What will the APU automatic fire protection provide in flight?

• A. Automatic shutdown of the APU, but not automatic discharge of the fire bottle.
• B. Automatic discharge of the fire bottle
• C. No automatic action
• D. Immediate engine shutdown

Answer: (A)

When fire protection detects heat in the APU, the priority is to stop supplying fuel and shut the APU down so the fire loses its energy source. That automatic shutdown happens in flight to quickly isolate the APU. The extinguishing bottle, however, is not released automatically as part of the in-flight protection. The crew must manually discharge the bottle if needed, or follow specific procedures for no automatic discharge during flight. This is why the correct understanding is that automatic shutdown of the APU occurs, but the fire bottle discharge is not automatic.