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

How is the APU started?

1. Manually with an AC switch

2. Using an air turbine starter

3. By pressing a button

4. With the help of ground crew

The correct answer is: Using an air turbine starter

The starting procedure for an Auxiliary Power Unit (APU) typically involves using an air turbine starter. This method is common because the air turbine starter is efficient and effective for initiating the APU's operation, providing the necessary rotational speed for the APU to begin its function. Unlike electrical or manual methods, using an air turbine starter ensures that the APU starts reliably, especially in a variety of environmental conditions and operational scenarios. Other methods, such as manual operation with an AC switch, might not be standard as they could lead to inconsistencies or reliance on specific conditions, while pressing a button typically refers to electrical systems and controls rather than the mechanical process of starting the APU with the required torque and speed. Additionally, while the ground crew may assist with pre-start checks and monitoring, the actual starting mechanism for the APU is primarily through the air turbine starter. This highlights the importance of understanding APU systems and their operational requirements in aviation contexts.