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

What has priority when RAT pressure is low, electric power or hydraulic power?

1. Electric power has priority

2. Hydraulic power has priority

3. They are equal

4. Neither has priority

The correct answer is: Hydraulic power has priority

When the ram air turbine (RAT) pressure is low, hydraulic power takes priority over electric power. This is due to the critical role that hydraulic systems play in aircraft operations, especially during emergencies. Hydraulic systems are essential for controlling various flight control surfaces, landing gear, and brakes, making it imperative that they are available even if there is a limitation on electric power supply. In situations where the RAT is deployed, it typically provides both hydraulic and electrical power to ensure the operation of essential systems. However, if the pressure generated is insufficient, it is crucial to maintain hydraulic capabilities first as they are vital for safety and control. Electric power is often less critical, as many non-essential systems can rely on alternative power sources or may not be required for the immediate safe operation of the aircraft. Conversely, the other options do not align with the priorities typically established in aircraft design and emergency procedures, where hydraulic systems are emphasized for their role in maintaining control and safety during critical situations.