What happens when you press the PWR FUEL switchlight for the APU?

What happens when you press the PWR FUEL switchlight for the APU?

• A. DIGS
• B. Door opens
• C. In BITE status message appears on ED2
• D. Gages appear on ED2

Answer: (A)

The PWR FUEL switchlight for the APU brings the APU online by powering its fuel system and triggering the status/diagnostic readout. When you press it, the APU’s DIGS—the diagnostic/status display for the APU—comes up to show its health and readiness. This is the immediate visible indication of selecting fuel power for the APU. Doors opening would be related to mechanical APU door logic and not to simply powering the APU. A BITE status message on ED2 would require a built-in test condition, not just initiating the APU fuel flow. Gauges appearing on ED2 typically occur once the APU is running and data is being displayed on the gauges. So DIGS appearing is the correct, expected result of pressing the PWR FUEL switchlight.

The PWR FUEL switchlight for the APU brings the APU online by powering its fuel system and triggering the status/diagnostic readout. When you press it, the APU’s DIGS—the diagnostic/status display for the APU—comes up to show its health and readiness. This is the immediate visible indication of selecting fuel power for the APU.

Doors opening would be related to mechanical APU door logic and not to simply powering the APU. A BITE status message on ED2 would require a built-in test condition, not just initiating the APU fuel flow. Gauges appearing on ED2 typically occur once the APU is running and data is being displayed on the gauges. So DIGS appearing is the correct, expected result of pressing the PWR FUEL switchlight.