When The Fin Falls Off?

[Iain]

I was wondering a couple things about the recent AA587 tragedy.
The tail must weight a lot, and being so after on the aircraft it could have taken the aircraft out of limits. Does this sound likely, and could it play a key role in the chain of events.
Also when the fin fell off I am sure the hydraulic lines where severed, I understand there are back up systems, but how would this effect the aircraft?
Thanks

[Roadtrip]

By tail I assume you mean the vertical stabilizer and not the entire empannage. Separation of the vertical stabilizer only would breach all three hydraulic systems. I don't believe there are any hydraulic fuses in those lines. Without hydraulics, the aircraft would be unflyable.

Aerodynamic consequences would be a severe degredation of yaw stability, with subsequent dutchroll, compounded by adverse yaw when using ailerons (for as long as the hydraulics lasted), and made worse by any rough air.

The CG would shift forward (don't know how much, but probably significant), greatly increasing the positive static stablility of the aircraft and the need for nose up control deflection, assuming constant speed. CG shift, in itself, would probably be controllable. Forward CG limits are usually dictated by the elevator authority needed to rotate the aircraft into a landing attitude for landing.

However, the CG shift pales in importance to the loss of all hydraulics and yaw stability.

Many years ago, a B-52 on a turbulence test flight (looking for mountain wave turb) found it in spades, and had almost all of its vertical stabilizer physically ripped off, except for a small portion of the forward attach points. The crew lowered the gear to help with yaw stability and made a successful (but I'm sure exciting) landing. A KC-135 had a reserve tank explosion that caused 27 feet of wing (tip to outboard engine) to depart the aircraft. I knew the guy who was flying it and he said the aircraft was well-controllable. There have been other incidents where one horizontal stabilator has departed the aircraft, and successful control and landings have been made.

Since there is only one, loss of a vertical stabilizer would be virtually unrecoverable, depending on the specific aircraft design.

With the A300, at least we've got all the parts and a real good idea of crew actions and circumstances. The NTSB is pretty darn good at sorting it out. Like Boeing, Airbus builds darn fine aeroplanes. We'll find out what happened, and we'll fix it.

[ 17 November 2001: Message edited by: Roadtrip ]

[englishal]

I can't believe that the loss of the tail section would cause all hydraulic systems to fail.....thats bad design !

[PaperTiger]

With the A300, at least we've got all the parts and a real good idea of crew actions and circumstances.

Obviously it's inappropriate to use the word fortunate here, but the investigation is certainly easier than if the fin had failed somewhere over the Atlantic between JFK and SDQ. Assuming the fin was about to let go in the next turbulence encounter of course.

[Iain]

Thanks for all the info, especially roadtrip.