When should a powerplant run-up be performed?

The correct reasoning for performing a powerplant run-up before every flight is rooted in ensuring safety and operational readiness. A powerplant run-up is a thorough check of an aircraft's engine performance and systems prior to takeoff. This procedure allows pilots to detect any anomalies, check for engine power, evaluate the functionality of critical systems, and confirm that the engine is responding correctly to throttle inputs.

By conducting this check consistently before each flight, pilots can identify potential issues early on, thereby minimizing the risk of engine failure during flight and ensuring that all systems are functioning properly. This practice helps in maintaining a high standard of operational safety and reliability, both for the pilot and for the aircraft.

The other options either imply that the run-up is only necessary under specific circumstances, which would not account for unanticipated issues that could arise unexpectedly before a flight. Regular checks are essential to a comprehensive safety protocol in aviation.