(b)
Gear Retract
To lock the L/G in the retracted position, the L/G selector-valve is energized. Hydraulic pressure is applied through port 'B', to make sure that the piston is fully retracted.
The L/G retracts and when the L/G pin strikes the upper hook jaw, it causes the hook to pivot to the closed position. The lock lever return spring causes the lock lever to pivot and engage the hook cam. This locks the hook in the closed position.
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During the operation of the lock mechanism, the target to proximity sensor position changes. This positional change causes an uplock 'locked' or 'unlocked' signal to be supplied to the LGCIU's.
When hydraulic fluid pressure is not available, the uplock is released by the mechanical operation of the free-fall release-cam. When the free-fall extension-handle is rotated, it rotates the cam shaft. Rotation of the cam shaft causes the release cam to disengage the lock lever from the hook cam. The hook pivots open due to the return spring and land gear pin forces.
The reset of the extension handle, resets the release cam, which
returns the uplock to its 'normal' open position.
L. MLG Door Uplock 5224GA(5225GA)
(Ref. Fig. 036, 037)
(1) Description
The MLG door uplock is a mechanical device that automatically locks the MLG doors in the closed position. The uplock is closed mechanically and opened hydraulically in the normal extension and retraction mode. The uplock can also be opened mechanically in Free Fall Extension (Ref. 32-33-00) and the Ground Door Opening (Ref. 32-12-00) modes. The primary components of the uplock are:
-
a casing
-
a hydraulic actuator
-two proximity sensors and their related targets
-
a locking mechanism
-
a free fall mechanical release mechanism
-
a ground door opening release mechanism.
The door uplock is attached to the airframe by two integeral mounting lugs.
Rigging pin holes are provided for initial installation and adjustment of the free fall/ground door opening systems.
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MLG Door Uplock (2520GM,2521GM) Figure 036
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MLG Door Uplock - Schematic Figure 037
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(a) Casing
The casing has two halves which are connected by bolts. The hydraulic actuator has a piston, and is attached to the casing. A spring keeps the piston retracted when there is no hydraulic pressure. The actuator has two hydraulic ports A and B. The casing has three holes for rigging pins which are used to:
-lock the uplock in the closed position to do a rigging check of the proximity sensors
-
permit a rigging check of the mechanism for the Free-Fall Extension System
-
permit a rigging check of the position of the mechanism for the Ground Door-Opening System.
(b)
Locking Mechanism
The primary components of the locking mechanism are a latch assembly and a hook. The latch assembly has a roller and two (proximity) targets. The roller, the latch assembly and the hook turn on pins at their centers. Tension springs connect the latch assembly and the hook to the casing. The hook has a cam which touches the roller.
(c)
Release Mechanism
Each mechanical release mechanism has a release lever connected to a splined drive shaft. One connects to the Free Fall Extension System (Ref. 32-33-00) and the other to the Ground Door-Opening System (Ref. 32-12-00).
(d)
Proximity Sensors
The proximity sensors are installed on the casing, and the targets are installed on the latch lever. They continuously supply an independent electrical signal to show the uplock configuration (uplock closed = 'target near' or uplock open = 'target far').
In the open condition, the bearing on the latch assembly is against the top face of the hook cam. The tension springs hold the latch assembly and hook in this position. The targets are not near the proximity sensors.
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(2) Operation
(a)
Doors Open
To open the L/G doors, the L/G door selector-valve is energized. Hydraulic pressure is applied through port A, which extends the piston and compresses the actuator spring. The piston strikes the latch assembly, which pivots to disengage the roller from the hook cam. The hook opens, due to the tension springs and door pin forces, and contacts the stop bolt. When the MLG doors are fully open, the two hydraulic ports open to system return and the actuator spring releases the piston. 中國航空網 www.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：A320飛機維護手冊 AMM LANDING GEAR 起落架4(43)
