(b)
Doors Close
To close and lock the L/G doors, the L/G door selector-valve is energized. Hydraulic pressure is applied through port B, to make sure that the piston is fully released. The door closes and the door pin strikes the upper hook jaw. This causes the hook to pivot and the roller 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, and locks the L/G door in position.
(c)
Proximity Sensors
During the operation of the locking 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.
(d)
Mechanical Release
When hydraulic fluid pressure is not available , the door uplock is released by mechanical operation of the manual release lever (free-fall system). When the free-fall extension handle is rotated, it rotates the splined shaft. Rotation of the splined shaft causes the release lever to disengage the roller from the hook cam. The hook opens due to the tension springs and door pin forces.
The reset of the manual release lever returns the door uplock to its 'normal' open condition.
(e) Ground Door Opening
The ground-door opening-system uses a separate cam but operates identically to the free-fall system.
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M. NLG Door Uplock 2534GM
(Ref. Fig. 038, 039)
(1) Description
The NLG door uplock is a mechanical device that automatically locks the NLG 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 the Free-Fall Extension (Ref. 32-33-00) and the Ground Door-Opening (Ref. 32-22-00) 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 mehanical release mechanism
-
a ground door opening release mechanism.
Two integeral attachment lugs are provided to attach the uplock to the airframe.
Rigging pin holes are provided for initial installation and subsequent adjustment of:
-
the free fall system
-
the ground door opening system.
-
the proximity sensors.
(a) Casing
The casing has two halves which are connected by bolts. The hydraulic actuator contains a piston and is connected to the casing. A spring keeps the piston retracted, when there is no hydraulic pressure. The actuator has two ports A and B. The casing has holes for rigging pins, which carry out these functions:
-
a rigging check of the position of the mechanism for the Free-Fall Extension System
-
a rigging check of the position of the mechanism for the Ground Door-Opening System
-
a rigging check of the proximity sensors.
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NLG Door Uplock (2534GM) Figure 038
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NLG Door Uplock - Schematic Figure 039
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(b)
Proximity Sensors
The proximity sensors are installed on the casing, and the targets are installed on the lock lever. They continuously supply an independent electrical signal to show the uplock position (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 rollers and two targets. Each roller 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 roller on the lock lever.
The mechanical release mechanisms have release cams attached to the splined drive shafts. The shafts connect to the Free Fall Extension System (Ref. 32-33-00) and the Ground Door Opening System (Ref. 32-12-00).
(2) Operation
(a)
Doors Open
To open the L/G doors, the L/G door selector-valve is energized. Hydraulic pressure is supplied through Port A, to extend the piston and compress the actuator spring. The piston strikes the lock lever, which pivots and disengages from the hook cam. The hook opens due to return spring and NLG door pin forces.
(b)
Doors Close
