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

If the ADIRU switch is ON and the battery switch is OFF, what happens when electric power is removed?

1. The ADIRU will shut down safely

2. The ADIRU will be powered from the hot battery bus

3. The ADIRU will trigger an emergency alarm

4. The ADIRU operates on backup power only

The correct answer is: The ADIRU will be powered from the hot battery bus

The correct answer highlights the functionality of the aircraft’s electrical systems, specifically regarding the ADIRU (Air Data Inertial Reference Unit) and its power sources. When the ADIRU switch is ON and the battery switch is OFF, the condition suggests that the main battery is not supplying power to the ADIRU. However, the ADIRU is designed to receive power from alternate sources, including the hot battery bus. In this scenario, even though the primary battery is off, the ADIRU can still receive power from the hot battery bus, which is a dedicated circuit that remains powered regardless of the main battery switch position. This ensures that crucial systems like the ADIRU can continue to operate, maintaining essential flight data and allowing pilots to have vital reference information even in situations where the main battery is not active. The other options would not occur under these circumstances. The ADIRU does not shut down safely because it continues to receive power from the hot battery bus, thus negating any safe shutdown. An emergency alarm does not get triggered purely from the power state of the ADIRU, allowing for normal operation. Finally, the option about operating on backup power only does not apply because the hot battery bus serves as the primary power