What is the maximum time you should not leave the aircraft unattended with the APU running?

What is the maximum time you should not leave the aircraft unattended with the APU running?

• A. 5 minutes
• B. 10 minutes
• C. 15 minutes
• D. 20 minutes

Answer: (A)

Five minutes is the limit. Running the APU on the ground provides essential power and air for the cabin, but it also uses fuel and produces heat and exhaust. If no one is watching, a fault, overheat, or other issue could go unnoticed, increasing the risk of damage or a safety problem. Keeping unattended APU operation to five minutes ensures there’s enough time for a quick task or check while still allowing someone to observe and shut it down if anything abnormal appears. If more time is truly needed, have a responsible crew member or maintenance personnel present or use an alternate power source.

Five minutes is the limit. Running the APU on the ground provides essential power and air for the cabin, but it also uses fuel and produces heat and exhaust. If no one is watching, a fault, overheat, or other issue could go unnoticed, increasing the risk of damage or a safety problem. Keeping unattended APU operation to five minutes ensures there’s enough time for a quick task or check while still allowing someone to observe and shut it down if anything abnormal appears. If more time is truly needed, have a responsible crew member or maintenance personnel present or use an alternate power source.