PPRuNe Forums - View Single Post - Air Asia Indonesia Lost Contact from Surabaya to Singapore
Old 15th Jan 2015, 08:56
  #2061 (permalink)  
Join Date: Dec 2001
Location: what U.S. calls ´old Europe´
Posts: 934
I have not had time to think about what kind of aerodynamic forces would shape this 'hand'.
It is very hard to imagine that a horizontal stabilizer fails due to overload (or a "hand").
Having significantly less span than the wing, high "twisting" loads due to roll are impossible, the wings will stop the aircraft rolling fast enough to create significant loads on the stabilizer.
Any high up or down forces would immediately result in big AoA changes, at cruise speed that would mean enormous g-loads, which would most probably rip of the wings before the stabilizer.
So the only aerodynamic scenario I could call remotely likely would be an asymmetric actuator fault, meaning one elevator deflecting up and the other one deflecting down (commanded by the computers to counteract the pitching moment caused by the faulty actuator). Given the fact that there are two actuators per elevator, and we never experienced such scenario, I would not consider this likely.
Thinking of the Alaska Air trim actuator accident, a scenario like that might be possible, but that would have most likely also resulted in an in flight breakup and a much wider field of much smaller debris.

So I do (so far) not believe in any horizontal stabilizer failure scenario. It all looks more like the Aircraft hit the water first with the tail, which caused all the damage.

With respect to cutting the tail section, I found the upper skin panel just behind the pressure bulkhead very interesting (don´t have the link to the photograph currently): All stringers are buckled, so obviously there has been high up-bending loads on the tail. Either due to high forward momentum from the VTP with high horizontal deceleration, or due to impact forces on the tail from below, indicating an impact with high AoA. Cutting in that area is probably destroying some evidence...
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