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FAA Issues Emergency Order on Boeing 747 Fuel Pumps

WASHINGTON - 12/03/98

The Federal Aviation Administration (FAA) today ordered operators of Boeing 747 aircraft to immediately change fuel pump procedures to prevent "dry operation" that could result in ignition of the center fuel or horizontal stabilizer tanks. This is an interim action while the FAA and The Boeing Company determine the cause of premature wear on some pump shaft bearings.

The FAA's Airworthiness Directive (AD) follows recent reports of pump failures due to premature wear of the shaft bearing. Operated in dry conditions, in which the parts are not covered by fuel, rotating parts could rub against other non-rotating parts. This metal-on-metal contact could cause hot spots and sparks, and a possible explosion. Therefore, the FAA has ordered operators to:

Cease operation of the horizontal stabilizer tank on Boeing 747-400 series aircraft. Normally, the pumps in the horizontal tank are run until the tank is dry.

Maintain a certain minimum level of fuel when using the center fuel tank on Boeing 747s. The pumps on these tanks are normally operated until the fuel in the tank is exhausted and the pump inlet is uncovered, exposing the pump to dry operation for a period of time during each flight that uses the center tank. The AD gives operators two options to prevent dry operation when using the center fuel tank. One procedure requires a minimum of 17,000 lbs. of fuel in the center tank before flight. The pumps must then be shut off when no less than 7,000 lbs. of fuel is left in the tank. Alternatively, a minimum of 50,000 lbs. of fuel must be loaded before flight with a shutoff point of 3,000 lbs. In both situations, the scavenge fuel pumps will continue to transfer fuel from the tank but at a slower rate. Both procedures depend on the duration of the flight.

There are approximately 700 suspect bearings in new and overhauled pumps, and part kits. The pumps normally operate for at least 20,000 hours before removal. The recently discovered problem pumps had only been operating for 200 hours.

This AD is unrelated to TWA-800 accident, which is still under active investigation by the National Transportation Safety Board. The wear conditions were not found on the center wing fuel tank override/jettison pumps that were recovered from that accident.

Worldwide there are 1,087 Boeing 747s in operation, 246 of which are U.S.-registered. Several major U.S. passenger and cargo airlines are affected by this AD. The cost to U.S. operators has not been determined.