Fixes to Prevent Explosions on 737s Will Be Mandated
Fixes to prevent the sort of fuel tank explosion that brought down Trans World Airlines Flight 800, a Boeing 747 jumbo jet, were proposed Thursday for another Boeing jetliner, the widely used 737.
The estimated cost of complying with the proposal to rework the fuel-sensor wiring systems on 1,140 of the U.S.-registered, narrow-body 737s is about $41 million.
The FAA said that an order mandating the repairs and installations on 737-100, -200, -300, -400 and -500 series planes probably will be issued in about 45 days. Then the airlines will have a year to complete the work.
About 2,800 of the 100 through 500 series 737s are in use around the globe, making them the most widely used transport aircraft in the world.
Last week, the National Transportation Safety Board, reacting to suspect wiring found in the wreckage of TWA Flight 800 and on some other 747s, urged the FAA to order inspections of fuel-sensor wiring systems on about 650 of the wide-body jets.
The NTSB still has not determined what touched off the center fuel tank explosion that tore Flight 800 apart on July 17, 1996, a few minutes after it had taken off from New York. All 230 on board were killed. However, NTSB investigators have said that a power surge in normally low-voltage fuel-sensor wiring that somehow had been stripped of protective insulation might have caused a spark that triggered the blast on the 747.
In its recommendations last week, the NTSB suggested that the FAA also survey the wiring on comparable fuel probes in other planes. Those planes apparently include the 737-100 to -500 series jetliners, which have “fuel system wire installations similar to that on the Model 747 series aircraft involved in the TWA 800 accident,” according to the FAA.
“Today’s actions are consistent with one of the latest NTSB recommendations, issued April 7, regarding surge protection systems,” the FAA said Thursday.
The statement was seen as a response to critics who have charged in recent years that the FAA has not responded quickly enough to some NTSB recommendations and has failed to deal promptly with important safety issues.
The FAA said that Thursday’s Notice of Proposed Rulemaking was prompted by TWA Flight 800 and by other fuel tank explosions, including one aboard a Philippine Airlines 737-300 in May 1990. The cause of the 737 blast, which killed eight people as the plane was taxiing beside a runway in the Philippines, has never been determined.
The FAA proposal requires the installation of electrical surge-suppression systems that may include special shielding and the rerouting of wiring to prevent shorts and the introduction of high-voltage current through induction from other circuits.
The proposal also requires the installation of flame arresters and pressure-relief valves on fuel vent systems. The devices would prevent flames generated by an external fire from entering fuel tanks through the vents.
