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Interesting note about AA Airbus crash in NYC

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Interesting note about AA Airbus crash in NYC

Old 23rd Dec 2006, 15:55
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Bubbers 44
I agree with you. I really do.
my faith in the NTSB has been shattered. my belief in backroom political dealings is reinforced.
737 and this airbus, while not identical crashes , just reminds me that the truth is often a compromise and not the truth.
I recall, way back when, in my first 20 hours of flying or so, that the instructor had me demonstrate remaining in a stalled condition and keeping the wings level using JUST rudder. while modern planes allow aileron useage into the stall, this was a nice maneuver. The rudder didn't come off of my PA 28, we didn't break apart in flight.
The DC9 I flew for many years had a rudder limiter, no one knocked the tail off the dc9.
I know of pilots who have transferred off the airbus 300 for the concerns we have outlined. I have told my friends to avoid this aircraft if possible. Until the repairs were made, I would have told them to avoid the L188 too.
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Old 23rd Dec 2006, 16:20
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How sure are they, that the FP's input was not increasing because of an already developing structural failure?

The feedback may have been so modified, that he was reaching further and further for a familiar response.
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Old 23rd Dec 2006, 16:22
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great question loose rivets!

one thing that would help us all in the future is a video/camera system that monitors all critical surfaces AND records this info/video in a black box system.

if the plane had started to come apart PRIOR to massive control inputs by the copilot, whose fault was that?

...

by the way, does anyone remember when AIRBUS was going to be called : JET, for Joint European Transport?
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Old 23rd Dec 2006, 17:09
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I would imagine that the DFDR would no longer be reading rudder surface position if the rudder/fin is no longer attached to the fuselage.
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Old 23rd Dec 2006, 17:23
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Ahhh...the old conspiracy theorists. No matter what reasonable arguement you put forward or studies are done, they just ask more and more hypothetical questions and come up with more and more theories. Reminds me of TWA 800 and also the Egyptian aircraft accident investigation board.
Hmmm. Now that I think about it, they all had to do with JFK departures.
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Old 23rd Dec 2006, 20:24
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litebulb

I think that the DFDR doesn't measure location/position of the rudder as much as it measures movement of rudder actuators...if the actuators moved, we might assume the rudder moved with it...unless the rudder fell off
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Old 23rd Dec 2006, 21:27
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If my theory is correct about the vertical stab failing initially from the front then the rudder inputs by Sten were probably to correct the stab causing the yaw. He was only trying to maintain heading so multiple reverse inputs would be what any pilot would do if the stab was causing severe yaw problems. If you were the captain would you let him thrash the plane around for a common wake turbulence event? I don't think so. Any flight attendant in the back would be severely injured if she was out of her seat for some reason. We all deal with wake turbulence and it is not an emergency, we just have to make that PA explaining how it is like being behind another boat to calm nervous passengers. A lot of politics was in that NTSB final findings.
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Old 23rd Dec 2006, 21:45
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Excessive use of rudder

There have been many professional views expressed here about the incident but surely common sense says that one does not use violent and full activation of the rudder in any aircraft - especially in one where the feedback to the pilot is not quantitive.

All my training - general and service avaition only and some time ago - taught smooth and increasing pressure, never rapid and opposite.
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Old 23rd Dec 2006, 22:16
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Originally Posted by jondc9 View Post
have we forgotten the A310 that lost a portion of the rudder climbing out of Cuba?
Hadn't heard about that one, it's important, but not likely to be related - I found this article, and it cautions that Airbus and Boeing were watching it closely.
http://findarticles.com/p/articles/m...1/ai_n13458444
Originally Posted by Graybeard View Post
It's folly to assume the NTSB is immune from political pressure
...
Five years and three accidents does not inspire confidence the NTSB got it right on AA 587.
I don't think anyone is assuming that, GB. Though their independence from the FAA/airline/manufacturer circle has been considered fairly sacrosanct since the aftermath of the DC10 decompression failure debacle, and that was nearly 30 years ago.
Originally Posted by jondc9 View Post
I recall, way back when, in my first 20 hours of flying or so, that the instructor had me demonstrate remaining in a stalled condition and keeping the wings level using JUST rudder. while modern planes allow aileron useage into the stall, this was a nice maneuver. The rudder didn't come off of my PA 28, we didn't break apart in flight.
The DC9 I flew for many years had a rudder limiter, no one knocked the tail off the dc9.
Jon, if you know your physics, you'll know full well that the aerodynamic stresses on a PA28 dont even compare with those on a large transport-category aircraft. I also doubt you were in a sideslip following a wake turbulence encounter when you performed that maneuvre. And I've already said that the DC9's rudder surface area in comparison with the A300's makes that comparision unfair too.
No-one 'blamed' the pilot - he was doing as he'd been trained. That training should not have been applied to all aircraft in the fleet. It was a systemic failure.

Also, I think that there's some confusion creeping in - no one was saying that putting full rudder in was the wrong thing to do. They were saying that putting in full rudder in opposite directions while in a sideslip was a bad idea.

Last edited by DozyWannabe; 24th Dec 2006 at 00:59.
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Old 23rd Dec 2006, 23:42
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jondc9

Surface position is a basic term relating to where the actuator/panel is relative to its datum. A DFDR will record that position. If that part of the structure has fallen off, then it may prove quite hard to record where it is. I would also imagine that the relevant actuators that move the surface would be at least damaged, if not deatched with the said rudder panel?!
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Old 24th Dec 2006, 01:37
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Bubbers said :
If my theory is correct about the vertical stab failing initially from the front then the rudder inputs by Sten were probably to correct the stab causing the yaw. He was only trying to maintain heading so multiple reverse inputs would be what any pilot would do if the stab was causing severe yaw problems. If you were the captain would you let him thrash the plane around for a common wake turbulence event? I don't think so. Any flight attendant in the back would be severely injured if she was out of her seat for some reason. We all deal with wake turbulence and it is not an emergency, we just have to make that PA explaining how it is like being behind another boat to calm nervous passengers. A lot of politics was in that NTSB final findings.

Any suststained contact with contemporary systems of "Law" and "Justice" will reveal they, like "legislation" are quite similar to sausage-making: First grind the source material (facts and information) into barely recognisable fragments, add some seasoning, then pack the results into the desired container (official conclusion). Selection of facts for particular emphasis, inclusion or exclusion of details that support a certain case, even the sequence of presentation and reveal of known information can be massaged to finesse a leaning of meaning in a particular inclination, eventually supporting the conclusion of choice. If the goal is to find truth, then it may be found. If the goal is to conceal truth, then it will be concealed for sure.

If I recall (someone please correct me if wrong - the facts are complex and memory sometimes imperfect late at night), the most important top-level conclusion in the NTSB analysis is that the pilot flying actively and frequently reversed the rudder direction using the pedals. More important, this concept is not had from source data showing his pedal position, but is derived from low-fidelity heavily filtered FDR data on the recording track obtained from the rudder position sensor. Assumed is the premise that the only active cause for changes in position sensor data was the movements of the rudder pedals. The analysis is, therefore, inferring the cause from a partially suspect and very imperfect report of the result - and from this inference is built a framework of cause-effect relationshps using assumptions about how and why the pedals traveled to cause the rudder to move.

The entire analysis is a cascade of suppositions designed to support the final conclusion, heavily reliant on selection of salient facts, including critical facts prepared and information provided (and not provided) by EADS-Airbus, an interested party with immense financial exposure hanging on the outcome.

Not reported but also highly pertinent is the truth that the accident occurs and the final analysis is later put forward in a period of political instability and military concern, when censorship and misinformation from the same government that employs the NTSB are reaching a crescendo in support of perceived strategic imperatives for dealing with some external threats.

The process of requiring full disclosure regarding conflicts of interest is increasingly put upon businessmen and political candidates. Why not also apply this to the bureaucrats? Perhaps in some more enlightened future time, "impartial" reports such as this one could include a soul-searching summary of "External Factors possibly affecting analysis and conclusions in the Final Report".

Suggestions will be welcome for additional reasons why NTSB dropped the ball regarding AA587.

Last edited by arcniz; 24th Dec 2006 at 01:47.
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Old 24th Dec 2006, 02:40
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FWIW, my initial - non conspiratorial - take on the events is:

The pilot's training regime was poorly thought-out in parts. The aspects relating to handling wake turbulence appear to exaggerate the effects, and encourage the pilot to respond quicker and harder than necessary.

This is coupled with unclear/misguided directions wrt rudder, and some missunderstanding.

The effects of the actual wake turbulence, which are impossible to accurately recreate may have been coincidentally reinforcing...

I'm no expert on wake turbulence, but, for the sake of imagery, imagine a boat encountering waves (parallel rather than perpendicular to travel) - the immediate effect is in one direction, then cresting the wave, in the other. If the pilot has commenced reacting to the first input, the second could reinforce the correction. If this was then followed by a second larger "wave", then the harmonics/sympathetic response would be significantly increased.


In such a scenario, once the pilot is preoccupied with the rudder and unexpected feedbacks, would such an outcome not be possible?


Feel free to shoot this down in flames! I'll admit I've only briefly looked over the report, etc.
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Old 24th Dec 2006, 05:47
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Here's the report.

http://www.ntsb.gov/publictn/2004/AAR0404.pdf

The company didn't disagree that the FO used the rudders. The union investigator(s) didn't disagree that the FO used the rudders. Both of these parties had problems with the design and certification of the A300.

The union's crash investigative report detailed the design differences in rudder control. Only the newer Boeings (747/757/767/777) have the better design. Rudder travel is always the same, as is leg pressure. Other designs, 727/DC9/DC10/737/all Airbus models, have the system where rudder travel is reduced and the force required to get full deflection is reduced. The union's investigators pointed out that the A300 is significantly more sensitive than other designs.(NTSB agrees, page 146 of the report, pg 160 of the .pdf file)

At 250 kts the A300 rudder is 2X as sensitive as it as at 165 kts(most rudder applications x-wind, etc, are below this speed)(from NTSB report)

AAMP did not advocate large rudder inputs(several references to this in testimony, ie pg 86-pg100 of .pdf) (read NTSB report starting on page 80, pg 94 of .pdf).

Airbus stated the full use of controls may be necessary to control the a/c. And said to use alternating rudder inputs in the checklist for gear extension problems. It wasn't until AFTER the crash they published rudder recommendation in their FCOM manual.

Industry experts advised that all transport catagory a/c can generate loads, even below manuevering speed, that exceed design loads for rudder and stabilizer inputs. Caution is advised!
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Old 24th Dec 2006, 05:50
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The result was an A300-600 design whose sensitivity increases with an increase in airspeed, unlike that of the B2/B4.
"We don't like the change in sensitivity from low speed to high speed," said John Clark, NTSB head of aviation accident investigations. "However, we don't know how far off the 240 knot point you need to be to have a safe system," he said, referring to the 0.02 G force imparted by pedal movement at that speed. "We want to buy more margin," he said, to reduce the potential for aircraft pilot coupling (APC).
APC is a phenomenon in which pilot control inputs can be out of phase with the airplane's reaction, tending to negatively reinforce an increasing deviation from desired to actual aircraft response. In the case of the Flight 587 accident, APC may well have been involved in the rapid series of rudder reversals leading to fin separation. Prior to the Flight 587 accident, few pilots were aware that APC was possible within the rudder circuit (i.e., around the yawing axis). Classic APCs have tended to be in pitch, with a minor number seen as instability around the fore-aft axis and known as roll-coupling. APC involves an involuntary interaction. The nature of the APC beast is that once the process is set in train, it is unlikely that any pilot will suddenly "get off" the controls. Disengagement is not intuitive.
Brenner, an NTSB human performance specialist, said, "APC events always reflect some underlying design characteristic."
"Staff concludes that the A300-600 is susceptible to potentially hazardous coupling at high airspeeds," Brenner said.
Magladry added that the pedal stop "is a moving target" that also depends on the functioning of the yaw damper.
While the board issued recommendations in early 2002 for pilots to be cautioned in training about the dangerous potential for rudder reversals (see ASW, Feb. 18, 2002), Vice Chairman Rosenker said, "At this point, we haven't done much about the rudder - its sensitivity."
Board Member Debbie Hersman said, "The sensitivity is more important than the AAMP program."
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Old 24th Dec 2006, 05:51
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How About HF?

Here's a curve that maybe wasn't considered before:

The HF antenna and antenna couplers are in the leading edge of the vertical fin in most modern transport aircraft. It is a shunt antenna which is fed by the coupler that converts transmit power up to 400 watts at 50 ohms impedance to very low impedance - on the order of ten milli-ohms. The current, therefore, is very high, and it is carried a short distance from the coupler to the vertical fin on a heavy copper cable. The coupler excites the fin and makes the whole airplane into the antenna, meaning that very high currents are flowing in the vertical fin and its junction with the fuselage.

Now I know very little about the construction of the vertical fin in the A-310, other than it's a composite structure - carbon fiber? Is it possible that high currents, coupled with other defects could have damaged the attach of the fin to fuselage? If such damage were caused, it would surely have had to occur over a period of time.

We know, of course, that AA 587 would not have been transmitting on HF at that time, but do we know if this plane had a recent history of HF squawks?

GB
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Old 24th Dec 2006, 05:53
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oops, previous post, and this post, from -


http://www.iasa.com.au/folders/Safet...stability.html
The Difference Between Certification Standards & The Real World

NTSB Member Debbie Hersman: If you are a line pilot, how likely would it be that you would get the full amount [of rudder]? Or get 1.2 inches of the pedal at 250 [knots airspeed]?
NTSB professional staff member David Ivey: If I were to put in rudder? And knowing what I had found that ... there was a very good chance you could put in full rudder [with 1.2 inches of travel]?
Hersman: And if you put in full rudder to the right, how likely is it that you're going to have to come back with the left rudder?
Ivey: I think I could speak for most pilots that if I had any input that had sent me to the right, for example, I'm not going to do what certification says and put my rudder to neutral. I am going to counter the effects that I have just experienced in my body or what I have seen and I'm going to put in opposite rudder to try to correct the problem ... But to answer your question, if I had a big yaw to the right I would put in left rudder. I certainly wouldn't put it in neutral.
Hersman: And once that happened, is it your belief that this pilot was in an APC?
Ivey: It is my belief. Source: NTSB
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Old 24th Dec 2006, 05:56
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http://www.ntsb.gov/publictn/2004/AAR0404.pdf

NTSB AA587 final report

http://ntsb.gov/Events/2001/AA587/default.htm

bascially a table of contents

http://ntsb.gov/Events/2001/AA587/board_mtg_anim.htm

animation of flight path and another with control inputs.
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Old 24th Dec 2006, 06:06
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One more observation:

The NTSB, and especially the FAA, will rarely identify a serious problem until there is a solution available. They really didn't want to ground every 737 in the world indefinitely, as they did the DC-10 in 1979.

By the time the 737 yaw damper problem was conceded, Boeing had a retrofit fix, and a longer term fix for new 737s in the form of a new fail active rudder they needed for CAT IIIb, anyhow.

Planes with wing mounted engines may be a lttle more efficient than those with tail mounted engines, btw, but they require a much larger and more powerful rudder to fly on one engine. That magnifies the seriousness of a wayward rudder.

GB
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Old 24th Dec 2006, 12:43
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"Planes with wing mounted engines may be a lttle more efficient than those with tail mounted engines, btw, but they require a much larger and more powerful rudder to fly on one engine. That magnifies the seriousness of a wayward rudder." G.B.


......Absolutley true, and I think most training organiziations do not emphsize this enough. HUGE loads involved. Makes for more of a handfull of airplane in a crosswind also. When I did IOE, I always tried to give students a couple of crosswind landings (once again, something not normally emphasized in the sim).
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Old 24th Dec 2006, 17:25
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Climb profile/noise abatement?

Just had a look at the flight path animation link posted by earlier poster.It,s a while since i've seen it but could someone explain the climb profile used?
IE: nose over/accelerate at 1000 ft. Flaps up.
I'm sure it's American airlines SOP,i've just never seen a profile like it.
Climb power 1500ft agl, accelerate 3000 agl. is all i can recall on many types in 22years.
Everyday is a schoolday though.
While i'm at it, the use of the word "kick" in relation to rudder use is a pet hate of mine. "push, rub, squeez" are closer to the required action(bar some fancy aerobatics in an aerobatic aircraft)
Even on the flight control check i try to encourage people to gently and smoothly move the rudder to the left, centre,pause for a fraction and then to the right. Not just for mechanical sympathy but bar sim checks it's the only chance you get to train your muscle memory in your legs as to the forces in the rudder.I know it's a ground check and the rudder is different in the air at different speeds, but it's something.

Without going too deep into the accident, it would appear that the rudder was used in an inappropriate way, that is full one way and then full the other. For a large transport category aircraft it looked like too much to me.
Like all major accidents in aviation we as a group learn something from it.
I think "use of rudder" and its limitations is now given more attention in training.

Finally, at this time of year, spare a thought for the families of the crew and passengers.
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