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

In which scenario will the ADIRU system logic prevent it from being unpowered during flight?

1. When airplane speed is greater than 30 knots on the ground

2. When the APU is shut down

3. When the flight crew selects OFF

4. When cabin pressure is normal

The correct answer is: When airplane speed is greater than 30 knots on the ground

The correct answer pertains to the ADIRU (Air Data Inertial Reference Unit) system's operational logic, which is designed to ensure that the system remains powered during critical phases of flight. When the airplane speed exceeds 30 knots on the ground, this speed serves as a trigger point for the ADIRU system to stay powered. Maintaining power during these conditions is crucial because it allows the continuous operation of the inertial reference systems that provide essential data for navigation and flight management. In scenarios where the APU (Auxiliary Power Unit) is shut down or the flight crew selects OFF, the ADIRU may not receive the necessary power, as both situations indicate a lack of required systems being active. Furthermore, normal cabin pressure has no bearing on the power status of the ADIRU, as it is more associated with safety and comfort rather than the functionality of onboard electronic systems. Thus, the operational need to maintain power to the ADIRU at higher speeds is critical for the safety and reliability of flight operations.