The flight and ground crews have control of the aircraft hydraulic systems through a control panel in the flight compartment center pedestal.

The location of the Hydraulic control panel is immediately to the right of the throttle quadrant. The switches are for the left (L PUMP), right (R PUMP), and auxiliary (AUX PUMP) DC motor-driven pumps (DCMPs). The L (R) PUMP switches can turn to three positions: OFF, AUTO, or ON. The AUX PUMP switch can turn to two positions: OFF or AUTO. There is a switch to energize the power transfer unit (PTU AUTO), which also turns to three positions: OFF, AUTO, or ON.

There are two pushbuttons which set the left (L SOV) or right (R SOV) firewall hydraulic shutoff valves to the open or closed position.

The engine-driven hydraulic pumps (EDPs) operate at all times when the engines turn. The two firewall hydraulic shutoff valves are usually open and the L SOV and R SOV pushbutton lights are off. The flight crew can use these pushbuttons to close the flow of hydraulic fluid to an EDP that has a malfunction. When the L SOV or the R SOV pushbutton is pushed, a light in the related switch comes on and shows the legend CLOSED.

During important periods of each flight (takeoff and landing), it is also necessary to operate the DCMPs. In these periods, the flight crew switches the L PUMP and R PUMP to ON. These pumps give an alternative supply of hydraulic pressure if the EDPs become defective.

At other times, the pilot turns the L PUMP and R PUMP to AUTO. With the switches in this position, if hydraulic pressure from the EDPs is not available, the DCMPs start automatically.

Note:
This is if the flaps are at zero degrees, a minimum of one generator operates and the EDP becomes defective while in flight.

The AUX PUMP switch controls the operation of the auxiliary DCMP. The flight crew can manually control the auxiliary DCMP with the AUX PUMP switch (OFF). In AUTO, the auxiliary DCMP only starts automatically if the pressure in the auxiliary system accumulator becomes less than 2,500 psig. It turns off if the auxiliary accumulator pressure becomes more than 3,350 psig.

There is a pushbutton which controls an alternative power supply for the flaps (ALTN FLAPS). Usually, the right hydraulic system energizes the flaps. If pressure is not available, the flight crew can push the pushbutton which lets the left hydraulic system pressure go to the flap selector valve. When the switch is pushed, a light in the switch comes on and shows the legend ON.