(8)  
When force is applied by the actuators, collar pins transmit a turning moment to the collar. The force is transferred through the torsion links to turn the inner cylinder to the right or left. This causes the axle to rotate and give steering action to the nose wheels.

 (9)  
When the nose gear is turned by the towing vehicle the steering actuator pistons act like pumps, forcing fluid out of the steering cylinders and creating a pressure differential across the bypass valve. The valve opens allowing equalizing flow to the actuator pistons. The inserted towing pin will prevent the summing lever from moving and hold the metering valve in neutral position. The net result is that pressure is equalized on the opposing sides of the steering actuator pistons. The bypass valve is held in the closed (null) position whenever the steering hydraulic system is pressurized. However the steering tiller and cable systems follow the nose wheel movement if the towing pin is removed and torsion links are connected. The force required to move the steering tiller to initiate a turn is 7 to 8 pounds.

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 32-51-00
 ALL  ú ú 01 Page 9 ú Jun 10/88
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 747-400 MAINTENANCE MANUAL
SNUB COMPENSATOR
RETURN
(TYP) VALVE CHECK  VALVE METERING STEERING SPRING CENTERING  STEER LEFT ACTUATORS WILL VALVE OUT STRAIGHT SLIDE NOSE WHEEL 
PRESSURE SYSTEM 
VALVE BYPASS 
CYLINDER LINE LEFT TURN  CYLINDER LINE RIGHT TURN 
ACTUATOR STEERING  ACTUATOR STEERING 
VALVES SWIVEL TRUNION 
COLLAR STEERING  SYSTEM PRESSURE PRESSURE SNUB COMPENSATOR RETURN 
Figure 5 (Sheet 1) Nose Wheel Steering Schematic 

U23299
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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 ALL  ú ú 01 Page 10 ú Jun 10/88
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
RIGHT LEFT ACTUATOR ACTUATOR
NOSE WHEEL STRAIGHT AHEAD. SHIMMY DAMP-ENING SUPPLIED BY SNUB CONPENSATOR
NOSE WHEEL TURNING LEFT LEFT-HAND STEERING ACTUATOR ON CENTER
NOSE WHEEL IN MAXIMUM LEFT TURN, LEFT-HAND STEERING ACTUATOR PAST CENTER
PISTON
STEERING COLLAR
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 32-51-00
FWD
54.4` 22.3`
FWD
85.0`
28.6`
FWD
Nose Wheel Steering SchematicFigure 5 (Sheet 2)
ALL  ú ú 01 Page 11 ú Jun 10/88
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 FAULT ISOLATION/MAINT MANUAL
NOSE WHEEL STEERING SYSTEM
COMPONENT  FIG. 102 SHT  QTY  ACCESS/AREA  REFERENCE 
X503,H87 ACTUATOR - RUDDER PEDAL INTERCONNECT,  1  2  FWD PASS CABIN 32-51-07 
ACTUATOR - STEERING 1  2  NOSE LANDING GEAR  32-51-05 
ASSEMBLY - METERING VALVE COMPENSATOR  1  1  NOSE LANDING GEAR, METERING VALVE  32-51-11 
CIRCUIT BREAKERS - 1  FLT COMPT, P7-2 
NOSE GR STRG PRI, C1212  1  7G25 
NOSE GR STRG ALTN, C2000  1  7G26 
COLLAR - STEERING  1  1  ACTUATOR ASSEMBLY NOSE LANDING GEAR, STEERING  32-51-06 
COMPENSATOR - CABLE  1  1  BAY, CABLE COMPENSATOR MECHANISM ELECTRONICS/ELECTRICAL EQUIPMENT  32-51-09 
DRUM - CABLE  1  2  LEFT OR RIGHT FLT COMPT  32-51-01 
LINK - PIVOT  1  1 NOSE GEAR WHEEL WELL, CABLE COMPENSATOR MECHANISM 32-51-10
PRI NOSE GEAR SQUAT, R853 ALT NOSE GEAR SQUAT, R854 RELAY (REF 31-01-39, FIG. 101) MECHANISM - RUDDER PEDAL STEERING  1  1  FWD PASS CABIN  32-51-02 
SWITCH - PEDAL STRG ACT MONITOR, S1349  1  1  FWD PASS CABIN, RUDDER PEDAL STEERING MECHANISM  * 
TILLER 1  2  FLT COMPT  32-51-01 
VALVE - METERING  1  1  ACTUATOR ASSEMBLY NOSE LANDING GEAR, STEERING  32-51-04 
　
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本文鏈接地址：747-400 AMM 飛機維護手冊 起落架 LANDING GEAR 7(179)