Which system is powered by the auxiliary hydraulic system?

The auxiliary hydraulic system primarily powers systems that require hydraulic power during normal operation, especially when the main hydraulic systems are not available or in case of failure. In this context, the lower rudder Power Control Unit (PCU) relies on the auxiliary hydraulic system to function effectively. This is significant because the rudder is a critical control surface that influences the aircraft's stability and directional control.

Proper operation of the lower rudder PCU ensures that pilots can maintain effective control of the aircraft, especially during situations where main hydraulic power may be compromised. The design of the aircraft systems often allows for redundancy, where vital components like the rudder can still operate using auxiliary sources.

While the landing gear system, flap actuator system, and wing spoiler system may involve hydraulic operations, they are primarily integrated with the main hydraulic system. Their failure modes and operational requirements differ from those of the lower rudder system, which is specifically designed to utilize auxiliary power for reliable control.