What is the required cooling time between APU start attempts?

The required cooling time between Auxiliary Power Unit (APU) start attempts is set at 20 minutes. This duration is crucial for preventing overheating and ensuring the APU components can recover from the thermal stress associated with a start attempt. By allowing this cooling period, you help to mitigate the risks of equipment failure and ensure that the APU can function efficiently during subsequent start attempts.

While the other durations listed may seem reasonable for various maintenance activities or other systems, they do not comply with the specific guidelines or operational protocols for APU start attempts, making them unsuitable for this scenario. Understanding the manufacturer's specifications and maintenance guidelines is essential for the safe and effective operation of the APU.