if the main

landing may be performed if the engine can maintain

drive shaft breaks. In this case, when the engine

sufficient rotor r.p.m. If there is insufficient power,

unloads, a tail rotor overspeed can result. If this hap-

enter an autorotation.

pens, close the throttle immediately and enter an

autorotation.

ABNORMAL VIBRATIONS

With the many rotating parts found in helicopters, some

HYDRAULIC FAILURES

vibration is inherent. You need to understand the cause

Most helicopters, other than smaller piston powered

and effect of helicopter vibrations because abnormal

helicopters, incorporate the use of hydraulic actuators

vibrations cause premature component wear and may

to overcome high control forces. A hydraulic system

even result in structural failure. With experience, you

consists of actuators, also called servos, on each flight

learn what vibrations are normal versus those that are

control; a pump, which is usually driven by the main

abnormal and can then decide whether continued flight

rotor gearbox; and a reservoir to store the hydraulic

is safe or not. Helicopter vibrations are categorized into

fluid. A switch in the cockpit can turn the system off,

low, medium, or high frequency.

11-14

LOW FREQUENCY VIBRATIONS

Computing course, time, speed, and distance informa-

Low frequency vibrations (100-500 cycles per minute)

tion in flight requires the same computations used

usually originate from the main rotor system. The

during preflight planning. However, because of the

vibration may be felt through the controls, the airframe,

limited cockpit space, and because you must divide

or a combination of both. Furthermore, the vibration

your attention between flying the helicopter, making

may have a definite direction of push or thrust. It may

calculations, and scanning for other aircraft, you should

be vertical, lateral, horizontal, or even a combination.

take advantage of all possible shortcuts and rule-of-

Normally, the direction of the vibration can be deter-

thumb computations.

mined by concentrating on the feel of the vibration,

which may push you up and down, backwards and

When in flight, it is rarely practical to actually plot a

forwards, or from side to side. The direction of the

course on a sectional chart and mark checkpoints and

vibration and whether it is felt in the controls or the

distances. Furthermore, because an alternate airport is

airframe is an important means for the mechanic

usually not very far from your original course, actual

to troubleshoot the source. Some possible causes

plotting is seldom necessary.

could be that the main rotor blades are out of track or

balance, damaged blades, worn bearings, dampers out

A course to an alternate can be measured accurately

of adjustment, or worn parts.

with a protractor or plotter, but can also be measured

with reasonable accuracy using a straightedge and the

MEDIUM AND HIGH FREQUENCY VIBRATIONS

compass rose depicted around VOR stations. This

Medium frequency vibrations (1,000 - 2,000 cycles per

approximation can be made on the basis of a radial

minute) and high frequency vibrations (2,000 cycles

from a nearby VOR or an airway that closely parallels

per minute or higher) are normally associated with out-

the course to your alternate. However, you must

of-balance components that rotate at a high r.p.m., such

remember that the magnetic heading associated with

as the tail rotor, engine, cooling fans, and components

a VOR radial or printed airway is outbound from

of the drive train, including transmissions, drive shafts,

the station. To find the course TO the station, it may

bearings, pulleys, and belts. Most tail rotor vibrations

be necessary to determine the reciprocal of the

can be felt through the tail rotor pedals as long as there

indicated heading.

are no hydraulic actuators, which usually dampen out

the vibration. Any imbalance in the tail rotor system is

Distances can be determined by using a plotter, or by

very harmful, as it can cause cracks to develop and

placing a finger or piece of paper between the two and

rivets to work loose. Piston engines usually produce a

then measuring the approximate distance on the

normal amount of high frequency vibration, which is

mileage scale at the bottom of the chart.

aggravated by engine malfunctions such as spark plug

fouling, incorrect magneto timing, carburetor icing

Before changing course to proceed to an alternate, you

and/or incorrect fuel/air mixture. Vibrations in turbine

should first consider the relative distance and route of

engines are often difficult to detect as these engines

flight to all suitable alternates. In addition, you should

operate at a very high r.p.m.

consider the type of terrain along the route. If circum-

TRACKING AND BALANCE

stances warrant, and your helicopter is equipped with

Modern equipment used for tracking and balancing the

navigational equipment, it is typically easier to navi-

main and tail rotor blades can also be used to detect

gate to an alternate airport that has a VOR or NDB

other vibrations in the helicopter. These systems use

facility on the field.

accelerometers mounted around the helicopter to detect

the direction, frequency, and intensity of the vibration.

After you select the most appropriate alternate, approx-

The built-in software can then analyze the information,

imate the magnetic course to the alternate using

pinpoint the origin of the vibration, and suggest the

a compass rose or airway on the sectional chart. If time

corrective action.

permits, try to start the diversion over a prominent

ground feature. However, in an emergency, divert

FLIGHT DIVERSION

promptly toward your alternate. To complete all

There will probably come a time in your flight career

plotting, measuring, and computations involved before

when you will not be able to make it to your destination.

diverting to the alternate may only aggravate an

This can be the result of unpredictable weather conditions,

actual emergency.

a system malfunction, or poor preflight planning. In any

case, you will need to be able to safely and efficiently

Once established on course, note the time, and then

divert to an alternate destination. Before any cross-

use the winds aloft nearest to your diversion point to

country flight, check the charts for airports or suitable

calculate a heading and groundspeed. Once you have

landing areas along or near your route of flight. Also,

calculated your groundspeed, determine a new arrival

check for navaids that can be used during a diversion.

time and fuel consumption.

11-15

You must give priority to flying the helicopter while

ries for each person on board, and it should be

dividing your attention between navigation and

stored in a sealed waterproof container. It should

planning. When determining an altitude to use while

have been inspected by the pilot or his represen-

diverting, you should consider cloud heights, winds,

tative within the previous six months, and bear a

terrain, and radio reception.

label verifying the amount and satisfactory con-

dition of the contents.

LOST PROCEDURES

•

A supply of water.

Getting lost in an aircraft is a potentially dangerous

situation especially when low on fuel. Helicopters have

•

Cooking utensils.

an advantage over airplanes, as they can land almost

anywhere before they run out of fuel.

•

Matches in a waterproof container.

•

A portable compass.

If you are lost, there are some good common sense

procedures to follow. If you are nowhere near or cannot

•

An ax at least 2.5 pounds with a handle not less

see a town or city, the first thing you should do is climb.

than 28 inches in length.

An increase in altitude increases radio and navigation

reception range, and also increases radar coverage. If

•

A flexible saw blade or equivalent cutting tool.

you are flying near a town or city, you may be able to

read the name of the town on a water tower or even land

•

30 feet of snare wire and instructions for use.

to ask directions.

•

Fishing equipment, including still-fishing bait

and gill net with not more than a two inch mesh.

If your helicopter has a navigational radio, such as a

VOR or ADF receiver, you can possibly determine

•

Mosquito nets or netting and insect repellent

your position by plotting your azimuth from two or

sufficient to meet the needs of all persons aboard,

more navigational facilities. If GPS is installed, or you

when operating in areas where insects are likely

have a portable aviation GPS on board, you can use it

to be hazardous.

to determine your position and the location of the

nearest airport.

•

A signaling mirror.

Communicate with any available facility using

•

At least three pyrotechnic distress signals.

frequencies shown on the sectional chart. If you are

•

A sharp, quality jackknife or hunting knife.

able to communicate with a controller, you may be

offered radar vectors. Other facilities may offer

•

A suitable survival instruction manual.

direction finding (DF) assistance. To use this

procedure, the controller will request you to hold

•

Flashlight with spare bulbs and batteries.

down your transmit button for a few seconds and

then release it. The controller may ask you to change

•

Portable ELT with spare batteries.

directions a few times and repeat the transmit

procedure. This gives the controller enough infor-

Additional items when there are no trees:

mation to plot your position and then give you vec-

tors to a suitable landing sight. If your situation

• Stove with fuel or a self-contained means of pro-

becomes threatening, you can transmit your prob-

viding heat for cooking.

lems on the emergency frequency 121.5 MHZ and

• Tent(s) to accommodate everyone on board.

set your transponder to 7700. Most facilities, and

even airliners, monitor the emergency frequency.

Additional items for winter operations:

EMERGENCY EQUIPMENT AND

• Winter sleeping bags for all persons when the

SURVIVAL GEAR

temperature is expected to be below 7°C.

Both Canada and Alaska require pilots to carry survival

gear. However, it is good common sense that any time

• Two pairs of snow shoes.

you are flying over rugged and desolated terrain, con-

• Spare ax handle.

sider carrying survival gear. Depending on the size and

storage capacity of your helicopter, the following are

• Honing stone or file.

some suggested items:

• Ice chisel.

• Food that is not subject to deterioration due to

heat or cold. There should be at least 10,000 calo-

• Snow knife or saw knife.

11-16

Attitude instrument flying in helicopters is essentially

Vertical

visual flying with the flight instruments substituted for

Speed

the various reference points on the helicopter and the

Airspeed

Indicator

Pitot

Indicator

(VSI)

Altimeter

natural horizon. Control changes, required to produce a

Heater Switch

Static Port

given attitude by reference to instruments, are identical

to those used in helicopter VFR flight, and your

OFF

thought processes are the same. Basic instrument train-

ing is intended as a building block towards attaining an

instrument rating. It will also enable you to do a 180°

Pitot

Drain

ALT

turn in case of inadvertent incursion into instrument

Tube

STATIC AIR

Opening

PULL ON

meteorological conditions (IMC).

Alternate Static Source

FLIGHT INSTRUMENTS

Figure 12-1. Ram air pressure is supplied only to the airspeed

When flying a helicopter with reference to the flight

indicator, while static pressure is used by all three instru-

instruments, proper instrument interpretation is the

ments. Electrical heating elements may be installed to pre-

vent ice from forming on the pitot tube. A drain opening to

basis for aircraft control. Your skill, in part, depends on

remove moisture is normally included.

your understanding of how a particular instrument or

system functions, including its indications and limita-

tions. With this knowledge, you can quickly determine

what an instrument is telling you and translate that

tion is needed is that an airspeed indicator and aircraft

information into a control response.

performance are affected equally by changes in air den-

sity. An indicated airspeed always yields the same

performance because the indicator has, in fact, com-

PITOT-STATIC INSTRUMENTS

pensated for the change in the environment.

The pitot-static instruments, which include the airspeed

indicator, altimeter, and vertical speed indicator, oper-

ate on the principle of differential air pressure. Pitot

pressure, also called impact, ram, or dynamic pressure,

is directed only to the airspeed indicator, while static

pressure, or ambient pressure, is directed to all three

Diaphragm

instruments. An alternate static source may be included

Pitot Tube

allowing you to select an alternate source of ambient

Ram Air

pressure in the event the main port becomes blocked.

[Figure 12-1]

Static Air Line

AIRSPEED INDICATOR

The airspeed indicator displays the speed of the heli-

Figure 12-2. Ram air pressure from the pitot tube is directed

copter through the air by comparing ram air pressure

to a diaphragm inside the airspeed indicator. The airtight

from the pitot tube with static air pressure from the

case is vented to the static port. As the diaphragm expands

static port-the greater the differential, the greater the

or contracts, a mechanical linkage moves the needle on the

speed. The instrument displays the result of this pres-

face of the indicator.

sure differential as indicated airspeed (IAS).

Manufacturers use this speed as the basis for determin-

ing helicopter performance, and it may be displayed in

INSTRUMENT CHECK-During the preflight, ensure

knots, miles per hour, or both. [Figure 12-2] When an

that the pitot tube, drain hole, and static ports are unob-

indicated airspeed is given for a particular situation,

structed. Before liftoff, make sure the airspeed indicator

you normally use that speed without making a correc-

is reading zero. If there is a strong wind blowing directly

tion for altitude or temperature. The reason no correc-

at the helicopter, the airspeed indicator may read higher

12-1

than zero, depending on the wind speed and direction.

VERTICAL SPEED INDICATOR

As you begin your takeoff, make sure the airspeed indi-

The vertical speed indicator (VSI) displays the rate of

cator is increasing at an appropriate rate. Keep in mind,

climb or descent in feet per minute (f.p.m.) by measur-

however, that the airspeed indication might be unreli-

ing how fast the ambient air pressure increases or

able below a certain airspeed due to rotor downwash.

decreases as the helicopter changes altitude. Since the

VSI measures only the rate at which air pressure

ALTIMETER

changes, air temperature has no effect on this instru-

The altimeter displays altitude in feet by sensing pres-

ment. [Figure 12-4]

sure changes in the atmosphere. There is an adjustable

barometric scale to compensate for changes in atmos-

Diaphragm

pheric pressure. [Figure 12-3]

Altitude

Indication

Altimeter

Aneroid

Scale

Setting Window

Wafers

10,000 ft

100 ft Pointer

Pointer

1,000 ft

Pointer

Direct Static

Calibrated

Pressure

Leak

Static Port

Crosshatch

Figure 12-4. Although the sealed case and diaphragm are

Altimeter Setting

Flag

Adjustment Knob

both connected to the static port, the air inside the case is

A crosshatched

area appears

restricted through a calibrated leak. When the pressures are

on some altimeters

equal, the needle reads zero. As you climb or descend, the

when displaying

an altitude below

pressure inside the diaphragm instantly changes, and the

10,000 feet MSL.

needle registers a change in vertical direction. When the

pressure differential stabilizes at a definite ratio, the needle

registers the rate of altitude change.

Figure 12-3. The main component of the altimeter is a stack of

sealed aneroid wafers. They expand and contract as atmos-

pheric pressure from the static source changes. The mechani-

cal linkage translates these changes into pointer movements on

There is a lag associated with the reading on the VSI,

the indicator.

and it may take a few seconds to stabilize when show-

ing rate of climb or descent. Rough control technique

and turbulence can further extend the lag period and

The basis for altimeter calibration is the International

cause erratic and unstable rate indications. Some air-

Standard Atmosphere (ISA), where pressure, tempera-

craft are equipped with an instantaneous vertical speed

ture, and lapse rates have standard values. However,

indicator (IVSI), which incorporates accelerometers to

actual atmospheric conditions seldom match the stan-

compensate for the lag found in the typical VSI.

dard values. In addition, local pressure readings within

a given area normally change over a period of time, and

INSTRUMENT CHECK-During the preflight, ensure

pressure frequently changes as you fly from one area to

that the static ports are unobstructed. Check to see that

another. As a result, altimeter indications are subject to

the VSI is indicating zero before lift-off. During takeoff,

errors, the extent of which depends on how much the

check for a positive rate of climb indication.

pressure, temperature, and lapse rates deviate from stan-

dard, as well as how recently you have set the altimeter.

SYSTEM ERRORS

The best way to minimize altimeter errors is to update

The pitot-static system and associated instruments are

the altimeter setting frequently. In most cases, use the

usually very reliable. Errors are generally caused when

current altimeter setting of the nearest reporting station

the pitot or static openings are blocked. This may be

along your route of flight per regulatory requirements.

caused by dirt, ice formation, or insects. Check the pitot

and static openings for obstructions during the preflight.

INSTRUMENT CHECK-During the preflight, ensure

It is also advisable to place covers on the pitot and static

that the static ports are unobstructed. Before lift-off, set

ports when the helicopter is parked on the ground.

the altimeter to the current setting. If the altimeter indi-

cates within 75 feet of the actual elevation, the altimeter

The airspeed indicator is the only instrument affected by a

is generally considered acceptable for use.

blocked pitot tube. The system can become clogged in two

12-2

ways. If the ram air inlet is clogged, but the drain hole

installed in helicopters are electrically powered, there

remains open, the airspeed indicator registers zero, regard-

may be a separate power switch, as well as a warning

less of airspeed. If both the ram air inlet and the drain hole

flag within the instrument, that indicates a loss of

become blocked, pressure in the line is trapped, and the

power. A caging or “quick erect” knob may be

airspeed indicator reacts like an altimeter, showing an

included, so you can stabilize the spin axis if the gyro

increase in airspeed with an increase in altitude, and a

has tumbled. [Figure 12-5]

decrease in speed as altitude decreases. This occurs as

long as the static port remains unobstructed.

Bank Index

Gimbal

Horizon

Rotation

Reference

If the static port alone becomes blocked, the airspeed

Arm

indicator continues to function, but with incorrect read-

ings. When you are operating above the altitude where

the static port became clogged, the airspeed indicator

reads lower than it should. Conversely, when operating

below that altitude, the indicator reads higher than the

correct value. The amount of error is proportional to

the distance from the altitude where the static system

became blocked. The greater the difference, the greater

the error. With a blocked static system, the altimeter

freezes at the last altitude and the VSI freezes at zero.

Both instruments are then unusable.

Some helicopters are equipped with an alternate static

Pitch

Roll

Gyro

Gimbal

source, which may be selected in the event that the main

static system becomes blocked. The alternate source gen-

Figure 12-5. The gyro in the attitude indicator spins in the

erally vents into the cabin, where air pressures are slightly

horizontal plane. Two mountings, or gimbals, are used so

different than outside pressures, so the airspeed and

that both pitch and roll can be sensed simultaneously. Due to

altimeter usually read higher than normal. Correction

rigidity in space, the gyro remains in a fixed position relative

to the horizon as the case and helicopter rotate around it.

charts may be supplied in the flight manual.

HEADING INDICATOR

GYROSCOPIC INSTRUMENTS

The heading indicator, which is sometimes referred to

The three gyroscopic instruments that are required for

as a directional gyro (DG), senses movement around

instrument flight are the attitude indicator, heading

the vertical axis and provides a more accurate heading

indicator, and turn indicator. When installed in helicop-

reference compared to a magnetic compass, which has

ters, these instruments are usually electrically powered.

a number of turning errors. [Figure 12-6].

Gyros are affected by two principles-rigidity in space and

Gimbal

Main

Compass

precession. Rigidity in space means that once a gyro is

Rotation

Drive Gear

Card Gear

spinning, it tends to remain in a fixed position and resists

external forces applied to it. This principle allows a gyro to

be used to measure changes in attitude or direction.

Precession is the tilting or turning of a gyro in response to

pressure. The reaction to this pressure does not occur at

the point where it was applied; rather, it occurs at a point

that is 90° later in the direction of rotation from where the

pressure was applied. This principle allows the gyro to

determine a rate of turn by sensing the amount of pres-

sure created by a change in direction. Precession can also

create some minor errors in some instruments.

Adjustment

Gimbal

Gyro

Adjustment Gears

Knob

ATTITUDE INDICATOR

Figure 12-6. A heading indicator displays headings based on

The attitude indicator provides a substitute for the nat-

a 360° azimuth, with the final zero omitted. For example, a 6

ural horizon. It is the only instrument that provides an

represents 060°, while a 21 indicates 210°. The adjustment

immediate and direct indication of the helicopter’s

knob is used to align the heading indicator with the magnetic

pitch and bank attitude. Since most attitude indicators

compass.

12-3

Due to internal friction within the gyroscope, preces-

Another part of both the turn coordinator and the turn-

sion is common in heading indicators. Precession

and-slip indicator is the inclinometer. The position of

causes the selected heading to drift from the set value.

the ball defines whether the turn is coordinated or not.

Some heading indicators receive a magnetic north ref-

The helicopter is either slipping or skidding anytime

erence from a remote source and generally need no

the ball is not centered, and usually requires an adjust-

adjustment. Heading indicators that do not have this

ment of the antitorque pedals or angle of bank to cor-

automatic north-seeking capability are often called

rect it. [Figure 12-8]

“free” gyros, and require that you periodically adjust

them. You should align the heading indicator with the

magnetic compass before flight and check it at 15-

minute intervals during flight. When you do an in-flight

alignment, be certain you are in straight-and-level,

unaccelerated flight, with the magnetic compass show-

ing a steady indication.

TURN INDICATORS

Turn indicators show the direction and the rate of turn.

Inclinometer

A standard rate turn is 3° per second, and at this rate

Figure 12-8. In a coordinated turn (instrument 1), the ball is

you will complete a 360° turn in two minutes. A half-

centered. In a skid (instrument 2), the rate of turn is too great

standard rate turn is 1.5° per second. Two types of

for the angle of bank, and the ball moves to the outside of the

indicators are used to display this information. The

turn. Conversely, in a slip (instrument 3), the rate of turn is

too small for the angle of bank, and the ball moves to the

turn-and-slip indicator uses a needle to indicate direc-

inside of the turn.

tion and turn rate. When the needle is aligned with the

white markings, called the turn index, you are in a

standard rate turn. A half-standard rate turn is indi-

INSTRUMENT CHECK-During your preflight, check

cated when the needle is halfway between the indexes.

to see that the inclinometer is full of fluid and has no

The turn-and-slip indicator does not indicate roll rate.

air bubbles. The ball should also be resting at its lowest

The turn coordinator is similar to the turn-and-slip

point. Since almost all gyroscopic instruments installed

indicator, but the gyro is canted, which allows it to

in a helicopter are electrically driven, check to see that

sense roll rate in addition to rate of turn. The turn coor-

the power indicators are displaying off indications.

dinator uses a miniature aircraft to indicate direction,

Turn the master switch on and listen to the gyros spool

as well as the turn and roll rate. [Figure 12-7]

up. There should be no abnormal sounds, such as a

Horizontal

grinding sound, and the power out indicator flags

Gyro

Gimbal

should not be displayed. After engine start and before

Gyro

Rotation

liftoff, set the direction indicator to the magnetic com-

TURN-AND-SLIP

pass. During hover turns, check the heading indicator

INDICATOR

for proper operation and ensure that it has not pre-

cessed significantly. The turn indicator should also

indicate a turn in the correct direction. During takeoff,

Gimbal

check the attitude indicator for proper indication and

Rotation

recheck it during the first turn.

Gimbal

Gyro

MAGNETIC COMPASS

Rotation

In some helicopters, the magnetic compass is the only

direction seeking instrument. Although the compass

appears to move, it is actually mounted in such a way

that the helicopter turns about the compass card as the

TURN

card maintains its alignment with magnetic north.

Canted Gyro

COORDINATOR

COMPASS ERRORS

The magnetic compass can only give you reliable

directional information if you understand its limitations

Figure 12-7. The gyros in both the turn-and-slip indicator and

the turn coordinator are mounted so that they rotate in a verti-

and inherent errors. These include magnetic variation,

cal plane. The gimbal in the turn coordinator is set at an angle,

compass deviation, and magnetic dip.

or canted, which means precession allows the gyro to sense

both rate of roll and rate of turn. The gimbal in the turn-and-slip

MAGNETIC VARIATION

indicator is horizontal. In this case, precession allows the gyro

to sense only rate of turn. When the needle or miniature aircraft

When you fly under visual flight rules, you ordinar-

is aligned with the turn index, you are in a standard-rate turn.

ily navigate by referring to charts, which are oriented

12-4

to true north. Because the aircraft compass is oriented

Magnetic dip is responsible for compass errors during

to magnetic north, you must make allowances for the

acceleration, deceleration, and turns.

difference between these poles in order to navigate

properly. You do this by applying a correction called

Acceleration and deceleration errors are fluctuations

variation to convert a true direction to a magnet direc-

in the compass during changes in speed. In the north-

tion. Variation at a given point is the angular differ-

ern hemisphere, the compass swings toward the north

ence between the true and magnetic poles. The amount

during acceleration and toward the south during decel-

of variation depends on where you are located on the

eration. When the speed stabilizes, the compass

earth’s surface. Isogonic lines connect points where

returns to an accurate indication. This error is most

the variation is equal, while the agonic line defines the

pronounced when you are flying on a heading of east

points where the variation is zero. [Figure 12-9]

or west, and decreases gradually as you fly closer to a

north or south heading. The error does not occur when

you are flying directly north or south. The memory

True

aid, ANDS (Accelerate North, Decelerate South) may

North Pole

help you recall this error. In the southern hemisphere,

Magnetic

this error occurs in the opposite direction.

North Pole

17°

Turning errors are most apparent when you are turning

Agonic

to or from a heading of north or south. This error

Line

increases as you near the poles as magnetic dip becomes

20°

more apparent. There is no turning error when flying

20°

near the magnetic equator. In the northern hemisphere,

15°

when you make a turn from a northerly heading, the

10°

5°

compass gives an initial indication of a turn in the

15°

0°

opposite direction. It then begins to show the turn in

10°

5°

the proper direction, but lags behind the actual head-

Isogonic Lines

ing. The amount of lag decreases as the turn continues,

then disappears as the helicopter reaches a heading of

east or west. When you make a turn from a southerly

Figure 12-9. Variation at point A in the western United States

is 17°. Since the magnetic north pole is located to the east of

heading, the compass gives an indication of a turn in

the true north pole in relation to this point, the variation is

the correct direction, but leads the actual heading. This

easterly. When the magnetic pole falls to the west of the true

error also disappears as the helicopter approaches an

north pole, variation is westerly.

east or west heading.

COMPASS DEVIATION

INSTRUMENT CHECK-Prior to flight, make sure that

Besides the magnetic fields generated by the earth, other

the compass is full of fluid. During hover turns, the

magnetic fields are produced by metal and electrical

compass should swing freely and indicate known head-

accessories within the helicopter. These magnetic fields

ings. Since that magnetic compass is required for all

distort the earth’s magnet force and cause the compass

flight operations, the aircraft should never be flown

to swing away from the correct heading. Manufacturers

with a faulty compass.

often install compensating magnets within the compass

housing to reduce the effects of deviation. These mag-

INSTRUMENT FLIGHT

nets are usually adjusted while the engine is running and

To achieve smooth, positive control of the helicopter

all electrical equipment is operating. Deviation error,

during instrument flight, you need to develop three

however, cannot be completely eliminated; therefore, a

fundamental skills. They are instrument cross-check,

compass correction card is mounted near the compass.

instrument interpretation, and aircraft control.

The compass correction card corrects for deviation that

occurs from one heading to the next as the lines of force

INSTRUMENT CROSS-CHECK

interact at different angles.

Cross-checking, sometimes referred to as scanning, is

the continuous and logical observation of instruments

MAGNETIC DIP

for attitude and performance information. In attitude

Magnetic dip is the result of the vertical component of

instrument flying, an attitude is maintained by reference

the earth’s magnetic field. This dip is virtually non-

to the instruments, which produces the desired result in

existent at the magnetic equator, since the lines of force

performance. Due to human error, instrument error, and

are parallel to the earth’s surface and the vertical com-

helicopter performance differences in various atmos-

ponent is minimal. As you move a compass toward the

pheric and loading conditions, it is difficult to

poles, the vertical component increases, and magnetic

establish an attitude and have performance remain

dip becomes more apparent at these higher latitudes.

constant for a long period of time. These variables make

12-5

it necessary for you to constantly check the instruments

essary for helicopter performance information. This dif-

and make appropriate changes in the helicopter’s atti-

fers from fixation in that you are using other instruments,

tude. The actual technique may vary depending on what

but are giving too much attention to a particular one.

instruments are installed and where they are installed,

as well as your experience and proficiency level. For

During performance of a maneuver, you may sometimes

this discussion, we will concentrate on the six basic

fail to anticipate significant instrument indications fol-

flight instruments discussed earlier. [Figure 12-10]

lowing attitude changes. For example, during leveloff

from a climb or descent, you may concentrate on pitch

At first, you may have a tendency to cross-check

control, while forgetting about heading or roll informa-

rapidly, looking directly at the instruments without

tion. This error, called “omission,” results in erratic

knowing exactly what information you are seeking.

control of heading and bank.

However, with familiarity and practice, the instrument

cross-check reveals definite trends during specific

In spite of these common errors, most pilots can adapt

flight conditions. These trends help you control the

well to flight by instrument reference after instruction

helicopter as it makes a transition from one flight

and practice. You may find that you can control the hel-

condition to another.

icopter more easily and precisely by instruments.

If you apply your full concentration to a single instrument,

INSTRUMENT INTERPRETATION

you will encounter a problem called “fixation.” This results

The flight instruments together give a picture of what

from a natural human inclination to observe a specific

is going on. No one instrument is more important than

instrument carefully and accurately, often to the exclusion

the next; however, during certain maneuvers or condi-

of other instruments. Fixation on a single instrument usu-

tions, those instruments that provide the most pertinent

ally results in poor control. For example, while performing

and useful information are termed primary instruments.

a turn, you may have a tendency to watch only the turn-and-

Those which back up and supplement the primary

slip indicator instead of including other instruments in your

instruments are termed supporting instruments. For

cross-check. This fixation on the turn-and-slip indicator

example, since the attitude indicator is the only instru-

often leads to a loss of altitude through poor pitch and bank

ment that provides instant and direct aircraft attitude

control. You should look at each instrument only long

information, it should be considered primary during

enough to understand the information it presents, then con-

any change in pitch or bank attitude. After the new atti-

tinue on to the next one. Similarly, you may find yourself

tude is established, other instruments become primary,

placing too much “emphasis” on a single instrument,

and the attitude indicator usually becomes the support-

instead of relying on a combination of instruments nec-

ing instrument.

Figure 12-10. In most situations, the cross-check pattern includes the attitude indicator between the cross-check of each of the

other instruments. A typical cross-check might progress as follows: attitude indicator, altimeter, attitude indicator, VSI, attitude

indicator, heading indicator, attitude indicator, and so on.

12-6

AIRCRAFT CONTROL

In order to fly a helicopter by reference to the

Controlling the helicopter is the result of accurately

instruments, you should know the approximate

interpreting the flight instruments and translating these

power settings required for your particular helicopter

readings into correct control responses. Aircraft control

in various load configurations and flight conditions.

involves adjustment to pitch, bank, power, and trim in

Trim, in helicopters, refers to the use of the cyclic center-

order to achieve a desired flight path.

ing button, if the helicopter is so equipped, to relieve all

possible cyclic pressures. Trim also refers to the use of

Pitch attitude control is controlling the movement of

pedal adjustment to center the ball of the turn indicator.

the helicopter about its lateral axis. After interpreting

Pedal trim is required during all power changes.

the helicopter’s pitch attitude by reference to the pitch

instruments (attitude indicator, altimeter, airspeed indi-

The proper adjustment of collective pitch and cyclic

cator, and vertical speed indicator), cyclic control

friction helps you relax during instrument flight.

adjustments are made to affect the desired pitch atti-

Friction should be adjusted to minimize overcontrol-

tude. In this chapter, the pitch attitudes illustrated are

ling and to prevent creeping, but not applied to such a

approximate and will vary with different helicopters.

degree that control movement is limited. In addition,

many helicopters equipped for instrument flight con-

Bank attitude control is controlling the angle made by

tain stability augmentation systems or an autopilot to

the lateral tilt of the rotor and the natural horizon, or,

help relieve pilot workload.

the movement of the helicopter about its longitudinal

STRAIGHT-AND-LEVEL FLIGHT

axis. After interpreting the helicopter’s bank instru-

Straight-and-level unaccelerated flight consists of

ments (attitude indicator, heading indicator, and turn

maintaining the desired altitude, heading, airspeed, and

indicator), cyclic control adjustments are made to attain

pedal trim.

the desired bank attitude.

PITCH CONTROL

Power control is the application of collective pitch with

The pitch attitude of a helicopter is the angular relation

corresponding throttle control, where applicable. In

of its longitudinal axis and the natural horizon. If avail-

straight-and-level flight, changes of collective pitch are

able, the attitude indicator is used to establish the

made to correct for altitude deviations if the error is

desired pitch attitude. In level flight, pitch attitude

more than 100 feet, or the airspeed is off by more than

varies with airspeed and center of gravity. At a constant

10 knots. If the error is less than that amount, use a

altitude and a stabilized airspeed, the pitch attitude is

slight cyclic climb or descent.

approximately level. [Figure 12-11]

PITCH CONTROL

Figure 12-11. The flight instruments for pitch control are the airspeed indicator, attitude indicator, altimeter, and vertical

speed indicator.

12-7

ATTITUDE INDICATOR

one-half bar correction is normally the maximum pitch

The attitude indicator gives a direct indication of the

attitude correction from level flight attitude. After you

pitch attitude of the helicopter. In visual flight, you

have made the correction, cross-check the other pitch

attain the desired pitch attitude by using the cyclic to

instruments to determine whether the pitch attitude

raise and lower the nose of the helicopter in relation to

change is sufficient. If more correction is needed to

the natural horizon. During instrument flight, you fol-

return to altitude, or if the airspeed varies more than 10

low exactly the same procedure in raising or lowering

knots from that desired, adjust the power.

the miniature aircraft in relation to the horizon bar.

ALTIMETER

You may note some delay between control application

The altimeter gives an indirect indication of the pitch

and resultant instrument change. This is the normal

attitude of the helicopter in straight-and-level flight.

control lag in the helicopter and should not be confused

Since the altitude should remain constant in level

with instrument lag. The attitude indicator may show

flight, deviation from the desired altitude shows a need

small misrepresentations of pitch attitude during

for a change in pitch attitude, and if necessary, power.

maneuvers involving acceleration, deceleration, or

When losing altitude, raise the pitch attitude and, if

turns. This precession error can be detected quickly by

necessary, add power. When gaining altitude, lower the

cross-checking the other pitch instruments.

pitch attitude and, if necessary, reduce power.

If the miniature aircraft is properly adjusted on the

The rate at which the altimeter moves helps in deter-

ground, it may not require readjustment in flight. If the

mining pitch attitude. A very slow movement of the

miniature aircraft is not on the horizon bar after level-

altimeter indicates a small deviation from the desired

off at normal cruising airspeed, adjust it as necessary

pitch attitude, while a fast movement of the altimeter

while maintaining level flight with the other pitch

indicates a large deviation from the desired pitch atti-

instruments. Once the miniature aircraft has been

tude. Make any corrective action promptly, with small

adjusted in level flight at normal cruising airspeed,

control changes. Also, remember that movement of the

leave it unchanged so it will give an accurate picture of

altimeter should always be corrected by two distinct

pitch attitude at all times.

changes. The first is a change of attitude to stop the

altimeter; and the second, a change of attitude to

When making initial pitch attitude corrections to main-

return smoothly to the desired altitude. If the altitude

tain altitude, the changes of attitude should be small

and airspeed are more than 100 feet and 10 knots low,

and smoothly applied. The initial movement of the

respectively, apply power along with an increase of

horizon bar should not exceed one bar width high or

pitch attitude. If the altitude and airspeed are high by

low. [Figure 12-12] If a further change is required, an

more than 100 feet and 10 knots, reduce power and

additional correction of one-half bar normally corrects

lower the pitch attitude.

any deviation from the desired altitude. This one and

There is a small lag in the movement of the altimeter;

however, for all practical purposes, consider that the

altimeter gives an immediate indication of a change, or

a need for change in pitch attitude.

Since the altimeter provides the most pertinent infor-

mation regarding pitch in level flight, it is considered

primary for pitch.

VERTICAL SPEED INDICATOR

The vertical speed indicator gives an indirect indication

of the pitch attitude of the helicopter and should be used

in conjunction with the other pitch instruments to attain

a high degree of accuracy and precision. The instrument

indicates zero when in level flight. Any movement of

the needle from the zero position shows a need for an

immediate change in pitch attitude to return it to zero.

Always use the vertical speed indicator in conjunction

with the altimeter in level flight. If a movement of the

vertical speed indicator is detected, immediately use the

proper corrective measures to return it to zero. If the

Figure 12-12. The initial pitch correction at normal cruise is

correction is made promptly, there is usually little or no

one bar width.

change in altitude. If you do not zero the needle of the

12-8

vertical speed indicator immediately, the results will

AIRSPEED INDICATOR

show on the altimeter as a gain or loss of altitude.

The airspeed indicator gives an indirect indication of

helicopter pitch attitude. With a given power setting

and pitch attitude, the airspeed remains constant. If the

The initial movement of the vertical speed needle is

airspeed increases, the nose is too low and should be

instantaneous and indicates the trend of the vertical

raised. If the airspeed decreases, the nose is too high

movement of the helicopter. It must be realized that

and should be lowered. A rapid change in airspeed indi-

a period of time is necessary for the vertical speed

cates a large change in pitch attitude, and a slow change

indicator to reach its maximum point of deflection

in airspeed indicates a small change in pitch attitude.

after a correction has been made. This time element

There is very little lag in the indications of the airspeed

is commonly referred to as “lag.” The lag is directly

indicator. If, while making attitude changes, you notice

proportional to the speed and magnitude of the pitch

some lag between control application and change of

change. If you employ smooth control techniques

airspeed, it is most likely due to cyclic control lag.

and make small adjustments in pitch attitude, lag is

Generally, a departure from the desired airspeed, due to

minimized, and the vertical speed indicator is easy

an inadvertent pitch attitude change, also results in a

to interpret. Overcontrolling can be minimized by

change in altitude. For example, an increase in airspeed

first neutralizing the controls and allowing the pitch

due to a low pitch attitude results in a decrease in alti-

attitude to stabilize; then readjusting the pitch atti-

tude. A correction in the pitch attitude regains both air-

tude by noting the indications of the other pitch

speed and altitude.

instruments.

BANK CONTROL

Occasionally, the vertical speed indicator may be

The bank attitude of a helicopter is the angular relation

slightly out of calibration. This could result in the

of its lateral axis and the natural horizon. To maintain a

instrument indicating a slight climb or descent even

straight course in visual flight, you must keep the

when the helicopter is in level flight. If it cannot be

lateral axis of the helicopter level with the natural hori-

readjusted properly, this error must be taken into con-

zon. Assuming the helicopter is in coordinated flight,

sideration when using the vertical speed indicator for

any deviation from a laterally level attitude produces a

pitch control. For example, if the vertical speed indica-

turn. [Figure 12-13]

tor showed a descent of 100 f.p.m. when the helicopter

was in level flight, you would have to use that indica-

ATTITUDE INDICATOR

tion as level flight. Any deviation from that reading

The attitude indicator gives a direct indication of the

would indicate a change in attitude.

bank attitude of the helicopter. For instrument flight,

BANK CONTROL

Figure 12-13. The flight instruments used for bank control are the attitude, heading, and turn indicators.

12-9

the miniature aircraft and the horizon bar of the attitude

the helicopter is still turning, make a small change of

indicator are substituted for the actual helicopter and

bank attitude to center the turn needle and stop the

the natural horizon. Any change in bank attitude of the

movement of the heading indicator.

helicopter is indicated instantly by the miniature air-

craft. For proper interpretations of this instrument, you

HEADING INDICATOR

should imagine being in the miniature aircraft. If the

In coordinated flight, the heading indicator gives an

helicopter is properly trimmed and the rotor tilts, a turn

indirect indication of the helicopter’s bank attitude.

begins. The turn can be stopped by leveling the miniature

When a helicopter is banked, it turns. When the lateral

aircraft with the horizon bar. The ball in the turn-and-slip

axis of the helicopter is level, it flies straight.

indicator should always be kept centered through proper

Therefore, in coordinated flight, when the heading indi-

pedal trim.

cator shows a constant heading, the helicopter is level

laterally. A deviation from the desired heading indi-

cates a bank in the direction the helicopter is turning.

The angle of bank is indicated by the pointer on the

A small angle of bank is indicated by a slow change of

banking scale at the top of the instrument. [Figure 12-

heading; a large angle of bank is indicated by a rapid

14] Small bank angles, which may not be seen by

change of heading. If a turn is noticed, apply opposite

observing the miniature aircraft, can easily be deter-

cyclic until the heading indicator indicates the desired

mined by referring to the banking scale pointer.

heading, simultaneously checking that the ball is cen-

tered. When making the correction to the desired head-

ing, you should not use a bank angle greater than that

required to achieve a standard rate turn. In addition, if

0°

30°

the number of degrees of change is small, limit the

bank angle to the number of degrees to be turned. Bank

angles greater than these require more skill and preci-

60°

sion in attaining the desired results. During straight-

and-level flight, the heading indicator is the primary

reference for bank control.

90°

TURN INDICATOR

During coordinated flight, the needle of the turn-and-

slip indicator gives an indirect indication of the bank

attitude of the helicopter. When the needle is dis-

placed from the vertical position, the helicopter is

turning in the direction of the displacement. Thus, if

the needle is displaced to the left, the helicopter is

turning left. Bringing the needle back to the vertical

position with the cyclic produces straight flight. A

close observation of the needle is necessary to accu-

rately interpret small deviations from the desired

position.

Figure 12-14. The banking scale at the top of the attitude indi-

cator indicates varying degrees of bank. In this example, the

helicopter is banked a little over 10° to the right.

Cross-check the ball of the turn-and-slip indicator to

determine that the helicopter is in coordinated flight. If

the rotor is laterally level and torque is properly com-

pensated for by pedal pressure, the ball remains in the

Pitch and bank attitudes can be determined simultane-

center. To center the ball, level the helicopter laterally

ously on the attitude indicator. Even though the miniature

by reference to the other bank instruments, then center

aircraft is not level with the horizon bar, pitch attitude can

the ball with pedal trim. Torque correction pressures

be established by observing the relative position of the

vary as you make power changes. Always check the

miniature aircraft and the horizon bar.

ball following such changes.

The attitude indicator may show small misrepresenta-

COMMON ERRORS DURING STRAIGHT-AND-

tions of bank attitude during maneuvers that involve

LEVEL FLIGHT

turns. This precession error can be immediately

Failure to maintain altitude.

detected by closely cross-checking the other bank

Failure to maintain heading.

instruments during these maneuvers. Precession nor-

Overcontrolling pitch and bank during corrections.

mally is noticed when rolling out of a turn. If, on the

Failure to maintain proper pedal trim.

completion of a turn, the miniature aircraft is level and

Failure to cross-check all available instruments.

12-10

POWER CONTROL DURING STRAIGHT-AND-

speed is to be changed any appreciable amount, adjust

LEVEL FLIGHT

the torque so that it is approximately five percent over or

Establishing specific power settings is accomplished

under that setting necessary to maintain the new airspeed.

through collective pitch adjustments and throttle

As the power approaches the desired setting, include the

control, where necessary. For reciprocating powered

torque meter in the cross-check to determine when the

helicopters, power indications are observed on the

proper adjustment has been accomplished. As the air-

manifold pressure gauge. For turbine powered helicop-

speed is changing, adjust the pitch attitude to maintain a

ters, power is observed on the torque gauge. (Since most

constant altitude. A constant heading should be main-

IFR certified helicopters are turbine powered, this

tained throughout the change. As the desired airspeed is

discussion concentrates on this type of helicopter.)

approached, adjust power to the new cruising power set-

ting and further adjust pitch attitude to maintain altitude.

At any given airspeed, a specific power setting deter-

Overpowering and underpowering torque approximately

mines whether the helicopter is in level flight, in a

five percent results in a change of airspeed at a moderate

climb, or in a descent. For example, cruising airspeed

rate, which allows ample time to adjust pitch and bank

maintained with cruising power results in level flight.

smoothly. The instrument indications for straight-and-

If you increase the power setting and hold the airspeed

level flight at normal cruise, and during the transition

constant, the helicopter climbs. Conversely, if you

from normal cruise to slow cruise are illustrated in fig-

decrease power and hold the airspeed constant, the heli-

ures 12-15 and 12-16 on the next page. After the airspeed

copter descends. As a rule of thumb, in a turbine-engine

has stabilized at slow cruise, the attitude indicator shows

powered helicopter, a 10 to 15 percent change in the

an approximate level pitch attitude.

torque value required to maintain level flight results in a

climb or descent of approximately 500 f.p.m., if the air-

The altimeter is the primary pitch instrument during

speed remains the same.

level flight, whether flying at a constant airspeed, or

during a change in airspeed. Altitude should not change

If the altitude is held constant, power determines the

during airspeed transitions. The heading indicator

airspeed. For example, at a constant altitude, cruising

remains the primary bank instrument. Whenever the

power results in cruising airspeed. Any deviation from

airspeed is changed any appreciable amount, the torque

the cruising power setting results in a change of air-

meter is momentarily the primary instrument for power

speed. When power is added to increase airspeed, the

control. When the airspeed approaches that desired, the

nose of the helicopter pitches up and yaws to the right

airspeed indicator again becomes the primary instru-

in a helicopter with a counterclockwise main rotor

ment for power control.

blade rotation. When power is reduced to decrease air-

speed, the nose pitches down and yaws to the left. The

The cross-check of the pitch and bank instruments to

yawing effect is most pronounced in single-rotor helicop-

produce straight-and-level flight should be combined

ters, and is absent in helicopters with counter-rotating

with the power control instruments. With a constant

rotors. To counteract the yawing tendency of the helicop-

power setting, a normal cross-check should be

ter, apply pedal trim during power changes.

satisfactory. When changing power, the speed of the

cross-check must be increased to cover the pitch and

To maintain a constant altitude and airspeed in level

bank instruments adequately. This is necessary to

flight, coordinate pitch attitude and power control. The

counteract any deviations immediately.

relationship between altitude and airspeed determines

the need for a change in power and/or pitch attitude. If

COMMON ERRORS DURING AIRSPEED CHANGES

the altitude is constant and the airspeed is high or low,

Improper use of power.

change the power to obtain the desired airspeed.

Overcontrolling pitch attitude.

During the change in power, make an accurate inter-

Failure to maintain heading.

pretation of the altimeter; then counteract any devia-

Failure to maintain altitude.

tion from the desired altitude by an appropriate change

Improper pedal trim.

of pitch attitude. If the altitude is low and the airspeed

is high, or vice versa, a change in pitch attitude alone

STRAIGHT CLIMBS (CONSTANT AIRSPEED

may return the helicopter to the proper altitude and air-

AND CONSTANT RATE)

speed. If both airspeed and altitude are low, or if both

For any power setting and load condition, there is only

are high, a change in both power and pitch attitude is

one airspeed that will give the most efficient rate of

necessary.

climb. To determine this, you should consult the climb

data for the type of helicopter being flown. The tech-

To make power control easy when changing airspeed, it

nique varies according to the airspeed on entry and

is necessary to know the approximate power settings for

whether you want to make a constant airspeed or con-

the various airspeeds that will be flown. When the air-

stant rate climb.

12-11

60 70

TORQUE

100

PERCENT

110

120

Primary Power

Supporting Pitch

Primary Pitch

Supporting

and Bank

Power

Supporting Bank

Primary Bank

Supporting Pitch

Figure 12-15. Flight instrument indications in straight-and-level flight at normal cruise speed.

ENTRY

accomplish the pitch change. If the transition from

To enter a constant airspeed climb from cruise airspeed,

level flight to a climb is smooth, the vertical speed indi-

when the climb speed is lower than cruise speed, simul-

cator shows an immediate upward trend and then stops

taneously increase power to the climb power setting

at a rate appropriate to the stabilized airspeed and atti-

and adjust pitch attitude to the approximate climb atti-

tude. Primary and supporting instruments for climb

tude. The increase in power causes the helicopter to

entry are illustrated in figure 12-17.

start climbing and only very slight back cyclic pressure

is needed to complete the change from level to climb

When the helicopter stabilizes on a constant airspeed

attitude. The attitude indicator should be used to

and attitude, the airspeed indicator becomes primary

60 70

TORQUE

100

PERCENT₁₁₀

120

Primary Power as Airspeed

Supporting Pitch

Primary Pitch

Primary

Approaches Desired Value

and Bank

Power

Initially

Supporting Bank

Primary Bank

Supporting Pitch

Figure 12-16. Flight instrument indications in straight-and-level flight with airspeed decreasing.

12-12

the particular helicopter being flown. Normally, in heli-

rate of climb is 500 f.p.m., initiate the leveloff approxi-

copters with low climb rates, 500 f.p.m. is appropriate,

mately 50 feet before the desired altitude. When the

in helicopters capable of high climb rates, use a rate of

proper lead altitude is reached, the altimeter becomes

1,000 f.p.m.

primary for pitch. Adjust the pitch attitude to the level

flight attitude for that airspeed. Cross-check the altime-

To enter a constant rate climb, increase power to the

ter and VSI to determine when level flight has been

approximate setting for the desired rate. As power is

attained at the desired altitude. To level off at cruise air-

applied, the airspeed indicator is primary for pitch until

speed, if this speed is higher than climb airspeed, leave

the vertical speed approaches the desired rate. At this

the power at the climb power setting until the airspeed

time, the vertical speed indicator becomes primary for

approaches cruise airspeed, then reduce it to the cruise

pitch. Change pitch attitude by reference to the attitude

power setting.

indicator to maintain the desired vertical speed. When

The leveloff from a constant rate climb is accomplished

the VSI becomes primary for pitch, the airspeed indica-

in the same manner as the leveloff from a constant air-

tor becomes primary for power. Primary and supporting

speed climb.

instruments for a stabilized constant rate climb are illus-

trated in figure 12-19. Adjust power to maintain desired

STRAIGHT DESCENTS (CONSTANT

airspeed. Pitch attitude and power corrections should be

AIRSPEED AND CONSTANT RATE)

closely coordinated. To illustrate this, if the vertical

A descent may be performed at any normal airspeed the

speed is correct but the airspeed is low, add power. As

helicopter is capable of, but the airspeed must be deter-

power is increased, it may be necessary to lower the

mined prior to entry. The technique is determined by

pitch attitude slightly to avoid increasing the vertical

whether you want to perform a constant airspeed or a

rate. Adjust the pitch attitude smoothly to avoid over-

constant rate descent.

controlling. Small power corrections usually will be

sufficient to bring the airspeed back to the desired indi-

ENTRY

cation.

If your airspeed is higher than descending airspeed, and

you wish to make a constant airspeed descent at the

LEVELOFF

descending airspeed, reduce power to the descending

The leveloff from a constant airspeed climb must be

power setting and maintain a constant altitude using

started before reaching the desired altitude. Although the

cyclic pitch control. When you approach the descend-

amount of lead varies with the helicopter being flown

ing airspeed, the airspeed indicator becomes primary

and your piloting technique, the most important factor is

for pitch, and the torque meter is primary for power. As

vertical speed. As a rule of thumb, use 10 percent of the

you hold the airspeed constant, the helicopter begins to

vertical velocity as your lead point. For example, if the

descend. For a constant rate descent, reduce the power

60 70

TORQUE

100

PERCENT₁₁₀

120

Primary Power

Supporting Pitch

Supporting

and Bank

Power

Supporting Bank

Primary Bank

Primary Pitch

Figure 12-19. Flight instrument indications in a stabilized constant rate climb.

12-14

to the approximate setting for the desired rate. If the

COMMON ERRORS DURING STRAIGHT CLIMBS

descent is started at the descending airspeed, the air-

AND DESCENTS

speed indicator is primary for pitch until the VSI

Failure to maintain heading.

approaches the desired rate. At this time, the vertical

Improper use of power.

speed indicator becomes primary for pitch, and the

Poor control of pitch attitude.

airspeed indicator becomes primary for power.

Failure to maintain proper pedal trim.

Coordinate power and pitch attitude control as was

Failure to level off on desired altitude.

described earlier for constant rate climbs.

TURNS

LEVELOFF

When making turns by reference to the flight instru-

The leveloff from a constant airspeed descent may be

ments, they should be made at a definite rate. Turns

made at descending airspeed or at cruise airspeed, if

described in this chapter are those that do not exceed a

this is higher than descending airspeed. As in a climb

standard rate of 3° per second as indicated on the turn-

leveloff, the amount of lead depends on the rate of

and-slip indicator. True airspeed determines the angle

descent and control technique. For a leveloff at

of bank necessary to maintain a standard rate turn. A

descending airspeed, the lead should be approximately

rule of thumb to determine the approximate angle of

10 percent of the vertical speed. At the lead altitude,

bank required for a standard rate turn is to divide your

simultaneously increase power to the setting necessary

airspeed by 10 and add one-half the result. For exam-

to maintain descending airspeed in level flight. At this

ple, at 60 knots, approximately 9° of bank is required

point, the altimeter becomes primary for pitch, and the

(60 ÷ 10 = 6 + 3 = 9); at 80 knots, approximately 12° of

airspeed indicator becomes primary for power.

bank is needed for a standard rate turn.

To level off at a higher airspeed than descending air-

speed, increase the power approximately 100 to 150 feet

To enter a turn, apply lateral cyclic in the direction of the

prior to reaching the desired altitude. The power setting

desired turn. The entry should be accomplished

should be that which is necessary to maintain the

smoothly, using the attitude indicator to establish the

desired airspeed in level flight. Hold the vertical speed

approximate bank angle. When the turn indicator indi-

constant until approximately 50 feet above the desired

cates a standard rate turn, it becomes primary for bank.

altitude. At this point, the altimeter becomes primary

The attitude indicator now becomes a supporting instru-

for pitch, and the airspeed indicator becomes primary

ment. During level turns, the altimeter is primary for

for power. The leveloff from a constant rate descent

pitch, and the airspeed indicator is primary for power.

should be accomplished in the same manner as the lev-

Primary and supporting instruments for a stabilized stan-

eloff from a constant airspeed descent.

dard rate turn are illustrated in figure 12-20. If an

60 70

TORQUE

100

PERCENT₁₁₀

120

Primary Power

Primary Bank Initially

Primary Pitch

Supporting

Supporting Pitch

Power

Primary Bank as

Supporting Pitch

Turn is Established

Figure 12-20. Flight instrument indications for a standard rate turn to the left.

12-15

increase in power is required to maintain airspeed, slight

You use the same cross-check and control technique in

forward cyclic pressure may be required since the heli-

making timed turns that you use to make turns to a pre-

copter tends to pitch up as collective pitch angle is

determined heading, except that you substitute the

increased. Apply pedal trim, as required, to keep the ball

clock for the heading indicator. The needle of the turn-

centered.

and-slip indicator is primary for bank control, the

altimeter is primary for pitch control, and the airspeed

To recover to straight-and-level flight, apply cyclic in

indicator is primary for power control. Begin the roll-in

the direction opposite the turn. The rate of roll-out

when the clock’s second hand passes a cardinal point,

should be the same as the rate used when rolling into

hold the turn at the calibrated standard-rate indication,

the turn. As you initiate the turn recover, the attitude

or half-standard-rate for small changes in heading, and

indicator becomes primary for bank. When the helicop-

begin the roll-out when the computed number of sec-

ter is approximately level, the heading indicator

onds has elapsed. If the roll-in and roll-out rates are the

becomes primary for bank as in straight-and-level

same, the time taken during entry and recovery need

flight. Cross-check the airspeed indicator and ball

not be considered in the time computation.

closely to maintain the desired airspeed and pedal trim.

If you practice timed turns with a full instrument panel,

TURNS TO A PREDETERMINED HEADING

check the heading indicator for the accuracy of your

A helicopter turns as long as its lateral axis is tilted; there-

turns. If you execute the turns without the heading indi-

fore, the recovery must start before the desired heading is

cator, use the magnetic compass at the completion of

reached. The amount of lead varies with the rate of turn

the turn to check turn accuracy, taking compass devia-

and your piloting technique.

tion errors into consideration.

As a guide, when making a 3° per second rate of turn,

CHANGE OF AIRSPEED IN TURNS

use a lead of one-half the bank angle. For example, if

Changing airspeed in turns is an effective maneuver for

you are using a 12° bank angle, use half of that, or 6°,

increasing your proficiency in all three basic instru-

as the lead point prior to your desired heading. Use this

ment skills. Since the maneuver involves simultaneous

lead until you are able to determine the exact amount

changes in all components of control, proper execution

required by your particular technique. The bank angle

requires a rapid cross-check and interpretation, as well

should never exceed the number of degrees to be

as smooth control. Proficiency in the maneuver also

turned. As in any standard rate turn, the rate of recov-

contributes to your confidence in the instruments dur-

ery should be the same as the rate for entry. During

ing attitude and power changes involved in more com-

turns to predetermined headings, cross-check the pri-

plex maneuvers.

mary and supporting pitch, bank, and power instru-

ments closely.

Pitch and power control techniques are the same as

those used during airspeed changes in straight-and-

TIMED TURNS

level flight. As discussed previously, the angle of bank

A timed turn is a turn in which the clock and turn-and-

necessary for a given rate of turn is proportional to the

slip indicator are used to change heading a definite

true airspeed. Since the turns are executed at standard

number of degrees in a given time. For example, using

rate, the angle of bank must be varied in direct pro-

a standard rate turn, a helicopter turns 45° in 15 sec-

portion to the airspeed change in order to maintain a

onds. Using a half-standard rate turn, the helicopter

constant rate of turn. During a reduction of airspeed,

turns 45° in 30 seconds. Timed turns can be used if

you must decrease the angle of bank and increase the

your heading indicator becomes inoperative.

pitch attitude to maintain altitude and a standard rate

turn.

Prior to performing timed turns, the turn coordinator

should be calibrated to determine the accuracy of its

The altimeter and the needle on the turn indicator

indications. To do this, establish a standard rate turn by

should remain constant throughout the turn. The

referring to the turn-and-slip indicator. Then as the

altimeter is primary for pitch control, and the turn nee-

sweep second hand of the clock passes a cardinal point

dle is primary for bank control. The torque meter is

(12, 3, 6, or 9), check the heading on the heading indi-

primary for power control while the airspeed is chang-

cator. While holding the indicated rate of turn constant,

ing. As the airspeed approaches the new indication, the

note the heading changes at 10-second intervals. If the

airspeed indicator becomes primary for power control.

helicopter turns more or less than 30° in that interval, a

smaller or larger deflection of the needle is necessary

Two methods of changing airspeed in turns may be

to produce a standard rate turn. When you have cali-

used. In the first method, airspeed is changed after the

brated the turn-and-slip indicator during turns in each

turn is established. In the second method, the airspeed

direction, note the corrected deflections, if any, and

change is initiated simultaneously with the turn entry.

apply them during all timed turns.

The first method is easier, but regardless of the method

12-16

used, the rate of cross-check must be increased as you

indicator, and make the necessary adjustments. After

reduce power. As the helicopter decelerates, check the

you have made this change, again check the altimeter

altimeter and VSI for needed pitch changes, and the

and vertical speed indicator to determine whether or

bank instruments for needed bank changes. If the needle

not the correction was adequate.

of the turn-and-slip indicator shows a deviation from

the desired deflection, change the bank. Adjust pitch

CLIMBING AND DESCENDING TURNS

attitude to maintain altitude. When the airspeed

For climbing and descending turns, the techniques

approaches that desired, the airspeed indicator becomes

described earlier for straight climbs and descents and

primary for power control. Adjust the torque meter to

those for standard rate turns are combined. For practice,

maintain the desired airspeed. Use pedal trim to ensure

start the climb or descent and turn simultaneously. The

the maneuver is coordinated.

primary and supporting instruments for a stabilized con-

stant airspeed left climbing turn are illustrated in figure

Until your control technique is very smooth, frequently

12-21. The leveloff from a climbing or descending turn

cross-check the attitude indicator to keep from over-

is the same as the leveloff from a straight climb or

controlling and to provide approximate bank angles

descent. To recover to straight-and-level flight, you may

appropriate for the changing airspeeds.

stop the turn and then level off, level off and then stop

the turn, or simultaneously level off and stop the turn.

30° BANK TURN

During climbing and descending turns, keep the ball of

A turn using 30° of bank is seldom necessary, or advis-

the turn indicator centered with pedal trim.

able, in IMC, but it is an excellent maneuver to increase

your ability to react quickly and smoothly to rapid

COMPASS TURNS

changes of attitude. Even though the entry and recov-

The use of gyroscopic heading indicators make head-

ery technique are the same as for any other turn, you

ing control very easy. However, if the heading indica-

will probably find it more difficult to control pitch

tor fails or your helicopter does not have one installed,

because of the decrease in vertical lift as the bank

you must use the magnetic compass for heading refer-

increases. Also, because of the decrease in vertical lift,

ence. When making compass-only turns, you need to

there is a tendency to lose altitude and/or airspeed.

adjust for the lead or lag created by acceleration and

Therefore, to maintain a constant altitude and airspeed,

deceleration errors so that you roll out on the desired

additional power is required. You should not initiate a

heading. When turning to a heading of north, the lead

correction, however, until the instruments indicate the

for the roll-out must include the number of degrees of

need for a correction. During the maneuver, note the

your latitude plus the lead you normally use in recov-

need for a correction on the altimeter and vertical speed

ery from turns. During a turn to a south heading, main-

indicator, then check the indications on the attitude

tain the turn until the compass passes south the number

60 70

TORQUE

100

PERCENT₁₁₀

120

Primary Pitch

Supporting Pitch

Primary

and Bank

Power

Primary Bank

Supporting Pitch

Figure 12-21. Flight instrument indications for a stabilized left climbing turn at a constant airspeed.

12-17

of degrees of your latitude, minus your normal roll-out

COMMON ERRORS DURING

lead. For example, when turning from an easterly

UNUSUAL ATTITUDE RECOVERIES

direction to north, where the latitude is 30°, start the

Failure to make proper pitch correction.

roll-out when the compass reads 037° (30° plus one-

Failure to make proper bank correction.

half the 15° angle of bank, or whatever amount is

Failure to make proper power correction.

appropriate for your rate of roll-out). When turning

Overcontrol of pitch and/or bank attitude.

from an easterly direction to south, start the roll-out

Overcontrol of power.

when the magnetic compass reads 203° (180° plus 30°

Excessive loss of altitude.

minus one-half the angle of bank). When making sim-

ilar turns from a westerly direction, the appropriate

EMERGENCIES

points at which to begin your roll-out would be 323°

Emergencies under instrument flight are handled simi-

for a turn to north, and 157° for a turn to south.

larly to those occurring during VFR flight. A thorough

knowledge of the helicopter and its systems, as well as

COMMON ERRORS DURING TURNS

good aeronautical knowledge and judgment, prepares

Failure to maintain desired turn rate.

you to better handle emergency situations. Safe opera-

Failure to maintain altitude in level turns.

tions begin with preflight planning and a thorough pre-

Failure to maintain desired airspeed.

flight. Plan your route of flight so that there are adequate

Variation in the rate of entry and recovery.

landing sites in the event you have to make an emer-

Failure to use proper lead in turns to a heading.

gency landing. Make sure you have all your resources,

Failure to properly compute time during timed turns.

such as maps, publications, flashlights, and fire extin-

Failure to use proper leads and lags during the

guishers readily available for use in an emergency.

compass turns.

Improper use of power.

During any emergency, you should first fly the aircraft.

Failure to use proper pedal trim.

This means that you should make sure the helicopter is

under control, including the determination of emergency

UNUSUAL ATTITUDES

landing sites. Then perform the emergency checklist

Any maneuver not required for normal helicopter instru-

memory items, followed by written items in the RFM.

ment flight is an unusual attitude and may be caused by

Once all these items are under control, you should notify

any one or a combination of factors, such as turbulence,

ATC. Declare any emergency on the last assigned ATC

disorientation, instrument failure, confusion, preoccupa-

frequency, or if one was not issued, transmit on the emer-

tion with cockpit duties, carelessness in cross-checking,

gency frequency 121.5. Set the transponder to the emer-

errors in instrument interpretation, or lack of proficiency

gency squawk code 7700. This code triggers an alarm or

in aircraft control. Due to the instability characteristics

a special indicator in radar facilities.

of the helicopter, unusual attitudes can be extremely crit-

ical. As soon as you detect an unusual attitude, make a

Most in-flight emergencies, including low fuel and a

recovery to straight-and-level flight as soon as possible

complete electrical failure, require you to land as soon

with a minimum loss of altitude.

as possible. In the event of an electrical fire, turn all non-

essential equipment off and land immediately. Some

To recover from an unusual attitude, correct bank and

essential electrical instruments, such as the attitude indi-

pitch attitude, and adjust power as necessary. All com-

cator, may be required for a safe landing. A navigation

ponents are changed almost simultaneously, with little

radio failure may not require an immediate landing as

lead of one over the other. You must be able to perform

long as the flight can continue safely. In this case, you

this task with and without the attitude indicator. If the

should land as soon as practical. ATC may be able to

helicopter is in a climbing or descending turn, correct

provide vectors to a safe landing area. For the specific

bank, pitch, and power. The bank attitude should be

details on what to do during an emergency, you should

corrected by referring to the turn-and-slip indicator and

refer to the RFM for the helicopter you are flying.

attitude indicator. Pitch attitude should be corrected by

reference to the altimeter, airspeed indicator, VSI, and

attitude indicator. Adjust power by referring to the air-

speed indicator and torque meter.

Land as soon as possible-Land without delay at the nearest suitable

area, such as an open field, at which a safe approach and landing is

Since the displacement of the controls used in recover-

assured.

ies from unusual attitudes may be greater than those for

normal flight, take care in making adjustments as

Land immediately-The urgency of the landing is paramount. The pri-

mary consideration is to assure the survival of the occupants. Landing in

straight-and-level flight is approached. Cross-check the

trees, water, or other unsafe areas should be considered only as a last

other instruments closely to avoid overcontrolling.

resort.

Land as soon as practical-The landing site and duration of flight are

at the discretion of the pilot. Extended flight beyond the nearest

approved landing area is not recommended.

12-18

AUTOROTATIONS

If an antitorque or collective servo fails, you might be

Both straight-ahead and turning autorotations should

able to continue to the next suitable landing site.

be practiced by reference to instruments. This training

will ensure that you can take prompt corrective action

INSTRUMENT TAKEOFF

to maintain positive aircraft control in the event of an

This maneuver should only be performed as part of

engine failure.

your training for an instrument rating. The procedures

and techniques described here should be modified, as

To enter autorotation, reduce collective pitch smoothly

necessary, to conform with those set forth in the operat-

to maintain a safe rotor r.p.m. and apply pedal trim to

ing instructions for the particular helicopter being

keep the ball of the turn-and-slip indicator centered.

flown.

The pitch attitude of the helicopter should be approxi-

Adjust the miniature aircraft in the attitude indicator,

mately level as shown by the attitude indicator. The

as appropriate, for the aircraft being flown. After the

airspeed indicator is the primary pitch instrument and

helicopter is aligned with the runway or takeoff pad, to

should be adjusted to the recommended autorotation

prevent forward movement of a helicopter equipped

speed. The heading indicator is primary for bank in a

with a wheel-type landing gear, set the parking brake

straight-ahead autorotation. In a turning autorotation, a

or apply the toe brakes. If the parking brake is used, it

standard rate turn should be maintained by reference to

must be unlocked after the takeoff has been completed.

the needle of the turn-and-slip indicator.

Apply sufficient friction to the collective pitch control to

minimize overcontrolling and to prevent creeping.

COMMON ERRORS DURING AUTOROTATIONS

Excessive friction should be avoided since this limits

1. Uncoordinated entry due to improper pedal trim.

collective pitch movement.

2. Poor airspeed control due to improper pitch attitude.

3. Poor heading control in straight-ahead autorotations.

After checking all instruments for proper indications,

4. Failure to maintain proper rotor r.p.m.

start the takeoff by applying collective pitch and a prede-

5. Failure to maintain a standard rate turn during turn-

termined power setting. Add power smoothly and

ing autorotations.

steadily to gain airspeed and altitude simultaneously and

to prevent settling to the ground. As power is applied and

SERVO FAILURE

the helicopter becomes airborne, use the antitorque ped-

Most helicopters certified for single-pilot IFR flight are

als initially to maintain the desired heading. At the same

required to have autopilots, which greatly reduces pilot

time, apply forward cyclic to begin accelerating to

workload. If an autopilot servo fails, however, you

climbing airspeed. During the initial acceleration, the

have to resume manual control of the helicopter. How

pitch attitude of the helicopter, as read on the attitude

much your workload increases, depends on which

indicator, should be one to two bar widths low. The pri-

servo fails. If a cyclic servo fails, you may want to land

mary and supporting instruments after becoming airborne

immediately as the workload increases tremendously.

are illustrated in figure 12-22. As the airspeed increases

60 70

TORQUE

100

PERCENT 110

120

Supporting Pitch

Primary Pitch

Supporting Pitch

Primary

Supporting Bank

Power

Supporting Bank

Primary Bank

Supporting Pitch

Figure 12-22. Flight instrument indications during an instrument takeoff.

12-19

Flying at night can be a very pleasant experience. The

air is generally cooler and smoother, resulting in better

Rods and

The rods and cones (film) of the retina

helicopter performance and a more comfortable flight.

Cones

are the receptors, which record the

You generally also experience less traffic and less radio

image and transmit it through the optic

congestion.

nerve to the brain for interpretation.

Fovea

NIGHT FLIGHT PHYSIOLOGY

(All Cones)

Before discussing night operations, it is important you

understand how your vision is affected at night and

The pupil (aperture) is the

how to counteract the visual illusions, which you might

opening at the center of

encounter.

Lens

the iris. The size of the

pupil is adjusted to

Iris

control the amount

VISION IN FLIGHT

Rod

Pupil

of light entering

Concentration

the eye.

Vision is by far the most important sense that you

Cornea

have, and flying is obviously impossible without it.

Most of the things you perceive while flying are

Retina

Light passes

visual or heavily supplemented by vision. The visual

Optic Nerve

through the cornea

sense is especially important in collision avoidance

(the transparent window on

and depth perception. Your vision sensors are your

the front of the eye) and then through

the lens to focus on the retina.

eyes, even though they are not perfect in the way they

function or see objects. Since your eyes are not

always able to see all things at all times, illusions and

Figure 13-1. A camera is able to focus on near and far objects

blindspots occur. The more you understand the eye

by changing the distance between the lens and the film. You

and how it functions, the easier it is to compensate for

can see objects clearly at various distances because the

these illusions and blindspots.

shape of your eye’s lens is changed automatically by small

muscles.

THE EYE

The eye works in much the same way as a camera. Both

Directly behind the lens, on the retina, is a small,

have an aperture, lens, method of focusing, and a sur-

notched area called the fovea. This area contains only

face for registering images. [Figure 13-1].

a high concentration of cone receptors. When you

look directly at an object, the image is focused

Vision is primarily the result of light striking a photo-

mainly on the fovea. The cones, however, do not

sensitive layer, called the retina, at the back of the eye.

The retina is composed of light-sensitive cones and

rods. The cones in your eye perceive an image best

when the light is bright, while the rods work best in low

light. The pattern of light that strikes the cones and rods

is transmitted as electrical impulses by the optic nerve

to the brain where these signals are interpreted as an

image. The area where the optic nerve meets the retina

contains no cones or rods, creating a blind spot in

vision. Normally, each eye compensates for the other’s

blind spot. [Figure 13-2]

CONES

Figure 13-2. This illustration provides a dramatic example of

Cones are concentrated around the center of the

the eye’s blind spot. Cover your right eye and hold this page

retina. They gradually diminish in number as the dis-

at arm’s length. Focus your left eye on the X in the right side

tance from the center increases. Cones allow you to

of the visual, and notice what happens to the aircraft as you

perceive color by sensing red, blue, and green light.

slowly bring the page closer to your eye.

13-1

function well in darkness, which explains why you

How well you see at night is determined by the rods in

cannot see color as vividly at night as you can during

your eyes, as well as the amount of light allowed into

the day. [Figure 13-3]

your eyes. The wider the pupil is open at night, the bet-

ter your night vision becomes.

Cones Active

NIGHT VISION

The cones in your eyes adapt quite rapidly to changes in

Focus on

light intensities, but the rods do not. If you have ever

Fovea

walked from bright sunlight into a dark movie theater, you

have experienced this dark adaptation period. The rods

can take approximately 30 minutes to fully adapt to the

dark. A bright light, however, can completely destroy your

night adaptation and severely restrict your visual acuity.

There are several things you can do to keep your eyes

Figure 13-3. The best vision in daylight is obtained by look-

ing directly at the object. This focuses the image on the

adapted to the dark. The first is obvious; avoid bright

fovea, where detail is best seen.

lights before and during the flight. For 30 minutes

before a night flight, avoid any bright light sources,

such as headlights, landing lights, strobe lights, or

RODS

flashlights. If you encounter a bright light, close one

The rods are our dim light and night receptors and are

eye to keep it light sensitive. This allows you to see

concentrated outside the fovea area. The number of

again once the light is gone. Light sensitivity also can

rods increases as the distance from the fovea increases.

be gained by using sunglasses if you will be flying from

Rods sense images only in black and white. Because

daylight into an area of increasing darkness.

the rods are not located directly behind the pupil, they

are responsible for much of our peripheral vision.

Red cockpit lighting also helps preserve your night

Images that move are perceived more easily by the rod

vision, but red light severely distorts some colors, and

areas than by the cones in the fovea. If you have ever

completely washes out the color red. This makes read-

seen something move out of the corner of your eye, it

ing an aeronautical chart difficult. A dim white light or

was most likely detected by your rod receptors.

carefully directed flashlight can enhance your night

reading ability. While flying at night, keep the instru-

Since the cones do not function well in the dark, you

ment panel and interior lights turned up no higher than

may not be able to see an object if you look directly at

necessary. This helps you see outside visual references

it. The concentration of cones in the fovea can make a

more easily. If your eyes become blurry, blinking more

night blindspot at the center of your vision. To see an

frequently often helps.

object clearly, you must expose the rods to the image.

This is accomplished by looking 5° to 10° off center of

Your diet and general physical health have an impact

the object you want to see. You can try out this effect

on how well you can see in the dark. Deficiencies in

on a dim light in a darkened room. When you look

vitamins A and C have been shown to reduce night acu-

directly at the light, it dims or disappears altogether. If

ity. Other factors, such as carbon monoxide poisoning,

you look slightly off center, it becomes clearer and

smoking, alcohol, certain drugs, and a lack of oxygen

brighter. [Figure 13-4]

also can greatly decrease your night vision.

NIGHT SCANNING

Rods Active

Good night visual acuity is needed for collision avoid-

ance. Night scanning, like day scanning, uses a series

of short, regularly spaced eye movements in 10° sec-

tors. Unlike day scanning, however, off-center viewing

is used to focus objects on the rods rather than the fovea

blindspot. When you look at an object, avoid staring at

it too long. If you stare at an object without moving

your eyes, the retina becomes accustomed to the light

Night Blindspot

intensity and the image begins to fade. To keep it

clearly visible, new areas in the retina must be exposed

Figure 13-4. In low light, the cones lose much of their visual

to the image. Small, circular eye movements help

acuity, while rods become more receptive. The eye sacrifices

eliminate the fading. You also need to move your eyes

sharpness for sensitivity. Your ability to see an object directly

in front of you is reduced, and you lose much of your depth

more slowly from sector to sector than during the day

perception, as well as your judgment of size.

to prevent blurring.

13-2

Red

White

Green

Red

Your Helicopter

White

Figure 13-5. By interpreting the position lights on other aircraft, you can determine whether the aircraft is flying away from you

or is on a collision course. If you see a red position light to the right of a green light, such as shown by aircraft number 1, it is

flying toward you. You should watch this aircraft closely and be ready to change course. Aircraft number 2, on the other hand,

is flying away from you, as indicated by the white position light.

AIRCRAFT LIGHTING

AUTOKINESIS

In order to see other aircraft more clearly, regulations

Autokinesis is caused by staring at a single point of

require that all aircraft operating during the night hours

light against a dark background, such as a ground light

have special lights and equipment. The requirements

or bright star, for more than a few seconds. After a few

for operating at night are found in Title 14 of the Code

moments, the light appears to move on its own. To pre-

of Federal Regulations (14 CFR) part 91. In addition to

vent this illusion, you should focus your eyes on

aircraft lighting, the regulations also provide a defini-

objects at varying distances and not fixate on one tar-

tion of nighttime, currency requirements, fuel reserves,

get, as well as maintain a normal scan pattern.

and necessary electrical systems.

NIGHT MYOPIA

Position lights enable you to locate another aircraft, as

Another problem associated with night flying is night

well as help you determine its direction of flight. The

myopia, or night-induced nearsightedness. With noth-

approved aircraft lights for night operations are a green

ing to focus on, your eyes automatically focus on a

light on the right cabin side or wingtip, a red light on

point just slightly ahead of your aircraft. Searching out

the left cabin side or wingtip, and a white position light

and focusing on distant light sources, no matter how

on the tail. In addition, flashing aviation red or white

dim, helps prevent the onset of night myopia.

anticollision lights are required for night flights. These

flashing lights can be in a number of locations, but are

most commonly found on the top and bottom of the

FALSE HORIZON

cabin. [Figure 13-5]

A false horizon can occur when the natural horizon is

obscured or not readily apparent. It can be generated by

VISUAL ILLUSIONS

confusing bright stars and city lights. [Figure 13-6] It

There are many different types of visual illusions that

can also occur while you are flying toward the shore of

you can experience at any time, day or night. The next

an ocean or a large lake. Because of the relative darkness

few paragraphs cover some of the illusions that com-

of the water, the lights along the shoreline can be mis-

monly occur at night.

taken for the stars in the sky. [Figure 13-7]

Actual Horizon

Apparent Horizon

Figure 13-6. You can place your helicopter in an extremely

Figure 13-7. In this illusion, the shoreline is mistaken for the

dangerous flight attitude if you align the helicopter with the

horizon. In an attempt to correct for the apparent nose-high

wrong lights. Here, the helicopter is aligned with a road and

attitude, a pilot may lower the collective and attempt to fly

not the horizon.

“beneath the shore.”

13-3

LANDING ILLUSIONS

visually for proper operation. Between sunset and

Landing illusions occur in many forms. Above feature-

sunrise, theses lights must be on any time the engine

less terrain at night, there is a natural tendency to fly a

is running.

lower-than-normal approach. Elements that cause any

type of visual obscuration, such as rain, haze, or a dark

All recently manufactured aircraft certified for night

runway environment also can cause low approaches.

flight, must have an anticollision light that makes the

Bright lights, steep surrounding terrain, and a wide run-

aircraft more visible to other pilots. This light is either

way can produce the illusion of being too low, with a

a red or white flashing light and may be in the form of

tendency to fly a higher-than-normal approach.

a rotating beacon or a strobe. While anticollision lights

are required for night VFR flights, they may be turned

off any time they create a distraction for the pilot.

NIGHT FLIGHT

The night flying environment and the techniques you use

One of the first steps in preparation for night flight is

when flying at night, depend on outside conditions.

becoming thoroughly familiar with the helicopter’s

Flying on a bright, clear, moonlit evening when the visi-

cockpit, instrumentation and control layout. It is rec-

bility is good and the wind is calm, is not much different

ommended that you practice locating each instrument,

from flying during the day. However, if you are flying

control, and switch, both with and without cabin lights.

on an overcast night over a sparsely populated area,

Since the markings on some switches and circuit

with little or no outside lights from the ground, the sit-

breaker panels may be hard to read at night, you should

uation is quite different. Visibility is restricted so you

assure yourself that you are able to locate and use these

have to be more alert in steering clear of obstructions

devices, and read the markings in poor light conditions.

and low clouds. Your options are also limited in the

Before you start the engine, make sure all necessary

event of an emergency, as it is more difficult to find

equipment and supplies needed for the flight, such as

a place to land and determine wind direction and

charts, notepads, and flashlights, are accessible and

speed. At night, you have to rely more heavily on the

ready for use.

aircraft systems, such as lights, flight instruments, and

navigation equipment. As a precaution, if the visibility

is limited or outside references are inadequate, you

ENGINE STARTING AND ROTOR

should strongly consider delaying the flight until con-

ENGAGEMENT

ditions improve, unless you have received training in

Use extra caution when starting the engine and engag-

instrument flight and your helicopter has the appropri-

ing the rotors, especially in dark areas with little or no

ate instrumentation and equipment.

outside lights. In addition to the usual call of “clear,”

turn on the position and anticollision lights. If condi-

tions permit, you might also want to turn the landing

PREFLIGHT

light on momentarily to help warn others that you are

The preflight inspection is performed in the usual man-

about to start the engine and engage the rotors.

ner, except it should be done in a well lit area or with a

flashlight. Careful attention must be paid to the aircraft

electrical system. In helicopters equipped with fuses, a

TAXI TECHNIQUE

spare set is required by regulation, and common sense,

Landing lights usually cast a beam that is narrow and

so make sure they are onboard. If the helicopter is

concentrated ahead of the helicopter, so illumination to

equipped with circuit breakers, check to see that they

the side is minimal. Therefore, you should slow your

are not tripped. A tripped circuit breaker may be an

taxi at night, especially in congested ramp and parking

indication of an equipment malfunction. Reset it and

areas. Some helicopters have a hover light in addition

check the associated equipment for proper operation.

to a landing light, which illuminates a larger area under

the helicopter.

Check all the interior lights, especially the instrument

and panel lights. The panel lighting can usually be con-

When operating at an unfamiliar airport at night, you

trolled with a rheostat or dimmer switch, allowing you

should ask for instructions or advice concerning local

to adjust the intensity. If the lights are too bright, a glare

conditions, so as to avoid taxiing into areas of con-

may reflect off the windshield creating a distraction.

struction, or unlighted, unmarked obstructions. Ground

Always carry a flashlight with fresh batteries to pro-

controllers or UNICOM operators are usually coopera-

vide an alternate source of light if the interior lights

tive in furnishing you with this type of information.

malfunction.

TAKEOFF

All aircraft operating between sunset and sunrise are

Before takeoff, make sure that you have a clear, unob-

required to have operable navigation lights. Turn

structed takeoff path. At airports, you may accomplish

these lights on during the preflight to inspect them

this by taking off over a runway or taxiway, however, if

13-4

you are operating off-airport, you must pay more atten-

time emergency landings. If available, turn on the land-

tion to the surroundings. Obstructions may also be dif-

ing light during the final descent to help in avoiding

ficult to see if you are taking off from an unlighted area.

obstacles along your approach path.

Once you have chosen a suitable takeoff path, select a

point down the takeoff path to use for directional refer-

COLLISION AVOIDANCE AT NIGHT

ence. During a night takeoff, you may notice a lack of

At night, the outside visual references are greatly

reliable outside visual references after you are airborne.

reduced especially when flying over a sparsely popu-

This is particularly true at small airports and off-airport

lated area with little or no lights. The result is that you

landing sites located in sparsely populated areas. To

tend to focus on a single point or instrument, making

compensate for the lack of outside references, use the

you less aware of the other traffic around. You must

available flight instruments as an aid. Check the altime-

make a special effort to devote enough time to scan for

ter and the airspeed indicator to verify the proper climb

traffic. You can determine another aircraft’s direction

attitude. An attitude indicator, if installed, can enhance

of flight by interpreting the position and anticollision

your attitude reference.

lights.

The first 500 feet of altitude after takeoff is considered

APPROACH AND LANDING

to be the most critical period in transitioning from the

Night approaches and landings do have some advan-

comparatively well-lighted airport or heliport into

tages over daytime approaches, as the air is generally

what sometimes appears to be total darkness. A takeoff

smoother and the disruptive effects of turbulence and

at night is usually an “altitude over airspeed” maneu-

excessive crosswinds are often absent. However, there

ver, meaning you will most likely perform a nearly

are a few special considerations and techniques that

maximum performance takeoff. This improves the

apply to approaches at night. For example, when land-

chances for obstacle clearance and enhances safety.

ing at night, especially at an unfamiliar airport, make

When performing this maneuver, be sure to avoid the

the approach to a lighted runway and then use the taxi-

cross-hatched or shaded areas of the height-velocity

ways to avoid unlighted obstructions or equipment.

diagram.

Carefully controlled studies have revealed that pilots

EN ROUTE PROCEDURES

have a tendency to make lower approaches at night

In order to provide a higher margin of safety, it is rec-

than during the day. This is potentially dangerous as

ommended that you select a cruising altitude somewhat

you have a greater chance of hitting an obstacle, such

higher than normal. There are several reasons for this.

as an overhead wire or fence, which are difficult to see.

First, a higher altitude gives you more clearance

It is good practice to make steeper approaches at night,

between obstacles, especially those that are difficult to

thus increasing any obstacle clearance. Monitor your

see at night, such as high tension wires and unlighted

altitude and rate of descent using the altimeter.

towers. Secondly, in the event of an engine failure, you

have more time to set up for a landing and the gliding

distance is greater giving you more options in making a

Another tendency is to focus too much on the landing

safe landing. Thirdly, radio reception is improved, par-

area and not pay enough attention to airspeed. If too

ticularly if you are using radio aids for navigation.

much airspeed is lost, a settling-with-power condition

may result. Maintain the proper attitude during the

During your preflight planning, it is recommended that

approach, and make sure you keep some forward air-

you select a route of flight that keeps you within reach

speed and movement until close to the ground. Outside

of an airport, or any safe landing site, as much of the

visual reference for airspeed and rate of closure may

time as possible. It is also recommended that you fly as

not be available, especially when landing in an

close as possible to a populated or lighted area such as

unlighted area, so pay special attention to the airspeed

a highway or town. Not only does this offer more

indicator

options in the event of an emergency, but also makes

navigation a lot easier. A course comprised of a series

Although the landing light is a helpful aid when mak-

of slight zig-zags to stay close to suitable landing sites

ing night approaches, there is an inherent disadvantage.

and well lighted areas, only adds a little more time and

The portion of the landing area illuminated by the land-

distance to an otherwise straight course.

ing light seems higher than the dark area surrounding

it. This effect can cause you to terminate the approach

In the event that you have to make a forced landing at

at too high an altitude, resulting in a settling-with-

night, use the same procedure recommended for day-

power condition and a hard landing.

13-5

Aeronautical decision making (ADM) is a systematic

A helicopter pilot, with limited experience flying in

approach to the mental process used by pilots to con-

adverse weather, wants to be back at his home airport

sistently determine the best course of action in response

in time to attend an important social affair. He is

to a given set of circumstances. The importance of

already 30 minutes late. Therefore, he decides not to

learning effective ADM skills cannot be overempha-

refuel his helicopter, since he should get back home

sized. While progress is continually being made in the

with at least 20 minutes of reserve. In addition, in spite

advancement of pilot training methods, aircraft equip-

of his inexperience, he decides to fly through an area of

ment and systems, and services for pilots, accidents

possible thunderstorms in order to get back just before

still occur. Despite all the changes in technology to

dark. Arriving in the thunderstorm area, he encounters

improve flight safety, one factor remains the

lightning, turbulence, and heavy clouds. Night is

same-the human factor. It is estimated that approxi-

approaching, and the thick cloud cover makes it very

mately 65 percent of the total rotorcraft accidents are

dark. With his limited fuel supply, he is not able to cir-

human factors related.

cumnavigate the thunderstorms. In the darkness and

turbulence, the pilot becomes spatially disoriented

Historically, the term “pilot error” has been used to

while attempting to continue flying with visual refer-

describe the causes of these accidents. Pilot error

ence to the ground instead of using what instruments

means that an action or decision made by the pilot was

he has to make a 180° turn. In the ensuing crash, the

the cause of, or a contributing factor that lead to, the

pilot is seriously injured and the helicopter completely

accident. This definition also includes the pilot’s fail-

destroyed.

ure to make a decision or take action. From a broader

perspective, the phrase “human factors related” more

By discussing the events that led to this accident, we

aptly describes these accidents since it is usually not a

can understand how a series of judgmental errors

single decision that leads to an accident, but a chain of

contributed to the final outcome of this flight. For

events triggered by a number of factors.

example, one of the first elements that affected the

pilot’s flight was a decision regarding the weather. The

The poor judgment chain, sometimes referred to as the

pilot knew there were going to be thunderstorms in the

“error chain,” is a term used to describe this concept of

area, but he had flown near thunderstorms before and

contributing factors in a human factors related acci-

never had an accident.

dent. Breaking one link in the chain normally is all that

is necessary to change the outcome of the sequence of

Next, he let his desire to arrive at his destination on

events. The following is an example of the type of sce-

time override his concern for a safe flight. For one

nario illustrating the poor judgment chain.

thing, in order to save time, he did not refuel the heli-

copter, which might have allowed him the opportunity

to circumnavigate the bad weather. Then he overesti-

mated his flying abilities and decided to use a route that

took him through a potential area of thunderstorm

activity. Next, the pilot pressed on into obviously dete-

Human Factors-The study of how

riorating conditions instead of changing course or

people interact with their environ-

ments. In the case of general avia-

landing prior to his destination.

tion, it is the study of how pilot

performance is influenced by such

issues as the design of cockpits, the

On numerous occasions during the flight, the pilot

function of the organs of the body,

could have made effective decisions that may have pre-

the effects of emotions, and the

interaction and communication

vented this accident. However, as the chain of events

with the other participants of the

unfolded, each poor decision left him with fewer and

aviation community, such as other

fewer options. Making sound decisions is the key to

crew members and air traffic con-

trol personnel.

preventing accidents. Traditional pilot training has

14-1

emphasized flying skills, knowledge of the aircraft, and

to: ground personnel, dispatchers, cabin crewmembers,

familiarity with regulations. ADM training focuses on

maintenance personnel, external-load riggers, and air

the decision-making process and the factors that affect

traffic controllers. Although the CRM concept origi-

a pilot’s ability to make effective choices.

nated as airlines developed ways of facilitating crew

cooperation to improve decision making in the cockpit,

ORIGINS OF ADM TRAINING

CRM principles, such as workload management, situa-

The airlines developed some of the first training pro-

tional awareness, communication, the leadership role

grams that focused on improving aeronautical decision

of the captain, and crewmember coordination have

making. Human factors-related accidents motivated the

direct application to the general aviation cockpit. This

airline industry to implement crew resource manage-

also includes single pilot operations since pilots of

ment (CRM) training for flight crews. The focus of

small aircraft, as well as crews of larger aircraft, must

CRM programs is the effective use of all available

make effective use of all available resources-human

resources; human resources, hardware, and informa-

resources, hardware, and information. You can also

tion. Human resources include all groups routinely

refer to AC 60-22, Aeronautical Decision Making,

working with the cockpit crew (or pilot) who are

which provides background references, definitions, and

involved in decisions that are required to operate a

other pertinent information about ADM training in the

flight safely. These groups include, but are not limited

general aviation environment. [Figure 14-1]

DEFINITIONS

ADM is a systematic approach to the mental process used by pilots to consistently determine the best course of action in

response to a given set of circumstances.

ATTITUDE is a personal motivational predisposition to respond to persons, situations, or events in a given manner that can,

nevertheless, be changed or modified through training as sort of a mental shortcut to decision making.

ATTITUDE MANAGEMENT is the ability to recognize hazardous attitudes in oneself and the willingness to modify them as

necessary through the application of an appropriate antidote thought.

CREW RESOURCE MANAGEMENT (CRM) is the application of team management concepts in the flight deck environment. It

was initially known as cockpit resource management, but as CRM programs evolved to include cabin crews, maintenance

personnel, and others, the phrase crew resource management was adopted. This includes single pilots, as in most general

aviation aircraft. Pilots of small aircraft, as well as crews of larger aircraft, must make effective use of all available resources;

human resources, hardware, and information. A current definition includes all groups routinely working with the cockpit crew who

are involved in decisions required to operate a flight safely. These groups include, but are not limited to: pilots, dispatchers, cabin

crewmembers, maintenance personnel, and air traffic controllers. CRM is one way of addressing the challenge of optimizing the

human/machine interface and accompanying interpersonal activities.

HEADWORK is required to accomplish a conscious, rational thought process when making decisions. Good decision making

involves risk identification and assessment, information processing, and problem solving.

JUDGMENT is the mental process of recognizing and analyzing all pertinent information in a particular situation, a rational

evaluation of alternative actions in response to it, and a timely decision on which action to take.

PERSONALITY is the embodiment of personal traits and characteristics of an individual that are set at a very early age and

extremely resistant to change.

POOR JUDGMENT CHAIN is a series of mistakes that may lead to an accident or incident. Two basic principles generally

associated with the creation of a poor judgment chain are: (1) One bad decision often leads to another; and (2) as a string of bad

decisions grows, it reduces the number of subsequent alternatives for continued safe flight. ADM is intended to break the poor

judgment chain before it can cause an accident or incident.

RISK ELEMENTS IN ADM take into consideration the four fundamental risk elements: the pilot, the aircraft, the environment, and

the type of operation that comprise any given aviation situation.

RISK MANAGEMENT is the part of the decision making process which relies on situational awareness, problem recognition, and

good judgment to reduce risks associated with each flight.

SITUATIONAL AWARENESS is the accurate perception and understanding of all the factors and conditions within the four

fundamental risk elements that affect safety before, during, and after the flight.

SKILLS and PROCEDURES are the procedural, psychomotor, and perceptual skills used to control a specific aircraft or its

systems. They are the airmanship abilities that are gained through conventional training, are perfected, and become almost

automatic through experience.

STRESS MANAGEMENT is the personal analysis of the kinds of stress experienced while flying, the application of appropriate

stress assessment tools, and other coping mechanisms.

Figure 14-1. These terms are used in AC 60-22 to explain concepts used in ADM training.

14-2

need to be taken to resolve the situation in the time

THE DECISION-MAKING PROCESS

available. The expected outcome of each possible

An understanding of the decision-making process pro-

action should be considered and the risks assessed

vides you with a foundation for developing ADM

before you decide on a response to the situation.

skills. Some situations, such as engine failures, require

you to respond immediately using established proce-

dures with little time for detailed analysis. Traditionally,

Your first thought was to pull up on the collective and

pilots have been well trained to react to emergencies,

yank back on the cyclic, but after weighing the conse-

but are not as well prepared to make decisions that

quences of possibly losing rotor r.p.m. and not being

require a more reflective response. Typically during a

able to maintain the climb rate sufficiently enough to

flight, you have time to examine any changes that

clear the canyon wall, which is now only a hundred

occur, gather information, and assess risk before reach-

yards away, you realize that your only course is to try

ing a decision. The steps leading to this conclusion

to turn back to the landing zone on the canyon floor.

constitute the decision-making process.

IMPLEMENTING THE DECISION AND

DEFINING THE PROBLEM

EVALUATING THE OUTCOME

Problem definition is the first step in the decision-making

Although a decision may be reached and a course of

process. Defining the problem begins with recognizing

action implemented, the decision-making process is not

that a change has occurred or that an expected change

complete. It is important to think ahead and determine

did not occur. A problem is perceived first by the

how the decision could affect other phases of the flight.

senses, then is distinguished through insight and expe-

As the flight progresses, you must continue to evaluate

rience. These same abilities, as well as an objective

the outcome of the decision to ensure that it is produc-

analysis of all available information, are used to deter-

ing the desired result.

mine the exact nature and severity of the problem.

As you make your turn to the downwind, the airspeed

While doing a hover check after picking up fire fight-

drops nearly to zero, and the helicopter becomes very

ers at the bottom of a canyon, you realize that you are

difficult to control. At this point, you must increase air-

only 20 pounds under maximum gross weight. What

speed in order to maintain translational lift, but since

you failed to realize is that they had stowed some of

the CG is aft of limits, you need to apply more forward

their heaviest gear in the baggage compartment,

cyclic than usual. As you approach the landing zone

which shifted the CG slightly behind the aft limits.

with a high rate of descent, you realize that you are in a

Since weight and balance had never created any

potential settling-with-power situation if you try to

problems for you in the past, you did not bother to cal-

trade airspeed for altitude and lose ETL. Therefore, you

culate CG and power required. You did, however, try

will probably not be able to terminate the approach in a

to estimate it by remembering the figures from earlier

hover. You decide to make as shallow of an approach as

in the morning at the base camp. At a 5,000 foot

possible and perform a run-on landing.

density altitude and maximum gross weight, the per-

formance charts indicated you had plenty of excess

The decision making process normally consists of sev-

power. Unfortunately, the temperature was 93°F and

eral steps before you choose a course of action. To help

the pressure altitude at the pick up point was 6,200

you remember the elements of the decision-making

feet (DA = 9,600 feet). Since there was enough power

process, a six-step model has been developed using the

for the hover check, you felt there was sufficient

acronym “DECIDE.” [Figure 14-2]

power to take off.

Even though the helicopter accelerated slowly during

the takeoff, the distance between the helicopter and the

DECIDE MODEL

ground continued to increase. However, when you

attempted to establish the best rate of climb speed, the

Detect the fact that a change has occurred.

nose wanted to pitch up to a higher than normal atti-

Estimate the need to counter or react to the change.

tude, and you noticed that the helicopter was not gain-

Choose a desirable outcome for the success of the flight.

ing enough altitude in relation to the canyon wall a

Identify actions which could successfully control the change.

couple hundred yards ahead.

Do the necessary action to adapt to the change.

Evaluate the effect of the action.

CHOOSING A COURSE OF ACTION

After the problem has been identified, you must evalu-

Figure 14-2. The DECIDE model can provide a framework for

ate the need to react to it and determine the actions that

effective decision making.

14-3

ROTORCRAFT FLYING HANDBOOK (2000) - page 2