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 ALL  ú ú 01 Page 2 ú Feb 10/91
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400 MAINTENANCE MANUAL
 LANDING GEAR CONTROL SYSTEM - DESCRIPTION AND OPERATION
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General (Fig. 1)
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 A.  The landing gear control system is operated by moving the control handle assembly in the landing gear control handle module. The control handle module is located on the right side of the pilots' center instrument panel. A cable system transmits control handle movement to two selector valves located in the body gear wheel wells. When positioned by the control handle, the selector valves direct hydraulic pressure to the actuators for gear and door retraction and extension. The control handle is provided with a landing gear lever lock to prevent movement to the gear UP position, when the airplane is supported on the gear. The landing gear lever lock can be bypassed by depressing the lock overide button. This manual overide can be used when performing certain tests or in an emergency.
Landing Gear Selector Valves (Fig. 2 and 3)
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 A.  Two identical landing gear selector valves direct hydraulic pressure to the landing gear up and down lines. One valve controls operation of the wing gear (figure 2) while the other controls operation of the body and nose gear. The valve controlling the wing gear is mounted on the outboard side of the right-hand body gear wheel well and the valve controlling the body and nose gears is mounted on the outboard side of the left-hand body gear wheel well as shown on figure 3. Linkage connects each selector valve to the control cable system. When the landing gear control handle is operated, motion from the handle is transferred through the cable system to a quadrant mounted above the selector valve in the right-hand body gear wheel well. This valve is then operated by a rod and crank from the quadrant. Additional cabling is installed across the airplane to a quadrant above the nose and body gear selector valve mounted in the left-hand body gear wheel well. This valve is then actuated by a rod and crank.
Landing Gear Control Cable System (Fig. 4)
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 A.  The landing gear control cable system transfers movement from the control handle module to the landing gear selector valves. The control cable system consists of ten 7 x 7 steel cables 3/32 inch in diameter. The cables run from the quadrant at the forward end of the control handle module down and aft through the ceiling of the main cabin and down to the right-hand body gear wheel well where they connect to the quadrant above the wing gear selector valve. Cables from this quadrant are routed across the airplane under the lower lobe (which encloses the top of the wheel well) to the quadrant above the nose and body gear selector valve mounted on the outboard side of the left-hand body gear wheel well.
Landing Gear Control Handle Module (Fig. 1)
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 A.  The landing gear control handle module includes various mechanical and electro-mechanical components.
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 32-31-00
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

SEE  A  STRUCTURE 
QUADRANT  A  MODULE SCREW CASE ATTACH 
FACE PLATE 

AHANDLE
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Landing Gear Control System Components Location Figure 1 (Sheet 1)
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 32-31-00
 ALL  ú ú 01 Page 2 ú Oct 10/88
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

Landing Gear Control System Components Location
Figure 1 (Sheet 2)

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