Table A5-17. Voice contact requests (downlink)
Message intent/use Message element URG ALRT RESP
20 Request for voice contact. REQUEST VOICE CONTACT N L Y
21 Request for voice contact on the specified frequency. REQUEST VOICE CONTACT (frequency) N L Y
Table A5-18. Route modification requests (downlink)
Message intent/use Message element URG ALRT RESP
22 Request to track from the present position direct to the specified position. REQUEST DIRECT TO (position) N L Y
23 Request for the specified procedure clearance. REQUEST (procedure name) N L Y
24 Request for a route clearance. REQUEST CLEARANCE (route clearance) N L Y
No. 2
Message intent/use Message element URG ALRT RESP
25 Request for a clearance. REQUEST (clearance type) CLEARANCE N L Y
26 Request for a weather deviation to the specified position via the specified route. REQUEST WEATHER DEVIATION TO (position) VIA (route clearance) N M Y
27 Request for a weather deviation up to the specified distance off track in the specified direction. REQUEST WEATHER DEVIATION UP TO (specified distance) (direction) OF ROUTE N M Y
70 Request a clearance to adopt the specified heading. REQUEST HEADING (degrees) N L Y
71 Request a clearance to adopt the specified ground track. REQUEST GROUND TRACK (degrees) N L Y
Table A5-19. Reports (downlink)
Message intent/use Message element URG ALRT RESP
28 Notification of leaving the specified level. LEAVING (level) N L N
29 Notification of climbing to the specified level. CLIMBING TO (level) N L N
30 Notification of descending to the specified level. DESCENDING TO (level) N L N
31 Notification of passing the specified position. PASSING (position) N L N
78 Notification that at the specified time the aircraft’s position was as specified. AT (time) (distance) (to/from) (position) N L N
32 Notification of the present level. PRESENT LEVEL (level) N L N
33 Notification of the present position. PRESENT POSITION (position) N L N
34 Notification of the present speed. PRESENT SPEED (speed) N L N
113 Notification of the requested speed. (speed type) (speed type) (speed type) SPEED (speed) N L N
35 Notification of the present heading in degrees. PRESENT HEADING (degrees) N L N
36 Notification of the present ground track in degrees. PRESENT GROUND TRACK (degrees) N L N
37 Notification that the aircraft is maintaining the specified level. MAINTAINING (level) N L N
72 Notification that the aircraft has reached the specified level. REACHING (level) N L N
76 Notification that the aircraft has reached a level within the specified vertical range. REACHING BLOCK (level) TO (level) N L N
Message intent/use Message element URG ALRT RESP
38 Read-back of the assigned level. ASSIGNED LEVEL (level) N M N
77 Read-back of the assigned vertical range. ASSIGNED BLOCK (level) TO (level) N M N
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