Manual Operation
Positioning either FLT CONTROL switch to STBY RUD:
- Activates the standby electric motor–driven pump.
- Shuts off the related hydraulic system pressure to ailerons, elevators and rudder by
closing the flight control shutoff valve. - Opens the standby rudder shutoff valve.
- Deactivates the related flight control LOW PRESSURE light when the standby rudder
shutoff valve opens. - Allows the standby system to power the rudder and thrust reversers.
FFM - Force Flight Monitor (Modified Rudder Installation)
The main rudder PCU contains a Force Fight Monitor (FFM) that detects opposing
pressure (force fight) between A and B actuators. This may occur if either system A or B
input is jammed or disconnected. The FFM output is used to automaticallyturn on the
Standby Hydraulic pump, open the standby rudder shutoff valve to pressurize the standby
rudder PCU, and illuminate the STBY RUD ON, Master Caution, and Flight Control (FLT
CONT) lights.
Alternate Flaps
In the event that hydraulic system B fails, an alternate method of extending the LE devices
and extending and retracting the TE flaps is provided. The TE flaps can be operated
electrically through the use of two alternate flap switches. The guarded ALTERNATE
FLAPS master switch closes a flap bypass valve to prevent hydraulic lock of the flap drive
unit and arms the alternate flaps position switch. The ALTERNATE FLAPS position switch
controls an electric motor that extends or retracts the TE flaps. The switch must be held in
the DOWN position until the flaps reach the desired position.
