When is the appropriate time to contact air traffic control after starting an aircraft engine?

The appropriate time to contact air traffic control after starting an aircraft engine is after engine run-up checks are complete. This timing ensures that the aircraft is ready for safe operation before it begins taxiing or departing. Engine run-up checks are critical for verifying that the engine and systems are functioning properly, and any issues discovered during this procedure should be addressed before communicating with air traffic control.

Once the checks confirm that the aircraft is in good working order, the pilot can confidently inform air traffic control of their intentions, whether for taxiing or launching into departure. This practice emphasizes safety, ensuring the aircraft is fully prepared for flight, which is a vital aspect of flight operations.

In contrast, contacting air traffic control immediately after engine start may not provide adequate assurance regarding the aircraft’s operational status. Not waiting until after the run-ups to communicate could lead to issues or misunderstandings if a mechanical concern arises during that initial phase. Similarly, reaching out before taxiing or at the time of departure lacks the preparatory detail that the run-up checks provide, which helps inform both parties of the aircraft's readiness.