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The uplink datalink message " AT [time] CLIMB TO AND MAINTAIN [altitude]" means:
  • A
    after the climb the specified altitude is to be maintained until the specified time.
  • B
    after the climb the specified altitude is to be maintained from the specified time.
  • C
    at the specified time the specified altitude is to be reached.
  • D
    at the specified time a climb to the specified altitude is to be started and the specified altitude is to be maintained.

The CPDLC is a FANS application that consists of transmitting datalink formatted messages between the pilot (the aircraft) and the ATC controller or the Company (the ground). A message sent by the aircraft to the ground is called a downlink message, the opposite is called an uplink message. Datalink messages may concern various requests such as route modifications, speed changes, voice contact requests (ex: transfer of ATC center), emergency messages (MAYDAY), crossing constraints, pre-departure clearances, ATIS, oceanic clearances, etc.

Datalink messages can be sent using different media such as HF datalink, VHF datalink, or SATCOM. The SATCOM has the fastest rate of transmission, while the HF datalink has the slowest. The SATCOM is particularly good as there is no line-of-sight limitation and no variable quality of signals disturbed by ionospheric conditions, however, this media is not installed on all airplanes.


Here you can find some of the messages and their respective meaning that you might be asked at your official exam:

AT [time] CLIMB TO AND MAINTAIN [altitude] at the specified time a climb to the specified altitude is to be started and the specified altitude is to be maintained.
AT [position] CLIMB TO [altitude] AND MAINTAIN at the specified position a climb to the specified altitude is to be started and the specified altitude is to be maintained.
CLIMB TO REACH [altitude]
BY [time]
a climb is to commence at a rate such that the specified level is reached at or before the specified time.
CHECK STUCK MICROPHONE [frequency] the ATC to the pilot to check microphone buttons due to a continuous transmission detected on the frequency.

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