Can the APU be operated with an inoperative APU Inlet Door actuator?

The APU (Auxiliary Power Unit) can indeed be operated with an inoperative APU inlet door actuator. The APU is designed to function within a range of operational parameters, and while the inlet door's primary function is to regulate airflow into the APU, its inoperative status does not immediately render the APU non-functional.

When the actuator fails, the inlet door can be in either an open or closed position, and if it is stuck in the open position, the APU can still receive airflow necessary for operation. The operational limits, however, may be compromised, requiring careful monitoring of performance parameters to ensure the APU does not overheat or operate inefficiently.

If the inlet door is stuck closed, it would prevent airflow and cause the APU to fail to start or operate properly, which explains why other answers suggest that there may be limitations or caution is necessary. Nonetheless, the design allows for flexibility, emphasizing the robustness of the APU system even with some components failing or operating outside ideal conditions.

Understanding this operational behavior is critical for ensuring efficient use of the APU in various situations, especially during missions where reliable auxiliary power is essential.