(3)
Set the engine start switches in the OFF position.
(4)
Set the fuel pump switches in the OFF position.
(5)
Set engine start levers in the CUTOFF position.
(6)
Shut off the APU.
I. Test Procedure (Alternative 2)
(1) Do the following steps to connect the pressure gage hose:
NOTE: It is recommended only one low pressure switch be disconnected at a time. This will prevent a fuel spill if the wrong boost pump is operated.
(a)
Remove the low pressure switch (AMM 28-42-11/401).
(b)
Make sure fuel boost pump removal valve is closed to keep fuel leakage to a minimum.
(c)
Connect the pressure gage hose to the fuel line (P/N 10-3067-3 pressure switch).
NOTE: Use a flareless nut sleeve fitting with a 0.5625-18 UNJF-3B thread on the pressure gage hose.
(d)
Connect the pressure gage hose to the fitting you removed the low pressure switch from (P/N 60B92400-3 pressure switch).
NOTE: Use a 0.4375-20 UNJF fitting on the pressure gage hose.
(2)
Open the removal valve for the boost pump.
(3)
Set the FUEL PUMP switch (on the overhead panel) to the ON position and wait approximately one minute for the pump to warm up.
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(a) To operate any of the fuel pumps, you must be in the flight compartment to continuously monitor the fuel quantity and the low pressure indication.
WARNING: DO NOT OPERATE ANY FUEL PUMP IF THE LOW PRESSURE LIGHT COMES ON AND STAYS ON. FUEL VAPORS IN THE TANK MAY IGNITE AND CAUSE A FIRE OR EXPLOSION.
1) Immediately set the applicable fuel pump switch 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.
(4)
Open the bleed valve on the pressure gage hose and drain approximately 0.25 gallon (1 liter) of fuel.
NOTE: Use a two gallon container to catch the fuel.
(5)
Close the bleed valve. Read the pressure gage 5 to 10 seconds after you close the bleed valve. Record this pressure as the "Pump ON" pressure.
(6)
Set the FUEL PUMP switch to the OFF position.
(7)
Open the bleed valve on the pressure gage hose until the remaining pressure from the pump is gone.
NOTE: The fuel may continue to flow slowly or may stop flowing from the bleed valve after the remaining pressure is gone. This depends on the level of fuel in the tank and the height of the bleed valve.
(8)
Close the bleed valve.
(9)
Record the pressure on the pressure gage as the "Pump OFF" pressure.
(10)
Subtract the "Pump OFF" pressure from the "Pump ON" pressure.
NOTE: This gives you the output pressure of the pump.
(a) If the output pressure of the pump is less than 36 psi, then replace the pump (AMM 28-22-41/401).
(11) Close the removal valve for the applicable boost pump.
J. Put the Airplane Back to Its Usual Condition (Alternative 2)
(1)
Disconnect the pressure gage hose.
(2)
Install the low pressure switch (AMM 28-42-11/401) with a new O-ring.
NOTE: Open the removal valve and do tests indicated.
(3)
Do the "Fuel Feed Low Pressure Indicating System Test" (AMM 28-42-0/501).
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FUEL LOW PRESSURE SWITCH - REMOVAL/INSTALLATION
1. General
A. Switches for tank No. 1 boost pumps and center tank (left side) boost pump are on left wing leading edge ribs, or front spar; switches for tank No. 2 boost pumps and center tank (right side) boost pump are on right wing leading edge ribs, or front spar.
2. Equipment and Materials
A. Leading Edge Flap Actuator Locks - F80048-36
3. Prepare for Fuel Low Pressure Switch Removal
A. Extend flaps and install leading edge flap locks (Ref 27-81-0, MP).
WARNING: REFER TO 27-81-0, MP FOR LOCK INSTALLATION PROCEDURE. FLAPS ARE FAST ACTING AND CAN CAUSE SERIOUS INJURY TO PERSONNEL.
B. Open boost pump and pump low pressure circuit breakers on P6 panel.
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