Scott International Procedures
The CPDLC welcome message is being replaced by an ATC uplink instructing operators to set a maximum uplink delay value, preventing action on expired clearances.
The familiar welcome message one gets after log on with CPDLC is being replaced with a request to set your Latency timer to a particular value. This has come about because there have been instances where a delayed CPDLC message was acted upon well after the permissible time frame, in some cases after the message should have expired and not be delivered.
To ensure no action is taken for an expired clearance, after login, ATC will send an uplink message to operators informing the operator to "SET MAX UPLINK DELAY VALUE TO (XXX) SECONDS".
Recall that the intended function of the latency monitor is to prevent pilots from acting on a CPDLC message that has been delayed in the network. The most serious of such cases would be the pilot executing a clearance that was no longer valid.
The full procedure to follow can be found in NAT Ops Bulletin 2018-002, published 10 Apr 2018 with an effective date of 24 May 2018.
REFERENCED REGULATIONS
FAA AC 91-70B
NAT Doc 007 Ver 2026.1
ICAO Doc 4444 PANS-ATM
ICAO Annex 11
NAT OPS Bulletin 2025-3
AUTHOR
The Scott IPC instructor team: retired corporate chief pilots, FAA procedures and safety personnel, and former military aviators who teach international procedures.
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