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He stepped on the Rudder and redefined Va

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He stepped on the Rudder and redefined Va

Old 5th Oct 2013, 18:53
  #261 (permalink)  
 
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there were a number of issues with this accident.

design. The -600 had different aileron control sensitivity to that of previous models. in turn, this led to the engineers tweaking the control loading required for max deflection, making the rudder more sensitive. this meant pio in yaw was increasingly likely.

this was a minor point; the big one was the negative training recieved in the simulator, in particular, the use of rudder to control roll during an upset. i believe, but am not certain, that the sim profile actually had the instructor turn down the control authority of aileron in the sim, and thus reinforcing the inappropriate use of rudder to control yaw.

a few on here need to do a bit of research. go off and read up on dynamic vs static loading requirements, then have a look at part 25 design requirements. understand the effects of moment of inertia, angular acceleration and aerodynamic damping and you will realise that no re-definition of Va has occurred.

do multiple, max amplitude in phase doublets on the rudder on any aircraft enough and you will snap the fin off.

Last edited by VinRouge; 5th Oct 2013 at 18:55.
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Old 5th Oct 2013, 20:24
  #262 (permalink)  
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I am going to have to get into an Airbus sim...

Slow flight, departure stalls, stall spin recoveries, wake turbulance, microbursts...

Probably all I will hear from the back of the sim...

'yeah, um, gee, try not to use the rudder to much...yeah I know the wings were 90 degrees and the plane was going to roll on it's back, but you know, um, well, gee, you see the tail hydros are really sensitive, and the tail, well, um, gosh, you see, well, the NTSB says the plane will right itself..oh, yeah, I know you were going to hit the ground, but you know, um, well, gosh, that's the recomendation, um, well, yeah, uh huh...'.

This probably has to be the most stupid conversaton on an aviation forum I have ever been part of.
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Old 5th Oct 2013, 20:36
  #263 (permalink)  
 
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Sorry to intrude lads, but back when this happened I was training in an MRO and our instructors ran the (approximate) maths to show the loading this fin was under. They came to the conclusion that any large jet transport aicraft would have lost the fin under that loading, composite or aluminium. The increase in load with each reversal was enormous. The fin on that A306 actually failed far above it's max load certification, our engineers were impressed at how long it held on for.

If you recreated the circumstances on a Boeing, Embraer or any medium or heavier aircraft, that many reversals at that speed that low will rip your tail off was their conclusion
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Old 5th Oct 2013, 21:53
  #264 (permalink)  
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UNA - There is no way your instructors were aeronautical engineers with the Airbus structural data, then punch in an accurate description of the wake turbulance event, then assuming they actually had the actual correct FDR inputs instead of some 'gamed' numbers, then of course found the only Arnold Swarzeneger pilot in the fleet that could bang 140 lb inputs back and forth in the sim to come up with 'sideloads' that imposed 'vertical loads' to take the tail off.

I mean I have been in the sim where I asked them to do a dual bucket deployment. ha. Trust me, these guys can't simulate the tail coming off. At best they can sit around a table with the numbers Airbus gave them, trying to convince the FAA that some perfect storm of rudder input and wake turbulance, conbined with a super special snowflake sensitive rudder system, that some how got through flight test cerfication, but you know, now needs to be recertified, because, you know..NOW they know it's quirky.

Come on.
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Old 6th Oct 2013, 01:56
  #265 (permalink)  
 
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I know that no one has asked, but … after reading the recent posts and looking again at the NTSB animation, I’d like to offer my thoughts … but before I do there are 2 things I need to explain:

1. Proprioception is awareness of the position of one’s body in time and a defined space; and the proprioceptors are located in subcutaneous tissues of muscles, tendons, joints that respond to stimuli applied to the body. There is conscious and subconscious proprioception – in a simplified description, one is recognized, processed by the brain, and recognizes a solution or response … and the other is not processed by the brain, the body simply responds … much like quickly jerking your hand away from a hot stove, or blinking your eye if it is threatened.
2. Anyone who flew the B727 very likely received a substantial amount of training on how to recover from a “dutch-roll.” And you probably recall that the primary control response was the aileron (control wheel) and the process was to recognize the direction of bank and apply a large amount of aileron opposite the roll, and immediately return the control to the neutral position. When the airplane began to roll in direction of your last aileron correction, and as soon as the airplane passed wings-level, again apply a large amount of aileron (control wheel) against the rising wing – or opposite the roll – and immediately return the controls to neutral. It’s the “return to neutral” part that is every bit as important as the control insertion to stop the “dutch-roll.” This is what all maximum control applications during certification require … return the control to the neutral position.

OK – now for my thoughts on the AA587 circumstance.

We know about the rudder sensitivity (if we call it that – but even then, the rudder shouldn’t have been all that much of an “unknown” to someone who’s flown the airplane as long as this crew had flown it) and we know that the F/O had quite successfully transitioned the first wingtip vortex (in fact, looking at the animation again – one could call it quite professionally – in that he allowed the inherent stability of the airplane to do it’s “thing”), but I think that encounter really heightened that F/O’s “fear factor” to the point that he was operating on “the panic bubble” – where he was not yet quite panicked, but he was right at the edge. Remember the F/O questioning the Captain about the ATC clearance, asking if the Captain was “comfortable” with the takeoff following distance? I believe the F/O was showing preliminary signs of nervousness, even before they pushed the throttles forward for takeoff. And I don’t think he had rid himself of that nervousness – I think it was peppering the back of his mind throughout the climb-out.

Pilots typically set up a mental regimen by which they fly (which might be described as …“scan – mentally process – feel – mentally process – scan – mentally choose a response – physically respond – scan – mentally process – feel the motion – visually confirm the motion cue – mentally process – etc.”). I think the F/O was riveted on flying the departure and controlling the airplane – and doing so more intently than he normally would. I think he was spending a lot of subconscious effort being concerned about where the JAL747 was ahead of them WHILE concentrating on his departure – still nervous but still performing. Then – bang, they encountered the 1st vortex. It jostled the airplane a bit – and I think the F/O did just what he was trained to do – keep the controls essentially neutral – correcting minor deviations as necessary – most notably, applying a very minor roll correction. And the vortex was successfully transitioned … but … and here’s the real BUT… I think that first event escalated the fear the F/O had been forcing down and brought it right up to scream in his face! I call it “the panic bubble.” He wasn’t panicked – yet. But he was nowhere near the calm F/O that questioned the Captain before the takeoff roll.

Had they not encountered that 2nd vortex, the F/O very likely would have taken a couple of deep breaths and, within the following 5 to 10 minutes, calmed down to the point that everything would have seemed to have been, and likely would have been, “back to normal.” I think he was beginning to mentally process what had just happened (what he saw, felt, heard … what controls he used, how much input, held for how long, any repetition required, etc.) as he began a turn to stay on the departure course … and he knew he had to continue the departure. I think the Captain noticed a change in his F/O – probably not overt … but a change nonetheless – and I think that was the reason he attempted to calm the F/O, and probably himself, by nonchalantly asking “a little turbulence there, eh?” just after the encounter subsided. But I believe that attempt at “down playing” what had just happened didn’t penetrate the F/O’s “panic bubble.”

He knew he had to maintain pitch, bank, heading, altitude, climb rate, airspeed, etc., follow the published departure AND follow ATC instructions – but I think he was more concerned about the JAL747 that he was following. I think those things grew and grew in significance and the panic bubble was growing, not reducing. Now he was trying to recall just how bad that turbulence had been and how bad it could have been. How close was that other airplane? In short, he was mentally pushed to the limits – but he was still trying to perform his duties of flying the airplane. However, before he could get things back into the regular process with which he was familiar … yep … BANG … 2nd vortex encounter. But here, the F/O was spooled up – quite a bit – and now, the panic bubble burst, and his response was one of panic – his proprioception receptors (recognition not requiring processing by the brain) fired, and knowing his airplane was being forced into more of a left bank – and having already established a 23° left bank – just like snapping your hand away from a hot stove, this F/O slammed a right control wheel and a corresponding right rudder control input – almost to the stops. Whether the following and all subsequent control applications (both wheel and rudder) were a result of his proprioception or his realization that what he just did was likely too much – I can’t say … but when you’re responding out of panic, there isn’t much room for recognizing magnitude and incorporating finesse.
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Old 6th Oct 2013, 02:17
  #266 (permalink)  
 
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Any pilot that takes 5 to 10 minutes to regain compsure isn't a safe pilot. By then it is all over. Maybe 5 seconds if he is slow. One second if he is normal. We don't have the luxury of time in the cockpit. Some things require immediate reflex actions, some don't.

Deciding to divert to an alternate, take your time. Wake turbulence or windshear a second is too long.
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Old 6th Oct 2013, 04:11
  #267 (permalink)  
 
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UNA - There is no way your instructors were aeronautical engineers with the Airbus structural data, then punch in an accurate description of the wake turbulance event, then assuming they actually had the actual correct FDR inputs instead of some 'gamed' numbers, then of course found the only Arnold Swarzeneger pilot in the fleet that could bang 140 lb inputs back and forth in the sim to come up with 'sideloads' that imposed 'vertical loads' to take the tail off.
So, Teldorserious, how do you explain that in the aftermath of the crash, Boeing structural engineers did the same analysis and came up with the same answer - that the same rudder inputs would have failed the tail on a Boeing aircraft?

You never directly answered my earlier question - do you honestly believe the NTSB is corrupt and falsified the data?

And if you're willing to answer yes to that, I have another question: Why would they do that? Why would a US Government Agency falsify data to protect a foreign company - a company that competes directly with one of the USA's largest companies? And why would Boeing go along with it?

Oh, and while you're at it, why would American Airlines go along with it - exposing themselves to untold millions in lawsuits - when they could have piled all the blame on Airbus for a defective aircraft?
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Old 6th Oct 2013, 04:26
  #268 (permalink)  
 
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Originally Posted by tdracer View Post
So, Teldorserious, how do you explain that in the aftermath of the crash, Boeing structural engineers did the same analysis and came up with the same answer - that the same rudder inputs would have failed the tail on a Boeing aircraft?
Or along the same lines, how do you explain that even before the AA crash, Boein issued an amendment to the Operating Manual of the KC-135 stating that reversals of rudder application can cause the vertical stabilizer to fail. (previously posted in this thread)

Interesting, isn't it, how Teldorserious just seems to ignore these things that don't fit her fantasy.
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Old 6th Oct 2013, 06:14
  #269 (permalink)  
 
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God, I hate having to repeat myself, but Teldorserious ain't an aviator in any form or fashion, so I fail to understand why any take his posts with any measure of credibility, or even engage him in conversation.
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Old 6th Oct 2013, 07:10
  #270 (permalink)  
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Brian;

It's interesting. Teldorserious started the thread and frankly, I like where the thread itself has gone; I have learned a great deal from others and am putting some of it to use in my flight data work.

But each poster sooner or later proves his or her capabilities as well as his or her disposition towards civility-above-all-else-including-ego, and serious discussion when engaging other like-minded serious professionals, many of whom come here for the joy at the level of such discussion as well as great information.

It's ironic that after beginning, his subsequent posts are puzzling, but there it is, not the first, nor the last occasion we'll see. He's been on my ignore list for some time.
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Old 6th Oct 2013, 10:22
  #271 (permalink)  
 
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Originally Posted by AirRabbit
1. Proprioception is awareness of the position of one’s body in time and a defined space; and the proprioceptors are located in subcutaneous tissues of muscles, tendons, joints that respond to stimuli applied to the body. There is conscious and subconscious proprioception – in a simplified description,oneisrecognized, processed by the brain, and recognizes a solution or response … and the other is not processed by the brain, the body simply responds … much likequicklyjerking your hand away from a hot stove, or blinking your eye if it is threatened
Originally Posted by Bubbers44
. I think we have all had vertigo. Training lets us overcome it. It saved my butt once.
As a freefaller we used unconscious proprioception and developed subcutaneous muscles and sensors like the dancers but we use too sight and other senses to control body attitude ref horizon or to join relative freefallers . During the freefall each time we leave the aircraft we fall first in low gravity and have to find the good dynamic balance with very little movements. As pilot, and specialy IFR pilot we do not trust proprioception. Itwould be a dangerous fault denying IFR flight possibility, but ONLY instrument informations -exception is position of the body in the armchair, neck position, and control of fingers, legs and fixing the inside of the body. As Bubbers44 says training overcomes vertigo created by contradictory proprioceptions. Performance in spinning armchair with blinded eyes used for astronauts training shows that difference : freefallers are much better than fighter pilots. Pilots trust instruments not body feelings.
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Old 6th Oct 2013, 13:24
  #272 (permalink)  
 
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Totally agree with the thrust of your post PJ2, only some have not learnt to ignore his exceedingly strange and ignorant posts. Renewing his instructors rating, give me a break.
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Old 6th Oct 2013, 14:25
  #273 (permalink)  
 
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I am going to have to get into an Airbus sim...

Slow flight, departure stalls, stall spin recoveries, wake turbulance, microbursts...
Teldo... this comes to mind!

http://virtualmystic.files.wordpress...6/simcrash.jpg
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Old 6th Oct 2013, 15:27
  #274 (permalink)  
 
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SMOC, The statement "Personally, I would'nt let Buba pull my kids wagon" certainly applies to our friend.
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Old 6th Oct 2013, 15:27
  #275 (permalink)  
 
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OK465 - thanks for the correction/clarification.

I've seen a chart listing breakout forces, force needed for full travel, pedal travel, etc. I thought it was in the submission but apparently it isn't.
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Old 6th Oct 2013, 18:02
  #276 (permalink)  
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Brain are you still mad that I outted you as a fraud? Why the mods put up with your incessant trolling is beyond me. Maybe they don't care?

Last edited by Teldorserious; 6th Oct 2013 at 18:03.
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Old 6th Oct 2013, 19:13
  #277 (permalink)  
 
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Originally Posted by bubbers44
Any pilot that takes 5 to 10 minutes to regain compsure isn't a safe pilot. By then it is all over. Maybe 5 seconds if he is slow. One second if he is normal. We don't have the luxury of time in the cockpit. Some things require immediate reflex actions, some don't.

Deciding to divert to an alternate, take your time. Wake turbulence or windshear a second is too long.
I’m not describing the necessity to compose one’s self … I’m describing the ability to not react out of panic, but rather function as you have been trained, choosing what your reaction will be – and I’ve described this in pilots as being somethink like …“scan – mentally process – feel – mentally process – scan – mentally choose a response – physically respond – scan – mentally process – feel the motion – visually confirm the motion cue – mentally process – etc.” this pilot was doing that up until the 2nd vortex … but I think he was on the verge of panic, keeping it under control, and likely, working his way out of it. Unfortunately, the 2nd vortex hit and burst that panic bubble – and from there everything he did (in my opinion) was the execution of what he knew but motivated out of panic. As I also said previously, most people think they know how to recognize someone who has panicked … perhaps some may … but I do know that when you’ve seen someone really panic, it’s something you won’t easily forget. And unless you know the person, or are really familiar with the circumstances, you might not recognize that the actions you see are very likely executed out of knowledge but that person is not calmly exercising that knowledge – he is being motivated out of panic – and that is something that is beyond the control of the person. In fact, the dictionary definition of panic is “… a sudden sensation of fear which is so strong as to dominate or prevent reason and logical thinking, replacing it with overwhelming feelings of anxiety and frantic agitation consistent with an animalistic fight-or-flight reaction.” To me, this is what I think that F/O was doing ... reacting with a skill set and doing so out of panic ... attempting to function without thinking logically or reasoning to any degree and was, instead, functioning out of an overwhelming feeling of anxiety and frantic agitation.

Last edited by AirRabbit; 6th Oct 2013 at 20:30.
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Old 6th Oct 2013, 19:40
  #278 (permalink)  
 
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APC and other Dutch rolls

@Owain Glyndwr
Dutch roll is certainly an oscillation, but it doesn't have to be one of increasing bank; in fact it would be a lousy aircraft for which that were true - very probably unflyable. Increasing bank as a result of suitably (mis)timed pilot inputs is quite another thing.

Sure the rolling motion is usually the most obvious sign of a dutch roll, but the motion is a combination of two oscillations -one around the roll axis and the other around the yaw - linked together by a common driver - sideslip.

Way back in the 1950s Ashkenas and McRuer established the importance of the roll/sideslip ratio as a parameter to describe the goodness/badness of dutch roll. The larger the number the worse the aircraft basically. So dutch roll can be triggered by rudder application, but as you say it is best controlled by aileron.

So far as I know, the A300 was not noted as having poor dutch roll characteristics.
I am holding that resonance definition of "dutch roll" from my automation teacher, an engineer working at the last French projects.

Iself had read conventional things about dutch roll in ATPL books but was interested by real dutch roll since 1979 from a Learjet Captain who feared it during any approach. I read and listening again.

And it happened that I decided to study automation after a background of pure and applied math, scientific informatik, and aeronautics.
One day (1985) the teacher resumed about stable/unstable systems : You know, phase planes, Lyapounov, Nyquist, Bode, sign of real part of poles, aso. And suddenly he had a thought, stopped one second, and said "Dutch roll is resonance tween the first degree system of roll of the aircraft, and action of pilot....

He ignored that at least one student from around 30 was concerned by dutch roll!
He came back to the class concerns, but the sentence was printed in my brain. I had not seen the learjet's or books' "dutch roll" in these terms. So I did nothing more during years with that declaration, despite all the respect I had for my teacher.

In my airline a MD 83 had in 1992 a dutch roll approaching NICE 05. They were very mute about it (well finished over the sea, the Captain leaved controls as he had learned as Cadet in USA. But the Airline head decided to let us discover the pleasures of dutch roll during the next off-line sim test. Nobody said they had all failed before me and I was the last one. The instructor was a former business pilot on Learjet! The first pilot started and lost 11000', we went on the back right and left... At the end the instructor said him very sad "You have seen it".

It was now to me. Suddenly I reminded to my automation teacher, and I thought that if "dutch roll" accorded to HIS definition, I could perhaps try to get it. I showed the animal,his position, speed, acceleration, counted seconds in my head, reckoned two easy differential equations in my head and piloted the result (nothing to do with the above B727 rolls described method).

And five times ago I was able to stop the "dutch roll" (in the sense of my former learjet instructor and the books) with a bank which was never more than 30°, in less than 30seconds, and never lost more than 1000 ft.

In my airline nobody asked me my method, included the instructor and the second pilot... Very sad,

I wrote it only in 1997 after I discovered that one of my former private pilot student had been killed as passenger from the Learjet which killed Baroin Sr perhaps in a dutch roll degenerating in a deepstall.Sad again.

I phoned to Leadair (LFPB) and finaly Learjet in Geneve (1998) . I told my story to the Chief Pilot, who answered they had finaly found a methodcagainst Leajet's dutch roll : ...sharing quickly the pedals... I asked me how it was possible to imagine that sequence.

On PPRuNe more recently I discovered that dutch roll was considered as a unworthy situation.

Machinbird who had written about PIO in the AF447 thread suggested me to read Mc Ruer's book about PIO and other APC.

I found there a world I had not found in aviation until that day : scientific methods and true solutions in the continuous and discontinuous domains of FBW and classical flights including the often missed rate limitations, omnipresent in FBW systems leading to oscillation (I don't remember mention in the FBW thread).

So I stay with my teacher's definition of dutch roll. I don't deny the roll and yaw reciprocity which conduced to the yaw damper conception, present on all airliners of course.

The failure of the yaw damper is the first cause of dutch roll or aggravated roll and yaw oscillations. If the pilot is not able to stop them quickly which is the most frequent case, the bank will really increase, also in the case where we still are in a first degree system in resonance with pilot's "normal" inputs...

About the stability of the "A300", the APA document refered by misd-agin is not so optimistic with the "FBW" technology version of the A300-600R. In any case iit needs its yaw-damper is functionning.

To mention too the sudden impulsion of yaw damper failure, and once again any brutality in piloting like quick reversals on rudder...

For the defense of some aircrafts major manufacturors I would like to remind that oscillation computation means are relatively recent.

Last edited by roulishollandais; 6th Oct 2013 at 21:59.
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Old 6th Oct 2013, 19:52
  #279 (permalink)  
 
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Originally Posted by teldorserious
I am going to have to get into an Airbus sim...

Slow flight, departure stalls, stall spin recoveries, wake turbulance, microbursts...

Probably all I will hear from the back of the sim...

'yeah, um, gee, try not to use the rudder to much...yeah I know the wings were 90 degrees and the plane was going to roll on it's back, but you know, um, well, gee, you see the tail hydros are really sensitive, and the tail, well, um, gosh, you see, well, the NTSB says the plane will right itself..oh, yeah, I know you were going to hit the ground, but you know, um, well, gosh, that's the recomendation, um, well, yeah, uh huh...'.

This probably has to be the most stupid conversaton on an aviation forum I have ever been part of.
It is apparent that you’ve likely never spent much time in a transport category airplane simulator – I would LOVE to hear about your “departure stall” and “stall-spin-recovery” maneuvers that you’ve done in simulators previously and that leaves me to wonder why the only “conversations on an aviation forum” that are stupid are those in which you have “been a part.”

Last edited by AirRabbit; 6th Oct 2013 at 20:15.
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Old 6th Oct 2013, 20:08
  #280 (permalink)  
 
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Originally Posted by A Squared
Quote:
Originally Posted by tdracer
So, Teldorserious, how do you explain that in the aftermath of the crash, Boeing structural engineers did the same analysis and came up with the same answer - that the same rudder inputs would have failed the tail on a Boeing aircraft?
Or along the same lines, how do you explain that even before the AA crash, Boein issued an amendment to the Operating Manual of the KC-135 stating that reversals of rudder application can cause the vertical stabilizer to fail. (previously posted in this thread)
Having my own membership card in the “professional gas-passers union” (active in the late 1960s through the early 1970s) I can say that, while the Ops Manual didn’t have a specific note in the text, a flight crew member couldn’t get through the “ground school” classes taught at Castle AFB without hearing (and I think my eardrums are still scarred) about the effectiveness of the rudder on that airplane, and how virtually ANY movement of it (powered or unpowered) was to be VERY sparingly used … and NEVER reversed!!!
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