SEE A
START VALVE MAIN GEARBOX
SEE SEE C B FWD A (QAD) ADAPTER QUICK ATTACH-DETACH STARTER
FLIGHT COMPARTMENT
ENGINE AUTOSTART OFF
ON
12 34 ELEC ENG CONTROL
NORM NORM NORM NORM w w w
w ALTN
ALTN ALTN ALTNa a a a
ENGINE IGNITION CONTROL MODULE EEC PANEL ASSEMBLY BC
Engine Starting System - Component Location
Figure 1
B60383
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C. The gears and bearings of the starter are splash-lubricated by a self-contained oil system. Fill, overflow, and drain ports are supplied in the housing for servicing. The magnetic chip detector (MCD) assembly, installed on the drain port, includes an inner MCD probe and an outer MCD housing. The MCD probe can be removed to look for metallic chips without draining the oil. A check valve in the MCD housing prevents draining when the MCD probe is removed.
D. An EICAS caution message STARTER CUTOUT # will show on the main EICAS
display, after a 5 second delay, when the corresponding engine start
valve is open or commanded open at more than 50 %N2 rpm.
NOTE: "#" denotes engines 1, 2, 3, or 4.
____
3. Start Valve (Fig. 3)
___________
A. The start valve controls compressed air flow to the starter. The start valve is a spring loaded closed, diaphragm-actuated, solenoid operated, butterfly type pneumatic shutoff valve. The start valve has three primary components; the valve body, actuator, and the position indicating switch.
B. The dual diaphragm, pneumatic actuator is torsion-spring loaded with a
solenoid valve and an externally mounted relief valve. The actuator is
connected to the butterfly shaft with a connecting link and arm. The
solenoid valve is a three-way ball valve. The bleed-off pressure
regulator is a spring loaded, poppet type, relief valve.
MCD DETECTOR (MCD) PROBE
OIL FILL PLUG
Starter
Figure 2
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////////////////////////A / PW4000 SERIES /747-400 / ENGINES /MAINTENANCE MANUAL ////////////////////////
HEAT SHIELD SOLENOID
VALVE
AMBIENT
VENT
PNEUMATIC
ACTUATOR
BLEED OFF REGULATOR
ELECTRICAL RECEPTACLE
CLOSED SOLENOID OPEN RATING ORIFICE OPENCLOSING
TORSION
SPRING CHAMBER A
CLOSING
POSITION
ORIFICE
INDICATOR
DIAPHRAGM A
SECTION
AMBIENT
SEE A
VENT
START VALVE BLEED OFF
REGULATOR
REGULATOR DIAPHRAGM B
ORIFICE
SQUARE DRIVE
SOCKET
FILTER CHAMBER B BUTTERFLY
AIR
FLOW ORIFICE
ELECTRICAL
CONNECTOR
OPEN POSITION
MANUAL OPERATINGINDICATOR SWITCHSTART VALVE
DRIVE AND POSITION MANUAL OVERRIDE
INDICATOR
CLOSED POSITION A
INDICATOR SWITCH
SQUARE DRIVE
ELECTRICAL CONNECTOR
Start Valve Figure 3
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C. The position indicating switch has two electrical switches in a housing installed on the valve body, opposite side of the valve actuator. A manual override and position indicator is installed on top of the position switch.
D. The valve body contains the butterfly shaft, bearings, pneumatic filter, and a butterfly plate. The position of the start valve butterfly plate is controlled by the solenoid valve. Air immediately upstream of the butterfly plate is filtered and routed through an orifice to chamber A, the solenoid valve, then chamber B. When the solenoid is energized, the ball valve moves to the opposite seat. This stops air pressure to chamber B and bleeds air pressure in chamber B to ambient through the opening rate orifice. Air pressure acts on the large diameter diaphragm against the combined force of the torsion spring and the upstream pressure acting on the small diameter diaphragm. The force from the opening diaphragm is transmitted through a mechanical linkage to turn the butterfly plate to the fully open position.
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