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AF 447 Thread No. 7

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AF 447 Thread No. 7

Old 11th Mar 2012, 19:59
  #801 (permalink)  
 
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HN39, You mean the question, "Was he perhaps trying to maintain 15 pitch attitude?"

That is a perfectly reasonable question. No doubt BEA Human Factors Group is wrestling with this question still.

My feeling is that he was unintentionally catching a piece of aft stick during his lateral stick thrashing, and the characteristic of the pitch axis law is to basically add up (i.e. integrate) all those pitch input pulses. That is what caused the nose to rise, IMHO.
The man's scan was obviously broken at that point. He was not monitoring pitch! He was as far behind the aircraft as you can get (in the aviation sense of the word).

My reasons for concluding in this direction have to do with the notorious Occam's razor. Having found one plentifully sufficient for losing control of the pitch attitude, why introduce another? His pitch problems started when the wings started wobbling. He didn't actually have sufficient free attention available to implement a pitch attitude.

The delayed implementation of the handover to the crew might be considerably longer than 20 seconds. As long as the system knows the gross weight, configuration,operating altitude, and initial conditions, there is actually no reason it could not fly for hours like that, with only a small loss in fuel efficiency.

As I have said previously, how did we cruise our jets in the old days before autothrottles?

Last edited by Machinbird; 11th Mar 2012 at 20:09. Reason: Address second part of HN39's statements.
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Old 11th Mar 2012, 20:08
  #802 (permalink)  
 
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HazelNuts39

"Was he trying to maintain 15 degrees NU?"

Fair question. I have another.

Was he trying to desperately keep the a/c tracking on a heading whilst keeping the wings level?

Your question has no basis in evidence. Mine does. The a/c has a demonstrable problem with YAW. What a/c behaviour might he have been trying to alleviate? A tendency to drop a wing? Slew to the right? Lose herself completely? Was the mush the only attitude the a/c could maintain and stay "airborne"? Did she have a desire to "lose it" with a ND?

Back to airloads. Her ROD touched 15thousand fpm. That is of course in addition to her forward progress. One hundred thirty knots down, plus forward, ~150? All her controls are working to put the mayonnaise in a carton, what were their loads? It is not pansy to entertain that this bird lost some feathers.

mach. "His Pitch problems started when the wings started rocking" qed. Were they "His" problems? Did they have possibly another genesis? BTW, the "Wings started to wobble" in autoflight, not after.

Last edited by Lyman; 11th Mar 2012 at 20:25.
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Old 11th Mar 2012, 20:24
  #803 (permalink)  
 
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mach. "His Pitch problems started when the wings started rocking" qed. Were they "His" problems? Did they have possibly another genesis?
Lyman, your reading assignment is here:http://www.mae.wmich.edu/faculty/Ro/ME540/FQ.pdf
and here: http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA319985
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Old 11th Mar 2012, 20:30
  #804 (permalink)  
 
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Thanks. Your point? If I read and become a better man, I won't ask questions?
I am not stating facts, nor conclusions. It occurred to me that, the wings having started their wobble in autoflight, that PF's efforts at leveling them may have been related to the autopilot's failure at doing so.
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Old 11th Mar 2012, 21:20
  #805 (permalink)  
 
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Lyman, if you read it, you will ask better informed, more pertinent questions. That is the intended result.
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Old 11th Mar 2012, 21:57
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Originally Posted by Machinbird
The man's scan was obviously broken at that point. He was not monitoring pitch!
If I may ask as a non-pilot: If you're struggling with roll control and your scan has narrowed to the ADI, is it plausible that you miss pitch altogether? Is it possible that he was aware of increasing pitch attitude, but didn't care because 15 was his target all along? Perhaps he only reluctantly and half-heartedly gave in to the PNF's urging "You're climbing, go down" until at 02:10:49 he changed his mind and went for 15 instead. Was there perhaps a similar mental process taking place at 02:11:32 when he admitted "I don't have control of the airplane anymore now (...) at all" and, after the PNF had taken control, abruptly took the controls back?
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Old 12th Mar 2012, 00:19
  #807 (permalink)  
 
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"effective system"

Hi,

roulishollandais,

I adopted your suggestion in recent post:

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Old 12th Mar 2012, 00:50
  #808 (permalink)  
 
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Limitations?

Hi,

PJ2:

We need to be practical and find a way to solve the issues when they arise.

I understand your position. It works and worked quite well with you and many others.

There are limitations on this procedure? Heavy turbulence, etc.?

Last edited by Jetdriver; 12th Mar 2012 at 16:56.
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Old 12th Mar 2012, 02:02
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Limitations

RR NBD,

Normally, I don't like to comment on thing like you pose here, but this time I am going to.

Your Quote: We need to be practical and find a way to solve the issues when they arise.
I have been around this business for a long time as you can see by my age, in fact it was my entire working career. I am not a pilot as I think you are not either. But, I have great respect for pilots, especially those who spent their careers or a part of their careers flying fly-by-wire aircraft and the exact aircraft we have been discussing here for 2 years. Clearly, there are times and this was one of them, where a flight crew has to fly the airplane absent some of the luxuries normally provided by the sophisticated electronic control system currently in place. I haven't heard any A-330 pilot say this can't be done and so therefore, it can be done and has been done. A good experienced flight crew a Captain, a First Officer and an additional First Officer could have and would have dealt with this situation in a successful manner. It comes part and parcel with training and experience and team coordination supported by carrying out the written down recipes for dealing with specific situations like AF447 experienced. Unfortunately, this was the wrong flight crew, in the wrong location, at the wrong time, a flight crew which apparently had only part of the aforementioned attributes.

No amount of additional bell, whistles, electronic devises, etc., will ever make up for a flight crew's absolute necessity and ability to fly the airplane absent some of the electronics. Now there might be some things in the present electronic systems that can be made better, but they will never replace good piloting when the chips are down. Flying the airplane is what this has been all about in my opinion.

Never think that a new invention will substitute for the three attributes listed above as "Murphy's Law" will find a way to prove you wrong. Listen to what the successful pilots have said.
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Old 12th Mar 2012, 04:12
  #810 (permalink)  
 
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Originally Posted by HN39
If I may ask as a non-pilot: If you're struggling with roll control and your scan has narrowed to the ADI, is it plausible that you miss pitch altogether? Is it possible that he was aware of increasing pitch attitude, but didn't care because 15 was his target all along?
I was reluctant to answer this too quickly. My basic training was half a century ago. I could fly instruments OK when I was a PPL and it saved my overly aggressive posterior one day as I was flying XC into lowering ceilings and snow showers (in mountainous terrain to make things even more interesting.) My subsequent military training was excellent and left me with an unbreakable scan. While instructing instrument students, I have seen individuals suffer dangerous scan breakdowns when fatigued, but if PF had a scan breakdown, it was as bad as it gets. The only reason a pilot with airline training would have a scan breakdown as bad as PF apparently had would be if confronted with an urgent problem that he did not understand. An out of control roll oscillation fits that description.

As to why he would apply additional nose up input at the second stall warning, he probably thought TOGA thrust would protect him from the consequences. This would then be a result of the obsolete stall procedure that was being used until recently (concentrating on minimizing altitude loss).
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Old 12th Mar 2012, 04:18
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Just confirming

Hi,

TD:

Listen to what the successful pilots have said.
I am not just listening. I completely agree.

I was confirming the "techniques" used for are in my opinion, wise, practical, time tested and effective.

My objective was only that!

Flying the airplane is what this has been all about in my opinion.
I agree.

Never think that a new invention will substitute for the three attributes listed above as "Murphy's Law" will find a way to prove you wrong.
I never did!

As a designer i consider impossible to substitute a creative, motivated and diligent professional when near limits.

I have the impression there was a misunderstanding of my post.

Last edited by Jetdriver; 12th Mar 2012 at 16:55.
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Old 12th Mar 2012, 04:40
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Priorities

Hi,

Machinbird:

So, elected this priority (acting as being at imminent risk) fighting a "completely new" problem? And wasting precious seconds neglecting the deadly pitch threat.

Makes a lot of sense for me.
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Old 12th Mar 2012, 05:00
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Hysteresis

Hi,

Machinbird:

The delayed implementation of the handover to the crew might be considerably longer than 20 seconds.
Why not?

The current situation shows INCOMPATIBILITY between AS probes "recovery time" and System handover.

After 30+ UAS cases this IMHO is a "persistent design flaw"
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Old 12th Mar 2012, 07:04
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Originally Posted by Machinbird
As to why he would apply additional nose up input at the second stall warning,...
The second stall warning came at 02:10:51, 2 seconds after he began pulling up again.
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Old 12th Mar 2012, 15:17
  #815 (permalink)  
 
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On its face, the NU prior to STALL WARN is consistent with what Machinbird describes, and it is consistent with a Training failure and the PF's preoccupation with overspeed. Because it is prior to, PF had other indications that she needed not to be low in the NOSE?

If the warning is due increased speed into the realm of STALL WARN proper function, and not its disapearance at arbitrary "low" speed, the a/c is accelerating, and likely because the NOSE is dropping.

We've been there, but w/o the dropping nose. Inappropriate 'Approach to STALL training', and the PF's obsession with overspeed. No one it seems, including the Captain and LHS, wanted this bird to drop her nose and fly. From the stubborn reluctance of Bonin at first, and the pleas of LHS, to this NU at STALL WARN (!), to "Climb, Climb..." "No, don't climb..." "Pull, Pull, PULL..."

Complete unfamiliarity with a tail low STALL? Fear of overspeed? Could it be she became completely uncontrollable as she approached level flight? What would cause that? Was fear of airstream noise and its implications the driver instead of the crew?

Because if the single unknown factor that caused this wreck is the hidden RHSS, someone has some splainin' to do.
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Old 12th Mar 2012, 16:06
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Originally Posted by HN39
The second stall warning came at 02:10:51, 2 seconds after he began pulling up again.
That does establish the chicken and the egg, doesn't it. Looks like I'll have to do some additional head scratching.
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Old 12th Mar 2012, 16:44
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Basically, something about approaching level attitude made PF pull up. It happened at a/p drop, and prior to STALL warn. (Both times).

Fear of overspeed? Possibly. I would not eliminate a/c behaviour. I say again, YAW? Bobbing, wing drop? To indict the PF without eliminating a/c damage or unflyability is wrong.

Directional handling problem is known. Captain mentions Rudder, and PNF says: "WATCH your Lateral". These two guys were not flying, but were seemingly content that PF was, so there may have been a problem undisclosed by BEA.

What would cause the a/c to slew about as she exits MUSH? It would be premature to mention, but some possibilities of handling problems v/v heading exist.
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Old 12th Mar 2012, 18:27
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Wink EFFECTIVE AIRCRAFT

Hi RR_NDB,

Thank you for your reply. I know you know this great loop !
I would like that all the airline pilots learn and use that expression , and that we no more have to add "(pilot & system)" . In this sense did I want to "generalize" it to all pilots, with your both benedictions ! (and Systemstech where I found the word ! Thanks).

roulishollandais
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Old 15th Mar 2012, 13:11
  #819 (permalink)  
 
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Finite State Machines and the need of "Graceful Degradation"

Hi,

I did study this issue and we could say the Systems placed in advanced planes like A330 are "somewhat" in this category.

These powerful mechanisms sometimes need a "Reset". There is the risk to enter some "States" and the Reset assures a "new begining".

My question is related to the need of "Graceful Degradation" on the planes, when submitted to anomalous "inputs" and requiring emergency manual "crew intervention"

Why A/P and A/THR are not "System designed" to "return" to the scene after an anomaly (like brief UAS) in this planes?


Mac

Last edited by RR_NDB; 15th Mar 2012 at 17:46. Reason: text ipvmt
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Old 15th Mar 2012, 13:54
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Originally Posted by RR_NDB
Why A/P and A/THR are not "System designed" to "return" to the scene after an anomaly (like briefly UAS) in this planes?

Graceful Degradation is an important concept, but you have to remember how quickly stuff can happen in an aircraft. First, that aircraft is changing position at the rate of ~ 8NM / minute and roll and pitch rates can also be pretty high, so anything more than a very brief interruption can cause too much variation for a reasonable reset.

Best approach would be to approximate what a human pilot should do under the circumstances and figure out how to automate those actions.

The good thing is that the computer can generally size up a situation in less than a second and apply all the corrective steps. No need to level off after a UAS during climb, just set a pitch attitude appropriate to the altitude and thrust available and keep on trucking after advising the crew of the problem..
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