CARD FILE OVERRIDE/JETTISON
PUMP CONTROL RELAY
(P414, P415)
OVERRIDE/JETTISON PUMP (INBOARD MAIN TANK)
Fuel Jettison System Simplified Schematic
Figure 2 (Sheet 3)
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28V DC
PMP CONTOVERRIDE/JETTISON(P180)
PUMP CONTROL SWITCH (P5)
OVERRIDE/JETTISON PUMP (CENTER WING TANK)
Fuel Jettison System Simplified Schematic
Figure 2 (Sheet 4)
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MAINTENANCE MANUAL
FUEL SYSTEM CARD FILE
OVERRIDE/JETTISON CONTROL
Fuel Jettison System Simplified Schematic
Figure 2 (Sheet 5)
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VALVE Fuel Jettison System Flow Diagram Figure 3
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(3)
When either fuel jettison nozzle valve switch is put in OPEN position, the fuel jettison operation begins. The operation is controlled by the fuel jettison control card, which continuously monitors the total fuel quantity onboard and compares it with the desired fuel to remain. While total fuel quantity is more than fuel to remain, the control card automatically supplies or removes ground for valve and pump control relays to maintain jettison configuration and correct fuel management.
(a)
Fuel jettison transfer valves in the center wing and inboard main tanks open.
(b)
Override/jettison pumps in the inboard main tanks turn on.
1) If fuel imbalance occurs between No. 2 and 3 main tanks (more than 4,000 pounds/1,815 kilograms difference), when the fuel jettison system is commanded on or during the fuel jettison operation, override/jettison pumps in the low tank will be commanded off, low pressure EICAS messages for affected pumps will show on the main EICAS display and flow patterns on the fuel synoptic for the affected pumps will not be show. When the No. 2 and 3 main tanks become balanced, override/jettison pumps will be commanded on, low pressure EICAS messages will not show and the flow patterns for affected pumps will show on the EICAS fuel synoptic.
FUEL QUANTITY TO REMAIN AFTER JETTISON
EICAS Main Display - Fuel Jettison Figure 4
A38840
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(4)
(5)
(6)
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2) If the main tank No. 2 and/or 3 override/jettison pumps are supplying engines and the fuel jettison control selector switch is set to position A or B, the No. 2 and 3 main tank override/jettison pumps will be commanded off while the fuel jettison nozzle valves are opening. Low pressure EICAS messages will be showm for each pump on main EICAS display and EICAS fuel synoptic flow patterns for the pumps will not be be shown. EICAS fuel synoptic flow patterns will show when the fuel jettison nozzle valves are opened. However, due to reduced back pressure caused by the open fuel jettison nozzle valves, low pressure EICAS messages for No. 2 and 3 main tank override/jettison pumps may remain shown. Correct operation of the fuel jettison system may be verified by observing EICAS fuel synoptic flow patterns and observing individual fuel tank quantities.
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