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6/17/21 

AIM 

TBL 5

3

Voice Communications Uplink Message Elements (COMU) 

CPDLC Message Sets 

Operational Definition in PANS

ATM (Doc 4444) 

FANS 1/A 

ATN B1 

Response 

Message 
Element 

Identifier 

Message Element 

Intended Use 

Format for 

Message Element 

Display 

UM117 CONTACT 

(ICAO unit name) 
(frequency) 

UM117 CON-
TACT 

(unit name) 

(frequency) 

W/U 

COMU

Instruction to es-
tablish voice con-
tact with the speci-
fied ATS unit on 
the specified fre-
quency. 

CONTACT 

(unit name) 
(frequency) 

UM120 MONITOR 

(ICAO unit name) 
(frequency) 

UM120 MONI-
TOR (

unit name) 

(frequency) 

W/U 

COMU

Instruction to mon-
itor the specified 
ATS unit on the 
specified frequen-
cy. The flight crew 
is not required to 
establish voice 
contact on the fre-
quency. 

MONITOR 

(unit name) 
(frequency) 

TBL 5

3

Voice Communications Downlink Message Elements (COMD) 

CPDLC Message Sets 

Operational Definition in PANS

ATM (Doc 4444) 

FANS 1/A 

ATN B1 

Response 

Message 
Element 

Identifier 

Message Element 

Intended Use 

Format for 

Message Element 

Display 

DM20 REQUEST 
VOICE CONTACT 

Note  

 Used when a 

frequency is not re-
quired. 

N/A 

COMD

Request for voice 
contact on the spec-
ified frequency. 

REQUEST 
VOICE 
CONTACT 

(frequency) 

TBL 5

3

10 

Emergency/Urgency Uplink Message Elements (EMGU) 

CPDLC Message Sets 

Operational Definition in PANS

ATM (Doc 4444) 

FANS 1/A 

ATN B1 

Response 

Message 
Element 

Identifier 

Message Element 

Intended Use 

Format for 

Message Ele-

ment Display 

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

Instruction to im-
mediately comply 
with the associated 
instruction to avoid 
imminent situation. 

Immediately 

En Route Procedures 

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