(d)  
Install the clamping bolt, the nut, and the cotter pin in the safety valve.

 (e)  
Remove the hydraulic caps and plugs from the hydraulic lines.

 (f)  
Connect the hydraulic lines to the safety valve.

 S 094-008
 WARNING: YOU MUST CAREFULLY DO THE STEPS IN THE TASKS BELOW TO REMOVE
_______ THE DOOR LOCKS FROM THE LANDING GEAR DOORS. THE DOORS CAN CLOSE QUICKLY IF YOU DO NOT REMOVE THE DOOR LOCKS CORRECTLY. THIS CAN CAUSE INJURY TO PERSONS OR DAMAGE TO EQUIPMENT.
 (3)  
Do this task: "Wing Landing Gear Door Lock Removal" (Ref 32-00-30/201).

 S 094-016

 (4)  
Do this task: "Body Landing Gear Door Lock Removal" (Ref 32-00-30/201).

 S 864-017
 WARNING: MAKE SURE THAT PERSONS AND EQUIPMENT ARE CLEAR OF ALL CONTROL
_______ SURFACES BEFORE YOU SUPPLY HYDRAULIC POWER. AILERONS, RUDDERS, ELEVATORS, FLAPS, SPOILERS, LANDING GEAR, AND THRUST REVERSERS CAN MOVE QUICKLY WHEN YOU SUPPLY HYDRAULIC POWER. THIS CAN CAUSE INJURY TO PERSONS AND DAMAGE TO EQUIPMENT.
 (5)  Supply hydraulic pressure to system No. 4 (Ref 29-11-00/201).
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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747-400 MAINTENANCE MANUAL
 S 714-010
 (6)  Do a check of the operation of the safety valve:
 WARNING: MAKE SURE ALL PERSONS AND EQUIPMENT ARE AWAY FROM THE DOOR
_______ OPERATION AREA. A FAST MOVEMENT OF THE DOORS CAN CAUSE INJURY TO PERSONS AND DAMAGE TO EQUIPMENT.
 (a)  
Move the ground release handle for the doors of the main landing gear to the DOORS OPEN position.

 (b)  
Do a check for hydraulic leaks.

 (c)  
Move the ground release handle for the doors of the main landing gear to the DOORS CLOSED position.

 (d)  
Do a check for hydraulic leaks.

 S 864-011
 (7)  Remove hydraulic pressure from hydraulic system No. 4 (Ref 29-11-00/201).
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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2.

3.

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747-400 MAINTENANCE MANUAL
 BODY GEAR AND DOOR EXTENSION AND RETRACTION -
_____________________________________________ DESCRIPTION AND OPERATION
_________________________
General (Fig. 1)
_______
 A.  The body gear extension system raises and lowers the body landing gear. The body gear retracts or extends simultaneously with the wing gear and the nose gear when the landing gear control handle is moved into the UP or DN detent. The retraction mechanism is comprised of the following components. The body gear actuator supplies the force required to raise or lower the gear. The actuator is attached to the landing gear strut forward of the trunnion. The other end of the actuator is attached to the airplane structure on the rear body gear wheel well bulkhead, well above the trunnion. The body gear locking mechanism, located on the after bulkhead of the body gear wheel well, locks the gear in the up position. Locking of the gear in the down position is accomplished by the downlock actuator assisted by a downlock spring bungee. The actuator and bungee position the upper and lower jury struts slightly overcenter to brace the upper and lower drag struts so they will not fold.
 B.  The wheel well doors are operated through linkage by a hydraulic actuator. When the landing gear control handle is placed in the DN position, hydraulic pressure through sequence valves causes the doors to open before the gear extends. After the gear is down and locked, these doors close. Additional doors attached to the shock strut and operated by it complete closure of the wheel well when the gear is up as shown in figure 2.
Body Gear Actuator (Fig. 3)
__________________
 A.  The body gear actuator provides the power required to retract and extend the body landing gear. The actuator is a hydraulic cylinder with a force piston. Snubbing action incorporated internally in the actuator slows the piston movement as the limits of its travel are approached in either direction. The head (cylinder) end of the actuator is attached to a structural fitting high on the after wheel well bulkhead. The piston rod end attaches to a fitting on the body gear shock strut forward and below the centerline of the trunnion. Three ports, UP DN and RET are incorporated in the head of the cylinder to supply hydraulic fluid for up or down actuation and return for displaced fluid.
　
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