Smiths Aerospace
Electronic Systems – Malvern
DOC NO.0134ED
MAINTENANCE MANUAL SUPPLEMENT
BOEING B737-100/200/300/400/500
28-41-04
TSU/Removal and Replacement
A. TSU
Removal
(1) Gain access to the TSU thru the extended flaps/slats at LES 118 for the No. 1&2 tanks. The
center tank TSU is located at LBL 55-61, WL 203
(2) Remove connectors from J1 and J2, and bonding strap from TSU ground stud.
CAUTION:
USE EXTREME CARE WHEN PERFORMING MAINTENANCE, AS DAMAGE TO
THE RECEPTACLE REQUIRES REPLACEMENT OF THE WIRE BUNDLE
ASSEMBLY.
(3) Remove four (4) screws and remove TSU from bracket.
(4) Using clean rags moistened with solvent, clean connectors and mounting area of bracket.
(5) Inspect connector, TSU and receptacle for any damage.
B. TSU
Installation
(1) Carefully mount TSU to the mount bracket with four (4) screws and torque to 30-35 inch-pounds.
(2) Install two grounding straps and hardware. Torque TSU ground stud to 15-18 inch-pounds.
CAUTION:
EXCEEDING SPECIFIED TORQUE OF TSU GROUND STUD CAN RESULT IN
BREAKAGE.
(3) Perform bonding resistance check (TSU ground stud, J1 and J2 shells to airframe), 8 milliohms
maximum. (Refer to Standard Wiring Practices Manual.)
(4) Carefully engage harness connector P1 to TSU connector J1, and harness connector P2 to TSU
connector J2.
(5) Restore Airplane to Normal (Refer to Paragraph 5).
5. Restore Airplane to Normal
A. If leading edge flaps were extended, remove safety locks and retract flaps.
WARNING: REFER TO 27-81-00 MP FOR LOCK REMOVAL PROCEDURE. FLAPS WILL
RETRACT IN 7 SECONDS AND MAY INJURE PERSONNEL.
WARNING: REFER TO 32-00-01 MP FOR LOCK REMOVAL PROCEDURE.
B. Close P6 circuit breakers previously opened (P6 panel).
(1) FUEL QUANTITY
(2) EP GROUND REFUELING
(3) FUEL PANEL INDICATOR
NOTE:
IN 4-TANK CONFIGURATION, CIRCUIT BREAKER FOR CENTER TANK WOULD READ
“FUEL QTY INDI-CTR AND AUX TANK.
6. Operational Check
A. Perform Operational Check per 28-41-04, page 501 and adjust fuel quantity indication system as
required.
Page 415
Apr 19/02
Airplanes with Smiths 2307 Model Fuel Quantity
Indicators with TSU
EFFECTIVITY