Be Shaken, But Not Stirred

Air Safety Week, Feb 21, 2005

Always seeking to prove that there's not a lot new under the sun, we turned up another example of the Kenya Airways A310's fatal stick-shaker syndrome off Abidjan, Cote d'Ivoire (ASW, Feb. 7). As you will see, it too was not to be a happy ending. An L-1011 Lockheed Tristar (registration N11002) on July 30, 1992, departed New York's John F. Kennedy International Airport as TWA843. The airplane was written off but the 292 souls on board survived. Checking the bits that poke out from the fuselage (and that can get bent) creates flight-worthy karma and airworthiness kismet.

The saga: Flight 843's takeoff was commenced at 17:40 hours. Rotate speed was reached at 17:41:03 and the aircraft lifted off the runway. At that moment the stick-shaker activated and the first officer, who was making the takeoff, sensed a loss of performance. The captain then took over control and, although airborne, aborted the takeoff. The TriStar touched down again (at a vertical descent rate of 14 feet/second -- the structural design limit being 6 feet/sec) after being airborne for about six seconds. Maximum braking and reverse thrust were applied but the airplane didn't decelerate as expected. When it became apparent that he would not be able to stop before hitting the blast fence at the end of the runway, the captain turned the plane left off the runway onto a field. The TriStar came to rest 296 feet to the left of the runway and caught fire.

It appeared that the right-hand Angle of Attack (AOA) sensor had experienced nine previous malfunctions. The intermittent malfunction was not detectable during pre-flight system tests by the pilots and didn't trigger a fault light. This permitted the sensor to cause a false warning when the airground sensor on the landing gear went into the air status on takeoff.

NTSB Calls It

"Design deficiencies in the stall warning system that permitted a defect to go undetected, the failure of TWA's maintenance system and inadequate crew coordination between the captain and first officer ... resulted in their inappropriate response to a false stall warning."

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