Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

New Theory and Speculation On AA A300 Crash In New York

Tech Log The very best in practical technical discussion on the web

New Theory and Speculation On AA A300 Crash In New York

Old 5th Jan 2002, 21:28
  #1 (permalink)  
Thread Starter
 
Join Date: Jan 2001
Location: A country that most people dislike but we adore
Posts: 109
Likes: 0
Received 0 Likes on 0 Posts
Thumbs down New Theory and Speculation On AA A300 Crash In New York

Moral of this story: If your plane is flying out of control, don't try and recover, you'll upset things: <img src="rolleyes.gif" border="0">

From the New York Times
[quote]Investigators looking into the crash of an American Airlines flight in Queens in November have so far found no pre-existing flaw in the jet's tail section and are now focusing on the performance of the pilots, who they believe triggered the airplane's wild rolling and yawing in the seconds before it went down.
The data recovered from American Airlines Flight 587 showed that the plane hit turbulence from a plane in front of it and seconds later, began to swing violently and break up before it fell 2,900 feet to the ground, killing 265 people. The vertical tail of the plane, and the rudder attached to it, were the first parts to break off, and investigators began to look early on at whether that caused the crash, possibly because of some undetected flaw.
But now, after extensive testing of the tail, they have found no pre-existing problem. And so they are intensely exploring whether the pilots, in trying to correct and control the plane after the turbulence, might have put more stress on the tail than it was designed to handle.
"A brand-new tail would have broken," said one investigator, underlining his belief that the effort by the pilots to control the plane set in motion the fatal series of events. Another investigator involved in the National Transportation Safety Board's inquiry pointed out that it is possible to take an airplane in perfect condition and maneuver it into a breakup, just as a driver could take a sport-utility vehicle in perfect condition and make a radical maneuver at high speed that results in a rollover or other accident.
The plane that crashed, an Airbus A300, is a long airplane — 177.5 feet — and with the fuselage acting like a long lever, sudden movements from side to side produce powerful pressures at the end, where the vertical tail sits. By international regulation, the tail is supposed to be able to withstand a force 50 percent stronger than the largest it is likely to ever encounter, and Airbus officials said that the A300 tail exceeded even that standard. But investigators now believe that the tail was overstressed.
The latest developments in the investigation come eight weeks after the American Airlines plane bound for the Dominican Republic went down in Belle Harbor, on the Rockaway Peninsula in Queens, shortly after takeoff from Kennedy International Airport on Nov. 12.
And although investigators are interested in the latest theory, they emphasize that they are far from declaring a definitive cause. Indeed, some are still trying to determine if the rudder moved differently from the way the pilots intended. The investigation is being led by the N.T.S.B., with the participation of the F.A.A., Airbus, American Airlines, the union that represents American Airlines' pilots and other aviation experts.
Investigators had focused originally on the rudder and the vertical portion of the tail to which it attaches, both of which fell off the plane. The tail is made of carbon-reinforced plastic, a composite material that has come into common use in airplane structures only in the last 15 years and investigators have relatively little experience with it.
The Safety Board had the tail trucked to a NASA laboratory in Hampton, Va., for analysis. But the lab has turned up no sign of fabrication error or damage to the tail before the accident, according to people involved in the investigation. Now, investigators think it tore off because of the increased strain placed on it by the pilots' maneuverings — rolling and skidding the plane in the air.
The Airbus had hit the wake of a Boeing 747 that was about five miles ahead of it, which is considered a safe distance. That preceding plane created what investigators say was a minor bump, but the encounter may have prompted the Airbus crew to try to compensate.
"They thought they had something from which they thought they needed to recover quickly," said one investigator, reflecting the current hypothesis. At the controls of the jet was the first officer, Sten Molin, 34. Mr. Molin was an experienced pilot, with 4,400 hours of flying time, 1,835 of them as co-pilot of an A300.
After using the flight controls to steady the airplane, the objective normally would have been to bring it back to its previous orientation — in this case climbing and banking slightly to the left in its first turn out of Kennedy.
"Before they could do that, something else happened," the investigator said.
Several investigators said the training of pilots would be carefully examined. Crews at American were trained in the mid-1990's to use the rudder to recover from "flight upsets," but Airbus, Boeing and the F.A.A. later warned against this practice, saying it could produce dangerous stresses. American said it changed its training in 1999 to de- emphasize use of the rudder. Evidence recovered from the plane's data recorder indicates that the pilots were using the rudder to try and stabilize the plane.
The investigators are finding their work slowed by limitations on their tools. One tool is a computer-driven simulator owned by Airbus, which can predict what happens to the plane with each change in rudder or other control surfaces.
But the computer does not make good predictions at dangerous angles, because it is difficult to conduct test flights to gather such data. "You don't do extremely weird things to airplanes" to gather such data, one investigator said. As a result, he said, "When you get in a situation way outside the envelope of the airplane, you don't know."<hr></blockquote>

I would expect more from the New York Times, to be quite honest. It is somewhat infuriating the way they can twist one of the various theories (without displaying objectivity and comparing it to others) to make a lay-public believe this nonsense.

Any comments?

SFly <img src="eek.gif" border="0">

[ 05 January 2002: Message edited by: SFly ]</p>
SFly is offline  
Old 5th Jan 2002, 22:13
  #2 (permalink)  
ENTREPPRUNEUR
 
Join Date: Jun 2001
Location: The 60s
Posts: 566
Likes: 0
Received 0 Likes on 0 Posts
Post

Perhaps an argument for the fly-by-wire protections featured on subsequent Airbus airliners?
twistedenginestarter is offline  
Old 5th Jan 2002, 22:25
  #3 (permalink)  
 
Join Date: Aug 1999
Location: U.K
Posts: 78
Likes: 0
Received 0 Likes on 0 Posts
Exclamation

There are no protections in Yaw, though.
Fast Erect is offline  
Old 5th Jan 2002, 22:30
  #4 (permalink)  
 
Join Date: Mar 2001
Location: Thames Valley
Posts: 110
Likes: 0
Received 0 Likes on 0 Posts
Thumbs down

Ofcourse no word about a design-manoeuvring speed........

<img src="rolleyes.gif" border="0">
E. MORSE is offline  
Old 5th Jan 2002, 22:56
  #5 (permalink)  
 
Join Date: Jan 2001
Location: Canada
Posts: 347
Received 0 Likes on 0 Posts
Post

It would be interesting to hear from someone with a knowledge of the design of rudder limiters and their protection.
innuendo is offline  
Old 6th Jan 2002, 02:04
  #6 (permalink)  
 
Join Date: May 1999
Location: Quite near 'An aerodrome somewhere in England'
Posts: 26,795
Received 270 Likes on 109 Posts
Post

Quite why anyone should attempt to use rudder as a primary control in a swept wing aircraft in flight, I cannot imagine - other than for spin recovery or to counter the initial effect of loss of engine thrust at high thrust settings. In the type I fly, the aileron and elevator artificial feel system is TAS related whereas the rudder feel is IAS related; as a result the rudder feel increasesfrom min to max much more quickly than the elvator and aileron feel, reducing the chance of inadvertant fin stress from pilot input. In the event of total feel failure, 2 of the 3 rudder PCUs are isolated to reduce rudder power. Rudder is never used to recover from a divergent Dutch roll (although we no longer practice this in the air) - the only time I make a conscious rudder deflection other than during a cross-wind flare is to apply a small rudder doublet to excite the lateral stability mode during air tests to check yaw damper operation.

[ 05 January 2002: Message edited by: BEagle ]</p>
BEagle is offline  
Old 6th Jan 2002, 04:53
  #7 (permalink)  
 
Join Date: Jun 2001
Location: UK
Posts: 3,982
Likes: 0
Received 1 Like on 1 Post
Post

I find this all a bit difficult to believe.

I thought that if you were below max maneuvering speed you could apply an individual control fully and would not overstress?

What speed were they doing when the initial "upset" occurred?

Surely you have to grossly mishandle to cause a break up during this phase of flight?

There must be some other factor in this accident.
fireflybob is offline  
Old 6th Jan 2002, 04:59
  #8 (permalink)  
 
Join Date: Oct 2001
Location: Ft, Lauderdale,FL
Posts: 199
Likes: 0
Received 0 Likes on 0 Posts
Post

It's the same old story. The pilots are dead so lets blame the whole thing on them. I'm not an A300 pilot but I do know that you should have full athority of pedal movement at any speed without breaking anything due to the rudder limiter. If you lose an engine at full thrust on that thing I guarantee that rudder is on the floor. What a load of crap! <img src="mad.gif" border="0">
Raas767 is offline  
Old 6th Jan 2002, 06:37
  #9 (permalink)  

Don Quixote Impersonator
 
Join Date: Jul 1999
Location: Australia
Age: 77
Posts: 3,403
Likes: 0
Received 0 Likes on 0 Posts
Post

I'm amazed.
I read the NY Times article before I came to this thread as a result, it had the ring of truth then and still does.

Maybe someone who knows the chapter and verse on Airbus product can help me, but I understood the design philosophy behind the whole FBW concept was that the computer control laws were such that they prevented inputs that would exceed the aerodynamic and structural envelopes.
That is, short of turning all the protections off it was almost impossible to "kill" the aircraft.
If I understood it correctly, this was supposed to allow higher design and structural limits and expand flight and stability envelopes to promote the overall operating economics.

Or is it that they'll only keep you safe as long as you remain within "normal limits" and in anything other set of conditions you are out there on your own <img src="frown.gif" border="0"> <img src="confused.gif" border="0">

I find the concept of training to one set of training skills for say engine failure, viz use of rudder and a different set for inflight excursiona in the after take off segment, ie. not use of rudder because we'll come to bits, difficult to grasp.

BEagle suggests, properly, that use of rudder "in flight";
"other than for spin recovery or to counter the initial effect of loss of engine thrust at high thrust settings" should be avoided.

Difficult to argue with that, but given that the wake turbulence from the preceding aircraft has been accepted as the event initiator, (?)
it is possible that the resulting aircraft behaviour that prompted the pilot inputs could have exhibited either of those effects (spin onset or large "apparent" assy).
Who amongst us wouldn't have reacted instinctively with rudder and/or who amongst us would have been aware of the apparent consequences.

Are we that far out on the "pushing the certification limits" bough that a single moments inattention by a pilot will break it off.

Only two things can operate here.
Either the certification process needs a seriously vigourous rethink and overhaul, and a seriously deep audit of the control laws.
or,
A couple of pilots are being hung out to dry for "killing" an aircraft by using control inputs made available to them by the computer controlled flight control system that they believed provided such protection and limits.

Either way?
gaunty is offline  
Old 6th Jan 2002, 09:10
  #10 (permalink)  
 
Join Date: Mar 2000
Location: Arizona USA
Posts: 8,571
Likes: 0
Received 0 Likes on 0 Posts
Post

gaunty--
The A300-600 is not a FBW aeroplane.
Can remember years ago dutch roll recovery training in the B707....better to keep OFF the rudder.
411A is offline  
Old 6th Jan 2002, 13:15
  #11 (permalink)  
 
Join Date: May 1999
Location: Quite near 'An aerodrome somewhere in England'
Posts: 26,795
Received 270 Likes on 109 Posts
Post

Quite right 411A; it is not so much a question of overstressing the fin by initial large rudder inputs, it is a question of causing a divergent lateral mode to develop which may lead to overcontrol, departure fromcontrolled flight, overstress, structural failure and an accident.

Without prejudice in any way to the deceased, one wonders quite how much in the way of manual flying is practised these days by most airline pilots.

..and yes, the A300 is not a FBW aeroplane.
BEagle is offline  
Old 6th Jan 2002, 14:05
  #12 (permalink)  
 
Join Date: Sep 2001
Location: Eagan, MN
Posts: 339
Likes: 0
Received 0 Likes on 0 Posts
Post

Assuming the delicacy of the tail assembly to high-speed gross rudder inputs (ref 411A & Beagle); just how gross do these inputs have to be at relatively low speeds (approx 250 IAS during low level departure) to do damage? BTW, was the autopilot possibly in use at the time?
Semaphore Sam is offline  
Old 6th Jan 2002, 15:28
  #13 (permalink)  

Don Quixote Impersonator
 
Join Date: Jul 1999
Location: Australia
Age: 77
Posts: 3,403
Likes: 0
Received 0 Likes on 0 Posts
Post

Thanks guys.
Well there you go, but I still feel uncomfortable with being able to "kill" the aircraft in that flight segment.
I'm with BEagle, with the youngsters first 'big one' now being 'fully automatic' and coming in with relatively low hours compared with the past just how well their manual skills can be maintained, particularly long haul.
In our State a unless you have learnt and pass your drivers license test on a manual car your license limits you to automatics. Dodgy parallel perhaps but you know what I mean.

411A mate is dutch roll recovery training currently included in type rating and is it done in the sim, or have they flicked that one over to the Yaw Damper too?
I ask the same question as Fireflybob and raas767.

In a related thread 'Plastic Bug' made a comment that made think
[quote] 587 managed to intersect a number of non related and normally insignifigant events that resulted in the departure of the vertical stabilizer.

The airplane, in my opinion, managed to bullseye the preceding airplanes wake turbulence not once, but twice.

While recovering from wake encounter number one, they hit number two.

With controls set to recover from a diversion in one direction and then encountering a diversion in the OPPOSITE direction, I am believing they found themselves outside of the envelope.

And that is where the tail went.

You may, of course, disagree.

<hr></blockquote>

Whatever, it seems it just wasn't their day and given the evidence and competing politics it would be a pity if they wore it.
gaunty is offline  
Old 6th Jan 2002, 20:00
  #14 (permalink)  
 
Join Date: Oct 2001
Location: Ft, Lauderdale,FL
Posts: 199
Likes: 0
Received 0 Likes on 0 Posts
Post

Given the fact that the A300-600 has experienced severe rudder deflection at full authority with no control input from the pilot, no less than twice that I am aware of (not including 587), should be a huge heads up to anyone investigating this accident. For the NYT to publish that article and insinuating that our pilots may have caused that crash before thay have even finished the full technical evaluation of the FDR is nothing short of criminal. I urge each of you to listen to the APA hotline at 1800 APA PILOT were the union responds to this nonesense. These men are dead with no way to defend themselves! <img src="mad.gif" border="0">
Raas767 is offline  
Old 6th Jan 2002, 20:41
  #15 (permalink)  
 
Join Date: Jun 2001
Location: In da north country
Age: 62
Posts: 452
Likes: 0
Received 0 Likes on 0 Posts
Post

Does anyone really understand an Airbus?
There are so many viable, decent scenarios posted here, but folks, we are SPECULATING!
Second guessing what happened to these guys is not fair. We weren't there and have no idea what they went through.
That article was way out of line.Lets just wait and see what the FDR has to say.
I've been through some wake from a Tri-star while I was in a Tri-star, and it was nothing short of violent!

Lets give these guys the respect that we would want.
Willit Run is offline  
Old 6th Jan 2002, 23:53
  #16 (permalink)  
747FOCAL
Guest
 
Posts: n/a
Angry

I have been in excess of 500 stalls in commercial aircraft(not flying). Over half at heavy aft CG, flaps and gear down. Half of those being wind ups. I have seen and heard noises coming from airplanes that 98% of pilots will, luckily, never hear or feel during their careers. I have watched rivets popping up out of wing skins, saw flames shooting forward out of engines as they swing back and forth and I have sat in the cockpit watching the pilots violently twisting the controls after one wings breaks early and the aircraft rolls over on its back and nothing but light covers and flaps delaminating(a bit). Nothing ever broke off, even in a 727(if you know stalls then you understand).

I just can't see how a pilot fighting a bit of turbulence can bust his airplane. If they broke that easy I wouldn't be here and you guys would be loosing friends on a daily basis. It just makes no sense to me. <img src="confused.gif" border="0">
 
Old 7th Jan 2002, 01:15
  #17 (permalink)  
 
Join Date: Oct 2001
Location: Ft, Lauderdale,FL
Posts: 199
Likes: 0
Received 0 Likes on 0 Posts
Post

I feel a big fat political whitewash coming at our expense. This is where the accident investigation committee of the union should and will raise a HUGE stink!
Raas767 is offline  
Old 7th Jan 2002, 01:18
  #18 (permalink)  
 
Join Date: Aug 2000
Location: Scotland
Posts: 21
Likes: 0
Received 0 Likes on 0 Posts
Post

On the stalls you witnessed you never saw the pilots putting in full rudder followed immediately by full opposite rudder.
Thats what breaks aeroplanes!
apfds is offline  
Old 7th Jan 2002, 03:48
  #19 (permalink)  
 
Join Date: Oct 2001
Location: Ft, Lauderdale,FL
Posts: 199
Likes: 0
Received 0 Likes on 0 Posts
Post

apfds.
There is no evidence at this point that the pilot made any rudder input at all. As you well know rudder dampening systems should prevent any overstress on the rudder even if the pilot did use full deflection, which is doubtful.
The bottom line is that we should all stop speculating about what caused this accident until all the FACTS are in. To do so is completely unprofessional, an insult to our fallen comrades, and worst of all it plays right in to the worst form of tabloid journalism. Accident investigation is a science. Good science takes time. lets wait and see.
Raas767 is offline  
Old 7th Jan 2002, 04:36
  #20 (permalink)  
747FOCAL
Guest
 
Posts: n/a
Post

apfds-I have seen them go hard one direction on the rudder while inputing oposite column input and then go the oposite rudder deflection with again oposite column input and back and forth to make the plane fish tail I think the most was about 8-10 times in a row in rapid succesion. Really tosses stuff around. Other than redlining an airframe, I doubt there is any input a pilot could do that should make control surfaces or the tail or engines come off a plane if it satisfies all FAR requirements for structural integrity.

Unless there was a 10 g gust that wasn't registered I just don't believe the pilot did it even on a ScareBus. Look at that Alitalia DC-8 that lost half its wing and one engine going through, and I forget the name of it, that rare wind pattern. Pilot puts in hard rudder one way plane goes the other he pushes harder, then the plane sails through the cross wind and the controls start to respond as they should now the pilot snaps the tail the other way to stop the fast roll and the wing snaped just outboard of the inner engine. He still landed the plane.
 

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.