What powers the APU door, and what powers the ECU?

What powers the APU door, and what powers the ECU?

• A. APU: Door; Main: ECU
• B. APU: ECU; Main: Door
• C. APU: Door; APU: ECU
• D. Main: Door; Main: ECU

Answer: (A)

The situation hinges on which power source feeds which subsystem. The APU door is part of the auxiliary power unit’s own air intake system and is actuated by the APU’s internal drive mechanism. It opens or closes as the APU starts up or runs, controlled by the APU’s own logic. The engine control unit, on the other hand, is part of the aircraft’s main engine management system and relies on the aircraft’s primary electrical power. Providing it from the main electrical system keeps the ECU powered reliably even when the APU isn’t running or when the APU’s power needs vary. So the best fit is: the APU powers the door, and the main electrical system powers the ECU. The other options mix up which system drives which, which isn’t how these subsystems are typically wired to keep operations predictable and safe.

The situation hinges on which power source feeds which subsystem. The APU door is part of the auxiliary power unit’s own air intake system and is actuated by the APU’s internal drive mechanism. It opens or closes as the APU starts up or runs, controlled by the APU’s own logic.

The engine control unit, on the other hand, is part of the aircraft’s main engine management system and relies on the aircraft’s primary electrical power. Providing it from the main electrical system keeps the ECU powered reliably even when the APU isn’t running or when the APU’s power needs vary.

So the best fit is: the APU powers the door, and the main electrical system powers the ECU. The other options mix up which system drives which, which isn’t how these subsystems are typically wired to keep operations predictable and safe.