How does an APU contribute to overall aircraft weight?

The Auxiliary Power Unit (APU) is a critical component in an aircraft, particularly in large aircraft like the C-5. While its primary function is to provide electrical power and pneumatic pressure when the main engines are not running, it also has implications for the overall weight of the aircraft.

An APU is a piece of machinery that has physical mass. Therefore, it contributes additional weight to the aircraft that must be accounted for in weight and balance calculations. This weight must be considered when performing load planning and ensuring that the aircraft remains within safe operational limits. Accurate weight and balance assessments are essential for flight safety, as exceeding weight limits can impact performance and maneuverability.

Understanding the total weight, including that added by the APU, is crucial for determining the aircraft's center of gravity, which affects stability and control during flight. Hence, the presence of the APU necessitates careful consideration in all weight specifications and operational procedures.