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No shocker there. The plane separated both engines and the tail during takeoff. The Feds stated it was due to turbulence from the flight that left 2:45 minutes ahead of it. First of all the turbulence after 2:45 minutes would be negligable. Secondly, separating both engines and the tail would not be a primary failure mode for a plane subject to turbulence.

No, the "Feds" did not say it was wake turbulence. What they said is that when the aircraft encountered wake turbulence, the First Officer at the controls, incorrectly implimented violent hard rudder movements - side to side rapidly. American Airlines had been teaching this to their pilots and has since stopped because the NTSB, FAA and safety experts told them it was ridiculous in large aircraft to do. As for 2.75 minutes - the time between a "heavy" and any aircraft following is considered 5 minutes. The wake of a heavy falls at 500 feet per minute. That means that 1,500 feet below the path on a calm day within 3 minutes of a heavy is a dangerous place to be - BUT it was not wake that did it - it was the REPONSE to the wake.

I am an airline pilot and an instructor. The FAA came by our training centers after the accident to make sure we weren't teaching such silly wake escape manuevers to our pilots (we weren't - we were taught that moving a 30 foot tall rudder with 3,000 psi should be done SLOWLY).

Greetings!

I don't know how much you follow the aircraft crash threads that pop up here, so if this is a first time, whacko theories abound.

Some people just cannot accept that at times things break. There was an article in USA Today (probably elsewhere as well) this past Tuesday that talked about the tail of AAL587 and the hard rudder movements that could have been the prime cause of the tail failure.

Thanks for your reasoned input.

MoodyBlu
Air Traffic Controller
Recreational pilot

...the First Officer at the controls, incorrectly implimented violent hard rudder movements - side to side rapidly.

Why would anyone design an aircraft with a rudder that can move at one level of stress and a rudder actuator that is designed to easily exceed the rudders maximum stress level?

There are limits, and the crew can destroy the aircraft through wrongful manipulation of the controls; but this aircraft was traveling at relatively low speeds, and performing a maneuver, that no matter how ill advised, was something that was actually taught and practiced as a routine part of their training regimen. The frame should not have failed, and if it failed, it was because something was wrong with that particular aircraft.

"...to make sure we weren't teaching such silly wake escape manuevers to our pilots (we weren't - we were taught that moving a 30 foot tall rudder with 3,000 psi should be done SLOWLY)."

If that is the case, then there is a major problem in the design that is not the fault of the pilot. If a hydraulic actuator has the power to break off a tail under any condition, then either the tail strength is underdesigned or the actuator strength is overdesigned, or the system damping is insufficient.

Design margin should exceed 1.0 by a sufficient amount, and aircraft standard is 1.2 or more depending on worst case external forces. Can you imagine the howls of protest if owners of some car model were told they shouldn't apply the brakes too hard or the knuckles would rupture and the wheels would fall off and send you out of control?