Vibrations spur 737 warning

After jet has tail problem, FAA sets limit on use of speed brakes

Saturday, April 13, 2002

By JAMES WALLACE
SEATTLE POST-INTELLIGENCER REPORTER

For the second time in a year, the Federal Aviation Administration has issued an emergency order to limit the speed at which pilots of Boeing 737 jetliners can deploy speed brakes during flight.

Yesterday's actions came after a 737-700 experienced severe vibrations of a key control surface on the tail when the speed brakes were deployed while the plane was flying at 315 knots. Such vibrations could potentially damage a plane enough to cause it to go out of control, the FAA said.

A total of 151 737s in the U.S. fleet are covered by the order. About 300 more of the jets are operated overseas.

The speed brakes are slats in the wing that pop up when a plane slows from its cruising speed in preparation for landing. Typically, pilots throttle back on the engines to slow the plane as it begins to descend and then deploy the speed brakes.

The FAA issued a similar airworthiness directive in June, but that was for the 737-800. The latest directive covers the 737-600 and 737- 700. All three models are part of the next-generation 737 family, along with the 737-900. Boeing has already made modifications to its new 737-900, which is being flown by Alaska Airlines and several other carriers, to prevent the vibration problem.

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