Flight Deck Fuel Quantity Indicator (Center Tank)

Apply sticker adjacent to affected Fuel Quantity Indicator and to Refueling panel.

Print the following information in the journey log sheet. FLIGHT DECK CENTER TANK FUEL QUANTITY INDICATOR INOP

None required. OPERATIONS NOTE: If desired, fuel remaining in the center tank can be determined using the fuel used indicators method or the operative tank indicators. Refer to MEL item 28-06 Operations procedure. If VNAV capability is desired, enter and periodically update current fuel on board into the FMC.

None required.

Verify the fuel quantity of the center tank (AMM 12-11-00) This procedure uses a bussing plug jumper harness fabricated per instructions below or obtain pre- fabricated jumper harness from supplier, Cinch, per Service Letter 737-SL-28-108 for the center tank FQIS deactivation. • If center tank fuel quantity indicator blanks intermittently or if the fuel quantity indicator shows an incorrect fuel quantity or presence of any of these faults (TANK UNIT Lo-Z OPEN/GND, Hi-Z OP/SHORT TO SHIELD, COMPENSATOR Lo-Z OP/GND, COMPENSATOR SHORTED or DENSITOMETER SIGNAL FAIL), deactivate the intermittent or non-functioning FQIS (AMM 28-00-00/901). • If two of the three tank FQIS indications on the airplane are intermittent or non- functional, the airplane cannot be dispatched. 1. Open FUEL FUELING CONT, FUEL FUELING IND, FUEL QTY 2 and FUEL QTY 1 circuit breakers on P6 panel. 2. Disconnect the external fuel tank bussing plug, D11316 per AMM Task 28-41-41-000-801. 3. Cap and stow the external fuel tank bussing plug connector and wiring (SWPM 20-10-11, Section 18). NOTE: Fold excess wires. Do not coil the wires. 4. Leave the wiring shields connected to ground stud (reference WDM 28-41-11) if the wire can be safely stowed without damaging the shield ground wire. 5. Install the pre-fabricated bussing plug jumper harness. a) Connect the jumper harness terminal lug to a ground stud GD490-ST or GD1964-ST or a nearby un-used ground stud at the spar. Verify that only case or shield grounds are terminated at the ground stud. NOTE: Current return ground studs (designated GDXXX-AC or GDXXX-DC) cannot be used. b) Verify the resistance between each of the following socket contacts to the spar is 1.0 Ohm or less: i) For airplanes not equipped with densitometer, connector positions 1, C1, 2, and 3 (Hi-Z, Hi-Z shield, Lo-Z, and compensator). For airplanes equipped with densitometer, connector positions 1, 2, C2, 4, 5, C5,16, 17, 18, 19, 20, and 21 (Hi-Z, Hi-Z shield, Lo-Z, compensator, Sense, sense shield, drive (+), drive (-), and calibration resistors KR0, KR1, KR2, and KR3). NOTE: The Hi-Z and sense is verified at the center conductor of the coax contact. The Hi-Z shield, and sense shield is verified at the outer conductor of the coax contact. c) Connect the pre-fabricated bussing plug jumper harness to the spar. Install lockwire to attach bussing plug jumper harness to the jamnut. NOTE: Fold excess wires. Do not coil the wires. 6. Close FUEL FUELING CONT, FUEL FUELING IND, FUEL QTY 2 and FUEL QTY 1 circuit breakers on P6 panel. 7. Verify that the display on the refuel indicator is blank (does NOT show fuel quantity). Also verify on the flight deck, CDU does NOT show total fuel quantity and that the fuel is blank in the upper display. To fabricate a bussing plug connector jumper harness Do the following steps to make the pre-fabricated bussing plug connector jumper harness (use an applicable spare bussing plug connector to make the bussing plug connector jumper harness). The wire harness must be no longer than 24 inches: 1. Make a shielded wire with a coax contact on one end, using 20 gauge wire (BMS 13-60, type 8 or type 11, class 1; or BMS 13-48, type 12, class 1). a) Terminate the wire and the shield to coax contact S283U007-7 (SWPM 20-61-11). NOTE: These wires will connect to tank connections for Hi-Z and shield. 2. Make two unshielded wires using 20 gauge wire (BMS 13-60, type 10, class 1; or BMS 13-48, type 31, class 1; or BMS 13-48, type 65, class 1). a) Terminate one end of each wire to contact BACC47CP2T (SWPM 20-61-11). NOTE: These wires will connect to tank connections: Lo-Z and compensator. 3. For airplanes equipped with densitometer, make another shielded wire with a coax contact on one end using 20 gauge wire (BMS 13-60 type 8 or type 11, class 1 or BMS 13-48 type 12, class 1). a) Terminate the wire and the shield to coax contact S283U007-7 (SWPM 20-61-11). NOTE: These wires will connect to tank connections: sense and shield. 4. For airplanes equipped with densitometer, make six additional unshielded wires, using 20 gauge wire (BMS 13-60, type 10, class 1; or BMS 13-48, type 31, class 1; or BMS 13-48, type 65, class 1). a) Terminate one end of each wire to contact BACC47CP2T (SWPM 20-61-11). NOTE: These wires will connect to tank connections: drive (+), drive (-), and calibration resistors (KR0, KR1, KR2, and KR3). 5. Terminate the other end of the wires into suitable terminal lugs (SWPM 20-30-11). NOTE: The following terminal lug configuration contributes to the operation of the suggested ground stud GD3950-ST or GD3982-ST for main tank 1 and GD3952-ST or GD3986-ST for main tank 2 (One terminal lug is installed at these locations): a) With densitometers: three terminal lugs with four wires each (12 wires total). b) Without densitometers: two terminal lugs with two wires each (4 wires total). 6. Insert the wires with the contacts into bussing plug jumper harness connector (SWPM 20-61-11): a) For non-densitometer configuration, insert the shielded wire with the coax contact into connector position 1 (Hi-Z and Hi-Z shield) and insert the unshielded wires into connector positions 2 and 3 (Lo-Z and compensator). b) For densitometer configuration, insert the shielded wires with the coax contacts into connector positions 2 and 5 (Hi-Z and Hi-Z shield; and sense and shield) and insert unshielded wires into connector positions 1, 4, 16, 17, 18, 19, 20, and 21 (Lo-Z, compensator, drive (+), drive (-), and calibration resistors KR0, KR1, KR2 and KR3).

FLIGHT DECK CENTER TANK FUEL QUANTITY INDICATOR INOP

(M#) Except for ER operations, may be inoperative provided: a) Both center tank boost pumps operate normally, and b) Fuel quantity in center tank is verified by an acceptable procedure.