The Nose Landing Gear (NLG) is a direct action type shock strut that is electrically started and hydraulically operated. The extension and retraction system is operated through hydraulic system No. 3. The NLG is hydraulically operated by the retraction actuator installed in the nose landing gear wheel bay.

The NLG forward doors are hydraulically operated to open and close. The doors are controlled by the landing gear selector valve. The forward doors open immediately before NLG extension, and close immediately after.

The NLG is retracted by the retraction actuator and kept in the NLG wheel bay. The retracted NLG is locked in the up position by the uplock. Immediately after the NLG is retracted, the forward doors close. The NLG is extended by the retraction actuator and locked in the down position by the downlock. Immediately after the NLG is extended, the forward doors close.

The nose gear retraction actuator is a two-position hydraulic actuator. The actuator is used to extend and retract the NLG. The actuator has a piston, a cylinder, three restrictors, and hydraulic seals. The cylinder end of the actuator is attached to the aircraft structure. The piston end is connected to the two lugs on top of the NLG shock strut.

The actuator cylinder is a steel part which has two hydraulic ports with restrictors. One port is used for fluid flow to extend the actuator piston. The other port is to permit fluid to move to the retract port on the opposite side of the cylinder. The restrictor is installed in the retract port and is used to control the speed of fluid movement during extension and retraction. The NLG actuator piston has a chrome plate layer and is installed in the cylinder. A scraper is installed to prevent damage to the internal seals by unwanted objects. 

The nose gear uplock assembly is a mechanical/hydraulic lock. It is used to lock the NLG in the retracted position. The lock is started mechanically and released hydraulically. The uplock is attached to the bottom of the flight compartment floor in the NLG wheel well.

There are two mechanical release levers installed on the body of the uplock. One lever is used to release the lock during emergency gear extension. The other is used for mechanical release during ground operations. A mounting bracket for the proximity sensor is installed between the actuator and the body of the uplock. The targets for the proximity sensors are installed on the manual release lever and on the emergency release lever.

The nose gear forward door actuator (written as the “actuator” in this procedure) is installed in the NLG wheel well.

The actuator is attached to the door uplock assembly at the cylinder end and the door tube mechanism at the piston end. It is attached at each location with a shoulder bolt which is safetied by a nut and a cotter pin.

The actuator is hydraulically operated by hydraulic system No. 3. The actuator transmits a mechanical force to the torque tube assembly. The door actuator has two hydraulic ports; an inlet and an outlet. The inlet port is connected to the hydraulic line. The outlet port is connected to the return line of the hydraulic system No. 3. 

The nose gear forward door uplock assembly (written as the “uplock assembly” in this procedure) is installed in the NLG wheel well. Theuplock assembly has:

• an uplock frame to support the latch subassembly
• two lock springs
• a lock subassembly
• a link subassembly
• a rocker subassembly
• an emergency lever subassembly

The forward door actuator cylinder is held in the rocker subassembly by a shoulder bolt. The shoulder bolt is safetied by a nut and a cotter pin.

When hydraulic pressure is applied to the actuator extend port, two operations occur at the same time. The piston will extend to cause the door torque tube to move; and the action of the actuator cylinder will move the rocker subassembly rearward. The rearward movement will cause the link subassembly to release the lock subassembly and the latch subassembly. This will let the doors open.

In the retraction mode, hydraulic pressure is applied to the actuator retract port. As the pressure moves the piston back, the mechanical action will move the door torque tube. As the torque tube moves, the door links will pull the forward doors closed. At the end of the piston retraction, the cylinder will momentarily move, this will make the rocker subassembly to move. This lets the lock subassembly and the latch subassembly move to the open position.

When the torque tube reaches the latch subassembly, the spring loaded latch will suddenly close. The latch subassembly is held closed by the lock subassembly which is controlled by the link subassembly. The forward door uplock has an emergency lever subassembly to release the uplock in an emergency. The lever is released by a cable and a tee handle found in the flight compartment. The emergency lever subassembly is also used by ground crew for regular maintenance.