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AF 447 Thread no. 4

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AF 447 Thread no. 4

Old 22nd Jun 2011, 20:11
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Thank you for taking the time to discuss seriously. I will now make a full review of PJ2 very sharp questions and hopefully come up with decent postable answers within 48 hours.

My opinion on the whole matter goes very close to what A33Zab proposed :
The failure of these sensors fooled AP, Protections AND human.
My only bias here is that I intend to examine the Flight Controls System first, because :
- it claims ultimate authority in some cases (this authority is built in the design, so to speak), therefore it should give answer first
- it is placed between pilot and aircraft in the control loop, which makes it absolutely necessary to question it when faced with a LoC accident

My insistence stems from the fact that my findings in this regard go much farther than the official ones. I am therefore tempted (by design ) to take their counterpoint. A kind of balancing act.

This does not exclude finding if & where crew actions could have been better, if & where they had it very wrong, or how pilot training and attitude could evolve for the greater good. I have already posted in this respect and will likely do it again.

But it comes second if one wishes to really understand what they really faced on their last flight, to hopefully come up with realistic answers, both collectively and individually for pilots flying these machines with innocent trusting human beings on board.

Best regards

PS : when disaster strikes, healthy Flight Controls are more important than satisfyingly turning engines. If I had to be left with only one of these two...
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Old 22nd Jun 2011, 20:19
  #282 (permalink)  
 
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What gums Didn't Say

......I shall ascribe a significant portion of the “cause” to the aircraft design.
Gums didn't say that aircraft design was the only cause of this accident. What he didn't say is that several other factors will be found;

1. Pilot training factors
2. Supervisory factors
3. Maintenance factors
...and possibly more.

In addition to considering aircraft design, no accident investigation is complete without at least considering the above. I believe that, at least, the first two have some bearing on what happened.
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Old 22nd Jun 2011, 22:29
  #283 (permalink)  
 
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Accident investigations

I throw my lot in with Sv, and his approach to the investigation of this terrible accident.

I apologize if I appear to be harsh with respect to my opinions of the Airbus design, but I feel I am more than qualified to comment on ANY CRAFT that is fly-by-wire. I base my opinions upon both my technical background and piloting background.

As Smilin' states, many factors can contribute to "cause", including supervisory, training, crew discipline, etc. However, first thing an accident board does is look at mechanical factors, then human factors. Sure, weather is a player, but only to the extent it may have precipitated an aircraft system problem or a situation that the crew could not handle.

My primary complaint is a reversion process that requires too much thought by the aircrew as to what is still working and what "protections" are lost and/or must be dealt with as in a "normal" aircraft. As Sv states, the flight controls are between the human and the aircraft control surfaces. So it bears the closest scrutiny, especially considering previous incidents involving the same type aircraft.

will answer specific questions later, as we await the next "interim" report/finding.
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Old 22nd Jun 2011, 23:59
  #284 (permalink)  
 
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will answer specific questions later, as we await the next "interim" report/finding.
Do we know approximately when that will be?
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Old 23rd Jun 2011, 00:14
  #285 (permalink)  
 
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Or, shorter gums, in a FBW plane, the pilot is merely a voting member of the flight.
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Old 23rd Jun 2011, 00:34
  #286 (permalink)  
 
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gums, don't you think the only reason an airbus pilot would pull the side stick all the way back at FL350 is because airbus said it couldn't stall?

No Boeing pilot would do that. They would hold the appropriate attitude and power for their altitude and weight. No one would pull back as they did. As the Airbus goes through it's laws degrading probably no one is trained for that so what ever law they ended up in let them go into a deep stall. I hope Airbus training corrects this so it doesn't happen again. I'm sure this post won't last long.
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Old 23rd Jun 2011, 01:05
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"Managing and handling" advanced Systems (Human machine interfacing issue)

The crew never should be "presented" (specially at critical moments) with System "outputs" that they are not capable to understand very fast.

The crews, "Redundant Systems, operators" always must "have chances" to "keep flying" their increasingly complex, and not perfect (never will be), machines.

It seems, is time now for a very serious effort (a/c designers and operators) for "better interfaces" between crew and the advanced planes Systems.

And i´m not speaking of just training. Complex R&D is required to simplify crew task in dealing with "non routine" situations.

What we have today is not we designers understand by "Fault tolerance" and Graceful degradation" in respect to System behavior, etc. being presented to the crew.

Mac

PS: And Airbus SAS share of responsibility in dealing with this effort is an opportunity for the company that introduced the commercial "advanced planes" (FBW+a new philosophy)

Last edited by RR_NDB; 23rd Jun 2011 at 13:41. Reason: glitches
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Old 23rd Jun 2011, 02:09
  #288 (permalink)  
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I'm sure this post won't last long.

bubbers44, why would you think that ? Someone further up the chain might agree with you but the post is fine by me for the moment.

At the end of the day, the investigatory conclusions will be what they will be.

The sequelae are the important things - what the Industry does to plug whatever the hole(s) in the dyke might turn out to be.

It is important that we all keep in mind that aeroplanes are not perfect and the whole operation is based on probabilities (and possibilities, as PJ2, I think, admonished) as well as sensibly mitigated risks.

The overall safety of aviation is a progressive dance sort of animal - we just keep nibbling away at it, improving things here and there and all the while enjoying the benefits.
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Old 23rd Jun 2011, 02:11
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Going back to a post I made a couple of days ago. It occurs to me that if the Flight Path Angle in the developed stall was around 45 degrees below the horizon, it would be necessary for the crew to push the nose down to at least 35 degrees below the horizon to break a stall.

No big deal to a fighter pilot with altitude.

A transport pilot, particularly one that really didn't understand why his aircraft was giving him no airspeed indications, and who was having trouble integrating the whole picture would have sold his first born in preference to stuffing the nose down 35 degrees below the horizon. That is likely why AF447's crew only gave a cursory attempt at getting the nose down to break the stall.

Would you have the courage to stuff the nose well down with similar indications in night IFR conditions while flying a 200 ton airliner??
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Old 23rd Jun 2011, 02:36
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gums, don't you think the only reason an airbus pilot would pull the side stick all the way back at FL350 is because airbus said it couldn't stall?

No Boeing pilot would do that. They would hold the appropriate attitude and power for their altitude and weight. No one would pull back as they did.

Boeing guys are a very special breed of course. But what about, say, Dash 8 pilots? They would never pull up in a stall and in any case there's still the stickpusher, right?

People doing the wrong thing because instinct overrules knowledge wasn't invented with FBW controls:
http://www.pprune.org/tech-log/45465...ml#post6528494
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Old 23rd Jun 2011, 02:43
  #291 (permalink)  
 
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J_T

sequelae
My first instinct was to bet you recently visited a medical professional, UNTIL I did a search and was amazed at the number of times that word has been used on Pprune.

Never argue or doubt the moderators! Or the erudition of the posters.

GF
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Old 23rd Jun 2011, 02:54
  #292 (permalink)  
 
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Rockwell-Collins has announced, at Paris, "panic button" that would "rescue" the plane by immediately recovering it from a stall or bringing it to straight and level at a reasonable speed; it might even land the plane. This way lies UAVs as passenger planes.

What are we coming to as pilots? If this is tried, we might has well hire to proverbial "bus driver" as long as conditions are fine, he'll do fine and when this goes wrong, push "PANIC" and wait for the landing.

WRT Machinbird's comment--if you are going downhill with boatloads of ROD, no indications of airspeed, nose 16 degrees above the horizon, pushing the nose down 35 degrees is better than whatever else has been tried. As D.P Davies said, given the choice between stalling and the alternative, try the alternative.

GF
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Old 23rd Jun 2011, 02:59
  #293 (permalink)  
 
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Accident Investigation

Gums,

Your posts and experiences on FBW aircraft have been extremely enlightening and most welcome as the PPruNe pilots and technical contributors continue to explore the factors causing the demise of AF447. There is no apology required for your conclusion that a certain amount of cause should be laid in the lap of the aircraft designer/producer. As Smilin-Ed points out, there are more causes that will/should be identified in the end. The facts are, things have changed from times ago. Then, there were basically two failure causes, airplane failure (the wing fell off or the engines quit) or pilot failure (poor judgement). Now there are multiple causes besides these two, computer failures, computer logic failures, computer messages that say one thing but mean another, nonexistent training for events that occur and the overall reliance on a man-made system that is deemed to prevent human error while ignoring the possibility that a system error could result in the same disastrous conclusion. The sophistication of today's FBW aircraft now translates into accident investigations, they in turn, become far more complex in determining root causes and recommendation measures.

I see quite a few people believing that substantial information will be forthcoming in the next BEA Interim Report, even some have mentioned causes being stated. I think the bar of expectations is set much too high in this regard. To date, we have received 50 pieces of a 750-1000 piece puzzle. In examining our 50 puzzle pieces, there is a diversity of opinions, theories and proposals as to what these 50 pieces represent. Now think about the BEA folks. Although they are "experts" in accident investigations, probably none of the investigative members are actually experts in the workings, flight handling and technology nuances of the A-330-200 aircraft, human capability under data overload and extreme stress, let alone its FBW system and logic. So they are dependent on contributing experts to assist them in analysis of all the data recovered, plus the recovered components of the aircraft and (sadly) the medical reports of the recovered passenger remains, human factors, pilot training, airline management decisions regarding available equipment and equipment up-grades. This is not and should not be a whizz-bang investigation reaching conclusions and disclosing information or data that is not clearly understood or where consensus has not yet been reached. IMO, the next interim report will give us another 50-75 pieces to examine. There is always the possibility of something of immediate concern being confirmed that will produce a safety recommendation. I don't look for much more.

Once all the data the BEA possesses has been thoroughly wrung out, tested and agreed to, can the process of assigning cause begin. IMO, this is the most difficult phase for committee agreement as it involves significant thought, logic, agreement consensus and legal implications (knowingly or not) going forward. There are different degrees, causes (primary), contributing causes (secondary), and undetermined causes (not enough data to determine). For a cause discussion example, Airbus now states:

For a given configuration, a given speed and a given altitude, Lift is only linked to AoA
For a given aircraft configuration and speed An aircraft stalls for a given AoA
Stall is only an AoA problem
When did Airbus know this? Was AOA available and in the forefront of presentations to the pilots in a moment of severe duress on AF447? If not why not? Is this a primary cause, a secondary cause or no cause at all?

IMO, I don't look for a final report from the BEA for a long time as they sort through everything.

Regards,

TD
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Old 23rd Jun 2011, 04:15
  #294 (permalink)  
 
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I have read a lot of speculation on possible failures or problems with the Airbus FBW system on this thread. It has all been very interesting and intelligently argued with lots of well argued logic. But...what seems to be clear is that it is just speculation. People seem over-ready to blame the aircraft because they don't know or understand how it works or how it was designed. The ones who are the most emphatic seem to be the ones with the least understanding. Whilst it is human to seek explanations one does need to consider a set of circumstances from the point of view of the actuality not what the writer would like to believe. So far, though, the evidence/information points in the direction of the human factor not the aircraft. All else could be considered wishful thinking.
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Old 23rd Jun 2011, 05:30
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So far, though, the evidence/information points in the direction of the human factor not the aircraft. All else could be considered wishful thinking.
Just remember, we are outside the aircraft trying to look in to what must have happened. It is very different when you are in the aircraft, with limited and confusing displays, feeling unusual forces, and the aircraft isn't responding in a way you were trained for.
We have to remember that what seems so foolish to us outside observers might make perfect sense given the inside viewpoint. Try to put yourself in the others guy's shoes given the information he was given to act on. The results might surprise you.
If the aircraft had been able to keep its airspeed measurement systems going, none of this would have happened.
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Old 23rd Jun 2011, 05:33
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Originally Posted by TurbineD
Now there are multiple causes besides these two, computer failures, computer logic failures, computer messages that say one thing but mean another, nonexistent training for events that occur and the overall reliance on a man-made system that is deemed to prevent human error while ignoring the possibility that a system error could result in the same disastrous conclusion. The sophistication of today's FBW aircraft now translates into accident investigations, they in turn, become far more complex in determining root causes and recommendation measures.
[emphasis added]
While all of that is inarguably true, the notion that a "pilot" can be so confused by his training that he's forgotten how to recognize and recover from a stall, is, to me, NOT "sophistication".

An airplane is just a dumb, flying machine. A stupid, GIGO, collection of 'stuff'... and it can fly. ...Just like the damned Wright Flyer. ...Forget how to make it fly right, and you're toast.

In this case, adding to the confusion (made extremely evident in these threads) over just how the beast behaves, ...this crew (a pair of FO's) were thrown into a nightmare.... Bad weather, lost airspeed indication, multiple failure annunciations, loss of confidence in any indications (apparently?), conflicting indications, inopportune loss, and then recovery of valid stall warning, darkness of night, absent Captain, poor to non-existent stall recognition/recovery training.....etc....

I don't think they had any chance, given all that.
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Old 23rd Jun 2011, 06:42
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While all of that is inarguably true, the notion that a "pilot" can be so confused by his training that he's forgotten how to recognize and recover from a stall, is, to me, NOT "sophistication".
Other than the rapidly unwinding altimeter, how do you recognize the stall when your aircraft adopts a relatively stable 16 degree nose up attitude. Is the unwinding altimeter real? (Well, yes, in this case.) Stall warning-its silent. Airspeed- nothing there indicated.
It isn't spinning. Just acts really funky on the roll channel and the pitch channel isn't responding. Sort of like a big easy chair. Has the computer gone stupid? Is this a bad dream? Sorry gentlemen time is up. You flunked the surprise test.

Prior to AF447, no one had characterized the A330 deep stall characteristics. Turns out it is relatively stable. I know there are a lot of professional pilots who must be surprised by this. They were spouting a lot of stall spin theories a year ago.
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Old 23rd Jun 2011, 07:19
  #298 (permalink)  
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Originally Posted by 3hole
the notion that a "pilot" can be so confused by his training that he's forgotten how to recognize and recover from a stall, is, to me, NOT "sophistication".
- it depends on your definition of 'sophisticated', actually, one of which is "deceptive; misleading.". Which takes me right back to my age-old proposal in my other thread that the fault lies with the training system which is NOT ready for the automation systems, and 'encourages' a belief that the 'system' will protect you.

As gums and bubbers have eloquently stated, your whole pysche and training 'spin' tells you that the system cannot let you down, just follow the procedures (in this case Airbus have 'taught' you) and you will be fine. As Machinbird says, I cannot see anyone 'brought up' in the modern/AB philosophy seeing the need to make such a drastic change of attitude as that which was required. After all, this aircraft CANNOT stall.

I still await ANYONE who can tell me how autotrim relates to 'received' IAS input OR what baro indications the crew actually were left with. Of more interest than a hairy bat?
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Old 23rd Jun 2011, 07:46
  #299 (permalink)  
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Since the BEA mini-Report came out on May 27th, I have been thinking about a way to represent what bit of data is given in the Report and somehow combining it with the ACARS messages in a graphic format to see "where" things happened.

The following puts together known data from the May 27th BEA Report with a representation of the altitude profile built from the few data points and timings available from the BEA mini-Report. The large areas of unknowns are filled in with reasonable rates of climb or descent to match known points from the BEA Report.

The intention is to provide an accessible visual profile of the pitch-up and subsequent descent.

Please NOTE: ACARS FLR event timings are best estimates only and are subject to further input and change as more becomes known. They are not the ground-receipt timings. Please feel free to posit alternate times.

To emphasize:

- the entire diagram is largely a guess but I think a reasonable one. It is not built from data that is not readily available from the BEA 1rst, 2nd and May 27th Reports.

- the order of ACARS messages is NOT definitive but representative of approximate placings in the overall flight path.

The diagram is presented purely for the purposes of further discussion through visualizing where, approximately, events occurred. I hope this may help some understand events better - it did for me.

PJ2



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Old 23rd Jun 2011, 08:19
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Other than the rapidly unwinding altimeter, how do you recognize the stall when your aircraft adopts a relatively stable 16 degree nose up attitude. Is the unwinding altimeter real? (Well, yes, in this case.) Stall warning-its silent. Airspeed- nothing there indicated.
Ok, so let's assume the altimeter isn't real. But then to what perceived situation 16 deg pitch up / TOGA would have been a reasonable response?
As uncomfortable as the though may be, one explanation is that they may just have reacted to a stall like countless poorly trained/caught off guard/panicked pilots before them? Their plane in any case seems to have reacted like planes have been doing for over 100 years, FBW or not, and crashed accordingly.
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