Technical Round Trip Delay

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The Technical Round Trip Delay (TRTD) is one of the general performance measures that are published. It is the time taken by the system to uplink a CPDLC message and receive its application level acknowledgement.


Technical Round-Trip Delay is measured using ground initiated transactions that require a LACK response. Only ground initiated transactions are considered to ensure that a common time source is used for both time measurements.

TRTD = First LACK response reception time – Uplink message transmission time

Note: For FANS aircraft the gateway in the ground system generates a LACK when it receives a message delivery assurance report from the ACARS data services processor.