CPDLC Ground Initiated Transaction Delay
The CPDLC Ground Initiated Transaction Delay is a part of the CPDLC ground initiated transactions performance statistics. It is the time taken between the message that initiates a transaction being sent and the corresponding message that closes the transaction being received.
Only transactions that are responded to by the flight crew are considered. Transactions that are triggered automatically by the ground system and automatically responded by the aircraft (for example UM160 Next Data Authority) are not considered as a part of this metric.
Each different type of transaction is considered separately to determine which message initiates the transaction and which closes it. If the initial response is an ERROR message then the transaction is not included in the statistic (since the transaction will not be closed) but the error is counted. Also if the initial response is a LACK but an ERROR message is received subsequently for this transaction (because the pilot or the controller did not respond before the timer expired) then the transaction is also not included in the statistic but again the error is counted.
If a STANDBY response is sent then the two elements of the transaction are measured separately as illustrated below.