HYDRAULIC PANEL and PUMPS.

Hydraulic panel
Hydraulic power is provided by two hydraulically separate, closed hydraulic systems, identified as the left and the right system. The two systems are basically identical except for component location and subsystems served.

Each system is equipped with a hydraulic fluid reservoir and an engine-driven pump which normally provides system pressure. An electrically driven auxiliary pump is installed in the right system as a backup of the right engine-driven pump.

The two hydraulic systems are mechanically interconnected by the alternate pump. The pump consists of two coupled hydraulic units so constructed that either unit can operate as a motor while the other operates as a pump. The alternate pump thus serves as a pressure backup for both systems as it may operate as a pump for one system driven by the motor from the other.

Each hydraulic system is divided into two sections by the priority valves. By these valves the subsystems which are not used during cruise, when the engine driven pumps are operated in low pressure mode, are isolated from the rest of the hydraulic power system.

    ALTERNATE PUMP switch
    - ON. The valves are open and in case of failure of one engine driven pump, the motor/pump will operate.
    - OFF. The valves are closed.
    ENGINE PUMP switches, LEFT and RIGHT.
    - HIGH. The pump will give a 3000psi output pressure.
    - LOW. The pump will give a 1500psi output pressure.
    - OFF. No pump output.
    AUXILIARY PUMP switch.
    - ON. The pump will operate, delivering 3000psi pressure. An overheat protection cuts he electric power in case of overload.
    - OFF. The pump is not operating.
    - OVRD. Operating of pump is possible in spite of overheat. This position is springloaded to OFF.
    The following system will not work with the pumps in low (1500psi).

    • Flaps.
    • Wheel brakes.
    • Nosewheel stearing.
    • Landing gear and doors.