To move the L/G to the extended position, the L/G selector-valve is energized. Hydraulic pressure is then applied through port A. This extends the piston and compresses the actuator spring. The piston strikes the latch assembly, which pivots to release the bearing from the hook cam. The hook opens due to the tension springs and L/G pin forces, and contacts the stop bolt. When the L/G has fully extended, the two hydraulic ports are opened to system return and the actuator spring releases the piston.
(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 released. The L/G retracts and the L/G pin strikes the upper hook jaw. This causes the hook to pivot and the bearing to move across the hook cam face. When the hook contacts the stop bolt, the tension springs pull the latch assembly over the hook cam, this locks the L/G in position.
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(c)
Proximity Sensors
During the operation of the locking mechanism, the target to proximity sensor relationship changes. This positional change causes an uplock 'locked' or 'unlocked' signal to be supplied to the LGCIU's.
(d)
Hydraulic Failure
When hydraulic pressure is not available, the uplock is released by mechanical operation of the release lever (free-fall system). When the free-fall extension-handle is rotated, the splined shaft rotates. Rotation of the splined shaft causes the release lever to release the bearing from the hook cam. The hook opens due to the tension springs and L/G pin-forces.
The reset of the extension handle, resets the release lever (free-fall system), which returns the uplock to its 'normal' open position.
K. NLG Uplock (2530GM)
(Ref. Fig. 034, 035)
(1) Description
The NLG uplock is a mechanical device that automatically locks the NLG in the retracted position. The uplock is closed mechanically and opened hydraulically in the normal extension and retraction mode. The uplock can also be opened mechanically in the free-fall extension mode (Ref. 32-33-00). 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) Casing
The casing has two halves which are connected with bolts. The hydraulic actuator has a piston, and is connected to the casing. A spring keeps the piston retracted, when there is no hydraulic pressure. The actuator has two hydraulic ports A and B.
Two internal attachment lugs are used to install the uplock to the airframe.
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NLG Uplock (2530GM) Figure 034
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NLG Uplock - Schematic Figure 035
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A rigging pin hole is provided for initial installation and subsequent adjustment of the free fall system.
(b)
Proximity Sensors
Two proximity sensors are attached to the casing and the targets are attached to the lock lever. They continuously supply an independent electrical signal to show the uplock configuration (uplock closed = 'target near' or uplock open = 'target far').
(c)
Lock Mechanism
The primary components of the lock mechanism are a lock lever and a hook. The lock lever has two bearings and two targets. Each bearing turns on a pin at its center. The lock lever and the hook also turn on pins at their centers. Springs tension the lock lever and the hook. The hook has a cam which touches the lower bearing on the lock lever.
The mechanical release mechanism has a release cam attached to a splined drive shaft. This shaft connects to the Free-Fall Extension System (Ref. 32-33-00).
(2) Operation
(a)
Gear Extend
To move the L/G to the extended position, the L/G selector-valve is energized. Hydraulic fluid goes through port 'A' which extends the piston and compresses the actuator spring. The piston strikes the lock lever, which pivots and releases from the hook cam. The hook opens due to return spring and L/G pin forces. The two hydraulic ports are opened to system return, and the actuator spring releases the piston. When the L/G has fully extended, the hydraulic ports open (to system return) which causes the actuator spring to retract the piston. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：A320飞机维护手册 AMM LANDING GEAR 起落架4(42)
