Aeronautical Information Manual

AIM 5-3-1

ARTCC Communications

This reproduces published FAA reference text for study. It does not replace the current official FAA publication or regulation.

Direct Communications, Controllers and Pilots. ARTCCs are capable of direct communications with IFR air traffic on certain frequencies. Maximum communications coverage is possible through the use of Remote Center Air/Ground (RCAG) sites comprised of both VHF and UHF transmitters and receivers. These sites are located throughout the U.S. Although they may be several hundred miles away from the ARTCC, they are remoted to the various ARTCCs by land lines or microwave links. Since IFR operations are expedited through the use of direct communications, pilots are requested to use these frequencies strictly for communications pertinent to the control of IFR aircraft. Flight plan filing, en route weather, weather forecasts, and similar data should be requested through FSSs, company radio, or appropriate military facilities capable of performing these services.

An ARTCC is divided into sectors. Each sector is handled by one or a team of controllers and has its own sector discrete frequency. As a flight progresses from one sector to another, the pilot is requested to change to the appropriate sector discrete frequency.

Controller Pilot Data Link Communications (CPDLC) is a system that supplements air/ground voice communications. The CPDLC's principal operating criteria are: Voice remains the primary and controlling air/ground communications means.

Participating aircraft will need to have the appropriate CPDLC avionics equipment in order to receive uplink or transmit downlink messages.

En Route CPDLC offers many services including the following: Altimeter Setting (AS), Transfer of Communications (TOC), Initial Contact (IC), route assignments, including airborne reroutes (ABRR), altitude assignments, speed assignments, crossing constraints, holding, and advisory and emergency messages. Altimeter settings will be uplinked automatically when appropriate after a Monitor TOC. Altimeter settings will also be uplinked automatically when an aircraft receives an uplinked altitude assignment below FL 180. A controller may also manually send an altimeter setting message. NOTE-

When conducting instrument approach procedures, pilots are responsible to obtain and use the appropriate altimeter setting in accordance with 14 CFR section 97.20. CPDLC issued altimeter settings are excluded for this purpose.

Initial contact is a safety validation transaction that compares a pilot's initiated altitude downlink message with an aircraft's stored altitude in the ATC automation system. When an IC mismatch or Confirm Assigned Altitude (CAA) downlink time-out indicator is displayed in the Full Data Block (FDB) and Aircraft List (ACL), the controller who has track control of the aircraft must use voice communication to verify the assigned altitude of the aircraft, and acknowledge the IC mismatch/time-out indicator.

Transfer of communications automatically establishes data link contact with a succeeding sector.

Menu text transmissions are scripted nontrajectory altering uplink messages.

The CPDLC Message Elements used in domestic en route operations are contained in TBL 5-3-1 through TBL 5-3-23, CPDLC Message Elements.

For CPDLC Message Elements used in FAA oceanic control areas (KZWY, KZAK, and PAZA), please refer to the U.S. AIP, ENR 7.2. NOTE-

The FAA is not implementing ATN B1.

TBL 5-3-1 Response Attribute of CPDLC Message Element Response

Attribute

Description

For Uplink Message

W/U

Response required.

Valid responses. WILCO, UNABLE, STANDBY, NOT CURRENT DATA AUTHORITY, NOT AUTHORIZED NEXT DATA AUTHORITY, LOGICAL ACKNOWLEDGEMENT (only if required), ERROR

Note – WILCO, UNABLE, NOT CURRENT DATA AUTHORITY, NOT AUTHORIZED NEXT DATA AUTHORITY and ERROR will close the uplink message. FANS 1/A.– WILCO, UNABLE, STANDBY, ERROR, NOT CURRENT DATA AUTHORITY.

A/N

Response required.

Valid responses. AFFIRM, NEGATIVE, STANDBY, NOT CURRENT DATA AUTHORITY, NOT AUTHORIZED NEXT DATA AUTHORITY, LOGICAL ACKNOWLEDGEMENT (only if required), ERROR

Note – AFFIRM, NEGATIVE, NOT CURRENT DATA AUTHORITY, NOT AUTHORIZED NEXT DATA AUTHORITY and ERROR will close the uplink message. FANS 1/A.– AFFIRM, NEGATIVE, STANDBY, ERROR, NOT CURRENT DATA AUTHORITY.

Response required.

Valid responses. ROGER, UNABLE, STANDBY, NOT CURRENT DATA AUTHORITY, NOT AUTHORIZED NEXT DATA AUTHORITY, LOGICAL ACKNOWLEDGEMENT (only if required), ERROR

Note – ROGER, NOT CURRENT DATA AUTHORITY, NOT AUTHORIZED NEXT DATA AUTHORITY and ERROR will close the uplink message.

FANS 1/A.– ROGER, STANDBY, ERROR, NOT CURRENT DATA AUTHORITY. FANS 1/A aircraft do not have the capability to send UNABLE in response to an uplink message containing message elements with an “R” response attribute. For these aircraft, the flight crew may use alternative means to UNABLE the message. These alternative means will need to be taken into consideration to ensure proper technical and operational closure of the communication transaction.

Response required.

Valid responses: Any CPDLC downlink message, LOGICAL ACKNOWLEDGEMENT (only if required).

No response required unless logical acknowledgement is required.

Valid Responses (only if LOGICAL ACKNOWLEDGEMENT is required). LOGICAL ACKNOWLEDGEMENT, NOT CURRENT DATA AUTHORITY, NOT AUTHORIZED NEXT DATA AUTHORITY, ERROR

FANS 1/A.– “N” is defined as “no response is required,” but not used. Under some circumstances, an ERROR message will also close an uplink message.

[Not defined in Doc 4444]

FANS 1/A.– The WILCO, UNABLE, AFFIRM, NEGATIVE, ROGER, and STANDBY responses are not enabled (NE) for flight crew selection. An uplink message with a response attribute NE is considered to be closed even though a response may be required operationally. Under some circumstances, a downlink error message may be linked to an uplink message with a NE attribute.

For Downlink Message

Response required. Yes

Valid responses. Any CPDLC uplink message, LOGICAL ACKNOWLEDGEMENT (only if required).

Response required. No, unless logical acknowledgement required.

Valid responses (only if LOGICAL ACKNOWLEDGEMENT is required). LOGICAL ACKNOWLEDGEMENT, SERVICE UNAVAILABLE, FLIGHT PLAN NOT HELD, ERROR

FANS 1/A.– Aircraft do not have the capability to receive technical responses to downlink message elements with an “N” response attribute (other than LACK or ERROR for ATN B1 aircraft). In some cases, the response attribute is different between FANS 1/A aircraft and Doc 4444. As an example, most emergency messages have an “N” response attribute for FANS 1/A whereas Doc 4444 defines a “Y” response attribute for them. As a consequence, for FANS 1/A aircraft, ATC will need to use alternative means to acknowledge to the flight crew that an emergency message has been received.

TBL 5-3-1 Route Uplink Message Elements (RTEU) CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

position

W/U

RTEU-2

Instruction to proceed directly to the specified position.

position

UM75 WHEN ABLE PROCEED DIRECT TO ( position )

Note – This message element is equivalent to SUPU-5 plus RTEU-2 in Doc 4444.

W/U

RTEU-2

Instruction to proceed, when able, directly to the specified position.

(position)

UM77 AT ( position ) PROCEED DIRECT TO ( position )

W/U

RTEU-4

Instruction to proceed, at the specified at position, directly to the next specified position.

AT (position) PROCEED DIRECT TO (position)

UM78 AT ( altitude ) PROCEED DIRECT TO ( position )

W/U

RTEU-5

Instruction to proceed, upon reaching the specified level, directly to the specified position.

AT (level) PROCEED DIRECT TO (position)

UM79 CLEARED TO ( position ) via ( route clearance )

W/U

RTEU-6

Instruction to proceed to the specified position via the specified route.

CLEARED TO (position) VIA (departure data[O]) (en-route data)

(route clearance)

W/U

RTEU-7

Instruction to proceed via the specified route.

CLEARED (departure data[O]) (en-route data) (arrival approach data)

UM83 AT (position) CLEARED (route clearance)

W/U

RTEU-9

Instruction to proceed from the specified position via the specified route.

AT (position) CLEARED (en-route data) (arrival approach data)

UM91 HOLD AT (position) MAINTAIN (altitude) INBOUND TRACK (degrees) (direction) TURN LEG TIME (leg type)

W/U

RTEU-11

Instruction to enter a holding pattern at the specified position in accordance with the specified instructions.

Note– RTEU-13 EXPECT FURTHER CLEARANCE AT TIME (time) is appended to this message when an extended hold is anticipated.

AT (position) HOLD INBOUND TRACK (degrees)(direction) TURNS (leg type) LEGS

UM92 HOLD AT (position) AS PUBLISHED MAINTAIN (altitude)

W/U

RTEU-12

Instruction to enter a holding pattern at the specified position in accordance with the published holding instructions.

Note – RTEU-13 EXPECT FURTHER CLEARANCE AT TIME (time) is appended to this message when an extended hold is anticipated.

(position)

(time)

W/U

RTEU-13

Notification that an onwards clearance may be issued at the specified time

(time)

UM137 CONFIRM ASSIGNED ROUTE

Note – NE response attribute.

W/U

RTEU-15

Request to confirm the assigned route.

CONFIRM ASSIGNED ROUTE

TBL 5-3-1 Route Downlink Message Elements (RTED) CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

position

RTED-1

Request for a direct clearance to the specified position.

position

DM23 REQUEST (procedure name)

RTED-2

Request for the specified procedure or clearance name

REQUEST (named instruction)

DM24 REQUEST (route clearance)

RTED-3

Request for the specified route.

REQUEST CLEARANCE (departure data[O]) (en-route data) (arrival approach data[O])

DM40 ASSIGNED ROUTE (route clearance)

RTED-9

Confirmation that the assigned route is the specified route.

ASSIGNED ROUTE (departure data[O]) (en-route data) (arrival approach data[O])

TBL 5-3-1 Lateral Uplink Message Elements (LATU) FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

UM82 CLEARED TO DEVIATE UP TO (distance offset) (direction) OF ROUTE

W/U

LATU-10

Instruction allowing deviation up to the specified distance(s) from the cleared route in the specified direction(s).

CLEARED TO DEVIATE UP TO (lateral deviation) OF ROUTE

UM127 REPORT BACK ON ROUTE

Note – R response attribute.

W/U

LATU-18

Instruction to report when the aircraft is back on the cleared route.

REPORT BACK ON ROUTE

TBL 5-3-1 Lateral Downlink Message Elements (LATD) CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

DM27 REQUEST WEATHER DEVIATION UP TO (specified distance) (direction) OF ROUTE

LATD-2

Request for a weather deviation up to the specified distance off track in the specified direction.

(specified distance) (direction)

DM41 BACK ON ROUTE

LATD-4

The aircraft has regained the cleared route.

BACK ON ROUTE

DM59 DIVERTING TO (position) VIA (route clearance)

Note 1. - H alert attribute

Note 2. - N

response attribute

See Note

LATD-5

Report indicating diverting to the specified position via the specified route, which may be sent without any previous coordination done with ATC.

DIVERTING TO (position) VIA (en-route data) (arrival approach data[O])

DM60

OFFSETTING (distance offset) (direction) OF ROUTE

Note 1. - H alert attribute

Note 2. - N

response attribute

See Note

LATD-6

Report indicating that the aircraft is offsetting to a parallel track at the specified distance in the specified direction off from the cleared route.

OFFSETTING (specified distance) (direction) OF ROUTE

DM80 DEVIATING (deviation offset) (direction) OF ROUTE

Note 1. - H alert attribute

Note 2. - N response attribute

See Note

LATD-7

Report indicating deviating specified distance or degrees in the specified direction from the cleared route.

DEVIATING (specified Deviation) (direction) OF ROUTE

NOTE-

ICAO Document 10037, Global Operational Data Link (GOLD) Manual, has these values set to Y in their table.

TBL 5-3-1 Level Uplink Message Elements (LVLU) CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

(altitude)

Note - Used for a single level

W/U

LVLU-5

Instruction to maintain the specified level or vertical range.

(level)

(altitude)

Note - Used for a single level

W/U

LVLU-6

Instruction that a climb to the specified level or vertical range is to commence and once reached is to be maintained.

level

(altitude)

Note - Used for a single level

W/U

LVLU-9

Instruction that a descent to the specified level or vertical range is to commence and once reached is to be maintained.

level

UM30 MAINTAIN BLOCK (altitude) TO (altitude)

Note – Used for a vertical range

W/U

LVLU-5

Instruction to maintain the specified level or vertical range.

(level)

UM31 CLIMB TO AND MAINTAIN BLOCK (altitude) TO (altitude)

Note – Used for a vertical range

W/U

LVLU-6

Instruction that a climb to the specified level or vertical range is to commence and once reached is to be maintained.

(level)

UM32 DESCEND TO AND MAINTAIN BLOCK (altitude) TO (altitude)

Note – Used for a vertical range

W/U

LVLU-9

Instruction that a descent to the specified level or vertical range is to commence and once reached is to be maintained.

(level)

(altitude)

Note - This message element is equivalent to SUPU-3 plus LVLU-6 in Doc 4444.

W/U

LVLU-6

Instruction that a climb to the specified level or vertical range is to commence and once reached is to be maintained.

level

(altitude)

Note – This message element is equivalent to SUPU-5 plus LVLU-9 in Doc 4444.

W/U

LVLU-9

Instruction that a descent to the specified level or vertical range is to commence and once reached is to be maintained.

level

(altitude)

Note - This message element is equivalent to EMGU-2 plus LVLU-6 in Doc 4444.

W/U

LVLU-6

Instruction that a climb to the specified level or vertical range is to commence and once reached is to be maintained.

level

(altitude)

Note - This message element is equivalent to EMGU-2 plus LVLU-9 in Doc 4444.

W/U

LVLU-9

Instruction that a descent to the specified level or vertical range is to commence and once reached is to be maintained.

level

UM135 CONFIRM ASSIGNED ALTITUDE

Note - NE response attribute

LVLU-27

Request to confirm the assigned level.

CONFIRM ASSIGNED LEVEL

UM177 AT PILOTS DISCRETION

See Note

An instruction used in conjunction with altitude assignments, means that ATC has offered the pilot the option of starting climb or descent whenever they wish and conducting the climb or descent at any rate they wish. The pilot may temporarily level off at any intermediate altitude. However, once the aircraft has vacated an altitude, it may not return to that altitude.

NOTE-

ICAO Document 10037, Global Operational Data Link (GOLD) Manual, does not include this in its tables.

TBL 5-3-1 Level Downlink Message Elements (LVLD) CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

(altitude)

Note - Used for a single level

LVLD-1

Request to fly at the specified level or vertical range.

(level)

DM7 REQUEST BLOCK (altitude) TO (altitude)

Note – Used for a vertical range.

LVLD-1

Request to fly at the specified level or vertical range.

level

(altitude)

LVLD-2

Request for a climb to the specified level or vertical range.

level

(altitude)

LVLD-3

Request for a descent to the specified level or vertical range.

level

(altitude)

Note - Used for a single level

LVLD-11

Confirmation that the assigned level or vertical range is the specified level or vertical range.

level

(altitude)

Note - urgent alert attribute

LVLD-14

Report indicating descending to the specified level.

level single

DM77 ASSIGNED BLOCK ( altitude ) TO ( altitude )

Note– Used for a vertical range

LVLD-11

Confirmation that the assigned level or vertical range is the specified level or vertical range.

(level)

TBL 5-3-1 Crossing Constraint Message Elements (CSTU) CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

UM46 CROSS ( position ) AT ( altitude )

Note – Used for a single level.

W/U

CSTU-1

Instruction that the specified position is to be crossed at the specified level or within the specified vertical range.

CROSS (position) AT (level)

UM49 CROSS ( position ) AT AND MAINTAIN ( altitude )

Note 1. - A vertical range cannot be provided.

Note 2. - This message element is equivalent to CSTU-1 plus LVLU-5 in Doc 4444.

W/U

CSTU-1

Instruction that the specified position is to be crossed at the specified level or within the specified vertical range.

CROSS (position) AT (level)

UM51 CROSS ( position ) AT (time)

W/U

CSTU-4

Instruction that the specified position is to be crossed at the specified time.

CROSS (position) AT TIME (time)

UM52 CROSS ( position ) AT OR BEFORE ( time )

W/U

CSTU-5

Instruction that the specified position is to be crossed before the specified time.

CROSS (position) BEFORE TIME (time)

UM53 CROSS ( position ) AT OR AFTER ( time )

W/U

CSTU-6

Instruction that the specified position is to be crossed after the specified time.

CROSS (position) AFTER TIME (time)

UM55 CROSS (position) AT (speed)

W/U

CSTU-8

Instruction that the specified position is to be crossed at the specified speed.

CROSS (position) AT (speed)

UM56 CROSS (position) AT OR LESS THAN (speed)

W/U

CSTU-9

Instruction that the specified position is to be crossed at or less than the specified speed.

CROSS (position) AT (speed) OR LESS

UM57 CROSS (position) AT OR GREATER THAN (speed)

W/U

CSTU-10

Instruction that the specified position is to be crossed at or greater than the specified speed.

CROSS (position) AT (speed) OR GREATER

UM61 CROSS (position) AT AND MAINTAIN (altitude) AT (speed)

Note 1. - A vertical range cannot be provided.

Note 2. - This message element is equivalent to CSTU-14 plus LVLU-5 in Doc 4444.

W/U

CSTU-14

Instruction that the specified position is to be crossed at the level or within the vertical range, as specified, and at the specified speed.

CROSS (position) AT (level) AT (speed)

TBL 5-3-1 Speed Uplink Message Elements (SPDU) CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

speed

W/U

SPDU-4

Instruction to maintain the specified speed.

(speed)

UM107 MAINTAIN PRESENT SPEED

W/U

SPDU-5

Instruction to maintain the specified speed.

MAINTAIN PRESENT SPEED

speed

W/U

SPDU-6

Instruction to maintain the specified speed or greater.

(speed)

speed

W/U

SPDU-7

Instruction to maintain the specified speed or less.

(speed)

UM116 RESUME NORMAL SPEED

W/U

SPDU-13

Instruction to resume a normal speed. The aircraft no longer needs to comply with a previously issued speed restriction.

RESUME NORMAL SPEED

UM134 CONFIRM SPEED

Note – NE response attribute.

SPDU-15

Request to report the speed defined by the speed type(s).

(speed types)

TBL 5-3-1 Speed Downlink Message Elements CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

speed

SPDD-3

Report indicating the speed defined by the specified speed types is the specified speed.

(speed types) SPEED (speed)

TBL 5-3-1 Air Traffic Advisory Uplink Message Elements CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

UM154 RADAR SERVICES TERMINATED

ADVU-2

Advisory that the ATS surveillance service is terminated.

SURVEILLANCE SERVICE TERMINATED

TBL 5-3-1 Voice Communications Uplink Message Elements (COMU) CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

UM117 CONTACT (ICAO unit name) (frequency)

W/U

COMU-1

Instruction to establish voice contact with the specified ATS unit on the specified frequency.

CONTACT (unit name) (frequency)

UM120 MONITOR (ICAO unit name) (frequency)

W/U

COMU-5

Instruction to monitor the specified ATS unit on the specified frequency. The flight crew is not required to establish voice contact on the frequency.

MONITOR (unit name) (frequency)

TBL 5-3-1 Voice Communications Downlink Message Elements (COMD) CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

DM20 REQUEST VOICE CONTACT

Note - Used when a frequency is not required.

COMD-1

Request for voice contact on the specified frequency.

(frequency)

TBL 5-3-1 Emergency/Urgency Uplink Message Elements (EMGU) CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

UM38 IMMEDIATELY CLIMB TO ( altitude )

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

EMGU-2

Instruction to immediately comply with the associated instruction to avoid imminent situation.

Immediately

UM39 IMMEDIATELY DESCEND TO ( altitude )

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

EMGU-2

Instruction to immediately comply with the associated instruction to avoid imminent situation.

Immediately

TBL 5-3-1 Emergency/Urgency Downlink Message Elements (EMGD) CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

Note - N response attribute

EMGD-1

Indication of an urgent situation.

PAN PAN PAN

Note - N response attribute

EMGD-2

Indication of an emergency situation.

MAYDAY

DM57 ( remaining fuel ) OF FUEL REMAINING AND ( remaining souls ) SOULS ON BOARD

Note - N response attribute

EMGD-3

Report indicating fuel remaining (time) and number of persons on board.

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

DM58 CANCEL EMERGENCY

Note - N response attribute

EMGD-4

Indication that the emergency situation is canceled.

CANCEL EMERGENCY

TBL 5-3-1 Standard Response Uplink Message Elements (RSPU) CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

UM0 UNABLE

RSPU-1

Indication that the message cannot be complied with.

UNABLE

UM1 STANDBY

RSPU-2

Indication that the message will be responded to shortly.

STANDBY

UM3 ROGER

RSPU-4

Indication that the message is received.

ROGER

TBL 5-3-1 Standard Response Downlink Message Elements (RSPD) CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

DM0 WILCO

RSPD-1

Indication that the instruction is understood and will be complied with.

WILCO

DM1 UNABLE

RSPD-2

Indication that the message cannot be complied with.

UNABLE

DM2 STANDBY

RSPD-3

Indication that the message will be responded to shortly.

STANDBY

DM3 ROGER

Note - ROGER is the only correct response to an uplink free text message.

RSPD-4

Indication that the message is received.

ROGER

TBL 5-3-1 Supplemental Uplink Message Elements (SUPU) CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

UM166 DUE TO TRAFFIC

SUPU-2

Indication that the associated message is issued due to the specified reason.

(specified reason uplink)

UM167 DUE TO AIRSPACE RESTRICTION

SUPU-2

Indication that the associated message is issued due to the specified reason.

(specified reason uplink)

TBL 5-3-1 Supplemental Downlink Message Elements (SUPD) CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

DM65 DUE TO WEATHER

SUPD-1

Indication that the associated message is issued due to the specified reason.

(specified reason uplink)

DM66 DUE TO AIRCRAFT PERFORMANCE

SUPD-1

Indication that the associated message is issued due to the specified reason.

(specified reason downlink)

TBL 5-3-1 Free Text Uplink Message Elements (TXTU) CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

free text

TXTU-1

A message or part of a message that does not conform to any standard message element in the PANS-ATM (Doc 4444).

free text

Note-M alert attribute.

free text

TXTU-1

free text

See Note

free text

UM169 ( free text )

“[facility designation]”

LOCAL ALTIMETER (for Altimeter Reporting Station)

See Note

free text

UM169 ( free text )

“[facility designation] LOCAL ALTIMETER MORE THAN ONE HOUR” OLD

See Note

free text

UM169 ( free text )

DUE TO WEATHER

See Note

free text

UM169 ( free text )

REST OF ROUTE UNCHANGED

See Note

free text

UM169 ( free text )

TRAFFIC FLOW MANAGEMENT REROUTE

See Note

free text

UM169 (free text) DUE TO SPACING

See Note

free text

See Note

free text

See Note

free text

NOTE-

These are FAA scripted free text messages with no GOLD equivalent.

TBL 5-3-1 Free Text Downlink Message Elements (TXTD) CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

(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 flight crew to include in the emergency message at their discretion.

TXTD-1

( free text )

Note - M alert attribute.

TBL 5-3-1 System Management Uplink Message Elements (SYSU) CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

(error information)

SYSU-1

System-generated notification of an error.

(error information)

(ICAO facility designation)

Note - The facility designation is required.

SYSU-2

System-generated notification of the next data authority or the cancellation thereof.

(facility designation [O])

TBL 5-3-1 System Management Downlink Message Elements (SYSD) CPDLC Message Sets

Operational Definition in PANS-ATM (Doc 4444)

FANS 1/A

Response

Message Element Identifier

Message Element Intended Use

Format for Message Element Display

(error information)

SYSD-1

System-generated notification of an error.

SYSD-1

DM63 NOT CURRENT DATA AUTHORITY

SYSD-3

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

SYSD-3

(ICAO facility designation)

Note - Use by FANS 1/A aircraft in B1 environments.

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 (CDA). Identity of the NDA, if any, is also reported.

SYSD-5

ATC Frequency Change Procedures. The following phraseology will be used by controllers to effect a frequency change: EXAMPLE-

(Aircraft identification) contact (facility name or location name and terminal function) (frequency) at (time, fix, or altitude).

NOTE-

Pilots are expected to maintain a listening watch on the transferring controller's frequency until the time, fix, or altitude specified. ATC will omit frequency change restrictions whenever pilot compliance is expected upon receipt.

The following phraseology should be utilized by pilots for establishing contact with the designated facility: When operating in a radar environment: On initial contact, the pilot should inform the controller of the aircraft's assigned altitude preceded by the words “level,” or “climbing to,” or “descending to,” as appropriate; and the aircraft's present vacating altitude, if applicable. EXAMPLE-

(Name)

CENTER, (aircraft identification), LEVEL (altitude or flight level).

(Name)

CENTER, (aircraft identification), LEAVING (exact altitude or flight level), CLIMBING TO OR DESCENDING TO (altitude of flight level).

NOTE-

Exact altitude or flight level means to the nearest 100 foot increment. Exact altitude or flight level reports on initial contact provide ATC with information required prior to using Mode C altitude information for separation purposes.

When operating in a nonradar environment: On initial contact, the pilot should inform the controller of the aircraft's present position, altitude and time estimate for the next reporting point. EXAMPLE-

(Name)

CENTER, (aircraft identification), (position), (altitude), ESTIMATING (reporting point) AT (time).

After initial contact, when a position report will be made, the pilot should give the controller a complete position report. EXAMPLE-

(Name)

CENTER, (aircraft identification), (position), (time), (altitude), (type of flight plan), (ETA and name of next reporting point), (the name of the next succeeding reporting point), AND (remarks).

REFERENCE-

AIM, Para 5-3-2 , Position Reporting.

At times controllers will ask pilots to verify that they are at a particular altitude. The phraseology used will be: “VERIFY AT (altitude).” In climbing or descending situations, controllers may ask pilots to “ VERIFY ASSIGNED ALTITUDE AS (altitude) .” Pilots should confirm that they are at the altitude stated by the controller or that the assigned altitude is correct as stated. If this is not the case, they should inform the controller of the actual altitude being maintained or the different assigned altitude. NOTE-

Pilots should not take action to change their actual altitude or different assigned altitude to the altitude stated in the controllers verification request unless the controller specifically authorizes a change.

ARTCC Radio Frequency Outage. ARTCCs normally have at least one back‐up radio receiver and transmitter system for each frequency, which can usually be placed into service quickly with little or no disruption of ATC service. Occasionally, technical problems may cause a delay but switchover seldom takes more than 60 seconds. When it appears that the outage will not be quickly remedied, the ARTCC will usually request a nearby aircraft, if there is one, to switch to the affected frequency to broadcast communications instructions. It is important, therefore, that the pilot wait at least 1 minute before deciding that the ARTCC has actually experienced a radio frequency failure. When such an outage does occur, the pilot should, if workload and equipment capability permit, maintain a listening watch on the affected frequency while attempting to comply with the following recommended communications procedures: If two‐way communications cannot be established with the ARTCC after changing frequencies, a pilot should attempt to recontact the transferring controller for the assignment of an alternative frequency or other instructions.

When an ARTCC radio frequency failure occurs after two‐way communications have been established, the pilot should attempt to reestablish contact with the center on any other known ARTCC frequency, preferably that of the next responsible sector when practicable, and ask for instructions. However, when the next normal frequency change along the route is known to involve another ATC facility, the pilot should contact that facility, if feasible, for instructions. If communications cannot be reestablished by either method, the pilot is expected to request communications instructions from the FSS appropriate to the route of flight. NOTE-

The exchange of information between an aircraft and an ARTCC through an FSS is quicker than relay via company radio because the FSS has direct interphone lines to the responsible ARTCC sector. Accordingly, when circumstances dictate a choice between the two, during an ARTCC frequency outage, relay via FSS radio is recommended.

Oakland Oceanic FIR. The use of CPDLC and ADS-C in the Oakland Oceanic FIR (KZAK) is only permitted by Inmarsat and Iridium customers. All other forms of data link connectivity are not authorized. Users must ensure that the proper data link code is filed in Item 10a of the ICAO FPL in order to indicate which satellite medium(s) the aircraft is equipped with. The identifier for Inmarsat is J5 and the identifier for Iridium is J7. If J5 or J7 is not included in the ICAO FPL, then the LOGON will be rejected by KZAK and the aircraft will not be able to connect.

New York Oceanic FIR. The use of CPDLC and ADS-C in the New York Oceanic FIR (KZWY) is only permitted by Inmarsat and Iridium customers. All other forms of data link connectivity are not authorized. Users must ensure that the proper data link code is filed in Item 10a of the ICAO FPL in order to indicate which satellite medium(s) the aircraft is equipped with. The identifier for Inmarsat is J5 and the identifier for Iridium is J7. If J5 or J7 is not included in the ICAO FPL, then the LOGON will be rejected by KZWY and the aircraft will not be able to connect.

Retrieved from ecfr.gov on July 20, 2026.