What is the maximum airspeed to start the APU?

Starting the Auxiliary Power Unit (APU) at the correct airspeed is crucial for both safety and operational efficiency. The maximum airspeed for starting the APU is set to ensure that the airflow does not interfere with the APU's ignition and start processes, as high speeds can lead to insufficient airflow or pressure, potentially resulting in a failed start.

In this context, the maximum airspeed of 285 knots is typically specified in aircraft operations manuals. Operating within this limit helps to ensure that the APU receives the proper conditions for a successful start while minimizing risks related to aerodynamic factors.

Other airspeeds listed are likely above this threshold, indicating they would not provide the optimal environment for APU ignition and operation. Therefore, understanding the technical limitations and operating parameters of the APU emphasizes the importance of adhering to these specified airspeed limits during start-up procedures.