Which action should be avoided during towing into or out of a hangar?

• A. Operating the APU
• B. Lifting the canopy
• C. Engaging the landing gear lock
• D. Raising wing flaps

Answer: (A)

When moving the aircraft in and out of a hangar, you want to minimize sources of heat, exhaust, and potential unexpected actions in a confined space. The action to avoid is turning on or running the Auxiliary Power Unit. The APU generates hot exhaust and uses fuel, and in the tight, enclosed environment of a hangar those exhaust gases can accumulate, creating a fire or carbon monoxide hazard for personnel and equipment. An APU starting sequence can also trigger unintended operation or vibrations that could jeopardize safe handling during the tow. For these reasons, the APU should remain off during towing into or out of a hangar. Other actions listed don’t pose the same confined-space risk and are not as critical to safety in this specific towing scenario.