Nose Gear Extension and Retraction Components Location 500
32-33-0 Figure 1 Apr 15/66
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
500 Nose Gear Actuator
Apr 15/66 Figure 2 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 32-33-0 Page 3
B. The nose gear actuator restricts the rate of extension and retraction of the gear, just as it approaches the up or the down position. Snubbing effect is obtained by the action of a spring-loaded sliding valve snubbing assembly. After the actuator has extended 0.65 inches, the snubbing valve opens and hydraulic flow is unrestricted. When the piston is one inch from the fully extended position, a stop on the piston contacts the snubber valve sleeve. Further movement of the piston pulls the sleeve against a compression spring to close ports. During remainder of piston travel, hydraulic flow must pass through a diminishing number of holes. The increasing restriction to hydraulic flow steadily slows the actuator extension rate until the piston reaches the end of its travel. The sequence repeats in reverse when the actuator retracts.
3. Nose Gear Lock Mechanism
A. The nose gear lock mechanism locks the gear in the gear up and the gear down positions. The mechanism also releases the lock just before gear retraction or extension. The mechanism includes a lock actuator, lock spring bungees and a lock strut consisting of a lock link and a lock brace assembly (Fig. 3). The lock strut is between structure and the drag brace. When the gear is extended the lock strut prevents the drag strut from folding when forces tending to retract the gear are applied. When the gear is retracted the lock strut and the upper drag brace form a pair of shear legs from which the gear hangs by the lower drag brace. In up or down positions, the hinge of the lock strut is over center to lock the gear in position. The lock actuator moves the lock strut across the overcenter position to release the gear. The bungee springs are under tension when the lock strut is in locked position, holding the hinge overcenter even when the lock actuator is depressurized. A pin inserted through holes drilled through the lock strut hinge provides a ground lock to prevent inadvertent gear retraction during ground operations.
500
32-33-0 Page 4 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Apr 15/66
500 Nose Gear Lock Mechanism
Nov 15/67 Figure 3 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 32-33-0 Page 5
4. Nose Gear Lock Actuator
A. The nose gear lock actuator locks and unlocks the nose gear, in either up or down position (Fig. 4). The actuator is a hydraulic piston type, and is mounted on the forward face of the aft bulkhead in the wheel well. The actuator retracts to move the lock strut over center, start the drag brace folding, and so begin the retraction cycle. For gear extension the lock actuator extends to unlock the gears. At the end of gear retraction or extension, the actuator forces the lock strut into the overcenter locked position, against the tension of the lock spring bungees.
5. Nose Gear Lock Spring Bungee
A. The nose gear lock spring bungees are arranged to apply a load to hold the lock strut in overcenter position. Bungees consist of tension springs, with one end attached to the lock brace pivot on structure, and the other end to a lock link lug, beyond the lock strut hinge. Bungees are tensioned to keep gear locked when hydraulic pressure is off the actuators
Nose Gear Lock Actuator Schematic 500
32-33-0Page 6 Figure 4 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Nov 15/66
6. Nose Gear Modular Package
A. The nose gear modular package contains all the valves required to modify hydraulic flow directed to the nose gear retraction and lock actuators (Fig. 5). Two flow limiting valves in the upline to the nose gear actuator are arranged to limit the rate-of-flow entering or leaving the up port of the actuator. The flow limiting valves prevent pressure surges in the system from varying the rate of actuator movement between snubbing points. A priority valve and a two-way restrictor are installed in parallel in both the up and the down lines to the nose gear lock actuator. Fluid entering the lock actuator ports, either up or down, passes through a two-way restrictor valve unrestricted. Fluid leaving the ports is blocked off by a priority valve, and must pass through a restrictor. Any pressure surges over 3500 psi are released by the priority valve. The valves in the modular package ensure smooth and accurate movement, when raising or lowering the gear. The modular package is mounted in the left upper aft corner in the nose wheel well.
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