D. Inspection of the Rudder Pedal Interconnect Actuator and Steering Control Path for Condition and Wear.
S 216-008
(1)
Do a careful visual inspection of the steering components that follow for corrosion, the condition, and worn areas:
(a)
The pilot's and the first officer's tillers
(b)
The interconnect actuator and the mechanism of the rudder pedal
(c)
The compensator and the pivot links
(d)
The summing mechanism.
S 216-009
(2)
Do a careful visual inspection of the pulleys and cables that follow for corrosion, damage, or worn areas (AMM 20-21-03/601):
(a)
NWS1A-1 through -4
(b)
NWS1B-1 through -4
(c)
NWS2A-1 through -2
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747-400 MAINTENANCE MANUAL
(d)
NWS2B-1 through -2
(e)
If you find corrosion, damage or wear (AMM 20-21-03/600), replace the cable (AMM 32-00-40/001 & 20-11-03/400).
E.
Put the Airplane Back to Its Initial Condition.
S 866-016
(1)
Remove the DO-NOT-CLOSE tags and close these circuit breakers:
(a)
P414 Main Power Distribution Panel
1) 414D08 CAPT PWR SEAT
(b)
P415 Main Power Distribution Panel
1) 415H32 F/O PWR SEAT
S 416-012
(2)
Install the sidewall panels on the left and right side of the control cabin below the steering tillers.
S 416-022
(3)
Install the left sidewall lining in the passenger cabin forward of the first door (AMM 25-59-01/401).
S 416-015
(4)
Install the forward floor panel in the electrical and electronics compartment.
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747-400 MAINTENANCE MANUAL
NOSE WHEEL STEERING SYSTEM - DESCRIPTION AND OPERATION
______________________________________________________
1. General (Fig. 1)_______
A. Nose wheel steering is provided for airplane directional control during ground maneuvers and taxiing. Hydraulic power is used to turn the nose wheels from zero to 70 (+2/-3) degrees on either side. When the nose wheels are turned | 20 degrees from the neutral position, the body gear steering system is armed. Steering is controlled by tillers on both sides of the flight compartment and by an interconnect mechanism from the rudder pedals. The system is spring loaded to the center position. The airplane can be towed through turns up to approximately 65 degrees withoug disconnecting the torsion links. Internal cams center the nose gear when the nose gear shock strut is fully extended. Hence, turning the wheels or towing should not be attempted when the nose gear inner cylinder is extended more than 18 inches.
B. Normal steering is accomplished by using the steering tiller wheel located on either sidewall forward of the crew position. Movement of the steering tiller in either direction is transmitted by cables to a steering metering valve which directs 3000-psi hydraulic fluid to the nose wheel steering actuators for turning the steerable portion of the nose gear. A steering tiller movement of 150 degrees will give 70 degrees of nose wheel turning.
C. Rudder pedal steering is available during takeoff, landing, and taxiing where small directional changes are required. The rudder pedal linkage is connected to the steering cables. Full deflection of the rudder pedals produces about 7 degrees of nose wheel turn. The rudder pedal steering mechanism is engaged for steering on the ground by two electric actuators. The electrical ground sensing mechanism consists of a nose gear squat switch and the electric actuators. The squat switch is composed of primary and alternate sensors installed on a switch mounting bracket on the forward side of the nose gear shock strut. The sensor actuator is mounted on a support bracket on the nose gear upper torsion link. Compression of the shock strut by more than 8 inches actuates the two electric actuators to position the lever stop to engage with the rudder pedal steering mechanism. In this position any movement of the rudder pedals will be transmitted into ground directional control of nose wheel through the action of the rudder pedal steering mechanism.
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