Air France 447 Tail Found

Posted on 08. Jun, 2009 by in Featured

The vertical stabilizer of the Airbus 330-200 from Air France 447 has been found. In my opinion it reveals the cause of the crash. From the picture it appears to be substantially intact; appearing to have been sheared near or at the forward attachment points. The rudder is also in place (60-70%). If the tail section was found apart from the rest of the aircraft and is the first piece in the field of wreckage then I believe the cause is probably verified.

Brazil Plane

Max Beta Q is the maximum dynamic pressure (side load) that the Empennage (Tail) is stressed to. As an aircraft accelerates the dynamic pressure increases on the entire airframe. Beta is yaw, an airliner is stressed to rudder throw and release (to counter yaw produced when an engine fails). With an increase in speed the rudder effectiveness also increases to the point it can damage the structure. To prevent this damage a rudder limiter is used to restrict the amount of rudder that can be deflected.

For example the EA-6B Prowler, a carrier based attack aircraft, on the ground with weight on wheels had 35 degrees of rudder authority. Once airborne the rudder was restricted to 23 degrees and when the flaps and slats were raised a mere 5 degrees. At speed the 5 degrees was enough to counter the yaw produced by an engine failure, but was not enough to damage the airframe. The limiter was mechanical and had a warning light associated with it.

The A 330 had an electrical limiter that was part of the fly by wire system. A fault code was sent before the aircraft broke up. If large rudder movements were input either by the failing computers or the crew it is likely Max Beta Q was exceeded resulting in the vertical tail failing from the side load. In effect the aircraft flies sideways which causes the relative wind to push on the side area of the tail instead of slicing cleanly threw the air with the leading edge. If it reaches a critical pressure (Max Beta Q) then catastrophic failure occurs. The black boxes may not reveal what caused the fly by wire system to fail.

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