(2)
When the pump is switched on, a circuit from the fuel system/EICAS interface card (FSEIC) is energized which, in turn, provides data to the EIUs via the ARINC 429 data bus. The pump pressure switch also supplies data to the EIUs. When both signals are present, the pump symbol on the EICAS fuel synoptic changes color from white to amber and displays a flow symbol. When the pump reaches normal operating pressure, the pressure switch signal is removed and the synoptic symbol changes color to green. If the pump is inoperative, a fault message is recorded in the CMCS.
(3)
When the tank is emptied, the pump fuel pressure decreases. When the pressure decreases below 4-7 psi, the contacts in the switch are allowed to close. The PRESS indicator light illuminates, the EICAS synoptic symbol changes color back to amber, and EICAS messages are generated.
(a)
FUEL PUMP (1,2,3,4) FWD or FUEL PUMP (1,2,3,4) AFT advisory and status messages are generated.
(b)
If both pumps in the same main tank are at low-pressure condition and the crossfeed valve is closed, a FUEL PRESS ENG (1,2,3,4) caution is generated.
C.
Operation of Center Wing Tank Override/Jettison Pump Pressure Indication
(1)
The operation of the center wing tank override/jettison pump pressure indication system is similar to the fuel boost pump pressure indication system, except that the PRESS indicator lights on the fuel management control module will not illuminate until the pumps are switched on.
(2)
When the pumps are in low-pressure condition, FUEL OVRD CTR (L,R) advisory and status level EICAS messages are generated.
D.
Operation of Main Tank Override/Jettison Pump Pressure Indication
(1)
The operation of the main tank override/jettison pump pressure indication is similar to the fuel boost pump pressure indication except that the system is not activated until the pumps are armed and commanded on by a fuel system control card.
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
28-42-00
ALL ú ú 05 Page 6 ú Oct 18/00
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
(2)
When the pumps are switched on, the synoptic symbols change color from white to blue to indicate armed condition. When the pumps are commanded on, the symbol changes color from blue to amber to green as the fuel pressure increases to normal operating pressure.
(3)
When the pump is operating and in the low-pressure condition, FUEL OVRD (2,3) FWD or FUEL OVRD (2,3) AFT advisory and status level EICAS messages are generated.
E.
Operation of APU DC Boost Pump Pressure Indication
(1)
The APU dc pump pressure indication controls the operation of the APU fuel feed system. When the APU is turned on, the APU fuel pump pressure switch provides a ground for the APU fuel pump control relay. The APU dc pump is turned on and APU PUMP ON signals are supplied to the fuel system/EICAS interface card and the EIUs. When the pump pressure reaches 4-7 psi, the switch opens and power is removed from the pump.
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
28-42-00
ALL ú ú 11 Page 7 ú Oct 18/00
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 FAULT ISOLATION/MAINT MANUAL
PRESSURE INDICATION SYSTEM
COMPONENT FIG. 102 SHT QTY ACCESS/AREA REFERENCE AMM
SWITCH - PRESSURE, APU BOOST PUMP, S435 4 1 SUPPORT BEAM, LEFT REAR SPAR TO LANDING GEAR 28-42-01
TANK - AFT, S62 SWITCH - PRESSURE, BOOST PUMP - NO. 1 MAIN 1,2 1 OF NO. 2 TANK END RIB - INBD MAIN TANK LEFT 573AB, REAR SPAR - 31 INCHES INBD 28-42-01
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