The nose gear door system helps keep the air flow over the aircraft smooth and continuous when the landing gear is extended or retracted. The nose gear door system uses two nose gear forward doors and a nose gear aft door to fully close the nose gear wheel well.

The nose gear has one small door, which moves with the gear and two forward doors that are positioned by one hydraulic actuator. The same door selector valve actuates all hydraulically actuated landing gear doors.

The nose gear bay is completely enclosed by an aft door mechanically linked to the nose gear, and by two hydraulically actuated forward doors. During normal operation, the forward doors open only during gear retraction and extension (transit) operation. The forward doors can be manually opened by the manual release system for ground maintenance operation when required. The forward gear doors may be closed via a push button at the forward external services panel with hydraulic system no. 3 powered. The aft door, linked to the nose gear, opens and closes with gear operation.

Hinged at the rear, the nose gear forward door moves with the gear. There are two mounting brackets near the fwd edge for adjustable control rods which have the other ends connected to the nose gear outer cylinder directly above the steering cuff.

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There are two nose gear forward doors, one on the left and one on the right of the nose gear wheel well.

The nose gear forward doors give a continuous aerodynamic shape to the nose gear wheel well when the landing gear is extended or retracted. When the landing gear control handle is moved up or down, the nose gear forward doors will open before the landing gear moves. The doors will close again when the extension or retraction cycle is complete. There is one forward door actuator, which uses a series of linkages and torque tubes to operate the two nose gear forward doors.

The nose gear forward doors close inward. The door uplock assembly is used to hold the nose gear forward doors up and locked. The forward door actuator is part of the door uplock assembly.

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There is one nose gear aft door. Two hinges at the top of the nose gear aft door connect the door to the aircraft structure.

Two push/pull rods connect the nose gear aft door to the NLG. The push/pull rods are bolted to a bracket on the main fitting of the NLG.When the NLG is retracted, the nose gear aft door completes the aerodynamic shape of the landing gear wheel well.

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The nose gear forward door mechanism has the two nose gear forward door push/pull rods, and the nose gear forward door spring. The nose gear forward door mechanism also has the nose gear forward door torque tube, the nose gear forward door uplock, and the nose gear forward door actuator. The forward door push/pull rods transmit movement from the torque tube to the left and right forward doors.

The nose gear forward door torque tube is attached to the aircraft structure on the left and right sides. The forward door actuator moves the forward door torque tube. The forward door spring is attached to the right side of the forward door torque tube. When the forward doors close, tension is put on the spring. When the forward doors are unlocked, the spring helps to open the doors.

The forward door uplock assembly is installed in the nose wheel well under the flight compartment floor. The forward door uplock assembly has the forward door actuator and a series of links. The door uplock assembly unlocks the forward doors before the landing gear is moved up or down. The door uplock assembly then locks the forward doors on completion of the cycle. If there is a hydraulic malfunction, the manual release handle in the flight compartment is used to open the forward doors. 

Nose Door Actuator

A hydraulically activated cylinder and piston assembly, the actuator positions the forward Nose Doors.

The cylinder is mounted to the Uplock assembly and the piston is connected to the NLG Door torque tube. Hydraulic System pressure No. 3 is used in the NLG Door actuator. The actuator extends to open the nose doors.

The torque tube is rotated by a hydraulic actuator. A roller engages with the lock mechanism when the door is closed. The lock is hydraulically released when the door actuator initially extends. As the actuator extends it moves the uplock rocker and causes the unlock link to release the door up latch from the door roller.

Further extension of the actuator overcomes the spring, rotates the latch allowing the torque tube to rotate and open the door. When the doors are fully open the lower links are in the overcenter position and held there by the actuator and springs. When the actuator retracts, it rotates the torque tube closing the doors until the roller engages the latch.

Nose Door Uplock

The nose door uplock is a mechanical, overcenter type device, spring-loaded to hold the nose doors in the fully closed position. The lock is mechanically released when the gear manual release system is activated.

This method is also used to open the landing gear doors for ground maintenance purposes. An overcenter spring attached to the left push/pull rod ensures the doors open fully during manual release activation. A ground safety pin installs on the forward right side of the torque tube to prevent closing during ground maintenance activities. A proximity sensor provides a locked indication signal to the LGECU.

Forward Door Torque Tube

The nose gear forward door torque tube is attached to the aircraft structure in the NLG wheel well. The torque tube has two torque arms, one on the left side and one on the right.

The forward door spring is connected between the right torque arm and the aircraft structure. The right side of the torque tube has the attach arm for the forward door actuator. The attach arm has the door uplock pin which engages in the door uplock latch when the doors are closed.

Forward Door Push/Pull Rod

There are two nose gear forward door push/pull rods, one on the left and the other on the right.

The forward door push/pull rods are attached to the forward door torque tube at one end and to the forward doors at the other. The function of the forward door push/pull rods is to open and close the forward doors. 

Forward Door Spring

The nose gear forward door spring is connected to the right torque arm at one end and to the aircraft structure at the other. The function of the forward door spring is to help the forward door actuator open the nose gear forward doors. If there is a hydraulic malfunction and a manual release is necessary, the forward door spring is used to open the forward doors.

Aft Door Control Rod

There are two nose gear aft door control rods, one on the left side of the aft door and one on the right. The aft door control rods are attached to the NLG beam and to the aft door bracket. The left and right aft door control rods are the same and are adjusted to the same length. When the NLG is retracted, the aft door control rods pull the aft door into position.

On a gear up or down selection, the LGECU energizes the door selector valve to hydraulically extend or retract the nose and main door actuators. The hydraulically activated doors are normally in the closed position. They open to allow the gear to extend or retract or for ground maintenance. When they are closed, there is no hydraulic pressure to the actuators. The doors are held in the closed position by the uplocks.

There is a proximity sensor on each main gear inner door uplock and the nose gear door uplock. The nose gear door mechanism and each main gear door have open and closed sensors. All doors must be open before any gear can extend or retract.

Opening and Closing for Maintenance

For ground maintenance purposes, pulling up on the manual release handle opens the doors. This isolates the actuators from the hydraulic system and manually releases the uplocks. The handle mechanically releases the door uplocks and blocks hydraulic system No. 3 pressure from the door actuators. Since there is no hydraulic pressure on the door actuators, the doors drop open. Safety collars are installed on the MLG door actuator arms and a safety pin is installed in the nose door torque tube mechanism, before stowing the release handle.

After removing the safety collars from the main gear doors and safety pin from the nose gear doors, pressurize hydraulic system No. 3. Pressing the door close pushbutton switch on the lower nose service panel on the left side of the nose fuselage energizes the door selector valve close solenoid. Hydraulic pressure then closes the doors and the button can be released, removing hydraulic pressure from the actuators.

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Component Location Index
IDENT	DESCRIPTION	LOCATION	IPC REF
-	NOSE-GEAR FORWARD DOOR	ZONE(S) 123	32-22-01 [ GX ] [ GXRS ] [ G5000 ]
-	NOSE-GEAR AFT DOOR	ZONE(S) 123	32-22-05 [ GX ] [ GXRS ] [ G5000 ]
-	NOSE-GEAR FORWARD-DOOR MECHANISM	ZONE(S) 123	32-22-09 [ GX ] [ GXRS ] [ G5000 ]
-	NOSE-GEAR FORWARD-DOOR TORQUE-TUBE	ZONE(S) 123	32-22-13 [ GX ] [ GXRS ] [ G5000 ]
-	NOSE-GEAR FORWARD-DOOR PUSH/PULL-ROD	ZONE(S) 123	32-22-17 [ GX ] [ GXRS ] [ G5000 ]
-	NOSE-GEAR FORWARD-DOOR SPRING	ZONE(S) 123	32-22-21 [ GX ] [ GXRS ] [ G5000 ]
-	NOSE-GEAR AFT-DOOR CONTROL-ROD	ZONE(S) 123	32-22-25 [ GX ] [ GXRS ] [ G5000 ]

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