27-21-23
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A
757 MAINTENANCE MANUAL
RUDDER AND ELEVATOR HYDRAULIC SYSTEMS - DESCRIPTION AND OPERATION
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1. General_______
A. Rudder and elevator shutoff valves stop the fluid flow in the L, C, and R hydraulic systems. This allows hydraulic line isolation to check for leaks and to perform maintenance on the rudder, stabilizer, and elevators while hydraulic systems are pressurized.
B. Rudder and elevator center hydraulic system fuses are installed to prevent the complete loss of hydraulic fluid in the event of a hydraulic system rupture downstream of the fuses. Without the fuses, complete loss of airplane control can occur.
2. Component Details_________________
A. Rudder/Elevator Hydraulic Shutoff Valves (Fig. 1 and 2)
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(1)
The valve is a two-position, rotary ball valve, operated by a 28-volt dc motor. There are two ports in the valve body, a pressure port and a cylinder port. The motor shaft rotates about 90 degrees to open or close the valve.
(2)
The left, center, and right system valves power is controlled by the FLT CONT S/O TAIL circuit breakers L, C, and R on overhead circuit breaker panel P11. The L and C systems are powered by bus L; R system is powered by bus R.
(3)
The valves are controlled by the FLT CONTROL SHUTOFF switches L, C, and R on right side panel P61. Each valve has an override handle for manual operation. Markings on the motor case, POS 1 (open) and POS 2 (close) indicate what position the valve and valve override handle are in. Air/ground relays prevent closure of the valves while airplane is in the air.
(4)
The valves are located on the main landing gear wheel well aft bulkheads, R system in the right well, L and C systems in the left well. Valve V101 controls the R (right) system, V102 the C (center) system and V103 the L (left) system.
(5)
An amber light in the FLT CONTROL SHUTOFF switches indicates the valve is closed. The switch legend "OFF" is backlighted by the amber light. An L, C, or R FLT CONT HYD EICAS alert message (level C) indicates which valve is closed.
B.
Rudder/Elevator Power Control Actuator (PCA) Monitor System
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(1) Each rudder and elevator PCA has a two-wire hydraulic pressure differential sensor installed in the relief valve cavity. The relief valve was provided to allow a jammed or disconnected PCA control valve to be overridden by the other PCAs. The sensor sends a signal to the monitor module. The monitor module sends a valid failure signal to the EICAS computer which retains a status and maintenance page message (RUDDER PCU, L or R ELEV PCU) for later display. The monitor sensors are controlled by the PCU MON SENSOR circuit breaker on overhead circuit breaker panel P11. The sensors are powered by 115 volt ac from bus L.
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27-23-00
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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757
MAINTENANCE MANUAL
V101 V103
RIGHT SYSTEM LEFT SYSTEM
ISOLATION VALVE ISOLATION VALVE
V102 CENTER SYSTEM ISOLATION VALVE
KEEL BEAM
KEEL BEAM
UP UP
FWD FWD
AFT BULKHEAD AFT BULKHEAD R WHEEL WELL L WHEEL WELL
HYDRAULIC
CONNECTOR
MANUAL OVERRIDE (POSITION INDICATOR)
HYDRAULIC
CONNECTOR
ELECTRICAL CONNECTOR
SHUTOFF VALVE (TYP)
Rudder/Elevator Hydraulic Shutoff ValveFigure 1
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27-23-00
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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757
MAINTENANCE MANUAL
SHUTOFF VALVE (3) VALVE
Shutoff Valve Control
Figure 2
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