When is the best time to perform a pre-flight inspection?

Performing a pre-flight inspection before the first flight of the day is the most effective approach for ensuring safety and proper functionality of the aircraft. This timing allows the pilot to thoroughly check the entire aircraft for any discrepancies or potential issues that may have developed overnight or before the start of the flying day. It also provides an opportunity to become familiar with the aircraft's condition, verify that all systems are in working order, and ensure that any maintenance issues have been addressed prior to flight.

Conducting a pre-flight inspection just before takeoff, while necessary, does not give the pilot adequate time to rectify any issues discovered during the inspection. It may also limit the pilot's ability to complete necessary checks in a calm and thorough manner, potentially overlooking critical safety concerns.

Performing the inspection after engine start is also not ideal because it does not allow for a comprehensive visual assessment of the aircraft while it is still static. Engine start introduces variables, such as vibrations and potential changes in accessibility, which may impede a thorough inspection of critical components that could affect flight safety. Thus, conducting a pre-flight inspection before the first flight of the day is the best practice for ensuring a safe and efficient flying experience.