What is the minimum safe distance recommended when operating the APU?

The minimum safe distance recommended when operating the Auxiliary Power Unit (APU) is 25 feet. This distance is crucial for ensuring the safety of personnel around the aircraft, as the APU can emit harmful exhaust gases and generate high noise levels. Maintaining a safe distance helps to mitigate the risk of exposure to these hazards, as well as protect against potential mechanical failures that could cause injury.

Moreover, the 25 feet guideline takes into account not only the physical hazards associated with operating the APU but also the need for effective response actions in case of emergencies. Being positioned at this distance allows personnel to remain safe while still being close enough to monitor APU operations if necessary. In contrast, the other distances provided may not sufficiently ensure safety in these operational scenarios.