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General
The nose wheel steering rudder pedal steering mechanism
Mixes the rudder pedal and steering wheel inputs to the nose
wheel steering metering valve.
Components
The rudder pedal steering mechanism has these parts:
* Steering crank
* Rudder pedal steering quadrant
* Clutch arm
* Clutch crank stop
* Centering spring
* Eccentric drum.
Airplane In The Air
When the airplane goes into the air, a signal from the air/ground
system sends power to the rotary actuator. The rotary actuator
moves the eccentric drum to the air position. This moves the
clutch arm away from the steering crank and will not let any
movement of the rudder pedals move the clutch arm. Rudder
pedal inputs do not move the steering quadrant.
Airplane On The Ground
When the airplane is on the ground, a signal from the air/
ground system sends power to the rotary actuator. The rotary
actuator moves the eccentric drum to the ground position. This
moves the clutch arm in contact with the steering crank stops
and permits movement of the rudder pedals to move the clutch
arm and then move the steering quadrant.
Movement of the steering wheel moves the control cable and
steering quadrant. When the steering quadrant turns, the clutch
arm contacts the steering crank stops and extends the
centering spring. Because the centering spring in the rudder
system is stronger than the centering spring in the pedal
steering mechanism, the steering crank will not move.
Movement of the steering wheel does not back drive the
rudder pedals.
The steering wheel always overrides rudder pedal input
because it goes directly to the metering valve through the
control cables.
Training Information Point
The rudder pedal input linkage connects to the steering crank
by a shear rod. If the steering system can not move freely,
heavy pressure on the rudder pedals shears the shear rod. This
removes the rudder pedal connection to the steering system.
This permits the rudder system to move freely when the
steering system can not move freely.
NOSE WHEEL STEERING SYSTEM - RUDDER PEDAL STEERING MECHANISM - FUNCTIONAL DESCRIPTION
EFFECTIVITY
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BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
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NOSE WHEEL STEERING SYSTEM - RUDDER PEDAL STEERING MECHANISM - FUNCTIONAL DESCRIPTION
NOSE WHEEL STEERING SYSTEM - RUDDER PEDAL STEERING MECHANISM - FUNCTIONAL DESCRIPTION
EFFECTIVITY
GUN ALL 32-51-00
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D633A101-GUN Feb 10/2003
BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
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NOSE WHEEL STEERING SYSTEM - RUDDER PEDAL STEERING MECHANISM - FUNCTIONAL DESCRIPTION
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D633A101-GUN Oct 10/2002
BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
General
The nose wheel steering summing mechanism mixes steering
wheel input and nose gear position feedback to control the nose
wheel steering metering valve.
The steering metering valve module controls the flow of
hydraulic pressure to the steering actuators.
Location
The summing mechanism is above the upper steering plate on
the front of the nose landing gear. A protective cover (not
shown) is on the summing mechanism.
The steering metering valve is on the upper steering plate on
the front of the nose landing gear.
Physical Description
The summing mechanism has these components:
* Summing lever
* Pulley (2)
* Input rod.
The pulleys connect to each side of the summing lever. The
control cable winds around each pulley.
The steering metering valve module has these components:
* Metering valve
* Dynamic load damper
* Bypass/relief valve (not shown)
* Compensator
* Towing shutoff valve and lever
* Swivel valve (2).
Summing Mechanism
The summing mechanism pivots about its center. The input rod
connects the summing mechanism to the steering metering
valve.
Steering Metering Valve Module
The metering valve controls hydraulic flow to the steering
actuators.
The hydro-mechanical dynamic load damper decreases
shimmy damping in the nose landing gear.
The compensator keeps backpressure in the steering metering
valve. The backpressure supplies a force to dampen shimmy,
and fluid for the actuators when the nose wheel steering system
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