DOC AIRBUS | AMM A320FMAIN GEAR DOORS - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
Three doors close each Main Landing Gear (MLG) bay. These are:
When the MLG retracts, all the doors close. When the MLG extends, the hydraulically operated doors close and the mechanically operated doors stay open.
A door opening mechanism lets the hydraulically operated doors open on the ground, for access to the MLG bay. A ground door-opening handle operates a bypass valve in the doors hydraulic circuit and releases the doors uplocks.
A ground lock-sleeve can be installed on each door actuator, to keep it open.
** ON A/C NOT FOR ALL Three doors close each Main Landing Gear (MLG) bay. These are:
Door and Fairings- a hydraulically-operated main door
- a mechanically-operated hinged-fairing door
- a fixed fairing door on the MLG leg.
When the MLG retracts, all the doors close. When the MLG extends, the hydraulically operated doors close and the mechanically operated doors stay open.
A door opening mechanism lets the hydraulically operated doors open on the ground, for access to the MLG bay. A ground door-opening handle operates a bypass valve in the doors hydraulic circuit and releases the doors uplocks.
A ground lock-sleeve can be installed on each door actuator, to keep it open.
2. Component Location
** ON A/C NOT FOR ALL | FIN | FUNCTIONAL DESIGNATION | PANEL | ZONE | ACCESS DOOR | ATA REF |
|---|---|---|---|---|---|
| ** ON A/C NOT FOR ALL | |||||
| 2520GM | UPLOCK ASSY-MLG DOOR, R | 744 | 148 | 32-31-33 | |
| ** ON A/C ALL | |||||
| 2523GM | ACTG CYL-MLG DOOR, L | 734 | 32-31-35 | ||
| 2522GM | ACTG CYL-MLG DOOR, R | 744 | 32-31-35 | ||
| 2517GM | BYPASS VALVE-MLG DOOR GROUND OPENING, L | 140 | 32-31-13 | ||
| 2518GM | BYPASS VALVE-MLG DOOR GROUND OPENING, R | 140 | 32-31-13 | ||
| 2521GM | UPLOCK ASSY-MLG DOOR, L | 147 | 32-31-33 | ||
| ** ON A/C NOT FOR ALL | |||||
| 2520GM | UPLOCK ASSY-MLG DOOR, R | 148 | 32-31-33 | ||
3. System Description
A. MLG Doors
When the MLG doors close:
When the MLG doors close:
- they keep the contour of the outer skin of the aircraft
- they protect the equipment in the bay from the airflow during flight.
(1) Main Door
Each main door has:
Each main door has hinges at the keel beam and closes outboard to an uplock in the fuselage. The main body of the door actuating cylinder attaches to a fitting on the keel beam. Steps on the internal surface of the door give access to the MLG bay, without other support equipment. Two ramps are installed on the inside of the main door. These ramps make sure that the main gear does not get caught on the door during a free-fall extension.
The MLG door actuating-cylinder operates the main door during the extension and retraction sequence. The door opens in sequence, before movement of the main gear. The door closes only when the main gear is locked in the fully extended or retracted position.
An uplock roller assembly, installed on the main door, engages with the MLG door uplock. The uplock roller assembly and the MLG door uplock keep the door in the closed position.
Each main door has:
- a related MLG door actuating-cylinder (Ref. AMM D/O 32-31-00-00)
- access steps
- two door ramps
- position proximity switches.
Each main door has hinges at the keel beam and closes outboard to an uplock in the fuselage. The main body of the door actuating cylinder attaches to a fitting on the keel beam. Steps on the internal surface of the door give access to the MLG bay, without other support equipment. Two ramps are installed on the inside of the main door. These ramps make sure that the main gear does not get caught on the door during a free-fall extension.
The MLG door actuating-cylinder operates the main door during the extension and retraction sequence. The door opens in sequence, before movement of the main gear. The door closes only when the main gear is locked in the fully extended or retracted position.
An uplock roller assembly, installed on the main door, engages with the MLG door uplock. The uplock roller assembly and the MLG door uplock keep the door in the closed position.
(2) Main Door
Each main door has:
Each main door has hinges at the keel beam and closes outboard to an uplock in the fuselage. The main body of the door actuating cylinder attaches to a fitting on the keel beam. Steps on the internal surface of the door give access to the MLG bay, without other support equipment. Two fixed ramps and one adjustable ramp, are installed on the inside of the main door. These ramps make sure that the main gear does not get caught on the door during a free-fall extension.
The MLG door actuating-cylinder operates the main door during the extension and retraction sequence. The door opens in sequence, before movement of the main gear. The door closes only when the main gear is locked in the fully extended or retracted position.
An uplock roller assembly, installed on the main door, engages with the MLG door uplock. The uplock roller assembly and the MLG door uplock keep the door in the closed position.
Each main door has:
- a related MLG door actuating-cylinder (Ref. AMM D/O 32-31-00-00)
- access steps
- fixed and adjustable ramps
- position proximity switches.
Each main door has hinges at the keel beam and closes outboard to an uplock in the fuselage. The main body of the door actuating cylinder attaches to a fitting on the keel beam. Steps on the internal surface of the door give access to the MLG bay, without other support equipment. Two fixed ramps and one adjustable ramp, are installed on the inside of the main door. These ramps make sure that the main gear does not get caught on the door during a free-fall extension.
The MLG door actuating-cylinder operates the main door during the extension and retraction sequence. The door opens in sequence, before movement of the main gear. The door closes only when the main gear is locked in the fully extended or retracted position.
An uplock roller assembly, installed on the main door, engages with the MLG door uplock. The uplock roller assembly and the MLG door uplock keep the door in the closed position.
(3) Hinged Fairing
The hinged fairing is installed on a hinge on the lower wing surface, and an adjustable rod connects it to the MLG leg. When the main gear operates, the adjustable rod causes the hinged fairing to move with the landing gear leg.
The hinged fairing is installed on a hinge on the lower wing surface, and an adjustable rod connects it to the MLG leg. When the main gear operates, the adjustable rod causes the hinged fairing to move with the landing gear leg.
(4) Fixed Fairing
The fixed fairing is attached to the outboard side of the landing-gear main fitting, by two types of attachment assembly:
The fixed fairing is attached to the outboard side of the landing-gear main fitting, by two types of attachment assembly:
- two adjustable studs, installed on the front of the main fitting
- three adjustable rod ends, one installed on the front of the main fitting, and two installed on the rear.
B. Ground Door-Opening Mechanism (Ref. 32-31-00)
Each main door has a ground door-opening mechanism to open the door for maintenance. The mechanism has these components:
The initial movement of the ground door-opening handle causes the bypass valve to:
More movement of the ground door-opening handle makes the rod on the layshaft turn a splined shaft on the door uplock (Ref. AMM D/O 32-31-00-00). This operates a release mechanism in the uplock, which releases the uplock hook, and lets gravity open the main door.
If the ground door-opening handle is put in the closed position, with the doors open, a hydraulic pressurization of the system will cause the doors to close. The locking plunger in the bypass valve will prevent movement of the ground door-opening handle to the doors-close position (unless the Green hydraulic system is pressurized). When the handle is moved to the doors-close position, the main doors close at the same time.
Each main door has a ground door-opening mechanism to open the door for maintenance. The mechanism has these components:
- a ground door-opening handle
- a bypass valve 2517GM (2518GM) (Ref. AMM D/O 32-31-00-00)
- a release mechanism in the door uplock 2520GM (2521GM) (Ref. AMM D/O 32-31-00-00).
The initial movement of the ground door-opening handle causes the bypass valve to:
- isolate the door actuating-cylinders from the door-close hydraulic line
(the Green hydraulic system does not have to be pressurized) - connect together the two chambers of each door actuating-cylinder, to move the hydraulic fluid during the actuating cylinder extension.
More movement of the ground door-opening handle makes the rod on the layshaft turn a splined shaft on the door uplock (Ref. AMM D/O 32-31-00-00). This operates a release mechanism in the uplock, which releases the uplock hook, and lets gravity open the main door.
If the ground door-opening handle is put in the closed position, with the doors open, a hydraulic pressurization of the system will cause the doors to close. The locking plunger in the bypass valve will prevent movement of the ground door-opening handle to the doors-close position (unless the Green hydraulic system is pressurized). When the handle is moved to the doors-close position, the main doors close at the same time.
C. Door Bypass Valve (Ref. 32-31-00)
The door bypass valve is installed in the close line of each MLG door actuating-cylinder. During the operation of the Normal Extension and Retraction System (Ref. AMM D/O 32-31-00-00), hydraulic fluid goes through the door bypass valve.
When the ground door-opening mechanisn is operated, the door bypass valve:
This prevents a hydraulic lock, and allows the hydraulic fluid to be released from under the door actuating-cylinder piston. The door then moves under gravity.
The door bypass valve is installed in the close line of each MLG door actuating-cylinder. During the operation of the Normal Extension and Retraction System (Ref. AMM D/O 32-31-00-00), hydraulic fluid goes through the door bypass valve.
When the ground door-opening mechanisn is operated, the door bypass valve:
- closes the hydraulic supply pressure
- connects each side of the door actuating-cylinder together.
This prevents a hydraulic lock, and allows the hydraulic fluid to be released from under the door actuating-cylinder piston. The door then moves under gravity.
D. Proximity Sensors
Proximity sensors and targets (Ref. AMM D/O 32-31-00-00) are used to show the position of the main door. The proximity sensors are installed on the center-fuselage keel-structure. The targets are installed on the main door, on a bracket at the door hinge line.
During the operation of the door, the positions of the proximity sensors change in relation to their targets. The sensors send a signal to the Landing Gear Control and Interface Units (LGCIUs) (Ref. AMM D/O 32-31-00-00). This signal shows when the door is 'fully open' or 'not fully open'. This data is used to:
Proximity sensors and targets (Ref. AMM D/O 32-31-00-00) are used to show the position of the main door. The proximity sensors are installed on the center-fuselage keel-structure. The targets are installed on the main door, on a bracket at the door hinge line.
During the operation of the door, the positions of the proximity sensors change in relation to their targets. The sensors send a signal to the Landing Gear Control and Interface Units (LGCIUs) (Ref. AMM D/O 32-31-00-00). This signal shows when the door is 'fully open' or 'not fully open'. This data is used to:
- control the retraction and extension sequences of the landing gear
- supply indication/failure data of the MLG doors, to the indication and warning system in the flight compartment.
4. Power Supply
Not applicable
** ON A/C NOT FOR ALL Not applicable
5. Interface
The systems that follow, interface with the main landing gear doors:
** ON A/C NOT FOR ALL The systems that follow, interface with the main landing gear doors:
- normal extension and retraction (Ref. AMM D/O 32-31-00-00)
- main landing gear (Ref. AMM D/O 32-11-00-00)
- main landing gear doors (Ref. AMM D/O 52-81-00-00).
6. Component Description
A. General
The MLG doors are made from Carbon-Fibre Reinforced-Plastic (CFRP) with a NOMEX honeycombe core. A detailed description of the MLG doors is given in (Ref. AMM D/O 52-81-00-00).
Each door has flexible seals at its structure interface which protect the CFRP/metal interfaces from damage by the airflow.
The MLG doors are made from Carbon-Fibre Reinforced-Plastic (CFRP) with a NOMEX honeycombe core. A detailed description of the MLG doors is given in (Ref. AMM D/O 52-81-00-00).
Each door has flexible seals at its structure interface which protect the CFRP/metal interfaces from damage by the airflow.
B. Main Door
The shape of the door agrees with the contour of the fuselage and has hinges at its inboard edge. The MLG door actuating-cylinder ram end is attached to the main door, at an attachment fitting on the forward edge. There are three access steps on the door, and ramps at the front and rear (two fixed and one adjustable). An uplock roller is attached to the forward, outboard end.
The shape of the door agrees with the contour of the fuselage and has hinges at its inboard edge. The MLG door actuating-cylinder ram end is attached to the main door, at an attachment fitting on the forward edge. There are three access steps on the door, and ramps at the front and rear (two fixed and one adjustable). An uplock roller is attached to the forward, outboard end.
C. Fixed Fairing
The fixed fairing has five adjustable attachments, for installation to the main gear.
The fixed fairing has five adjustable attachments, for installation to the main gear.
D. Hinged Fairing
The hinged fairing has one hinge and an attachment point for the MLG attachment rod.
The hinged fairing has one hinge and an attachment point for the MLG attachment rod.
E. Ground Door-Opening Handle
The ground door-opening handle is a lever with a forked end that is attached to the structure. A teleflex cable attaches to the apex of the fork. A release plunger at the hand grip releases a self latching mechanism (which operates to hold the handle in the open or the closed position). A locking pin prevents accidental operation of the handle.
The ground door-opening handle is a lever with a forked end that is attached to the structure. A teleflex cable attaches to the apex of the fork. A release plunger at the hand grip releases a self latching mechanism (which operates to hold the handle in the open or the closed position). A locking pin prevents accidental operation of the handle.
F. Bypass Valve FIN: 2517-GM FIN: 2518-GM
A detailed description of the bypass valve is given in (Ref. AMM D/O 32-31-00-00).
A detailed description of the bypass valve is given in (Ref. AMM D/O 32-31-00-00).
7. Operation/Control and Indicating
A. Ground Door-Opening for Maintenance
When the ground door-opening handle is operated, it pulls a teleflex cable which moves the lever on the bypass valve through 90 degrees. The initial movement of the ground door-opening handle causes the bypass valve to:
At the same time, the hook of the door uplock is released. Gravity then opens the main door, which causes the hydraulic fluid to move from one side of the door actuating-cylinder to the other. The main door opens slowly because some cavitation occurs in the door actuating-cylinder.
A more detailed operation sequence is given in (Ref. AMM D/O 32-31-00-00).
When the ground door-opening handle is operated, it pulls a teleflex cable which moves the lever on the bypass valve through 90 degrees. The initial movement of the ground door-opening handle causes the bypass valve to:
- isolate the door-close hydraulic supply from the door actuating-cylinder
- connect the two chambers of the MLG door actuating-cylinder together.
At the same time, the hook of the door uplock is released. Gravity then opens the main door, which causes the hydraulic fluid to move from one side of the door actuating-cylinder to the other. The main door opens slowly because some cavitation occurs in the door actuating-cylinder.
A more detailed operation sequence is given in (Ref. AMM D/O 32-31-00-00).
B. Ground Door-Closing after Maintenance
The Green hydraulic system must be pressurized before the ground door-opening handle can be moved. A locking plunger in the bypass valve stops movement of the handle, if the hydraulic system is not pressurized.
When the ground door-opening handle is turned towards the closed position, it pushes the teleflex cable. This moves the lever of the bypass valve. The valve then isolates the chambers of the main door actuator from each other and connects them to the hydraulic supply. At the same time, the rod to the uplock moves the ground release mechanism in the door uplock to its initial position. The main door actuator then closes the main door, and the uplock closes to hold the door actuating-cylinder in the closed position.
A more detailed operation sequence is given in (Ref. AMM D/O 32-31-00-00).
The Green hydraulic system must be pressurized before the ground door-opening handle can be moved. A locking plunger in the bypass valve stops movement of the handle, if the hydraulic system is not pressurized.
When the ground door-opening handle is turned towards the closed position, it pushes the teleflex cable. This moves the lever of the bypass valve. The valve then isolates the chambers of the main door actuator from each other and connects them to the hydraulic supply. At the same time, the rod to the uplock moves the ground release mechanism in the door uplock to its initial position. The main door actuator then closes the main door, and the uplock closes to hold the door actuating-cylinder in the closed position.
A more detailed operation sequence is given in (Ref. AMM D/O 32-31-00-00).
8. BITE Test
Not applicable
Not applicable