What initiates the automatic operation of the standby hydraulic system?

The automatic operation of the standby hydraulic system is initiated by the PCU (Power Control Unit) Force Fight Monitor tripping. This system is a critical fail-safe mechanism designed to ensure that in the event of a malfunction or failure in the main hydraulic system, hydraulic power is maintained for essential flight controls.

When the Force Fight Monitor detects that the forces being exerted by the main hydraulic system are outside acceptable parameters—indicating a potential issue or failure—it triggers the standby hydraulic system to engage. This allows the aircraft to maintain control and operational capability despite problems in the primary hydraulic system, safeguarding against loss of control during critical phases of flight.

While loss of power to the main engine or lower operating pressure in the main hydraulic system may also lead to deactivation or failure of hydraulic systems, these conditions do not specifically trigger the automatic response of the standby system in the way that a trip from the Force Fight Monitor does. Similarly, movement of the flaps to the takeoff position does not directly control the operation of the standby hydraulic system. Therefore, the correct initiation process revolves around the oversight function of the PCU Force Fight Monitor, highlighting its importance in maintaining safety and functionality in hydraulic systems.