General Authority of Civil Aviation (GACA) Aeronautical Information Publication (AIP) Practice Exam

When will the APU to Pack Takeoff configuration be armed?

1. After both engines have started

2. Before engine start when selecting the FMC (THRUST LIMIT SEL-APU)

3. During cruise flight

4. Only on the ground with engines off

The correct answer is: Before engine start when selecting the FMC (THRUST LIMIT SEL-APU)

The APU to Pack Takeoff configuration being armed before engine start when selecting the FMC (THRUST LIMIT SEL-APU) is correct because this configuration allows for the proper management of thrust and environmental control prior to initiating engine operations. This step is crucial as it prepares the aircraft systems by ensuring that the Auxiliary Power Unit (APU) is set to provide power to the air conditioning packs, which is essential for maintaining passenger comfort and equipment functionality during the takeoff phase. By arming this configuration before engine start, the flight crew ensures that the aircraft systems are integrated and that the APU is ready to take over the necessary loads as the engines come online. This proactive measure contributes to a smoother transition and operational efficiency, particularly in situations where immediate takeoff thrust is critical. The other options do not align with standard operational procedures. For example, arming this configuration after both engines have started would negate the benefits of preparing systems ahead of time. This is particularly relevant in efficient and safety-oriented flight operations. Additionally, arming it during cruise flight is not applicable since APU use is generally restricted during this phase, and similarly, having it only on the ground with engines off would not utilize the APU effectively nor benefit takeoff readiness.