Air France 447 Crash Theory Now Focused On Tail Snapping Off (Again)

As soon as the photo appeared of Air France 447’s vertical stabilizer floating in the Atlantic, concerns arose that the crash might have been caused by another Airbus plane tail snapping off in mid-air.

If so, this would be the latest in a long string of tail problems for Airbus.  And the problems could be extremely expensive to fix.

The crash of an Airbus 300 just after takeoff at JFK in 2001 was the result of the stabilizer snapping off.  The NTSB investigation eventually blamed the pilots for overreacting to wake turbulence and hitting the rudder pedals too hard.  Pilots have long been sceptical of this conclusion, however, especially as other Airbus rudder problems have occurred over the years (planes suddenly rolling or pitching down as the computers controlling the rudder went haywire and triggered “uncommanded” movements.)

Airbus tails are designed differently than Boeing tails (composites versus metal, etc.), and Airbuses are “fly-by-wire” aircraft that don’t have direct hydraulic connections between the cockpit controls and the flaps, rudder, and other flight controls.  Some suspect that the AF 447 crash and other Airbus problems may be the result of a computer problem or other design flaw. 

Addressing this could be extremely expensive for Airbus.

Christian Science Monitor: As they work to unravel the mystery of Air France Flight 447, aviation analysts and pilots are now urging investigators to focus attention on the plane’s tail fin, known as the vertical stabilizer, in addition to the design of the Airbus’s computerized flight controls.

The vertical stabilizer is one of the largest intact pieces of the plane recovered so far, and the Times of London reported this week that “one of the 24 automatic messages sent from the plane minutes before it disappeared pointed to a problem in the ‘rudder limiter,’ a mechanism that limits how far the plane’s rudder can move.”

Aviation analysts note that several Airbus 300 series jets have had tail fin and rudder problems in the past…

The most recent incident was in 2005, when the rudder suddenly ripped off the stabilizer of an Airbus 310 flying at 35,000 feet from Cuba to Quebec, Canada. That plane managed to land safely.

The most deadly event was the 2001 crash of American Airlines Flight 587, in which 265 people died when the plane’s vertical stabilizer tore off soon after takeoff. Investigators blamed that crash on “over use” of the rudder pedal by the co-pilot. But critics note that just prior to take off, that plane also had problems with a computer tied to the rudder. That computer was reset by a technician prior to takeoff…

The NTSB eventually concluded the cause of the crash was not a computer problem, but the co-pilot over-using the rudder pedal during some wake turbulence.

The animation in this NTSB simulation shows the pilots pushing the rudder pedals abruptly and sharply to the floor, which is what investigators believed caused the plane to lose its vertical stabilizer and crash.

But some pilots familiar with the A300 series jets still doubt that conclusion. They say that it would be physically very difficult for a pilot to make the kind of abrupt rudder pedal movements indicated in the simulation, particularly while going 250 knots, which the NTSB indicated was the plane’s speed at the time.

“I just don’t see the co-pilot making the kind of abrupt movement at that speed,” says an A330 pilot with more than 20 years experience in military and commercial aviation. “At 250 knots I don’t think you can move the rudder pedal that far. It’s going full deflection [which means it would be extremely difficult to push down as far as the simulation asserts].”

This pilot suggests that a computer malfunction could also have caused the rudder to fluctuate wildly, particularly because of the past incidences of uncommanded rudder movements in some Airbus jets.

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