G41384
500 Leading Edge Slat Actuator
May 15/71 Figure 3 27-81-0
Page 11
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
8. Hydraulic Fuse
A. A hydraulic fuse is installed in the leading edge flap and slat standby hydraulic system pressure line. (See figure 1.) The hydraulic fuse is located near the forward bulkhead in the left wheel well below hydraulic system B pump No. 1. If an actuator failure or a line rupture occurs, the fuse will close to prevent complete loss of standby system hydraulic fluid. The fuse will reset automatically when hydraulic pressure on both sides of the fuse is equalized within 5 psi.
9. Flow Limiting Valve
A. A flow limiting valve is installed in the standby system hydraulic line downstream of the standby system modular package. (See figure 1.) It is located on the keel beam in the left wheel well just below the standby hydraulic system reservoir. The flow limiting valve controls the rate of standby system fluid flow to the leading edge flap and slat actuators. At normal temperatures with a hydraulic pressure of 200 to 3000 psi, fluid flow to the actuators is regulated at 1.35 to
1.58 gallons per minute.
10. Leading Edge Standby Drive Shutoff Valve
A. Operation of the leading edge flap and slat alternate hydraulic system is controlled by the standby drive shutoff valve. The motor operated, two-position valve is contained in the standby modular package. It is located on the wheel well aft bulkhead above the keel beam. The standby drive shutoff valve connects the standby system pressure line to the leading edge flap and slat actuators. The shutoff valve is actuated by arming the alternate flap master switch and by moving the alternate flap drive control switch to DOWN. This positions the standby drive shutoff valve to allow standby pressure to extend the leading edge flaps and slats. Moving the alternate flap master switch to OFF closes the standby drive shutoff valve, thus connecting the leading edge flap and slat actuator standby pressure lines to standby return. However, the leading edge flap and slat actuators will remain extended until system A hydraulic pressure is restored.
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27-81-0 Page 12 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Feb 15/71
11. Operation
A. The leading edge flaps and slats are controlled by the trailing edge flap system. When the trailing edge flaps are retracted, the leading edge flap and slat control valve is closed. With the control valve in this position, the leading edge flap and slat actuators are held in the retracted position by hydraulic system A pressure. In addition, internal mechanical locks keep the leading edge slat actuators retracted in the absence of extend pressure (Fig. 4). When the trailing edge flaps are extended to the 0- to 1-unit range, the control valve moves to its intermediate position. In this position, the leading edge flaps fully extend and all leading edge slats (1 thru 6) extend to the intermediate position. Extension of the trailing edge flaps to the 10-unit range and beyond fully opens the control valve . In this position, hydraulic fluid is ported to fully extend all leading edge slats (1 thru 6) while the leading edge flaps remain extended. If hydraulic system A pressure drops below 2000 psi, the flap and slat actuator blocking valves will hydraulically lock the actuators in the position at which the loss of pressure occurred. This locking action prevents aerodynamic blowback of the leading edge flaps and slats.
B. Retraction of the trailing edge flaps also retracts the leading edge flaps and slats. As the trailing edge flaps retract to the 5- to 10-unit range, the leading edge flap and slat control valve moves to its intermediate position. This retracts all leading edge slats (1 thru 6) to the intermediate position, while leading edge flaps 5 remain fully extended. Further retraction of the trailing edge flaps to the 0- to 1-unit range closes the leading edge flap and slat control valve, retracting al1 leading edge flaps and slats.
C. The standby hydraulic system will extend the leading edge flaps and slats if system A hydraulic pressure is lost. The standby system is activated by the alternate flap master switch on the overhead panel. Actuation of the master switch to ARM energizes the standby system. Moving the alternate flap drive control switch to DOWN completes a circuit which opens the leading edge flap standby drive shutoff valve. Standby system hydraulic pressure opens the standby system blocking valve in each leading edge flap and slat actuator and extends the leading edge devices simultaneously. The leading edge flaps and slats will remain extended until system A hydraulic pressure is restored.
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