What should be done prior to starting an annual or 100-hour inspection on an aircraft?

Prior to starting an annual or 100-hour inspection on an aircraft, thoroughly cleaning the aircraft and engine is essential. This step is crucial because a clean environment allows for a more accurate and efficient inspection process. It helps in identifying any potential issues or discrepancies that may be obscured by dirt, grease, or contaminants. A clean aircraft and engine facilitate the inspection by providing clear access to components for visual checks, ensuring that inspectors can scrutinize every part of the aircraft without the obstruction of debris. This practice not only improves inspection effectiveness but also contributes to the safety and reliability of the aircraft, as it becomes easier to identify wear and potential failures in critical components.

Other steps, such as ensuring systems are operational, performing flight tests, or checking registration numbers, are important elements of aircraft maintenance but are not specifically the preparatory action required immediately before beginning an inspection. These tasks typically occur during the maintenance or operation phases rather than as a preparatory measure for an inspection.