W32469 G07311
 Rudder Standby Actuator  500 
27-21-1  Figure 6  May 01/03 
Page 14 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

500  Standby Rudder Actuator Shutoff Valve 
May 01/03  Figure 7  27-21-1 
Page 15 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

12. Rudder Pressure Reducer (Fig. 8)
A.  A Rudder Pressure Reducer (RPR) is connected to the "A" system hydraulic line upstream of the main rudder PCU.  Hydraulic pressure to the rudder is reduced from 3000 psi to 1800 psi when the airplane climbs above 1000 feet above ground level (AGL).  Hydraulic pressure is restored from 1800 psi to 3000 psi when the airplane descends through 700 feet AGL. The RPR defaults to high pressure following loss of electric power or loss of B hydraulic system.
B.  The same control logic is used for the rudder pressure reducer (RPR) and rudder pressure limiter (RPL) and is located within the yaw damper coupler.  The RPL, however, is not disengaged when A hydraulic system is depressurized.
C.  The function of the RPR and RPL is to reduce the rudder authority by approximately one-third at higher speed condition. The reduced rudder deflection will permit more effective lateral control in countering rudder inputs, and will give the pilot more time to recover from a full rudder input, regardless of the cause.
D.  The RPR does not involve the system-B portion of the rudder power and control, and will has no effect on the yaw damper system operation.  The RPR is monitored by the yaw damper coupler.  Failure of the RPR to disengage when commanded or a failure resulting in reduced pressure less than 500 psi is indicated by illumination of FLT CONTROL A LOW PRESSURE warning lamp on the Pilot’s Overhead Panel P5-3 (Fig. 9).  The yaw damper coupler also has BITE for the rudder pressure reducer (AMM 22-12-01/001).
E.  The RPR can be commanded to high pressure using the manual lever. In this configuration, the RPR will not respond to yaw damper coupler command to reduce pressure.
13.  Standby Rudder Actuator Shutoff Valve (Fig 7)
A.  The standby rudder actuator shutoff valve is located on the aft bulkhead of the main wheel well. The unit is mounted on the standby system modular unit by four bolts.  The valve is electrically operated from a 28 volt-dc source, and consists of a motor spool sleeve and cartridge.  The cartridge containing the spool and sleeve fits into a cavity in the modular package.  The electric motor is splined to a cam which converts rotary motor action into linear spool travel in the sleeve.  The valve is equipped with a manual override lever and position indicator.  The manual override allows the valve to be positioned with electrical power off. The valve is on when the lever is in position 1, and off when the lever is in position 2.
14.  Standby Rudder Actuator (Fig 6)
A.  The standby rudder actuator positions the rudder when hydraulic systems A and B are not available.  The actuator consists of a bypass valve, control valve, and the actuating cylinder.  Standby hydraulic power for the standby actuator is controlled by system A and B switches on the overhead flight controls panel.
B.  The STBY RUD ON light on the P5-3 overhead panel will illuminate when the standby rudder actuator is pressurized.  The standby rudder actuator is pressurized when either A or B flight control switch on the P5-3 panel is switched to standby or when the main PCU force fight monitor trips.  The Master Caution and the Flight Control annunciators will also illuminate.
C.  Hydraulic pressure supplied from the standby system operates the actuator.  Rotation of the input crank will position the control valve to port fluid to the actuating cylinder.
500 
27-21-0 Page 16  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  May 01/03 

W32654 W32663
500  Rudder Pressure Reducer 
May 01/03  Figure 8 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  27-21-1 Page 17 

Rudder Hydraulic System Schematic  500 
27-21-1  Figure 9  May 01/03 
Page 18 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

15.  Operation
A.  The rudder control system is operated by two sets of pedals, one for each pilot.  Pedal movement is transmitted to forward quadrants and jackshafts by rods.  The two forward quadrants are interconnected by a bus rod.  Cables transmit forward quadrant motion to the aft quadrant located in the vertical fin.  Rotation of the aft quadrant in turn causes rotation of the rudder control torque tube.
　
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