DOC AIRBUS | AMM A320FNOSE GEAR - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
A. Nose Gear
The nose gear is of the direct acting type with an integral shock absorber. The gear retracts forward into the fuselage.
The gear is therefore favorably assisted by the aerodynamic moments in the downlocking direction during gear extension.
The sliding tube assembly, which includes the wheel axle, is inclined 9 degrees forward. Because of this the wheels return freely to the center position.
The shock strut is made of aluminum alloy and hangs on the structure from two trunnions.
A rotating tube made of steel is installed inside the shock strut. A pinion gear installed on the tube is engaged with a rack which is connected to the steering actuating cylinder. The steering actuating cylinder transmits hydraulic power through the rack and pinion mechanism which steers the wheels.
The sliding tube is made of steel and is connected to the rotating tube by torque links.
The shock absorber includes 2 centering cams which engage with each other after take-off of the aircraft. This causes the wheels to return to the center position before gear retraction.
The nose gear is of the direct acting type with an integral shock absorber. The gear retracts forward into the fuselage.
The gear is therefore favorably assisted by the aerodynamic moments in the downlocking direction during gear extension.
The sliding tube assembly, which includes the wheel axle, is inclined 9 degrees forward. Because of this the wheels return freely to the center position.
The shock strut is made of aluminum alloy and hangs on the structure from two trunnions.
A rotating tube made of steel is installed inside the shock strut. A pinion gear installed on the tube is engaged with a rack which is connected to the steering actuating cylinder. The steering actuating cylinder transmits hydraulic power through the rack and pinion mechanism which steers the wheels.
The sliding tube is made of steel and is connected to the rotating tube by torque links.
The shock absorber includes 2 centering cams which engage with each other after take-off of the aircraft. This causes the wheels to return to the center position before gear retraction.
B. Drag Strut and Lockstay Assembly
The folding drag strut assembly with a lockstay locks the gear leg in the extended position. At the top of the assembly is a forestay, made of aluminum, and at the bottom a tubular arm made of steel. The forestay and the tubular arm are connected by a universal joint. This assembly gives primary bracing.
The lockstay assembly gives secondary bracing.
The lockstay assembly includes two parts connected by a spherical bearing:
Nose Gear - Forestay Attachments ** ON A/C NOT FOR ALL
Nose Gear - Forestay Attachments ** ON A/C NOT FOR ALL
A hydraulic cylinder on the nose gear lockstay locks and unlocks both brace assemblies in Normal operation.
If the hydraulic pressure is not available, two traction springs pull and hold the leg in the extended locked position in Free Fall extension mode.
One spring is sufficient to operate the lockstay mechanism.
The folding drag strut assembly with a lockstay locks the gear leg in the extended position. At the top of the assembly is a forestay, made of aluminum, and at the bottom a tubular arm made of steel. The forestay and the tubular arm are connected by a universal joint. This assembly gives primary bracing.
The lockstay assembly gives secondary bracing.
The lockstay assembly includes two parts connected by a spherical bearing:
- the upper link made of forged aluminum alloy, which hinges on the leg,
- the lower link made of forged steel.
Nose Gear - Forestay Attachments ** ON A/C NOT FOR ALL Nose Gear - Forestay Attachments ** ON A/C NOT FOR ALL If the hydraulic pressure is not available, two traction springs pull and hold the leg in the extended locked position in Free Fall extension mode.
One spring is sufficient to operate the lockstay mechanism.
C. Nose Gear Uplock
The nose gear uplock assembly holds the gear in the retracted position.
The uplock roller is installed on the upper hinge pin of the drag strut universal joint.
The nose gear uplock assembly holds the gear in the retracted position.
The uplock roller is installed on the upper hinge pin of the drag strut universal joint.
D. Nose Gear Actuating Cylinder
A double-acting actuating cylinder with a spherical bearing at each end, operates the nose gear. The cylinder body is attached to the rear wall of the nose gear well. The cylinder sliding rod is attached to the gear leg. The actuating cylinder contains devices for metering the hydraulic fluid.
These slow down movement of the gear at the end of retraction and during the complete extension cycle.
A double-acting actuating cylinder with a spherical bearing at each end, operates the nose gear. The cylinder body is attached to the rear wall of the nose gear well. The cylinder sliding rod is attached to the gear leg. The actuating cylinder contains devices for metering the hydraulic fluid.
These slow down movement of the gear at the end of retraction and during the complete extension cycle.
E. NLG Tires
The radial type tires or conventional type tires are installed on the gear.
The dimensions of these tires are 30 x 8.8 -15 and 30 x 8.8 R15.
On the 64.4T version, the inflation pressure is 11.3 bars.
On the 66T version, the inflation pressure is 10.8 bars.
On the 68T/70T versions, it is 11 bars and on the 73.5T/75.5T/77T versions it is 11.8 bars.
The radial type tires or conventional type tires are installed on the gear.
The dimensions of these tires are 30 x 8.8 -15 and 30 x 8.8 R15.
Inflation pressure of the tires on the 82.2T version is 10.1 bars. On the 83T versions, it is 10.4 bars.
The radial type tires or conventional type tires are installed on the gear.
The dimensions of these tires are 30 x 8.8 -15 and 30 x 8.8 R15.
On the 64.4T version, the inflation pressure is 11.3 bars.
On the 66T version, the inflation pressure is 10.8 bars.
On the 68T/70T versions, it is 11 bars and on the 73.5T/75.5T/77T versions it is 11.8 bars.
The radial type tires or conventional type tires are installed on the gear.
The dimensions of these tires are 30 x 8.8 -15 and 30 x 8.8 R15.
Inflation pressure of the tires on the 82.2T version is 10.1 bars. On the 83T versions, it is 10.4 bars.
F. Nose Gear Doors
The gear well is closed off by 5 doors when the gear is retracted:
The gear well is closed off by 5 doors when the gear is retracted:
- 2 main door assemblies operated by hydraulic power,
- 2 aft door assemblies connected by a mechanical linkage to the leg,
- 1 leg door assembly on the rear part of the leg.
2. Component Location
Nose Gear - Component Location ** ON A/C NOT FOR ALL
Nose Gear - Component Location ** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL Nose Gear - Component Location ** ON A/C NOT FOR ALL Nose Gear - Component Location ** ON A/C NOT FOR ALL | FIN | FUNCTIONAL DESIGNATION | PANEL | ZONE | ACCESS DOOR | ATA REF |
|---|---|---|---|---|---|
| ** ON A/C ALL | |||||
| 2528GM | STRUT ASSY-NLG DRAG | 711 | 32-21-16 | ||
| ** ON A/C NOT FOR ALL | |||||
| 2881GM | LEG ASSY-NLG,NON-CUSTOMIZED | 711 | 32-21-11 | ||
3. Component Description
A. Gear Shock Absorber
The shock absorber is of the single chamber type without a separator piston and is double acting.
The shock absorber is filled with hydraulic fluid (FHS) and nitrogen through a single standard servicing valve at the upper part of the leg.
Calibration of the metering devices in the shock absorber is the same for the different versions of the aircraft (64,4 T, 66 T, 68 T, 70 T, 73,5 T, 75,5 T and 77 T).
Hole is included in the leg to show possible leaks from the dynamic seal of the shock absorber.
It should be noted that the dynamic seal is located at the top part of the shock absorber (between the plunger tube and the sliding rod). The dynamic seal is therefore in a protected area which is not subjected to side loads during ground maneuvers.
It is possible to remove the shock absorber without drainage of the hydraulic fluid (removal of retaining ring at upper part of leg).
Main data:
The shock absorber includes 2 centering cams, one is part of the plunger tube and the other is part of the sliding tube.
When the shock absorber is fully extended the pressure of the nitrogen causes the cams to engage.
The wheels then return automatically to the center position.
The shock absorber is of the single chamber type without a separator piston and is double acting.
The shock absorber is filled with hydraulic fluid (FHS) and nitrogen through a single standard servicing valve at the upper part of the leg.
Calibration of the metering devices in the shock absorber is the same for the different versions of the aircraft (64,4 T, 66 T, 68 T, 70 T, 73,5 T, 75,5 T and 77 T).
Hole is included in the leg to show possible leaks from the dynamic seal of the shock absorber.
It should be noted that the dynamic seal is located at the top part of the shock absorber (between the plunger tube and the sliding rod). The dynamic seal is therefore in a protected area which is not subjected to side loads during ground maneuvers.
It is possible to remove the shock absorber without drainage of the hydraulic fluid (removal of retaining ring at upper part of leg).
Main data:
- total travel: 430 mm,
- filling pressure: 19 bars,
- threshold load: 1351 daN,
- volume of fluid: 5.577 liters.
The shock absorber includes 2 centering cams, one is part of the plunger tube and the other is part of the sliding tube.
When the shock absorber is fully extended the pressure of the nitrogen causes the cams to engage.
The wheels then return automatically to the center position.
B. Nose Wheel Steering Control
Refer to 32-51 for the description of the control system.
Refer to 09-00-00 for information related to towing.
Steering mechanical stops are located at 95 degrees on each side of the Nose Landing Gear center line.
Any possible leakage of the steering actuating cylinder can be detected by means of a drainage hole at the bottom of the leg.
The steering actuating cylinder is parallel to the aircraft centerline to keep to a minimum the risk of damage by tire tread shedding.
The towing lug has two bolts that break if the towing load is more than the specified limit. This prevents the risk of damage to the sliding rod.
Refer to 32-51 for the description of the control system.
Refer to 09-00-00 for information related to towing.
Steering mechanical stops are located at 95 degrees on each side of the Nose Landing Gear center line.
Any possible leakage of the steering actuating cylinder can be detected by means of a drainage hole at the bottom of the leg.
The steering actuating cylinder is parallel to the aircraft centerline to keep to a minimum the risk of damage by tire tread shedding.
The towing lug has two bolts that break if the towing load is more than the specified limit. This prevents the risk of damage to the sliding rod.
C. Shock Absorber and Nose Wheels Position Information
A control mechanism with full redundancy controls the proximity detectors which monitor the shock absorber and wheel position.
The data "Ground" is given when the shock absorber is at more than 4.4 mm (0.1732 in.) to 8 mm (0.3150 in.) from its extended position.
The data "Ground" is also given when the nose wheels are at more than 1.95 to 5.28 degrees from their centered position.
If not, the data "Flight" is given and retraction of the nose gear is then possible.
A control mechanism with full redundancy controls the proximity detectors which monitor the shock absorber and wheel position.
The data "Ground" is given when the shock absorber is at more than 4.4 mm (0.1732 in.) to 8 mm (0.3150 in.) from its extended position.
The data "Ground" is also given when the nose wheels are at more than 1.95 to 5.28 degrees from their centered position.
If not, the data "Flight" is given and retraction of the nose gear is then possible.
(1) The lockstay assembly controls alignment of the folding drag strut.
(2) The stable position of the lockstay assembly is set overcenter (approx. 13 mm) to give added safety in the downlocked position.
(3) Within this range, downlock indicating is given by 2 proximity detectors. Each proximity detector is installed on two separate brackets.
(4) If rupture of the internal stop in the lockstay occurs, movement of the lockstay is limited by the internal stop of the lockstay downlock actuator.
(5) The lockstay downlock actuator (Ref. AMM D/O 32-31-00-00) has these characteristics:
This decreases loads caused by downlocking of the gear.
- Lock release section: 2.78 square centimeters,
- Locking section: 5.61 square centimeters,
- Travel: 85.6 mm.
This decreases loads caused by downlocking of the gear.
(6) If failure of the lockstay hydraulic cylinder occurs, two springs help downlocking. Each spring puts a load of 43 daN on the lockstay.
(7) On the ground, a safety pin prevents accidental release of the gear.
This safety pin locks the two arms of the lockstay. It is only possible to put the pin into the two arms if the lockstay is in the locked position.
This safety pin locks the two arms of the lockstay. It is only possible to put the pin into the two arms if the lockstay is in the locked position.
E. Nose Gear Actuating Cylinder (Ref. 32-3)
This actuating cylinder has these characteristics:
Each end fitting is equipped with a spherical bearing that is replaceable.
This actuating cylinder has these characteristics:
- Retraction section: 39.69 square centimeters,
- Extension section: 49.24 square centimeters,
- Travel: 287.9 mm.
- At the end of retraction of the gear to make sure that the gear locks in the retracted position without shocks.
- Permanently during extension.
Each end fitting is equipped with a spherical bearing that is replaceable.
F. Steering System Components (Ref. 32-51-00)
These include :
These include :
(1) A servo control for nose wheel steering.
(2) Two anti-shimmy valves.
(3) A rotating joint.
(4) Two feedback sensors to show the position of the rotating tube.
(5) An electrical box for the deactivation of the nose wheel steering system before towing.
G. APPLETON ground connector
The APPLETON ground connector is used for connection of the gear to the ground during maintenance operations.
The APPLETON ground connector is used for connection of the gear to the ground during maintenance operations.
4. Materials and Technology
A. Materials
- Shock strut: Aluminum alloy 7010, R more than or equal to 500 MPa
- Sliding tube, including axle = 35NCD 16 steel, R more than or equal to 1800 MPa
- Rotating tube = 35NCD 16 steel, R more than or equal to 1230 MPa
- Drag strut: forestay = Aluminum alloy 7010 and lower arm = 35NCD 16 steel
- Actuating cylinder: cylinder = 35CD4 steel, R more than or equal to 1180 MPa and rod = 35NCD 16 steel, R more than or equal to 1230 MPa
B. Technology
The main elements of the structure are interchangeable without any adjustment.
All the hinges have replaceable bronze bushes.
Lubricators are provided on all the rotating or fixed hinges which are installed without interference.
The chromium-plated end fittings and pins have thickness allowances for repair.
All the spherical bearings are installed in replaceable cages.
A 3-coat paint is applied to all the external or internal surfaces (not chromium-plated).
The minimum thickness of chromium deposit is 100 microns.
The main elements of the structure are interchangeable without any adjustment.
All the hinges have replaceable bronze bushes.
Lubricators are provided on all the rotating or fixed hinges which are installed without interference.
The chromium-plated end fittings and pins have thickness allowances for repair.
All the spherical bearings are installed in replaceable cages.
A 3-coat paint is applied to all the external or internal surfaces (not chromium-plated).
The minimum thickness of chromium deposit is 100 microns.