JEPPESEN GENERAL AIRWAY MANUAL (Issue Date 1 JUL 21)

System management downlink message elements (SYSD) (continued)

Operational definition in PANS-ATM (Doc 4444)

CPDLC message sets

SYSD-6

Indication that
the received
message has a
latency greater
than the require-
ment.

MESSAGE RE-
CEIVED TOO
LATE, RESEND
MESSAGE OR
CONTACT BY
VOICE

DM67 ‘MESSAGE
RECEIVED TOO
LATE, RESEND
MESSAGE OR
CONTACT BY
VOICE’
NOTE: Sent with
DM62.

DM98 ‘MESSAGE
RECEIVED TOO
LATE, RESEND
MESSAGE OR
CONTACT BY
VOICE’
NOTE: Sent with
DM62.

SYSD-7

System-gener-
ated notification
that the aircraft
is in the inhibited
state.

AIRCRAFT
CPDLC INHIBI-
TED

N/A

DM 98 ‘AIRCRAFT
CPDLC INHIBI-
TED’

MESSAGE ELEMENTS RECOMMENDED NOT TO USE

FANS 1/A uplink message elements

Message element

Justification

UM49 CROSS (position) AT AND MAINTAIN
(altitude)

Avoid use of this message due to inability of
aircraft automation to maintain the altitude re-
striction.

UM62 AT (time) CROSS (position) AT AND
MAINTAIN (altitude)
UM85 EXPECT (route clearance)

Avoid use of this message element due to po-
tential misinterpretation.

UM86 AT (position) EXPECT (route clearance)
UM87 EXPECT DIRECT TO (position)

UM88 AT (position) EXPECT DIRECT TO (po-
sition)

UM89 AT (time) EXPECT DIRECT TO (posi-
tion)

UM90 AT (altitude) EXPECT DIRECT TO (posi-
tion)

UM162 SERVICE UNAVAILABLE

UM6 EXPECT (altitude)

A.6

A.6.1

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DATA LINK OPERATIONS

Message element

Justification

UM11 EXPECT CRUISE CLIMB AT (time)

UM12 EXPECT CRUISE CLIMB AT (position)

UM13 AT (time) EXPECT CLIMB TO (altitude)

UM14 AT (position) EXPECT CLIMB TO (alti-
tude)

UM15 AT (time) EXPECT DESCENT TO (alti-
tude)

UM16 AT (position) EXPECT DESCENT TO
(altitude)

UM17 AT (time) EXPECT CRUISE CLIMB TO
(altitude)

UM18 AT (position) EXPECT CRUISE CLIMB
TO (altitude)

UM33 CRUISE (altitude)

UM34 CRUISE CLIMB TO (altitude)

UM35 CRUISE CLIMB ABOVE (altitude)

UM40 IMMEDIATELY STOP CLIMB AT (alti-
tude)

UM41 IMMEDIATELY STOP DESCENT AT (al-
titude)

UM175 REPORT REACHING (altitude)

UM42 EXPECT TO CROSS (position) AT (alti-
tude)

UM43 EXPECT TO CROSS (position) AT OR
ABOVE (altitude)

UM44 EXPECT TO CROSS (position) AT OR
BELOW (altitude)

UM45 EXPECT TO CROSS (position) AT AND
MAINTAIN (altitude)

UM103 AT (time) EXPECT (speed) TO (speed)
UM104 AT (position) EXPECT (speed) TO
(speed)

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DATA LINK OPERATIONS

Message element

Justification

UM105 AT (altitude) EXPECT (speed) TO
(speed)

UM165 THEN

UM235 ROGER 7500

UM168 DISREGARD

Not operationally required.
NOTE: These messages have been excluded
from future B2 implementation.

UM176 MAINTAIN OWN SEPARATION AND
VMC

UM152 WHEN CAN YOU ACCEPT (specified
distance) (direction) OFFSET

UM115 DO NOT EXCEED (speed)

UM182 CONFIRM ATIS CODE

UM169 ‘TRANSMIT ADS-B IDENT’

Use of SQUAWK IDENT is recommended.

UM169 ‘IDENTIFICATlON TERMINATED’

Use of SURVEILLANCE SERVICE TERMINA-
TED is recommended.

UM132 CONFIRM POSITION

Use of ADS-C is recommended.

UM133 CONFIRM ALTITUDE

UM138 CONFIRM TIME OVER REPORTED
WAYPOINT

UM139 CONFIRM REPORTED WAYPOINT

UM140 CONFIRM NEXT WAYPOINT

UM141 CONFIRM NEXT WAYPOINT ETA

UM142 CONFIRM ENSUING WAYPOINT

UM146 REPORT GROUND TRACK

UM181 REPORT DISTANCE (to/from) (posi-
tion)

UM145 CONFIRM HEADING

UM177 AT PILOTS DISCRETION

Not globally accepted. See Appendix B, 3.2.1
for its use.

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DATA LINK OPERATIONS

FANS 1/A downlink message elements

Message element

Justification

DM69 REQUEST VMC DESCENT

Avoid use of this message element due to po-
tential misinterpretation.

DM75 AT PILOTS DISCRETION
DM67 ‘WHEN CAN WE EXPECT DESCENT
TO (altitude)’

Avoid use of this message due to potential mis-
interpretation of subsequent response. Use of
LVLD-6 WHEN CAN WE EXPECT HIGHER
LEVEL and LVLD-7 WHEN CAN WE LOWER
HIGHER LEVEL is recommended.

DM67 ‘WHEN CAN WE EXPECT CLIMB TO
(altitude)’
DM74 REQUEST TO MAINTAIN OWN SEPA-
RATION AND VMC

Not operationally required.
NOTE: These messages have been excluded
from future B2 implementation.

DM8 REQUEST CRUISE CLIMB TO (altitude)

DM54 WHEN CAN WE EXPECT CRUISE
CLIMB TO (altitude)

DM72 REACHING (altitude)

DM79 ATIS (atis code)

DM67 ‘MONITORING (unit name) (frequency)’
DM16 AT (position) REQUEST OFFSET
(specified distance) (direction) OF ROUTE

DM17 AT (time) REQUEST OFFSET (specified
distance) (direction) OF ROUTE

DM26 REQUEST WEATHER DEVIATION TO
(position) VIA (route clearance)
DM33 PRESENT POSITION (position)

Use of ADS-C is recommended.

DM36 PRESENT GROUND TRACK (degrees)
DM42 NEXT WAYPOINT (position)

DM43 NEXT WAYPOINT ETA (time)

DM44 ENSUING WAYPOINT (position)

DM45 REPORTED WAYPOINT (position)

DM46 REPORTED WAYPOINT (time)

A.6.2

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DATA LINK OPERATIONS

Message element

Justification

DM78 AT (time) (distance) (to/from) (position)

DM32 PRESENT ALTITUDE (altitude)

DM35 PRESENT HEADING (degrees)
DM19 REQUEST (speed) TO (speed)

Use of SPDD-1 REQUEST (speed) is recom-
mended.

DM50 WHEN CAN WE EXPECT (speed) TO
(speed)

ATN B1 uplink message element

Message element

Justification

UM165 THEN

Avoid use of this message element due to po-
tential misinterpretation.

ATN B1 downlink message element

Message element

Justification

DM89 MONITORING (unit name) (frequency)

Not operationally required.
NOTE: This message has been excluded from
future B2 implementation.

A.6.3

A.6.4

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REGIONAL/STATE - SPECIFIC INFORMATION

GENERAL

This Appendix provides Regional/State specific information grouped per ICAO Regions pertaining
to the data link operations.

European (EUR) Region

Administrative Provisions related to Data Link Operations

ANSP Service Provision

B.2.1.1.2 European regulations require ATN B1 data link services be provided above FL285,
however individual states are free to provide services below that level. Refer to the AIP of each
State for details.
B.2.1.1.3 The use of CPDLC is conducted at the discretion of each responsible ACC and at the
initiative of the flight crew. CPDLC is used for routine exchanges during enroute operations in the
upper airspace and is not for time-critical situations. Communication exchanges by voice have pri-
ority over CPDLC exchanges at all times.

EUR - NSAP Address Registry

B.2.1.2.1  In order to allow the air crew to perform a first LOGON with any of the participating
ATN B1 ACCs, Context Management application addressing information of the ATS units involved
in the ATN/OSI based Air/Ground Data Link Communications, is required in the ATN avionics
system.
B.2.1.2.2  The ATN NSAP addresses for all EUR ACCs are published in EUR Doc 028 - EUR
NSAP Address Registry.
B.2.1.2.3  The focal point for the EUR NSAP Address Registry is the EUR/NAT ICAO Regional
Office. All requests, modifications and proposals concerning should be forwarded to:
http://icaoeurnat@paris.icao.int
NOTE 1: The ICAO EUR/NAT Office ensures that the information is forwarded to the appropriate
working groups (e.g. AFSG Planning Group).
NOTE 2: The EUR NSAP Address Registry is available at the ICAO website: http://www.icao.int/
EURNAT/Pages/EUR-and-NAT-Document.aspx.

Flight Plan Provisions

B.2.1.3.1 In the EUR airspace where ATN B1 CPDLC is available and aircraft are equipped and
capable ATN B1 CPDLC, J1 shall be included in Item 10a of the flight plan:

a. Operators of FANS 1/A-ATN B1 (independent or integrated) equipped aircraft shall insert

one or more of the appropriate indicators among J1-J7 in Item 10a.

b. For flights conducted wholly or partly in the EUR airspace where ATN B1 CPDLC is available

but not equipped with CPDLC capabilities but which have been granted an exemption, the

Appendix B

B.1

B.2

B.2.1

B.2.1.1

B.2.1.2

B.2.1.3

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letter Z shall be included in Item 10A and the indicator DAT/CPDLCX shall be included in
Item18 of the flight plan.

B.2.1.3.2 For a flight operating based on a repetitive flight plan (RPL), during which the pilot
intends to use CPDLC, a modification message (CHG) shall be submitted to indicate that the flight
is capable of, and authorized for CPDLC.
B.2.1.3.3 When there is a change to the CPDLC capability status, the operator should send a
modification message (CHG) with the appropriate indications in the relevant items of the ICAO
flight plan form, including any change to the aircraft address. A modification message for the day
of operation should be sent not earlier than 20 hours before the estimated off-block time.

Logon Criteria

B.2.1.4.1 In addition to the logon FPL correlation criteria the CPDLC aircraft equipment capabili-
ties in Item 10a are also used as criterion for a successful logon. Absence of item J1 and/or one
or more of the items J2 to J7 in Item 10a will lead to a logon rejection.

Lack Timer

B.2.1.5.1 Logical Acknowledgement (LACK) messages (downlink message element DM 100
and uplink message element UM 227 are used in ATN B1 based ACL and ACM message
exchanges.
NOTE 1: Ground systems do not request a LACK for the messages ERROR UM 159, Service
Unavailable UM 162 and LACK UM 227.
NOTE 2: When a LACK is received after expiry of the LACK timer, the LACK may be discarded.

Flight Crew Procedures

General

Reception of uplink messages received by FANS 1/A aircraft

B.2.3.1.1.1  Some of the FANS 1/A-ATN B1 ATS units ‘prepend’ a free text message UM 169,
containing the FID, to each uplink message, sent to a FANS 1/A aircraft.
B.2.3.1.1.2  Flight crew should verify that the ‘prepended’ FID matches with the aircraft’s FID as
filed in the flight plan, Item 7a.
B.2.3.1.1.3  In case the FID doesn’t match, the flight crew should reject the uplinked message,
revert to voice communications to notify the ATS unit of the misdelivered message.

Reverting from CPDLC to voice

B.2.3.1.2.1 The following circumstances describe potential situations where the flight crew com-
munications should revert to voice:

a. When it is required to clarify the meaning or the intent of any unexpected, inappropriate or

ambiguous CPDLC message;

b. Whenever corrective actions are required with respect to unintended or spurious request that

have been sent using CPDLC. The flight crew should be aware that once a message is sent

B.2.1.4

B.2.1.5

B.2.3

B.2.3.1

B.2.3.1.1

B.2.3.1.2

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via CPDLC, no means exist to cancel or to recall that message. The following actions should
be taken by the flight crew after the controller has reverted to voice:

1. If response to the referred CPDLC message was sent, cancel any action initiated on the

basis of the initial CPDLC message and comply with the voice message;

2. If the referred message is not responded to or not displayed, let the dialogue close on

time-out. Since it may be possible to be asked to ignore a message that was not yet
displayed, the flight crew should take all measures to ensure that the message is no
longer valid;

3. In case the flight crew has already received an operational response to the initial

CPDLC message, he/she shall use appropriate voice phrases to stop/cancel the actions
of the addressee; and

NOTE: In case of reversion to voice, flight crew should be aware of the possibility that the
CPDLC message they want the addressee to ignore may not be yet displayed to the addres-
see.

c. Whenever a system generates a time-out or an error for a CPDLC message.

Use of concatenated messages - air initiated

B.2.3.1.3.1 Aircraft and ground systems should allow for a downlink concatenated message
containing a maximum of two message elements.
B.2.3.1.3.2 The only downlink concatenated messages, which ground systems are required to
support, are those that result from a concatenation of one message element from the left column
and one message element from the right column.

First Message Element in Message

Second Message Element in Message

DM 6 REQUEST (level)

DM 65 DUE TO WEATHER

DM 9 REQUEST CLIMB TO (level)

DM 66 DUE TO AIRCRAFT PERFORMANCE

DM 10 REQUEST DESCENT TO (level)

DM 22 REQUEST DIRECT TO (position)

Responding to concatenated message elements with response attribute
other than Y

B.2.3.1.4.1 The permitted response will be messages containing one of the following message
elements: DM 100 LOGICAL ACKNOWLEDGMENT (if required), DM 2 STANDBY, DM 0 WILCO,
DM 1 UNABLE, DM 63 NOT CURRENT DATA AUTHORITY, DM 107 NOT AUTHORIZED NEXT
DATA AUTHORITY or DM 62 ERROR message element.
B.2.3.1.4.2 The closure response message will be a message containing one of the following
message elements: DM 0 WILCO, DM 1 UNABLE, DM 63 NOT CURRENT DATA AUTHORITY,
DM 107 NOT AUTHORIZED NEXT DATA AUTHORITY or DM 62 ERROR message element.

B.2.3.1.3

B.2.3.1.4

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DATA LINK OPERATIONS

B.2.3.1.4.3 The DM 0 WILCO or DM 1 UNABLE response messages will operationally apply to
the entire uplink concatenated message.
B.2.3.1.4.4 As responses to a ground initiated dialogue, ground systems are required to also
support the following downlink concatenated messages:

First Message Element in Message

Second Message Element in Message

DM 1 UNABLE

DM 65 DUE TO WEATHER

DM 82 WE CANNOT ACCEPT (level)

DM 66 DUE TO AIRCRAFT PERFORMANCE

Latency Time Monitor (LTM)

B.2.3.2.1  In accordance with safety requirement SR-ACL-13 of ED120/DO290, the message
latency monitor defined in ED100A/DO258A, paragraph 4.6.6.9, and ED110B/DO280B (ATN),
paragraph 3.3.4, provides to the ANSP a means to mitigate the effects of an excessively delayed
CPDLC message. In Europe, this message latency monitor is referred to as the Latency Time
Monitor (LTM).
NOTE: The LTM function is not used by FANS 1/A+ aircraft.
B.2.3.2.2  An ATN B1 compliant aircraft has a Latency Time Monitor (LTM) function in the form
of a hard-coded LTM value in the avionics. The LTM value is set at 40 seconds.
B.2.3.2.3  Upon activation of the LTM, the aircraft system will:

Upon activation of LTM, the aircraft system will:

a. Display the message to the flight crew with a delayed message indication. The flight crew

should contact the controller and advise him/her of the situation and/or request verification of
ATC intent; or

b. Discard the message without any indication to the flight crew and notify the controller with a

message consisting of DM 62 ERROR (error information) and DM 98 (UPLINK DELAYED IN
NETWORK AND REJECTED. RESEND OR CONTACT BY VOICE). The controller should
revert to voice to clarify the situation.

Operational use of LACK

B.2.3.3.1  Each time the flight crew downlinks an operational message, the ATN B1 ground
system returns a UM 227 logical acknowledgement (LACK).
B.2.3.3.2  The LACK timer value should be set by the aircraft system at 40 seconds.
B.2.3.3.3  If the aircraft system does not receive a UM 227 LACK within 40 seconds, the flight
crew will be notified.
NOTE 1: The aircraft system does not request a UM 227 LACK for messages DM 62 (ERROR),
DM 63 NOT CURRENT DATA AUTHORITY), DM 100 (LACK) and DM 107 (NOT AUTHORIZED
NEXT DATA AUTHORITY).

B.2.3.2

B.2.3.3

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DATA LINK OPERATIONS

NOTE 2: Local implementers may decide whether the flight crew is notified on the receipt of each
LACK (positive feedback) or is only notified upon a LACK time out (negative feedback).
NOTE 3: When a UM 227 LACK is received after expiry of the LACK timer, the UM 227 LACK
may be discarded.

Operational Timers used by the Aircraft

Controller initiated dialogue

B.2.3.4.1.1 When an ATN B1 aircraft system receives an uplink message, requiring a response,
it starts the timer-responder (ttr), whose value for the response to be sent is set at 100 seconds.

a. The ttr expires if the flight crew fails to respond within 100 seconds. The flight crew is notified

and reverts to voice to complete the dialogue;
NOTE: FANS 1/A aircraft do not have a ttr timer.

b. The ATN B1 aircraft system closes the dialogue and sends an error response ‘AIRSYSTEM

TIME-OUT’. The error response ensures that the dialogue will also be closed within the ATS
unit.
NOTE: In normal circumstances, the aircraft-timer (ttr) expires before the ground-timer (tts)
expires.

B.2.3.4.1.2 If the flight crew responds to a clearance with a DM 2 STANDBY, the aircraft- and
ground timers are re-started.

Flight crew initiated dialogue

B.2.3.4.2.1 When the flight crew sends a CPDLC request, requiring an operational response,
and when implemented, the ATN B1 aircraft system starts the tts. If used, the timer value for the
operational response to be received is set at 270 seconds.

a. The tts expires, if no operational response has been received by the aircraft system within

270 seconds. The flight crew is notified and reverts to voice to resolve the situation.

b. The dialogue is closed locally by the aircraft system, ensuring that the dialogue doesn’t

remain open at the aircraft side.
NOTE: ATN B1 ground systems have implemented ground-timer. In normal circumstances,
the ground-timer (ttr) expires before the aircraft-timer (tts) expires.

B.2.3.4.2.2 If the controller responds to a request with a UM 1 STANDBY, the aircraft and
ground timers are re-started.

Use of Degrees in ACL Messages

B.2.3.5.1 The display of (degrees) parameter is used in the following three CPDLC messages:

a. UM 94 TURN (direction) HEADING (degrees)
b. UM 190 FLY HEADING (degrees)

c. UM 215 TURN (direction) (degrees) DEGREES

B.2.3.4

B.2.3.4.1

B.2.3.4.2

B.2.3.5

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DATA LINK OPERATIONS

B.2.3.5.2  UM 94 and UM 190 represent an absolute change towards the instructed HEADING,
while UM 215 is a relative change with reference to the current HEADING.
B.2.3.5.3  ICAO requires that the HEADING in UM 94 and UM 190 is expressed in 3 digits (e.g.
015°) and should be displayed accordingly.
B.2.3.5.4  Flight crews should be aware that Airframe and avionics manufacturers are adding a
leading ‘0’ for degrees less than 100° for UM 94 and UM 190.
B.2.3.5.5  However, UM 215 is expressed in two digits (e.g. 15 degrees). To ensure that flight
crews execute UM 215 as a relative change, UM 215 is displayed as TURN (direction) (degrees)
DEGREES (e.g. TURN RIGHT 15 DEGREES).

Transfer of Data Communications with open Dialogues

Open air-initiated dialogues

B.2.3.6.1.1 When there are open air-initiated dialogues, the ground system closes each of these
dialogues with a closure response before sending the transfer instruction. The closure uplink
responses are one of the following:

a. UNABLE (UM 0), or
b. REQUEST AGAIN WITH NEXT UNIT (UM 237), or

c. Concatenated message ‘ERROR’ (UM 159) + REQUEST AGAIN WITH NEXT UNIT (UM

183 - free text), or

d. REQUEST AGAIN WITH NEXT UNIT (UM 183 - free text)

B.2.3.6.1.2 When there are open air-initiated dialogues, and the flight crew responds to the
transfer instruction with a DM 0 WILCO, the airborne system cancels all open air initiated dia-
logues. When responding with DM 1 UNABLE or DM 2 STANDBY, the aircraft system maintains
the open dialogues.

Multiple Open Requests for a same Type

To avoid ambiguity and request being discarded by the ATS unit, the flight crew should avoid
sending multiple requests for a same type of dialogue, dialogue type being one of the following: a)
level; b) heading; c) speed; d) route.
NOTE: The flight crew should be aware that only one downlink request for a single type will be
presented to the controller and that this open dialogue must be closed before a second request of
that type may be treated.

Abnormal Situations

Inability to contact the assigned voice communication channel

B.2.3.8.1.1 When the flight crew is unable to contact the assigned voice communication channel
when instructed to do so by the transferring controller via CPDLC, the flight crew should revert to
the voice communication channel of the transferring ATC unit for instructions.

B.2.3.6

B.2.3.6.1

B.2.3.7

B.2.3.8

B.2.3.8.1

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Use of CPDLC in the event of voice radio communication failure

B.2.3.8.2.1 The existence of a CPDLC connection between the ATS unit and the aircraft should
not preempt the flight crew and ACC from applying all the ICAO provisions in the event of radio
communication failure.
B.2.3.8.2.2 When the flight crew cannot comply with the requirement above, it will have to apply
the provisions stipulated for the event of radio communication failure.

Flight crew-commanded CPDLC termination

B.2.3.8.3.1 When flight crew initiates CPDLC termination, the ATN B1 airborne system sends a
CPDLC user-abort to the ground system. The controller is notified of the abort.
NOTE: Subject to local designs, ground systems may not provide facilities for CPDLC connect
request to be re-issued upon notification by the flight crew that they want to resume CPDLC with
the ground.
B.2.3.8.3.2 To reinstate CPDLC after a flight crew-initiated commanded termination, the flight
crew initiates a CM-logon request.

Uplink Error Messages

B.2.3.9.1  ATN B1 systems use a set of error messages, when the ATN B1 ground system does
not behave according to the ATN B1 requirements or local constraints prevent an operational
response.
B.2.3.9.2  Table B-EUR-3 provides a list of operational error messages displayed to the flight
crew.
B.2.3.9.3  When receiving an ‘ERROR’ (UM 159) + free text message (UM 183) in response to
operational downlink messages, the flight crew should revert to voice to clarify the situation with
the controller.

B.2.3.8.2

B.2.3.8.3

B.2.3.9

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Table B-EUR-3. Operational Error Uplink Messages

Free Text Message

Description

Procedure

DOWNLINK MESSAGE RE-
QUEST REJECTED - SEND
(number) ELEMENTS

The ground system receives a
message that contains more
message elements than it can
support in a message.
EXAMPLE: The flight crew
sends a combined message
(DM 6 REQUEST (level), DM
70 REQUEST HEADING (de-
grees), DM 65 DUE TO
WEATHER) and the ground
system accepts only a maxi-
mum of two message ele-
ments.
NOTE: It is a local choice of
the ground system to reject
downlink messages containing
more than 1, 2 or 3 message
elements or to accept up to 5
message elements.

The flight crew may resend the
request in the form of separate
messages, or make the re-
quest/s by voice.

(Dialogue type) NOT AVAILA-
BLE AT THIS TIME - USE
VOICE
Dialogue type is one of the fol-
lowing: LEVEL, HEADING,
SPEED, ROUTE REQUEST

The ground system receives a
downlink message that is dis-
carded because the associated
dialogue type is disabled.

The flight crew should make
the request by voice.

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Table B-EUR-3. Operational Error Uplink Messages (continued)

Free Text Message

Description

Procedure

ELEMENT COMBINATION
REJECTED - USE VOICE

The ground system receives a
concatenated downlink mes-
sage that it does not support
(invalid element combination,
or at least one message ele-
ment is not supported, or inva-
lid element order).
NOTE: Whether a combination
of message elements is valid
or not, is determined through
local choice of the ground sys-
tem. Examples of obvious inva-
lid combinations: Request
Climb To + Request Descend
To; WILCO + UNABLE, etc.

The flight crew may resend the
message/request in the form of
separate messages, or make
the request/s by voice.

TOO MANY (dialogue type)
REQUESTS - EXPECT ONLY
ONE REPLY
Dialogue type is one of the fol-
lowing: LEVEL, HEADING,
SPEED, ROUTE.

The ground system receives a
downlink request, and there is
an existing open downlink re-
quest containing the same type
and it discards the second re-
quest.

The flight crew should be
aware that only one downlink
request for a single type will be
presented to the controller, and
that this open dialogue must be
closed before a second re-
quest of that type may be trea-
ted.

REQUEST REJECTED - RE-
PLY TO (dialogue type) UP-
LINK FIRST
Dialogue type is one of the fol-
lowing: LEVEL, HEADING,
SPEED, ROUTE

The ground system receives a
downlink request, and there is
an existing open uplink con-
taining the same type. The
downlink request is discarded.
NOTE: Ground systems only
accept one data link exchange
of a given type at the same
moment.

The flight crew must respond
to the uplink before being able
to send a downlink request of
this type.

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Table B-EUR-3. Operational Error Uplink Messages (continued)

Free Text Message

Description

Procedure

TOO MANY CPDLC RE-
QUESTS - USE VOICE

The ground system receives a
downlink request, and discards
a message because the maxi-
mum number of open opera-
tional dialogues with the air-
craft is exceeded and there is
no pending uplink message.
NOTE: The total number of da-
ta link exchanges with an air-
craft may be limited by some
ground systems. This means
that further requests will be re-
jected.

The flight crew should make
the request/s by voice.
If there are only downlink re-
quests, the flight crew cannot
do anything about it.
If there is at least one uplink
expecting a response, the flight
crew can respond to that clear-
ance first to enable reception
of a downlink request.

CPDLC TRANSFER NOT
COMPLETED - REPEAT RE-
QUEST

Until CPDLC is enabled, the
ground system rejects any
downlink message; except DM
99 (CURRENT DATA AU-
THORITY), DM 89 (MONITOR-
ING), DM 62 (ERROR), and
DM 62 concatenated with DM
98 (ERROR + Free text).

The flight crew cannot use data
link now, but when CPDLC is
fully operational, a CPDLC
message is uplinked and dis-
played to the flight crew, indi-
cating the name and function
of the current ATC unit.
The flight crew should not at-
tempt to repeat the request un-
til the CPDLC transfer has
been completed and they are
under the control of the ACC,
being the CDA.

ATC TIME OUT - REPEAT
REQUEST

If the controller fails to respond
within 250 seconds the timer-
responder (ttr) expires. The
ground system closes the dia-
logue and automatically uplinks
an error message in response
to the downlink message re-
quest.

The flight crew is notified that
the controller has not respon-
ded in the due time.
The flight crew should repeat
the request/s by voice.

DOWNLINK DELAYED - USE
VOICE

The ground system receives a
message and discards the
message because it contains a
timestamp that is older than
the allowed limit.

The flight crew should revert to
voice.

CONTROLLER PILOT DATA LINK COMMUNICATION

(CPDLC)

1487

DATA LINK OPERATIONS

Table B-EUR-3. Operational Error Uplink Messages (continued)

Free Text Message

Description

Procedure

DOWNLINK DELAYED - USE
VOICE

Upon activation of the latency
time monitor, the ground sys-
tem automatically uplinks an
error message.
NOTE: The use of the LTM
function for the ATSU is a rec-
ommendation.

The flight crew should revert to
voice.

DOWNLINK TIMESTAMP IN-
DICATES FUTURE TIME

The ground system receives a
message timestamp that indi-
cates a future time greater than
2 seconds from the current
time.

The flight crew should revert to
voice.

MESSAGE NOT SUPPORTED
BY THIS ATS UNIT

The ground system receives a
downlink message that it does
not support, whether or not the
message contains a message
reference number, and dis-
cards the received message.

The flight crew should revert to
voice.

FREE TEXT MESSAGE TOO
LARGE - USE VOICE

The ground system receives a
downlink free text message el-
ement containing more than 80
characters, and the system
cannot support the number of
characters in a free text mes-
sage element, and discard the
received message.

The flight crew should revert to
voice.
NOTE: Ground systems may
not accept downlink free text
messages, or may not display
them to the controller.

CPDLC MESSAGE FAILED -
USE VOICE

A CPDLC downlink message is
received that results in an error
that is not already covered in
the ATN SARPs, and the
ground system discards the
message.

The flight crew should revert to
voice.

CONTROLLER PILOT DATA LINK COMMUNICATION

(CPDLC)

1488

DATA LINK OPERATIONS

Table B-EUR-3. Operational Error Uplink Messages (continued)

Free Text Message

Description

Procedure

INVALID USE OF FREE TEXT
MESSAGE - CONTACT ATC

The ground system does not
support a message containing
a free text message element
because the message does not
also contain the DM 62 ER-
ROR (error information) mes-
sage element and discards the
message.

The flight crew should revert to
voice.

RADAR TRACKING TERMI-
NATED - TERMINATING
CPDLC

The ground system decides to
terminate a CPDLC connection
with an aircraft because it has
lost radar data.

The flight crew should revert to
voice.

CPDLC FOR (dialogue type)
FAILED - USE VOICE
Dialogue type is one of the fol-
lowing: LEVEL, HEADING,
SPEED, ROUTE

The ground system receives a
downlink message containing a
dialogue type that it does not
support and discards the mes-
sage.

The flight crew should revert to
voice.

MESSAGE DOES NOT CON-
TAIN FACILITY NAME

The ground system receives a
downlink message that con-
tains the unitname data type,
but rejects the message be-
cause it does not also contain
the facilityname data type and
discards the message.

The flight crew should revert to
voice.

NORTH-AMERICA (NAM) REGION

Flight Crew Procedures

Use of AT PILOTS DISCRETION

In airspace managed by the United States, when the flight crew receives UM 177 AT PILOTS
DISCRETION in conjunction with altitude assignments, the associated instruction to climb or
descend may be executed when convenient and at any preferred rate. The aircraft may tempora-
rily maintain intermediate levels but once the aircraft has vacated a level it may not return to that
level.

B.3

B.3.3

B.3.3.1

CONTROLLER PILOT DATA LINK COMMUNICATION

(CPDLC)

1489

DATA LINK OPERATIONS

NORTH ATLANTIC (NAT) REGION

Reporting Requirements in NAT Airspace where ADS-C is available

B.4.1.4.1  In the NAT Region, if the estimated time for the next position last provided to air traffic
control is found to be in error by 3 minutes or more, the flight crew should provide a revised esti-
mated time.
B.4.1.4.2  The flight crew may assume that the estimate for the next waypoint, shown on the
FMS at the time a waypoint is crossed, is the estimate transmitted to ATC.
B.4.1.4.3  The flight crew should provide the revised estimate to the controlling ATS unit as soon
as possible via voice or CPDLC using free text DM 67 REVISED ETA (position) (time).

Flight crew procedures

Voice Communication Procedures

Flight crew – contact with radio station

B.4.3.1.1.1  The integrity of the ATC service remains wholly dependent on establishing and
maintaining HF or VHF voice communications with each ATS unit along the route of flight. The
procedures in this section are applicable only in NAT airspace and pertain only to ATS data link
operations.
B.4.3.1.1.2  Prior to or upon entering each NAT oceanic CTA, the flight crew should contact the
appropriate radio station.
B.4.3.1.1.3  If the flight enters an oceanic CTA followed by another oceanic CTA, the flight crew
should on initial contact:

a. Not include a position report;
b. After the radio operator responds, request a SELCAL check and state the next CTA.

NOTE: The radio operator will assign primary and secondary frequencies, perform the
SELCAL check and designate the position and frequencies to contact the aeronautical radio
station serving the next oceanic CTA.

c. If the communications instructions are not issued at this stage, assume that the frequencies

to use prior or upon entering the next CTA will be delivered at a later time by CPDLC or
voice.

Example (initial contact from eastbound flight entering Gander Oceanic):
GANDER RADIO, AIRLINE 123, SELCAL CHECK, SHANWICK NEXT
AIRLINE 123, GANDER RADIO, HF PRIMARY 5616 SECONDARY 2899, AT 30 WEST CON-
TACT SHANWICK RADIO HF PRIMARY 8891 SECONDARY 4675 (SELCAL TRANSMITTED)
GANDER RADIO, AIRLINE 123, SELCAL OKAY, HF PRIMARY 5616 SECONDARY 2899. AT 30
WEST CONTACT SHANWICK RADIO, HF PRIMARY 8891 SECONDARY 4675
B.4.3.1.1.4 If the flight will exit an oceanic CTA into continental airspace or surveillance air-
space, on initial contact with the oceanic CTA, the flight crew should:

B.4

B.4.1.4

B.4.3

B.4.3.1

B.4.3.1.1

CONTROLLER PILOT DATA LINK COMMUNICATION

(CPDLC)

1490

DATA LINK OPERATIONS

a. not include a position report;
b. after the radio operator responds, request a SELCAL check.

Example (Initial contact from an eastbound flight about to enter the Shanwick Oceanic)
SHANWICK RADIO, AIRLINE 123, SELCAL CHECK
AIRLINE 123, HF PRIMARY 2899 SECONDARY 5616 (SELCAL TRANSMITTED)
SHANWICK RADIO, AIRLINE 123, SELCAL OKAY, HL PRIMARY 2899 SECONDARY 5616
B.4.3.1.1.5  Depending on which data link services are offered in the oceanic CTA and the
operational status of those services, the radio operator will provide appropriate information and
instructions to the flight crew.
B.4.3.1.1.6  If a data link connection cannot be established, maintain normal voice communica-
tion procedures. In the event of data link connection failure in a NAT CTA after a successful
logon, revert to voice and notify the appropriate radio station and AOC in accordance with estab-
lished problem reporting procedures.
B.4.3.1.1.7  For ADS-C flights, the flight crew should not submit position reports via voice to
reduce frequency congestion, unless otherwise advised by the aeronautical radio operator.
B.4.3.1.1.8  ADS-C flights are exempt from all routine voice meteorological reporting, however
the flight crew should use voice to report unusual meteorological conditions such as severe turbu-
lence to the aeronautical radio station.
B.4.3.1.1.9  The flight crew should use CPDLC for any inquiries regarding the status of ADS-C
connections. Should the ATS unit fail to receive an expected position report, the controller will
follow guidelines for late or missing ADS-C report.
B.4.3.1.1.10  When leaving CPDLC/ADS-C or ADS-C-only airspace, the flight crew should
comply with all communication requirements applicable to the airspace being entered.
B.4.3.1.1.11  If the flight crew does not receive its domestic frequency assignment by 10 minutes
prior to the flight’s entry into the next CTA, the flight crew should contact the aeronautical radio
station and request the frequency, stating the current CTA exit fix or coordinates.

PACIFIC (PAC) REGION

Exchange of Turbulence Information in Fukuoka FIR

B.5.1.2.1 In the Fukuoka FIR, the flight crew should report moderate or severe turbulence infor-
mation. Turbulence information is provided for aircraft which fly around location of observation
within height difference of ±4,000 feet from altitude of observation and will pass within two hours
from time of observation.
B.5.1.2.2 The flight crew may use CPDLC for reporting and receiving moderate or severe turbu-
lence information. For aircraft which does not have a CPDLC connection, the exchange of turbu-
lence information is implemented by voice. The turbulence information provided to flight crews,
whether by CPDLC or voice, will be the same.

B.5

B.5.1.2

CONTROLLER PILOT DATA LINK COMMUNICATION

(CPDLC)

1491

DATA LINK OPERATIONS

Report of turbulence information by CPDLC

When reporting turbulence information via CPDLC, aircraft should downlink in the following form
by free text message:
DM 67 (MOD or SEV) TURB (location of observation) (altitude of observation) (time of observa-
tion) Z.
NOTE 1: Aircraft should report location of observation in the following form. When observing tur-
bulence continuously, aircraft is able to report location of observation in the following form;
“[beginning location of observation] [end location of observation]“.

a. FIX (e.g. “NIPPI“)
b. Distance and radial from FIX (e.g. “20NM SW NIPPI“)

c. Latitude and longitude (e.g. “4020N14532E”)

d. When observing turbulence continuously (e.g. “RIPKI GARRY”)

NOTE 2: When observing turbulence while cruising, aircraft is able to report by omitting altitude of
observation. When observing turbulence continuously while climbing or descending, aircraft
should report altitude of observation in the following form; “[lower limit altitude of observation]
[upper limit altitude of observation]“ (e.g. “FL330 FL350”).
NOTE 3: When reporting turbulence information within 5 minutes after observing, aircraft is able
to report by omitting time of observation.
Examples of downlink messages:
“SEV TURB 35N160E FL330 0924Z”
“MOD TURB 20NM N ASEDA 35NM S ASEDA FL350 1152Z”
“MOD TURB NIPPI 2114Z”
“SEV TURB 3530N15451E FL370 FL390 0304Z”
“SEV TURB POXED FL320”
“MOD TURB CELIN”

Provision of turbulence information by CPDLC

B.5.1.2.4.1 When providing via CPDLC, turbulence information is uplinked in the following form
by free text message:
UM 169 (MOD or SEV) TURB (location of observation) (altitude of observation) (time of observa-
tion) Z (type of aircraft)
B.5.1.2.4.2 The downlink response DM 3 ROGER should be used to acknowledge receipt of tur-
bulence information issued.
Examples of uplink messages:
“MOD TURB NIPPI F360 0130Z B772”
“SEV TURB FM 37N160E TO 37N158E F320 0418Z A332”

B.5.1.2.3

B.5.1.2.4

CONTROLLER PILOT DATA LINK COMMUNICATION

(CPDLC)

1492

DATA LINK OPERATIONS

Extracted from the following ICAO publications:
RULES OF THE AIR, ANNEX 2
AIRCRAFT OPERATIONS, ANNEX 6
AERONAUTICAL TELECOMMUNICATIONS, ANNEX 10, VOLUMES I II
SEARCH AND RESCUE, ANNEX 12
PROCEDURES FOR AIR NAVIGATION SERVICES — AIR TRAFFIC MANAGEMENT, PANS-
ATM (Doc 4444)
PROCEDURES FOR AIR NAVIGATION SERVICES — AIRCRAFT OPERATIONS, PANS-OPS
(Doc 8168)
Within this chapter, references to the following ICAO Documents are made, however they
are not published herein:
REGIONAL SUPPLEMENTARY PROCEDURES (Doc 7030)
INTERNATIONAL AERONAUTICAL AND MARITIME SEARCH AND RESCUE (IAMSAR)
MANUAL (DOC 9731)

DEFINITIONS

Refer to Introduction/Chart Glossary.

EMERGENCY PROCEDURES

GENERAL

2.1.1 The various circumstances surrounding each emergency situation preclude the establish-
ment of exact detailed procedures to be followed. (Doc 4444, 15.1.1)
2.1.2 Air traffic control units shall maintain full and complete coordination, and personnel shall
use their best judgement in handling emergency situations. (Doc 4444, Part III, 16.1.1)
NOTE: To indicate that it is in a state of emergency, an aircraft equipped with an SSR trans-
ponder might operate the equipment as follows:

a. on Mode A, Code 7700; or
b. on Mode A, Code 7500, to indicate specifically that it is being subjected to unlawful interfer-

ence.

PRIORITY

2.2.1 An aircraft known or believed to be in a state of emergency, including being subjected to
unlawful interference, shall be given priority over other aircraft. (Doc 4444, 15.1.2)

DISTRESS FREQUENCIES

2.3.1 The ICAO Communication Procedures require that an aircraft in distress when it is air-
borne should use the frequency in use for normal communications with aeronautical stations at
the time. However, it is recognized that, after an aircraft has crashed or ditched, there is a need

2.1

2.2

2.3

EMERGENCY DATA - INTERNATIONAL CIVIL

AVIATION AUTHORITY

1496

INTERNATIONAL CIVIL AVIATION ORGANIZATION (ICAO)

for designating a particular frequency or frequencies to be used in order that uniformity may be
attained on a world-wide basis, and so that a guard may be maintained or set up by as many sta-
tions as possible including direction-finding stations, and stations of the Maritime Mobile Service.
2.3.2   The frequency 2182 kHz is the international distress frequency for radiotelephony to be
used for that purpose by ship, aircraft and survival craft stations when requesting assistance from
the maritime service.
2.3.3   The frequency 4125 kHz is also authorized to enable communications between stations in
the maritime mobile service and aircraft stations in distress.
2.3.4   Similarly, the frequency 500 kHz is the international distress frequency for radiotelegraphy
to be used for that purpose by ship, aircraft and survival craft stations when requesting assistance
from the maritime service.
2.3.5  With respect to survival craft stations the following emergency / distress frequencies are
provided:

a. VHF — 121.5 MHz;
b. UHF — 243.0 MHz;

c. HF — 500 kHz, 2182 kHz, 8364 kHz.

(Annex 10, Vol V, Chapter 2 Introduction)

TRANSPONDER OPERATIONS — EMERGENCY

2.4.1 The pilot of an aircraft in a state of emergency shall set the transponder to Mode A Code
7700 unless ATC has previously directed the pilot to operate the transponder on a specified code.
In the latter case, the pilot shall continue to use the specified code unless otherwise advised by
ATC. However, a pilot may select Mode A Code 7700 whenever there is a specific reason to
believe that this would be the best course of action. (Doc 8168, Vol I, Part III, Section 3, Chapter
1, 1.4).

DISTRESS AND URGENCY SIGNALS

NOTE: None of the provisions in this section shall prevent the use, by an aircraft in distress, of
any means at its disposal to attract attention, make known its position and obtain help.

Distress Signals

2.5.1.1 The following signals, used either together or separately, mean that grave and imminent
danger threatens, and immediate assistance is requested:

a. a signal made by radiotelegraphy or by any other signalling method consisting of the group

SOS (. . . - - - . . . in the Morse Code);

b. a radiotelephony distress signal consisting of the spoken word

MAYDAY;

c. a distress message sent via data link which transmits the intent of the word

MAYDAY;

d. rockets or shells throwing red lights, fired one at a time at short intervals;
e. a parachute flare showing a red light.

2.4

2.5

2.5.1

EMERGENCY DATA - INTERNATIONAL CIVIL

AVIATION AUTHORITY

1497

INTERNATIONAL CIVIL AVIATION ORGANIZATION (ICAO)

(Annex 2, Appendix 1, 1.1)

Urgency Signals

2.5.2.1 The following signals, used either together or separately, mean that an aircraft wishes to
give notice of difficulties which compel it to land without requiring immediate assistance:

a. the repeated switching on and off of the landing lights; or
b. the repeated switching on and off of the navigation lights in such a manner as to be distinct

from flashing navigation lights.

(Annex 2, Appendix 1, 1.2.1)
2.5.2.2 The following signals, used either together or separately, mean that an aircraft has a
very urgent message to transmit concerning the safety of a ship, aircraft or other vehicle, or of
some person on board or within sight;

a. a signal made by radiotelegraphy or by any other signalling method consisting of the group

XXX;

b. a radiotelephony urgency signal consisting of the spoken words

PAN, PAN.

c. an urgency message sent via data link which transmits the intent of the words

PAN, PAN.

(Annex 2, Appendix 1, 1.2.2)

UNLAWFUL INTERFERENCE

GENERAL

3.1.1 An aircraft which is being subjected to unlawful interference shall endeavor to notify the
appropriate ATS unit of this fact, any significant circumstances associated therewith and any devi-
ation from the current flight plan necessitated by the circumstances, in order to enable the ATS
unit to give priority to the aircraft and to minimize conflict with other aircraft. (Annex 2, 3.7)
3.1.2 When an air traffic services unit knows or believes that an aircraft is being subjected to
unlawful interference, no reference shall be made in ATS air-ground communications to the
nature of the emergency unless it has first been referred to in communications from the aircraft
involved and it is certain that such reference will not aggravate the situation. (Annex 11, 5.6.2)

TRANSPONDER OPERATIONS — UNLAWFUL INTERFERENCE WITH

AIRCRAFT IN FLIGHT

3.2.1 If there is unlawful interference with an aircraft in flight, the pilot-in-command shall attempt
to set the transponder to Mode A Code 7500 in order to indicate the situation: If circumstances so
warrant, Code 7700 should be used instead. (Doc 8168, Vol I, Part III, Section 3, Chapter 1,
1.6.1).
3.2.2 If a pilot has selected Mode A Code 7500 and has been requested to confirm this code by
ATC (in accordance with 1.1.5), the pilot shall, according to circumstances, either confirm this or
not reply at all. (Doc 8168, Vol I)

2.5.2

3.1

3.2

EMERGENCY DATA - INTERNATIONAL CIVIL

AVIATION AUTHORITY

1498

INTERNATIONAL CIVIL AVIATION ORGANIZATION (ICAO)

NOTE: If the pilot does not reply, ATC will take this as confirmation that the use of Code 7500 is
not an inadvertent false code selection.

PROCEDURES

3.3.1  The following procedures are intended as guidance for use by aircraft when unlawful inter-
ference occurs and the aircraft is unable to notify an ATS unit of this fact. (Annex 2, Attachment
B)
3.3.2  Unless considerations aboard the aircraft dictate otherwise, the pilot-in-command should
attempt to continue flying on the assigned track and at the assigned cruising level at least until
able to notify an ATS unit or within radar coverage. (Annex 2, Attachment B, 2.1)
3.3.3  When an aircraft subjected to an act of unlawful interference must depart from its assigned
track or its assigned cruising level without being able to make radiotelephony contact with ATS,
the pilot-in-command should, whenever possible;

a. attempt to broadcast warnings on the VHF emergency frequency and other appropriate fre-

quencies, unless considerations aboard the aircraft dictate otherwise. Other equipment such
as on-board transponders, data links, etc., should also be used when it is advantageous to
do so and circumstances permit; and

b. proceed in accordance with applicable special procedures for in-flight contingencies, where

such procedures have been established and promulgated in ICAO Document 7030 —
Regional Supplementary Procedures; or

c. if no applicable regional procedures have been established, proceed at a level which differs

from the cruising levels normally used for IFR flight by:

1. 150m (500 ft) in an area where a vertical separation minimum of 300m (1000 ft) is

applied; or

2. 300m (1000 ft) in an area where a vertical separation minimum of 600m (2000 ft) is

applied.

(Annex 2, Attachment B, 2.2)

EMERGENCY DESCENT

INITIAL ACTION BY THE AIR TRAFFIC CONTROL UNIT

4.1.1 Upon receipt of advice that an aircraft is making an emergency descent through other traf-
fic, all possible action shall be taken immediately to safeguard all aircraft concerned. When
deemed necessary, air traffic control units shall immediately broadcast by means of the appropri-
ate radio aids, or if not possible, request the appropriate communications stations immediately to
broadcast an emergency message. (Doc 4444, Part III, 15.1.4)

ACTION BY THE PILOT-IN-COMMAND

4.2.1 It is expected that aircraft receiving such a broadcast will clear the specified areas and
standby on the appropriate radio frequency for further clearances from the air traffic control unit.
(Doc 4444 Part III, 15.1.4)

3.3

4.1

4.2

EMERGENCY DATA - INTERNATIONAL CIVIL

AVIATION AUTHORITY

1499

INTERNATIONAL CIVIL AVIATION ORGANIZATION (ICAO)

SUBSEQUENT ACTION BY THE AIR TRAFFIC CONTROL UNIT

4.3.1 Immediately after such an emergency broadcast has been made the area control center,
the approach control office, or the aerodrome control tower concerned shall forward further clear-
ances to all aircraft involved as to additional procedures to be followed during and subsequent to
the emergency descent. The ATS unit concerned shall additionally inform any other ATS units
and control sectors which may be affected. (Doc 4444, Part III, 15.1.4)

DISTRESS AND URGENCY RADIOTELEPHONY

COMMUNICATION PROCEDURES

GENERAL

5.1.1  The radiotelephony distress signal MAYDAY and the radiotelephony urgency signal PAN
PAN shall be used at the commencement of the first distress and urgency communication respec-
tively. (Annex 10, Vol II, 5.3.1.2)
5.1.1.1  At the commencement of any subsequent communication in distress and urgency traffic,
it shall be permissible to use the radiotelephony distress and urgency signals. (Annex 10, Vol II,
5.3.1.2.1)
5.1.2  The originator of messages addressed to an aircraft in distress or urgency condition shall
restrict to the minimum the number and volume and content of such messages as required by the
condition. (Annex 10, Vol II, 5.3.1.3)
5.1.3  If no acknowledgement of the distress or urgency message is made by the station
addressed by the aircraft, other stations shall render assistance, as prescribed in 5.2.2 and 5.3.2
respectively. (Annex 10, Vol II, 5.3.1.4)
NOTE: “Other stations” is intended to refer to any other station which has received the distress or
urgency message and has become aware that it has not been acknowledged by the station
addressed.
5.1.4  Distress and urgency traffic shall normally be maintained on the frequency on which such
traffic was initiated until it is considered that better assistance can be provided by transferring that
traffic to another frequency. (Annex 10, Vol II, 5.3.1.5)
NOTE: 121.5 MHz or alternative available VHF or HF frequencies may be used as appropriate.
5.1.5  In cases of distress and urgency communications, in general, the transmissions by radio-
telephony shall be made slowly and distinctly, each word being clearly pronounced to facilitate
transcription. (Annex 10, Vol II, 5.3.1.6)

RADIOTELEPHONY DISTRESS COMMUNICATIONS

Action by the Aircraft in Distress

5.2.1.1 In addition to being preceded by the radiotelephony distress signal MAYDAY, preferably
spoken three times, the distress message to be sent by an aircraft in distress shall:

a. be on the air-ground frequency in use at the time;

4.3

5.1

5.2

5.2.1

EMERGENCY DATA - INTERNATIONAL CIVIL

AVIATION AUTHORITY

1500

INTERNATIONAL CIVIL AVIATION ORGANIZATION (ICAO)

b. consist of as many as possible of the following elements spoken distinctly and, if possible, in

the following order:

1. name of the station addressed (time and circumstances permitting);
2. the identification of the aircraft;
3. the nature of the distress condition;
4. intention of the person in command;
5. present position, level (i.e., flight level, altitude, etc., as appropriate) and heading.

(Annex 10, Vol II, 5.3.2.1.1)
NOTE:

a. The foregoing provisions may be supplemented by the following measures;

1. the distress message of an aircraft in distress being made on the emergency frequency

121.5 MHz or another aeronautical mobile frequency, if considered necessary or desira-
ble. Not all aeronautical stations maintain a continuous guard on the emergency fre-
quency;

2. the distress message of an aircraft in distress being broadcast, if time and circumstan-

ces make this course preferable;

3. the aircraft transmitting on the maritime mobile service radiotelephony calling frequen-

cies;

4. the aircraft using any means at its disposal to attract attention and make known its con-

ditions (including the activation of the appropriate SSR mode and code);

5. any station taking any means at its disposal to assist an aircraft in distress;
6. any variation on the elements listed under b. above, when the transmitting station is not

itself in distress, provided that such circumstance is clearly stated in the distress mes-
sage.

b. The station addressed will normally be that station communicating with the aircraft or in

whose area of responsibility the aircraft is operating.

Action by the Station Addressed or First Station Acknowledging the
Distress Message

5.2.2.1 The station addressed by aircraft in distress, or first station acknowledging the distress
message shall:

a. immediately acknowledge the distress message;
b. take control of the communications or specifically and clearly transfer that responsibility,

advising the aircraft if a transfer is made;

c. take immediate action to ensure that all necessary information is made available, as soon as

possible, to:

5.2.2

EMERGENCY DATA - INTERNATIONAL CIVIL

AVIATION AUTHORITY

1501

INTERNATIONAL CIVIL AVIATION ORGANIZATION (ICAO)

1. the ATS unit concerned;
2. the aircraft operating agency concerned, or its representative, in accordance with pre-

established arrangements;
NOTE: The requirement to inform the aircraft operating agency concerned does not
have priority over any other action which involves the safety of the flight in distress, or of
any other flight in the area, or which might affect the progress of expected flights in the
area.

d. warn other stations, as appropriate, in order to prevent the transfer of traffic to the frequency

of the distress communication.

(Annex 10, Vol II, 5.3.2.2.1)

Imposition of Silence

5.2.3.1 The station in distress, or the station in control of distress traffic, shall be permitted to
impose silence, either on all stations of the mobile service in the area or on any station which
interferes with the distress traffic. It shall address these instructions “to all stations”, or to one sta-
tion only, according to circumstances. In either case, it shall use:

–

STOP TRANSMITTING;

– the radiotelephony distress signal

MAYDAY.

(Annex 10, Vol II, 5.3.2.3.1)
5.2.3.2 The use of the signals specified in 5.2.3.1shall be reserved for the aircraft in distress and
for the station controlling the distress traffic. (Annex 10, Vol II, 5.3.2.3.2)

Action by All Other Stations

5.2.4.1 The distress communications have absolute priority over all other communications, and
a station aware of them shall not transmit on the frequency concerned, unless:

a. the distress is cancelled or the distress traffic is terminated;
b. all distress traffic has been transferred to other frequencies;

c. the station controlling communications gives permission;

d. it has itself to render assistance.

(Annex 10, Vol II, 5.3.2.4.1)
5.2.4.2 Any station which has knowledge of distress traffic, and which cannot itself assist the
station in distress, shall nevertheless continue listening to such traffic until it is evident that assis-
tance is being provided. (Annex 10, Vol II, 5.3.2.4.2)

Termination of Distress Communications and of Silence

5.2.5.1 When an aircraft is no longer in distress, it shall transmit a message cancelling the dis-
tress condition. (Annex 10, Vol II, 5.3.2.5.1)

5.2.3

5.2.4

5.2.5

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5.2.5.2 When the station which has controlled the distress communication traffic becomes
aware that the distress condition is ended, it shall take immediate action to ensure that this infor-
mation is made available, as soon as possible, to:

a. the ATS unit concerned;
b. the aircraft operating agency concerned, or its representative, in accordance with pre-estab-

lished arrangements.

(Annex 10, Vol II, 5.3.2.5.2)
5.2.5.3 The distress communication and silence conditions shall be terminated by transmitting a
message, including the words “

DISTRESS TRAFFIC ENDED”, on the frequency or frequencies

being used for the distress traffic. This message shall be originated only by the station controlling
the communications when, after the reception of the message prescribed in 5.2.5.1 , it is author-
ized to do so by the appropriate authority. (Annex 10, Vol II, 5.3.2.5.3)

RADIOTELEPHONY URGENCY COMMUNICATIONS

Action by the Aircraft Reporting an Urgency Condition (except Medical
Transports)

5.3.1.1 In addition to being preceded by the radiotelephony urgency signal PAN PAN, preferably
spoken three times and each word of the group pronounced as the French word “panne”, the
urgency message to be sent by an aircraft reporting an urgency condition shall:

a. be on the air-ground frequency in use at the time;
b. consist of as many as required of the following elements spoken distinctly and, if possible, in

the following order:

1. the name of the station addressed;
2. the identification of the aircraft;
3. the nature of the urgency condition;
4. the intention of the person in command;
5. present position, level (i.e., flight level, altitude, etc., as appropriate) and heading;
6. any other useful information.

(Annex 10, Vol II, 5.3.3.1.1)
NOTE:

a. The foregoing provisions are not intended to prevent an aircraft broadcasting an urgency

message, if time and circumstances make this course preferable.

b. The station addressed will normally be that station communicating with the aircraft or in

whose area of responsibility the aircraft is operating.

5.3

5.3.1

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Action by the Station Addressed or First Station Acknowledging the
Urgency Message

5.3.2.1 The station addressed by an aircraft reporting an urgency condition, or first station
acknowledging the urgency message, shall:

a. acknowledge the urgency message;
b. take immediate action to ensure that all necessary information is made available, as soon as

possible, to:

1. the ATS unit concerned;
2. the aircraft operating agency concerned, or its representative, in accordance with pre-

c. if necessary, exercise control of communications.

(Annex 10, Vol II, 5.3.3.2.1)

Action by Other Stations

5.3.3.1 The urgency communications have priority over all other communications, except dis-
tress, and all stations shall take care not to interfere with the transmission of urgency traffic.
(Annex 10, Vol II, 5.3.3.3.1)

Action by an Aircraft Used for Medical Transports

5.3.4.1 The use of the signal described in 5.3.4.2, shall indicate that the message which follows
concerns a protected medical transport pursuant to the 1949 Geneva Conventions and Additional
Protocols. (Annex 10, Vol II, 5.3.3.4.1)
5.3.4.2 For the purpose of announcing and identifying aircraft used for medical transports, a
transmission of the radiotelephony urgency signal

PAN PAN, preferably spoken three times, and

each word of the group pronounced as the French word “panne”, shall be followed by the radiotel-
ephony signal for medical transports

MAY-DEE-CAL, pronounced as in the French “medical”. The

use of the signals described above indicates that the message which follows concerns a protec-
ted medical transport. The message shall convey the following data:

a. the call sign or other recognized means of identification of the medical transports;
b. position of the medical transports;

c. number and type of medical transports;

d. intended route;
e. estimated time enroute and of departure and arrival, as appropriate; and

5.3.2

5.3.3

5.3.4

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JEPPESEN GENERAL AIRWAY MANUAL (Issue Date 1 JUL 21) - page 47