Door and Fairings
Figure 001
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MLG Fairings
Figure 002
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MLG Main Door - Fittings
Figure 003
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-they protect the equipment in the bay from the airflow during flight.
**ON A/C 001-049, 051-099, 101-149, 201-299,
(1) Main Door
Each main door has:
-a related MLG door actuating-cylinder (Ref. 32-31-00)
-access steps
-two door ramps
-position proximity switches.
R **ON A/C 151-199, 301-399, 401-499,
(1) Main Door
Each main door has:
-a related MLG door actuating-cylinder (Ref. 32-31-00)
-access steps
-fixed and adjustable ramps
-position proximity switches.
**ON A/C ALL
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.
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(2) Hinged Fairing
(Ref. Fig. 002)
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.
(3) Fixed Fairing
(Ref. Fig. 004)
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)
R **ON A/C 301-399,
R (Ref. Fig. 005)
R **ON A/C ALL
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. 32-31-00)
-
a release mechanism in the door uplock 2520GM (2521GM) (Ref. 32-31-00).
Access to the ground door-opening handle is by the panel 195BB (196BB), which is in the center fuselage, adjacent to its related MLG door. This location gives the operator a safe position and a clear view of the door travel. The handle connects, through a push-pull cable, to a layshaft on the door by-pass valve on the outboard side of the MLG bay.
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.
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MLG Fixed Fairing - Fittings Figure 004
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R MLG Door - Ground Opening Mechanism
R Figure 005
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More movement of the ground door-opening handle makes the rod on the layshaft turn a splined shaft on the door uplock (Ref. 32-31-00). 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.
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