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

When all demand pumps are in 'AUTO', which pump runs continuously when on the ground?

1. L hydraulic system demand pump

2. R hydraulic system demand pump

3. C1 hydraulic system demand pump

4. C2 hydraulic system demand pump

The correct answer is: R hydraulic system demand pump

When all demand pumps are set to 'AUTO' on the ground, the right hydraulic system demand pump is designed to operate continuously. This design is typically rooted in the need for consistent hydraulic pressure to control various systems, especially during critical phases such as pre-flight checks and ground operations. In many aircraft hydraulic systems, priority is given to ensuring that the right side hydraulic system can maintain operational readiness, providing essential power for critical systems while the aircraft is stationary. This is particularly important to ensure that hydraulic pressure is available for functions such as landing gear, brakes, and other systems requiring immediate response times. Other pumps, while also important for the overall operation of the hydraulic systems, do not have the same priority for continuous operation on the ground under normal conditions when autopumps are activated. Their operation may be intermittent or linked to specific system demands rather than a need for constant pressure, making the right hydraulic system demand pump distinct in its role when all demand pumps are set to 'AUTO' on the ground.