S 712-048

 (2)  
Move the control lever to the UP position and monitor the hydraulic lines as follows:

 (a)  
Make sure the flexible hydraulic lines connected to the downlock actuator for the right main landing gear move when the control lever is moved to UP (Fig. 203).

 S 862-049
 (3)  
Move the control lever to the DN position.

 E.
Put the Airplane Back to Its Usual Condition

 S 862-050
 (1)  Make sure the fluid in the hydraulic reservoir is at the correct level. Fill if it is necessary (AMM 12-12-01/301).
 S 092-051
 WARNING:_______OBEY THE REMOVAL PROCEDURE FOR THE DOOR LOCKS. THE DOORS OPEN AND CLOSE QUICKLY. THE MOVEMENT OF THE DOORS CAN CAUSE INJURIES TO PERSONS AND DAMAGE TO EQUIPMENT.
 (2)  
Remove the door locks (AMM 32-00-15/201).

 S 862-052

 (3)  
Remove the pressure from the left hydraulic system if it is not necessary (AMM 29-11-00/201).

 (4)
Remove electrical power if it is not necessary (AMM 24-22-00/201).

 S 862-053
 

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757 MAINTENANCE MANUAL
 NOSE GEAR EXTENSION AND RETRACTION - DESCRIPTION AND OPERATION
______________________________________________________________
 1.  General_______
 A.  The extension and retraction system for the nose landing gear hydraulically retracts and extends the nose landing gear. Pressure is supplied by the left hydraulic system.
 2.  Component Details_________________
 A.  Retract Actuator (Fig. 1)
________________
 (1)  
The actuator is attached to the aft wall of the wheel well for the nose landing gear and to the shock strut trunnion. The actuator hydraulically retracts to retract the landing gear. Hydraulic pressure is supplied to the retract actuator only during landing gear retraction.

 B.  
Lock Actuator (Fig. 2)

_____________
 (1)  
The lock actuator hydraulically pushes the lock links into the overcenter position. This locks the nose landing gear in the extended or retracted position. The actuator also hydraulically pushes the lock links out of the overcenter position when the extension and retraction cycles start.

 (2)  
The actuator extends during landing gear extension to lock the lock link. The actuator retracts during landing gear retraction to move the lock link from the locked position. The actuator is connected to the aft wall of the wheel well and the aft lock link.

SEE A
WHEEL WELL WALL
RETRACT
ACTUATOR

A
SHOCK
STRUT

Retract Actuator Figure 1

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MAINTENANCE MANUAL

 C. Gear-Operated Sequence Valve (Fig. 3)
____________________________
 (1)  
The gear-operated sequence valve makes sure that the nose landing gear is fully extended or retracted before the doors close. The valve is mechanically connected to the drag strut assembly. It is installed on the aft wall of the wheel well. The valve sends hydraulic fluid to the lock actuator and the door actuator.

 D.
Door-Operated Sequence Valve (Fig. 4)

____________________________
 (1)  
The door-operated sequence valve is attached to the forward wall of the wheel well. The valve is connected to the door actuator with rods and cranks. The valve makes sure that the doors are open before the landing gear extends or retracts. Hydraulic fluid flows through the valve to the lock actuator and the gear sequence valve bypass valve.

 E.
Gear Sequence Valve Bypass Valve (Fig. 5)

________________________________
 (1)  The gear sequence valve bypass valve receives a mechanical input from the drag strut. This permits hydraulic fluid to flow to the retract actuator, around the door-operated sequence valve, as the nose landing gear gets near the retracted position. The module is installed on the left wall of the wheel well.
LOCK SPRING
SEE  A WHEEL WELL WALL 
AFT LOCK LINK 
LOCK ACTUATOR 

FWD
A
Lock Actuator Figure 2

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 F. Door Actuator
_____________
 (1)  
　
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本文鏈接地址：757 AMM 飛機維護手冊 起落架 CHAPTER 32 - LANDING GEAR 2(74)