27-11-00
ALL ú ú 01 Page 12 ú Dec 10/88
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
7. Aileron Power Control Packages (Fig. 2)
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A. Each of the four ailerons is positioned by a single aileron power package. Two independent hydraulic supply systems provide hydraulic fluid at 3000 psi to each package with distribution as shown in Fig. 4. The two hydraulic systems are isolated within the package so that loss of one hydraulic system cannot cause loss of the second system. Thus, the package will continue to operate with only one hydraulic source available at the package.
B. Input to each power package is provided by cable runs and control linkage positioned by one of the CLCPs. The input operates through an overtravel mechanism to position a single spool tandem control valve. The overtravel mechanism compensates for additional input after the valve spool has reached full travel.
C. Hydraulic fluid from the supply systems is provided to the control valve through filters and check valves which prevent reverse flow in the pressure lines. Positioning of the control valve ports both hydraulic systems to a tandem actuator. As the CLCP moves to position the aileron, it also repositions the input linkage to the power package. This follow-up closes the control valve when the aileron reaches the desired position as determined by the initial input. In the event of linkage failure, a bias spring will position the control valve spool to the aileron full down position.
D. A compensator is installed in the package for each hydraulic return system. Each compensator stores a small quantity of hydraulic fluid at return pressure. With the package inoperative, a spring within the compensator forces fluid into the package to compensate for loss from temperature change or leakage.
E. The pressure and return lines of each hydraulic system within the package are connected with two anticavitation check valves. The check valves permit hydraulic fluid to flow from the extend to return side of a piston to prevent a hydraulic lock which would occur with one hydraulic supply system shut off.
F. Snubbing of the motion of the actuator is provided by the aft piston. Snubbing lands on the piston close the return line as the piston approaches the end of travel. Final travel is thus restricted, providing gust damping in the hydraulic power-off condition and snubbing for power-on ground operations. At the opposite end of the actuator, the pressure and return lines are routed to the ends of the cylinder to provide power to the piston if it is bottomed against the end of the cylinder. Bottoming of the piston provides the stop which limits the travel of the aileron.
8. Outboard Aileron Lockout Mechanisms (Fig. 2)
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A. An outboard aileron lockout mechanism is located in each wing to isolate the outboard ailerons from the lateral control system during high speed flight. The mechanism consists of a housing, cable quadrant, input crank, output crank and a series of levers and links, that, when in certain positions, will either transmit or prevent the transmission of motion from the control wheel to the aileron power package. The lockout mechanism is electrically controlled by an actuator installed on the mechanism housing.
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本文链接地址：747-400 AMM 飞机维护手册 飞行操纵 FLIGHT CONTROLS 1(48)
