Boost Pump Wiring Chafing Prompts FAA To Issue AD On Boeing 737 Aircraft
On may 7, 1998, the FAA issued telegraphic ad T98-10-51, applicable to all model 737-100, -200, -300, -400, and -500 series airplanes, to require removal of the fuel boost pump wiring in the conduits of the wing (main) fuel tanks; a one-time inspection to detect damage of the wiring; and reinstallation of the wiring with teflon sleeving, or replacement of damaged wiring with new wiring and teflon sleeving. This a result of a long investigation on the July 17, 1996, TWA flight 800, a Boeing 747-100 crashing shortly after takeoff from Kennedy International Airport.
That telegraphic Ad was prompted by reports of severe wear of the fuel boost pump wiring due to chafing between the wiring and the surrounding conduit inside the fuel tank, and Pin-hole-sized holes in the conduit that appear to be the result of arc-through of the conduit. The actions required by that telegraphic ad are intended to detect and correct such chafing, which could result in arc-through of the conduit, and Consequent fire or explosion of the fuel tank.
Since the issuance of telegraphic ad T98-10-51, the FAA received a report from an operator of a model 737-200 series airplane that had accumulated approximately 60,000 Flight hours indicating that the left main tank boost pump power wire conductor was exposed at three areas inside a conduit. At least one of the areas exhibited signs of arcing to the wall of the conduit. Additionally, several more reports of severe Wire chafing were received. Based on these reports, in addition to the report that Prompted issuance of the previous telegraphic ad, the FAA has concluded that exposed or arcing boost pump power wires may exist on other 737-100, -200, -300, -400, and -500 Series airplanes that have accumulated 50,000 or more total flight hours.
Chafing and electrical arcing between the fuel boost pump wiring and the Surrounding conduit, if not corrected, could result in arc-through of the conduit, And consequent fire or explosion of the fuel tank. Therefore, the FAA has determined that there is sufficient cause to require that the fuel boost pump power wires for the number one and number two main tank aft boost pumps on model 737-100, -200, -300, -400, And -500 series airplanes be inspected prior to further flight.
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