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LANDING GEAR ALTN EXTENSION SYSTEM -DOOR RELEASE/SAFETY VALVE MODS -FUNCTIONAL DESCRIPTION

General
Each door release/safety valve module contains these components:
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Door release actuator

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Door safety valve

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Safety valve latch

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Safety valve latch position sensing switch

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Solenoid-operated valve.

The door release/safety valve modules are part of the alternate extension system. They are also connected to the normal landing gear extension-retraction system. The hydraulic fluid to close the landing gear doors flows through the door release/ safety valve modules.
Door Release Actuator
The door release actuator extends when it gets hydraulic pressure from the alternate extend power pack.
Each MLG door release actuator releases the gear door uplock mechanism. The NLG door release actuator releases the lock inside the NLG door actuator. This permits the doors to open.
After it extends, each door release actuator permits hydraulic pressure to go to the gear alternate uplock release actuator.
An internal spring returns the door release actuator to its retracted position after the power pack stops operation.
Door Safety Valve
The safety valve is a two-position valve: SAFE and NORMAL.
During normal operation of the landing gear extension-retraction system, the valve is in the NORMAL position. In the NORMAL position, door close hydraulic pressure can go to the door actuator to close the door.
The door release actuator moves the safety valve to the SAFE position as it extends. In the SAFE position, the door close pressure cannot go to the door actuator.
A latch keeps the safety valve in the SAFE position. A position sensing switch controls the gear door unsafe light.
Solenoid-Operated Valve
The solenoid-operated valve is a two-position valve.
A signal to close the landing gear door energizes the solenoid. This moves the valve and permits hydraulic pressure to unlatch the safety valve. To close the door, you must have door close hydraulic pressure and the door-close signal at the same time.
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LANDING GEAR ALTN EXTENSION SYSTEM -DOOR RELEASE/SAFETY VALVE MODS -FUNCTIONAL DESCRIPTION

After hydraulic pressure releases the latch, a spring moves the safety valve to the NORMAL position. The hydraulic pressure then goes to the door actuator and the door closes.
Training Information Point
A door safety pin hole is on each module. The safety pin keeps the safety valve in the SAFE position. You cannot close the door with the safety pin installed in the door release/safety valve module.
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LANDING GEAR ALTN EXTENSION SYSTEM -DOOR RELEASE/SAFETY VALVE MODS -FUNCTIONAL DESCRIPTION

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LANDING GEAR ALTERNATE EXTENSION SYSTEM -MLG ALTERNATE UPLOCK RELEASE ACTUATOR

General
The MLG alternate uplock release actuators supply the force to unlock the MLG uplocks. This permits the MLG to extend by gravity and airloads.
There is one MLG alternate uplock release actuator for each main landing gear.
Physical Description
The actuators extend when they get alternate extend pressure.
The MLG alternate uplock release actuators turn cranks which touch the gear uplock mechanisms to release the overcenter locks of the gear uplock mechanisms.
Springs inside the actuators return the actuators to the retracted position when there is low alternate extension hydraulic pressure.
Location
The MLG alternate uplock release actuators are in each wheel well on the MLG uplock assembly.
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LANDING GEAR ALTERNATE EXTENSION SYSTEM -MLG ALTERNATE UPLOCK RELEASE ACTUATOR

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LANDING GEAR ALTERNATE EXTENSION SYSTEM -NLG ALTERNATE UPLOCK RELEASE ACTUATOR

Purpose
The nose landing gear alternate uplock release actuator supplies the force to unlock the nose landing gear lock link mechanism. This permits the nose landing gear to extend by gravity and airloads.
Location
The nose landing gear alternate uplock release actuator is in the aft-top corner of the nose wheel well.
Functional Description
The actuator extends when it gets alternate extend pressure.
The nose gear alternate uplock release actuator moves a crank. A roller on the crank moves and unlocks the nose landing gear lock links.
　
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