Why is it significant to inspect the APU before flight operations?

Inspecting the Auxiliary Power Unit (APU) before flight operations is significant primarily to ensure all systems are operational. The APU provides essential power and pneumatic pressure to various aircraft systems while on the ground and during flight. A thorough inspection helps identify any potential issues that could affect the performance of the APU, ensuring that it is fully functional when needed. This reliability is critical, especially in emergency situations when the APU might be required to operate essential systems in the absence of main engine power.

If the APU is not functioning properly before takeoff, it could lead to critical failures during operations, affecting everything from environmental control systems to electrical power supply. Thus, confirming that the APU is operational before flight is a key safety measure to facilitate safe and efficient flight operations.