(c)
Damping
The end of stroke damping occurs in the two directions. The damping effect occurs when the piston head goes into the damping chamber, which causes the removed fluid to pass through the damping holes. On extension, the damping effect increases when one damping hole is closed by the piston.
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H. NLG Door Actuating Cylinder (2531GM)
(Ref. Fig. 030, 031)
(1) Description
The door actuator is a hydraulic actuator with rate control devices. The piston and piston rod are contained in a cylinder. The shape of the internal bore, the position of the return orifices, and the restrictor valve, control the damping.
(a) Actuating Cylinder
The NLG door actuating-cylinder is a two-acting type. A valve-housing on the body of the actuating-cylinder contains a check-valve. The movable part of the check-valve has a slot in the face that touches the valve seat.
The actuating-cylinder connects:
-
the door control-rod bellcrank at the piston-rod end
-
the roof of the landing gear bay at the fixed end.
(b) Restrictor
An in-line restrictor (2536GM) is installed in the line to the
annular side of the actuating cylinder. It controls the speed at
which the piston-rod operates.
The actuating cylinders range-of-travel is controlled by:
-the NLG door uplock as the NLG doors close
-an internal stop as the NLG doors open.
(2) Operation
(a) Doors Close
With the NLG doors set to CLOSE, the pressurized hydraulic fluid goes into the annular side of the actuating-cylinder. The piston-rod retracts and closes the NLG doors. On the other side of the piston, the hydraulic fluid goes to return through the main return orifice and the slot in the closed check-valve. Near the end of the piston-rod travel, the piston closes the main return orifice. This causes a large decrease in the flow of fluid to return, which damps the end of the piston-rod travel.
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NLG Door Actuating Cylinder (2531GM) Figure 030
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NLG Door Actuating Cylinder - Schematic Figure 031
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(b) Doors Open
With the NLG doors set to OPEN, the aerodynamic loads help the doors to open. The restrictor (2536GM) decreases the return flow of fluid from the actuating-cylinder. This causes a damping-pressure on the annular side of the piston to control the speed at which the NLG doors open. The restrictor-valve (2535GM) keeps a limit on the damping-pressure. To do this, the valve decreases the flow of pressurized fluid to the extend side of the actuating-cylinder.
J. MLG Uplock (2509GM,2510GM)
(Ref. Fig. 032, 033)
(1) Description
The MLG uplock is a mechanical device that automatically locks the main gear 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 with their related targets
-
a locking mechanism
-
a free-fall mechanical-release mechanism.
(a) Casing
The casing has two halves, which are connected by 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. The casing has two holes for rigging pins and are positioned for these functions: - one pin hole is for a rigging check of the position of the
mechanism for the Free Fall Extension System - one pin hole locks the uplock in the closed position and is for a rigging check of the proximity sensors.
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MLG Uplock (2509GM,2510GM) Figure 032
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MLG Uplock - Schematic Figure 033
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(b) Proximity Sensors
The proximity sensors are attached to the casing and the targets to the latch assembly. They continuously supply an independent electrical signal to show the uplock configuration (uplock closed = 'target near' or uplock open = 'target far').
The primary components of the locking mechanism are a latch assembly and a hook. The latch assembly has a bearing and two targets. The bearing turns on a pin at its center, as do the latch assembly and the hook. Tension springs connect the latch assembly to the hook. The hook has a cam which touches the bearing.
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