During flight, what action occurs when the APU detects and annunciates a fire?

During flight, what action occurs when the APU detects and annunciates a fire?

• A. Auto shuts down, manually discharge fire bottle
• B. Auto restarts after 5 seconds
• C. Auto shuts down and auto discharge fire bottle
• D. No automatic action

Answer: (A)

When an APU fire is detected, the system is designed to shut the APU down automatically to isolate the fire and stop fuel flow, helping prevent the fire from growing. The extinguishing agent is released by the crew, using the APU fire extinguisher switch to discharge the bottle manually. This combination ensures rapid shutdown of the source and controlled application of the extinguishing agent. Automatic restart after a delay isn’t how this system works, and the extinguisher bottle isn’t discharged automatically—it's deployed by the crew when they command it.

When an APU fire is detected, the system is designed to shut the APU down automatically to isolate the fire and stop fuel flow, helping prevent the fire from growing. The extinguishing agent is released by the crew, using the APU fire extinguisher switch to discharge the bottle manually. This combination ensures rapid shutdown of the source and controlled application of the extinguishing agent. Automatic restart after a delay isn’t how this system works, and the extinguisher bottle isn’t discharged automatically—it's deployed by the crew when they command it.