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  The most serious of such cases would be the pilot executing a clearance that was no longer valid.

I won't bloviate on the procedure to follow as you can read about it in the following NAT Ops bulletin: 2018-002 put out on 10 Apr 2018 with effective date of 24 May 2018.

Written by Shawn Scott    05/04/2018 

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