AC 90-117

editorial update

Advisory circular · Data Link Communications

Approved
September 12, 2018
Last reviewed
July 29, 2024
This change
Editorial Update to AC 90-117 (9/12/18).
Cancels
AC120-70C
Family
AC 90-117 · 2 versions
14 CFR parts
91, 121, 125, 129, 135

Guidance, not mandatory unless a rule or AD requires it. DRS record last changed November 22, 2025.

Show pages 121–132
Page 133Open in PDF

Appendix F Table F-19. Emergency/Urgency Uplink Messages (EMGU) Operational Definition in PANS-ATM (Doc 4444) CPDLC Message Sets Message Element Identifier Message Element Intended Use Format for Message Element Display Resp. FANS 1/A ATN B1 EMGU-1 Request to provide the fuel remaining (time) and the number of persons on board.

REPORT ENDURANCE

AND PERSONS ON BOARD Y UM131 REPORT

REMAINING FUEL

AND SOULS ON BOARD Note: NE response attribute.

N/A EMGU-2 Instruction to immediately comply with the associated instruction to avoid imminent situation.

IMMEDIATELY N Used in combination with LVLU-6 and LVLU-9, which is implemented in FANS 1/A as:

UM38

IMMEDIATELY CLIMB TO (altitude) UM39

IMMEDIATELY

DESCEND TO (altitude) N/A EMGU-3 Request to confirm an ADS- C indicated emergency.

CONFIRM ADS-C

EMERGENCY A/N UM169 ‘CONFIRM ADS-C EMERGENCY’ Note: R response attribute.

N/A F-44

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Appendix F Table F-20. Emergency/Urgency Downlink Messages (EMGD) Operational Definition in PANS-ATM (Doc 4444) CPDLC Message Sets Message Element Identifier Message Element Intended Use Format for Message Element Display Resp. FANS 1/A ATN B1 EMGD-1 Indication of an urgent situation. PAN PAN PAN Y DM55 PAN PAN PAN Note: N response attribute.

N/A EMGD-2 Indication of an emergency situation.

MAYDAY MAYDAY MAYDAY Y DM56 MAYDAY

MAYDAY MAYDAY Note: N response attribute.

N/A EMGD-3 Report indicating fuel remaining (time) and number of persons on board.

(remaining fuel) ENDURANCE AND (persons on board) PERSONS ON BOARD Y DM57 (remaining fuel)

OF FUEL REMAINING AND (remaining souls)

SOULS ON BOARD Note: N response attribute.

N/A EMGD-4 Indication that the emergency situation is cancelled.

CANCEL EMERGENCY Y DM58 CANCEL

EMERGENCY Note: N response attribute.

N/A F-45

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Appendix F Table F-21. Standard Response Uplink Messages (RSPU) Operational Definition in PANS-ATM (Doc 4444) CPDLC Message Sets Message Element Identifier Message Element Intended Use Format for Message Element Display Resp. FANS 1/A ATN B1 RSPU-1 Indication that the message cannot be complied with.

UNABLE N UM0 UNABLE UM0 UNABLE RSPU-2 Indication that the message will be responded to shortly.

STANDBY N UM1 STANDBY UM1 STANDBY RSPU-3 Indication that a long term delay in response can be expected.

REQUEST DEFERRED N UM2 REQUEST

DEFERRED N/A RSPU-4 Indication that the message is received.

ROGER N UM3 ROGER UM169 ‘ROGER MAYDAY’ Note 1: R response attribute.

Note 2: Used to acknowledge emergency downlink reports.

UM169 ‘ROGER PAN’ Note 1: R response attribute.

Note 2: Used to acknowledge urgency downlink reports.

UM3 ROGER RSPU-5 Indication that ATC is responding positively to the message.

AFFIRM N UM4 AFFIRM UM4 AFFIRM RSPU-6 Indication that ATC is responding negatively to the message.

NEGATIVE N UM5 NEGATIVE UM5 NEGATIVE F-46

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Appendix F Operational Definition in PANS-ATM (Doc 4444) CPDLC Message Sets Message Element Identifier Message Element Intended Use Format for Message Element Display Resp. FANS 1/A ATN B1 RSPU-7 Indication that the request has been forwarded to the next control unit.

REQUEST FORWARDED N UM169 ‘REQUEST FORWARDED’ Note: R response attribute.

UM211 REQUEST

FORWARDED RSPU-8 Request to confirm the referenced request since the initial request was not understood. The request should be clarified and resubmitted.

CONFIRM REQUEST N UM143 CONFIRM

REQUEST N/A Table F-22. Standard Response Downlink Messages (RSPD) Operational Definition in PANS-ATM (Doc 4444) CPDLC Message Sets Message Element Identifier Message Element Intended Use Format for Message Element Display Resp. FANS 1/A ATN B1 RSPD-1 Indication that the instruction is understood and will be complied with.

WILCO N DM0 WILCO DM0 WILCO RSPD-2 Indication that the instruction cannot be complied with.

UNABLE N DM1 UNABLE DM1 UNABLE RSPD-3 Indication that the message will be responded to shortly.

STANDBY N DM2 STANDBY DM2 STANDBY RSPD-4 Indication that the message is received.

ROGER N DM3 ROGER Note: ROGER is the only correct response to an uplink free text message.

DM3 ROGER RSPD-5 Indication of a positive response to a message.

AFFIRM N DM4 AFFIRM DM4 AFFIRM RSPD-6 Indication of a negative response to a message.

NEGATIVE N DM5 NEGATIVE DM5 NEGATIVE F-47

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Appendix F Table F-23. Supplemental Uplink Messages (SUPU) Operational Definition in PANS-ATM (Doc 4444) CPDLC Message Sets Message Element Identifier Message Element Intended Use Format for Message Element Display Resp. FANS 1/A ATN B1 SUPU-1 Indication that the associated instruction is to be executed when the pilot is ready.

WHEN READY N UM164 WHEN READY N/A SUPU-2 Indication that the associated message is issued due to the specified reason.

DUE TO (specified reason uplink) N UM166 DUE TO

TRAFFIC UM167 DUE TO

AIRSPACE

RESTRICTION N/A SUPU-3 Instruction to execute the associated instruction at the aircraft’s best performance rate.

EXPEDITE N Used in combination with LVLU-6, which is implemented in FANS 1/A as:

UM36 EXPEDITE CLIMB TO (altitude).

N/A SUPU-4 Indication that the associated instruction is either a revision to a previously issued instruction or is different from the requested clearance.

REVISED (revision reason[O]) N UM170 ‘REVISED (revision reason[O])’ Note: R response attribute.

N/A SUPU-5 Indication that the associated instruction is to be executed at the earliest point when the pilot is able.

WHEN ABLE N N/A Note: This message element is part of UM75.

N/A F-48

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Appendix F Table F-24. Supplemental Downlink Messages (SUPD) Operational Definition in PANS-ATM (Doc 4444) CPDLC Message Sets Message Element Identifier Message Element Intended Use Format for Message Element Display Resp. FANS 1/A ATN B1 SUPD-1 Indication that the associated message is issued due to specified reason.

DUE TO (specified reason downlink) N DM65 DUE TO

WEATHER DM65 DUE TO

WEATHER SUPD-1 Indication that the associated message is issued due to specified reason.

DUE TO (specified reason downlink) N DM66 DUE TO

AIRCRAFT

PERFORMANCE DM66 DUE TO

AIRCRAFT

PERFORMANCE Table F-25. Free Text Uplink Messages (TXTU) Operational Definition in PANS-ATM (Doc 4444) CPDLC Message Sets Message Element Identifier Message Element Intended Use Format for Message Element Display Resp. FANS 1/A ATN B1 TXTU-1 (free text) Note: M alert attribute.

R UM169 (free text) UM203 (free text) TXTU-2 (free text) Note: M alert attribute.

N UM169 (free text) Note: R response attribute.

UM183 (free text) TXTU-3 (free text) Note: N alert attribute.

N UM169 (free text) Note: R response attribute.

N/A TXTU-4 (free text) Note: M alert attribute.

W/U UM169 (free text) Note: R response attribute.

UM196 (free text) TXTU-5 (free text) Note: M alert attribute.

A/N UM169 (free text) Note: R response attribute.

UM205 (free text) F-49

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Appendix F Table F-26. Free Text Downlink Messages (TXTD) Operational Definition in PANS-ATM (Doc 4444) CPDLC Message Sets Message Element Identifier Message Element Intended Use Format for Message Element Display Resp. FANS 1/A ATN B1 TXTD-1 (free text) Note: M alert attribute.

Y DM68 (free text) Note 1: Urgency or Distress Alr (M).

Note 2: Selecting any of the emergency message elements will result in this message element being enabled for the pilot to include in the emergency message at their discretion.

N/A TXTD-2 (free text) Note: M alert attribute.

N DM67 (free text) DM98 (free text) F-50

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Appendix F Table F-27. System Management Uplink Messages (SYSU) Operational Definition in PANS-ATM (Doc 4444) CPDLC Message Sets Message Element Identifier Message Element Intended Use Format for Message Element Display Resp. FANS 1/A ATN B1 SYSU-1 System-generated notification of an error.

ERROR (error information) N UM159 ERROR (error information) UM159 ERROR (error information) SYSU-2 System-generated notification of the next data authority or the cancellation thereof.

NEXT DATA AUTHORITY (facility designation[O]) N UM160 NEXT

DATA AUTHORITY (ICAO facility designation) Note: The facility designation is required.

UM160 NEXT DATA

AUTHORITY (facility) Note: Facility parameter can specify a facility designation or no facility.

SYSU-3 System-generated notification that received message is not supported.

MESSAGE NOT

SUPPORTED BY THIS ATC UNIT N UM169 ‘MESSAGE

NOT SUPPORTED

BY THIS ATC UNIT’ Note: R response attribute.

UM162 MESSAGE NOT

SUPPORTED BY THIS

ATS UNIT SYSU-4 System-generated notification that the received is acceptable for display.

LOGICAL

ACKNOWLEDGEMENT N N/A UM227 LOGICAL

ACKNOWLEDGEMENT SYSU-5 System-generated message indicating that requests for logical acknowledgements are not permitted.

USE OF LOGICAL

ACKNOWLEDGEMENT

PROHIBITED N N/A UM233 USE OF LOGICAL

ACKNOWLEDGEMENT

PROHIBITED Note: ATN B1 ground systems may not use UM (as par ETSI CS) since the use of LACK is required.

F-51

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Appendix F Operational Definition in PANS-ATM (Doc 4444) CPDLC Message Sets Message Element Identifier Message Element Intended Use Format for Message Element Display Resp. FANS 1/A ATN B1 SYSU-6 Advisory providing the maximum one-way uplink message transmission delay.

LATENCY TIME VALUE (latency value) N UM169 ‘SET MAX

UPLINK DELAY VALUE TO (delayed message parameter) SECONDS’ Note 1: R response attribute.

Note 2: On FANS 1/A aircraft, this message requires specific action from the pilot to manually set the latency value.

N/A SYSU-7 Indication that the received message has a latency greater than the requirement.

MESSAGE RECEIVED TOO

LATE, RESEND MESSAGE

OR CONTACT BY VOICE N N/A UM159 ERROR (error information) + UM183 ‘DOWNLINK DELAYED USE – VOICE’ Note: The error information is set to the value (2).

F-52

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Appendix F Table F-28. System Management Downlink Messages (SYSD) Operational Definition in PANS-ATM (Doc 4444) CPDLC Message Sets Message Element Identifier Message Element Intended Use Format for Message Element Display Resp. FANS 1/A ATN B1 SYSD-1 System-generated notification of an error.

ERROR (error information) N DM62 ERROR (error information) DM62 ERROR (error information) SYSD-2 System-generated notification that the received message is acceptable for display.

LOGICAL

ACKNOWLEDGEMENT N N/A DM100 LOGICAL

ACKNOWLEDGEMENT SYSD-3 System-generated rejection of any CPDLC message sent from a ground facility that is not the current data authority.

NOT CURRENT DATA

AUTHORITY N DM63 NOT CURRENT

DATA AUTHORITY DM63 NOT CURRENT

DATA AUTHORITY SYSD-4 System-generated notification that the ground facility is now the current data authority.

CURRENT DATA

AUTHORITY N N/A DM99 CURRENT DATA

AUTHORITY SYSD-5 System-generated notification that the ground system is not designated as the next data authority (NDA), indicating the identity of the Current Data Authority. Identity of the Next Data Authority, if any, is also reported.

NOT AUTHORIZED NEXT

DATA AUTHORITY (facility designation) (facility designation[O]) N DM64 (ICAO facility designation) Note: Use by FANS 1/A aircraft in B1 environments.

DM107 NOT AUTHORIZED

NEXT DATA AUTHORITY Note: CDA and NDA cannot be provided.

SYSD-6 Indication that the received message has a latency greater than the requirement.

MESSAGE RECEIVED TOO

LATE, RESEND MESSAGE

OR CONTACT BY VOICE N DM67 ‘MESSAGE

RECEIVED TOO

LATE, RESEND

MESSAGE OR

CONTACT BY VOICE’ Note: Sent with DM62.

DM 98 ‘MESSAGE

RECEIVED TOO LATE,

RESEND MESSAGE OR CONTACT BY VOICE’ Note: Sent with DM62.

SYSD-7 System-generated notification that the aircraft is in the inhibited state.

AIRCRAFT CPDLC

INHIBITED N N/A DM 98 ‘AIRCRAFT CPDLC

INHIBITED' F-53

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Appendix F Table F-29. FANS 1/A Uplink Messages Not Recommended for Use 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 restriction.

UM62 AT (time) CROSS (position) AT AND MAINTAIN (altitude) Avoid use of this message due to inability of aircraft automation to maintain the altitude restriction.

UM85 EXPECT (route clearance) Avoid use of this message element due to potential misinterpretation.

UM86 AT (position) EXPECT (route clearance) Avoid use of this message element due to potential misinterpretation.

UM87 EXPECT DIRECT TO (position) Avoid use of this message element due to potential misinterpretation.

UM88 AT (position) EXPECT DIRECT TO (position) Avoid use of this message element due to potential misinterpretation.

UM89 AT (time) EXPECT DIRECT TO (position) Avoid use of this message element due to potential misinterpretation.

UM90 AT (altitude) EXPECT DIRECT TO (position) Avoid use of this message element due to potential misinterpretation.

UM162 SERVICE UNAVAILABLE Avoid use of this message element due to potential misinterpretation.

UM6 EXPECT (altitude) Avoid use of this message element due to potential misinterpretation.

UM11 EXPECT CRUISE CLIMB AT (time) Avoid use of this message element due to potential misinterpretation.

UM12 EXPECT CRUISE CLIMB AT (position) Avoid use of this message element due to potential misinterpretation.

UM13 AT (time) EXPECT CLIMB TO (altitude) Avoid use of this message element due to potential misinterpretation.

UM14 AT (position) EXPECT CLIMB TO (altitude) Avoid use of this message element due to potential misinterpretation.

UM15 AT (time) EXPECT DESCENT TO (altitude) Avoid use of this message element due to potential misinterpretation.

UM16 AT (position) EXPECT DESCENT TO (altitude) Avoid use of this message element due to potential misinterpretation.

UM17 AT (time) EXPECT CRUISE CLIMB TO (altitude) Avoid use of this message element due to potential misinterpretation.

UM49 CROSS (position) AT AND MAINTAIN (altitude) Avoid use of this message element due to potential misinterpretation.

UM62 AT (time) CROSS (position) AT AND MAINTAIN (altitude) Avoid use of this message element due to potential misinterpretation.

UM18 AT (position) EXPECT CRUISE CLIMB TO (altitude) Avoid use of this message element due to potential misinterpretation.

UM33 CRUISE (altitude) Avoid use of this message element due to potential misinterpretation.

UM34 CRUISE CLIMB TO (altitude) Avoid use of this message element due to potential misinterpretation.

F-54

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Appendix F Message Element Justification UM35 CRUISE CLIMB ABOVE (altitude) Avoid use of this message element due to potential misinterpretation.

UM40 IMMEDIATELY STOP CLIMB AT (altitude) Avoid use of this message element due to potential misinterpretation.

UM41 IMMEDIATELY STOP DESCENT AT (altitude) Avoid use of this message element due to potential misinterpretation.

UM175 REPORT REACHING (altitude) Avoid use of this message element due to potential misinterpretation.

UM42 EXPECT TO CROSS (position) AT (altitude) Avoid use of this message element due to potential misinterpretation.

UM43 EXPECT TO CROSS (position) AT OR ABOVE (altitude) Avoid use of this message element due to potential misinterpretation.

UM44 EXPECT TO CROSS (position) AT OR BELOW (altitude) Avoid use of this message element due to potential misinterpretation.

UM45 EXPECT TO CROSS (position) AT AND MAINTAIN (altitude) Avoid use of this message element due to potential misinterpretation.

UM103 AT (time) EXPECT (speed) TO (speed) Avoid use of this message element due to potential misinterpretation.

UM104 AT (position) EXPECT (speed) TO (speed) Avoid use of this message element due to potential misinterpretation.

UM105 AT (altitude) EXPECT (speed) TO (speed) Avoid use of this message element due to potential misinterpretation.

UM165 THEN Avoid use of this message element due to potential misinterpretation.

UM235 ROGER 7500 Avoid use of this message element due to potential misinterpretation.

UM168 DISREGARD Not operationally required.

Note: These messages have been excluded from future B2 implementation.

UM176 MAINTAIN OWN SEPARATION AND VMC Not operationally required.

Note: These messages have been excluded from future B2 implementation.

UM152 WHEN CAN YOU ACCEPT (specified distance) (direction) OFFSET Not operationally required.

Note: These messages have been excluded from future B2 implementation.

UM115 DO NOT EXCEED (speed) Not operationally required.

Note: These messages have been excluded from future B2 implementation.

UM182 CONFIRM ATIS CODE Not operationally required.

Note: These messages have been excluded from future B2 implementation.

UM169 ‘TRANSMIT ADS-B IDENT’ Use of SQUAWK IDENT is recommended.

UM169 ‘IDENTIFICATION TERMINATED’ Use of SURVEILLANCE SERVICE TERMINATED is recommended.

UM132 CONFIRM POSITION Use of ADS-C is recommended.

UM133 CONFIRM ALTITUDE Use of ADS-C is recommended.

F-55