(b)
Disconnect airplane wiring connector plug at boost pump receptacle
(AMM 28-22-41/401).
(c)
Connect applicable boost pump/PCU cable assembly between PCU and airplane.
NOTE: Check marker instructions on cable assembly and chart for correct airplane model and fuel component connections (Fig. 204).
(d)
Disconnect airplane wiring connector plug at applicable boost pump low pressure warning switch on wing front spar (AMM 28-42-11/401).
(e)
Connect applicable boost pump pressure switch/PCU cable assembly between PCU and pressure switch on wing front spar. Observe instructions of note in step (10)(c).
(f)
Connect terminal lug end of power supply cable assembly to ground power cart(s) which supply 3-phase 115V AC and 28V DC.
(g)
Check that PCU 28V DC and 115V AC circuit breakers are in open position and all pump switches on PCU control panel are in OFF position.
(h)
Connect plug P1 of power supply cable assembly to J1 of PCU.
(i)
Close 28V DC and 115V AC main power control unit circuit breakers on PCU control panel. Check that 28V DC AVAIL and 115V AC AVAIL panel indicator lights are illuminated.
(j)
Depress MSTR PWR ON button on control panel for minimum of one second and release. Check that MSTR PWR ON indicator light is illuminated.
(11)
Defuel the fuel tank.
(a)
Close fuel boost pump A, B circuit breakers on PCU control panel.
NOTE: If only one fuel tank boost pump is cabled up to operate, close applicable circuit breaker.
(b)
Turn applicable pump switch(es) on PCU control panel to ON position. Check that corresponding fuel low pressure warning light(s) come on momentarily as boost pump(s) come up to speed. 1) To operate any of the fuel boost pumps, you must continuously monitor the fuel
quantity and the low pressure indication in the fuel tank.
WARNING: DO NOT OPERATE ANY FUEL BOOST PUMP IF THE LOW PRESSURE LIGHT COMES ON AND STAYS ON. FUEL VAPORS IN THE TANK MAY IGNITE AND CAUSE A FIRE OR EXPLOSION.
a) Immediately put the applicable fuel boost pump switch(es) to OFF if the LOW PRESSURE light comes on and stays on.
NOTE: When defueling or transferring fuel with minimum backpressure to the pumps, it is possible for the low pressure light(s) to be on. In this case, monitor the tank quantity and put the pump switch(es) to OFF if the tank quantity is not changing.
504
May 01/03 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 28-23-0 Page 209
T52738 T52739 T52740
Auxiliary Defueling External Power Control Unit 504
28-23-0 Figure 204 (Sheet 1) May 15/80
Page 210
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
504 Auxiliary Defueling External Power Control Unit
Jun 20/84 Figure 204 (Sheet 2) 28-23-0
Page 211
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
Auxiliary Defueling External Power Control Unit 504
28-23-0 Figure 204 (Sheet 3) Jun 20/84
Page 212
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
(c)
Start the fuel truck suction pump, if so equipped.
(d)
Continue defueling until fuel quantity remaining in tank is as desired or until low pressure warning light on PCU control panel comes on indicating that pump inlet is above fuel level.
(e)
Stop the fuel truck suction pump, if used.
(f)
Put the pump switch(es) on PCU control panel in OFF position.
(g)
Depress MSTR PWR OFF switch on control panel and check that MSTR PWR indicator light goes off.
(h)
Open 28V DC and 115V AC main power circuit breakers on PCU control panel. Check that 28V DC AVAIL and 115V AC AVAIL indicator lights are off.
(i)
Disconnect cable to ground power carts from PCU and cable from PCU to airplane.
(j)
Stow PCU and cables in storage box.
(k)
Reconnect airplane boost pump wiring connector plug(s) and install dry bay access panels (AMM 28-22-41/401).
(l)
Close defueling valve on airplane wing front spar by moving manual lever to CLOSE position. Close access door.
(m)
Close fueling truck nozzle fuel flow shutoff handle. Disconnect defueling hose nozzle and disconnect nozzle grounding jack.
(n)
Install fueling receptacle cap and close fueling station access door.
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