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AF 447 Thread No. 12

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AF 447 Thread No. 12

Old 21st Sep 2014, 15:57
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Originally Posted by PT6Driver
Machinebird
Not often I post on here but..
The PIO is somthing of a side issue, because his imediate reaction is to pitch up. The slowing speed will surely then have compounded the roll control problems.
There was a complete and utter breakdown of the methodology in dealing with non normal events. No one called the correct failures, no one allocated tasks, no one had any command of the cockpit far less the aircraft.
PF's initial reaction to pitch is what killed him and everyone else.
We need to look at why he pitched up and why did the pair of them not follow any known procedure for dealing with problems.
PT6Driver, First, let me welcome you to the discussion.
Your response is about what I would expect from 99%+ of the pilot population, however it is evident to me that you do not understand/believe the nature of the PIO experience.

It appears to me that the initial pull up that Bonin experienced was largely an unintended consequence of his battle with stabilizing the aircraft in roll, and I'll try to explain why.

Ask yourself what your response would be to an aircraft that is not following your control inputs. Would you calmly begin going through the checklist, or would you stabilize the aircraft first?

As pilots, we are trained to control aircraft rather precisely. If a wing drops, we pick it up. If the nose gets a little high we ease it down. That is all that Bonin initially did. He tried to pick up a low wing the way he always did and it over corrected with extreme rapidity. As pilots we automatically correct for errors on the subconscious level, so he again corrected the overshoot in the manner he was accustomed to and the aircraft again overshot his roll target.

With our hindsight viewpoint, we know that 100% of the roll oscillation was being generated by Bonin, but he did not know that. In his mind, he could not stop trying to tame this strange flight characteristic, he was the pilot flying, and he knew the autopilot was definitely out.

From my past analysis of the AF447 roll information, I know that the rapidity of his inputs then increased. The only thing that makes sense is that he determined that he was just a little slow in responding to to the roll rate and he could stop it if he was a little quicker about it. But the roll oscillation continued........... About this time, the aircraft began pitching up significantly.

Do you still hold the view that PIO is a tangential issue?
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Old 21st Sep 2014, 16:29
  #422 (permalink)  
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Hi Machinbird;

Re, "Do you still hold the view that PIO is a tangential issue?"

If I may enter a response to your question to PT6Driver, yes, I continue to hold that view because PIO doesn't explain the PF's simultaneous instant pitch-up, which continued to be held in until the stall.

Also, even if PIO occurred and even as quickly as the stick was moved, the stick movements and the airplane's excursions are not significant - at most 10deg of roll throughout until he got control of the roll, whereas the stick movement rearward and resultant pitch-up was within a second or two of the loss of airspeed information to the point of triggering the first stall warning, and continued upwards well past the time the roll was under control. In fact, the bank angle did not increase beyond about 10deg until almost 90 seconds after the initial loss of airspeed information and about 45 seconds after the stall warning had begun.

If as you say, pilots automatically correct for errors at the subconscious level and thus the PF corrected the roll, why was the pitch not similarly corrected, but actually increased, with an obvious, certain outcome for a transport aircraft at cruise altitudes?

I understand a slight delay while the airplane is stabilized and control maintained, but once control of the roll was achieved, SOPs for the abnormality would then be called for. However, by pitching up and thereby significantly destabilizing the aircraft, an abnormality became a loss of control and obviously rendered the calling for the original drill ineffective because they had another problem on their hands.

What, and where is the root-cause link between PIO and the loss of control less than a minute later?

PIO is not causal here, nor has the initial pitch-up been explained even though I had posited that the PF was "recalling" the UAS drill for right after takeoff, pitching the airplane to the memorized-15-deg attitude. It's simply a theory among others.

We're back to my original comment in July of 2009 on the second thread - if the PF had "done nothing", (meaning, just maintained pitch and power as the airplane doesn't care about loss of an airspeed indication), the stall would not have occurred and the roll would have been controlled.

Last edited by PJ2; 21st Sep 2014 at 17:11. Reason: syntax
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Old 21st Sep 2014, 18:58
  #423 (permalink)  
 
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PJ2
We're back to my original comment in July of 2009 on the second thread - if the PF had "done nothing", (meaning, just maintained pitch and power as the airplane doesn't care about loss of an airspeed indication), the stall would not have occurred and the roll would have been controlled.
I think we all respect and share this point of view, but the discussion imho at the moment is what went wrong when Bonin did what he did and why did he do it.
Besides doing nothing an expierienced crew should be able to do something without diregarding basic aerodynamics and without crashing within 4 minutes from FL 350

Multiple reasons had been mentioned, the startle factor in the report, the PIO effect discussed here, the former mentioned wish by Bonin to climb to higher altidude, suspected uncorrect seat position, to name a few. Most probably it was a combination of different factors, and i would not exclude PIO as one part of the unsuspected behaviour which might have left Bonin without any confidence into the aircraft and its feedback and its imstruments indications. He was pretty fast out of the loop, and he managed to kick Robert out of the loop as well. Both together managed to express so little information to the later arriving captain Dubuois, that he remained out of the loop as well. There must be reason for this total breakdown of professionalism we expect from pilots, and i think it is vital to dig deeper than the official report goes. I have expierienced PIO myself (assume in the same type like machinbird) after Take off, therefore i can follow this line of arguments.

We discussed another point in former threads, which might have played an aditional role. Without airspeed indication the FBW system uses preset gaines for deflecting flightcontrols in relation to SS deflection. I do not remember wether we came to a conclusion for which speeds those would be optimized. But sure Bonin was not used to them as such training (loss of airspeed in high altitudes at high speeds) was not done in normal training. The control inputs might well have been inapropriate for the preset (but unknown) gains thus causing flightcontrol deflectins and thus aircraft reactions not encountered before in all three axis.

Last edited by RetiredF4; 22nd Sep 2014 at 15:31.
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Old 21st Sep 2014, 19:51
  #424 (permalink)  
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Thank you for your response, RF4. Yes, I do recall the various theories as to why the continued pitch. I'm not sure it's possible to know for sure though I do agree that digging deeper is necessary.

I'm not averse to new notions and am open to theories which move possible cause(s) some distance away from pure human performance factors, but I'm still not clear for example on how PIO is connected to a sustained pitch-up and stall. It does no good to say 99% of pilots don't know what they're talking about as regards PIO, (I've experienced it in Alternate law in the A330 sim but one gets used to it and is careful with the stick), and if that's true and it may possibly lead to a LOC, then there's a problem! In the meantime, we both know even viscerally, (subconsciously) that such pitch attitudes are just never achieved in a transport aircraft because we know the airplane will rapidly lose energy because the engines are right very near their max delivery of thrust and there's just no reserve power for recovery, so how come this one is an exception?

To me the rapid loss of focus and discipline is a more significant series of causes than all other explanations including PIO, the point being that if we are to learn something from this accident, it is in the area of human performance, the clarity of interface design, (warnings, drills) and the presentation of complex situations to those who must assess quickly but who might face such events once in an otherwise quiet, full career.

The Vanity Fair article says something quite valuable in its conclusion:

This is another unintended consequence of designing airplanes that anyone can fly: anyone can take you up on the offer. Beyond the degradation of basic skills of people who may once have been competent pilots, the fourth-generation jets have enabled people who probably never had the skills to begin with and should not have been in the cockpit. As a result, the mental makeup of airline pilots has changed. On this there is nearly universal agreement—at Boeing and Airbus, and among accident investigators, regulators, flight-operations managers, instructors, and academics. A different crowd is flying now, and though excellent pilots still work the job, on average the knowledge base has become very thin.

It seems that we are locked into a spiral in which poor human performance begets automation, which worsens human performance, which begets increasing automation. The pattern is common to our time but is acute in aviation. Air France 447 was a case in point. In the aftermath of the accident, the pitot tubes were replaced on several Airbus models; Air France commissioned an independent safety review that highlighted the arrogance of some of the company’s pilots and suggested reforms; a number of experts called for angle-of-attack indicators in airliners, while others urged a new emphasis on high-altitude-stall training, upset recoveries, unusual attitudes, flying in Alternate Law, and basic aeronautical common sense. All of this was fine, but none of it will make much difference. At a time when accidents are extremely rare, each one becomes a one-off event, unlikely to be repeated in detail. Next time it will be some other airline, some other culture, and some other failure—but it will almost certainly involve automation and will perplex us when it occurs. Over time the automation will expand to handle in-flight failures and emergencies, and as the safety record improves, pilots will gradually be squeezed from the cockpit altogether. The dynamic has become inevitable. There will still be accidents, but at some point we will have only the machines to blame.
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Old 22nd Sep 2014, 02:42
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Owain Glyndwr, Rudderrudderrat, DozyWannabe thank you for your replies and inputs.
I subscribe to
“I'm away off with work.., so if I don't respond it's not because I'm ignoring people”
BEA doesn't remark any PIO because it wasn't.
Here is a quote from final report:
"When the autopilot disconnected, the roll angle increased in two seconds from 0 to +8.4 degrees without any inputs on the sidesticks. The PF was immediately absorbed by dealing with roll, whose oscillations can be explained by:
- A large initial input on the sidestick under the effect of surprise;
- The continuation of the oscillations, in the time it took to adapt his piloting at high altitude, while subject to an unusual flight law in roll (direct law)"

“Mayonnaise Stirring” is just normal and characteristic to any AB-FBW aircraft
https://www.youtube.com/watch?v=pJrLKLoJG_o#t=201

Simply, that type of input at cruise speed is overcontrol, not to be confused with PIO. Pitch input was too much either, then the aircraft ended up in coffin corner, at almost 38000 ft. THS moved at NU stop. So, at that point, they were already doomed. From there, any other excellent crew would end-up pancake on ocean surface.

See how the longitudinal stability works for a non FBW aircraft
“...et rapidement les choses revient normale”, "...and things quickly returned normal"
https://www.youtube.com/watch?v=WAiA6ep95Sc#t=1508

Also, it's interesting to revise an accurate tv reconstruction. Robert acknowledge verbally “STALL”, in CVR transcript is (!), that was at only 50 seconds after AP disconnect, 30 seconds later, nothing else matter, either with “mayonnaise stirring” or with an expert touch
Sometimes, we can not see the forest due to leaves:
https://www.youtube.com/watch?v=WAiA6ep95Sc#t=268

Last edited by _Phoenix_; 22nd Sep 2014 at 02:46. Reason: spelling
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Old 22nd Sep 2014, 04:49
  #426 (permalink)  
 
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Originally Posted by 1. Vanity Fair, 2. PJ2
It seems that we are locked into a spiral in which poor human performance begets automation, which worsens human performance, which begets increasing automation. The pattern is common to our time
If we are agreeing with that, we are loosing the highest part of humanity : FREEDOM and RESPONSIBILITY.
I'm sure some resistant Folks are able to fight with success again for these old values high in the sky, high on our flags around the World. That cannot be written on closed SOPs and algorithms. Human must be able to close the loop.
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Old 22nd Sep 2014, 06:03
  #427 (permalink)  
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roulishollandais, it is such a temptation to engage the philosophical question implied!
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Old 22nd Sep 2014, 06:30
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maybe we all should read on the matter of PIO, or better on APC, as that's the term now used.

Pilot Induced Oscillation

A few points from the article


Traditionally, the letters P.I.O. have been taken to mean "Pilot-Induced-Oscillation". Today there has been some movement towards redefining PIO to move away from the traditional "blame the pilot" mindset. In that vein, PIO came to be defined as Pilot-Involved-Oscillation. The USAF Fight Test Center prefers the term as "pilot-in-the-loop oscillation", and many in the field have replaced the letters PIO completely by a new acronym, "APC", or Aircraft-Pilot-Coupling, although APC can refer to either an open or closed loop event.1 The NRC states: "Aircraft-pilot-coupling (APC) events" are inadvertent, unwanted aircraft attitude and flight path motions that originate in an anomalous interaction between the aircraft and the pilot.
A PIO can occur in any axis, although pilots are most familiar with oscillation in pitch and roll.
There are many ways to manipulate the controls and still perform with the certification standards required to pass checkrides. Some pilots fly by making small inputs, predicting what is needed (known as "low-gain"), while at the other end of the spectrum we have pilots who tend to use relatively large control inputs to accomplish the same task (high-gain). While this is, to some extent, attributable to pilot experience and technique, there are events that can drive a "low gain pilot" towards the "high gain" side, and high-gain can precipitate APC.
The "startle factor" is actually a term used in the test flight community. It can be due to a system failure, ice accumulation, TCAS RA or an unexpected mode change in the flight control system. For example, a pilot is flying in cruise when the autopilot disconnects due to an out of trim condition or similar anomaly. The pilot now tries to bring the aircraft back to the assigned cruise altitude with a large control input. The sudden necessity for the pilot to intervene often results in a much bigger correction than needed, and if conditions are right, a PIO may result.
And now we are back to PJ2's point.

First, it should be recognized that by definition, APC/PIO cannot happen unless the pilot is making inputs that are sustaining the maneuver, i.e., the pilot is in the loop. Consequently, the first step is to get out of the loop.
Because a pilot may be highly focused on a task when PIO develops, it is important that the pilot-not-flying assist the pilot-flying in recognizing the situation. It may take forceful intervention to get the pilot to reduce his gain, freeze the controls or, in particular, release the controls altogether.

Last edited by RetiredF4; 22nd Sep 2014 at 15:33.
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Old 22nd Sep 2014, 06:32
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The most revealing part of the VF article is the following:

Over time the automation will expand to handle in-flight failures and emergencies, and as the safety record improves, pilots will gradually be squeezed from the cockpit altogether. The dynamic has become inevitable. There will still be accidents, but at some point we will have only the machines to blame.
Right now if you dare blaming any machine, you get grilled and shouted down by the usual crowd, or should i say lobbyists. The machine seems to get away with almost everything, it's always the failure of the human of not having memorised well enough the ways the machine wants to get interpreted and operated.

The last sentence points at a almost philosophical (yes, PJ2), albeit inevitably realistic fact, that at some point even all the manufacturers and regulators will have to get out of their denial mode, pull their heads out of the sand and they will be confronted with only their machine.

What will happen then? It's anyones guess, but i gather that there will be no reversal of the trend, there will simply be another machine invented and sold overpriced to supervise and control the former machine. And by then it most probably also be capable of making a selfie!

It's only the world we are craving for.
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Old 22nd Sep 2014, 19:09
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Originally Posted by Gretchenfrage
Right now if you dare blaming any machine, you get grilled and shouted down by the usual crowd, or should i say lobbyists. The machine seems to get away with almost everything, it's always the failure of the human of not having memorised well enough the ways the machine wants to get interpreted and operated.

The last sentence points at a almost philosophical (yes, PJ2), albeit inevitably realistic fact, that at some point even all the manufacturers and regulators will have to get out of their denial mode, pull their heads out of the sand and they will be confronted with only their machine.
Until the machines design build and maintain themselves (at which point it will likely be their world not ours), there will always be a human to blame.

But in this case, you are forgetting, the machine was blamed, judged and punished - straight after the accident. The AA summarily removed from service and the more capable BA equally damned by association, all long before anyone knew how the pilots had mishandled the situation. In some ways this is unfair on the machine - the limits to its capabilities were already known, previous incidents dutifully reported to its human masters, its designers had already created a more capable replacement, and the aircraft mfr had recommended replacement. All well over a year before the crash.

One airline (at least) however refused/delayed replacement, presumably because some human there thought that that airline's humans in the cockpit could cope just fine with the less capable machine. That turned out to be spectacularly wrong.

So, where does the fault lie in the end ? With the machine that suffered the fault, but was already due for replacement precisely because of that fault, or with the humans who failed to cope with the fault, or with the human(s) who decided the fault was not a risk and could be handled by the other humans ?
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Old 22nd Sep 2014, 20:17
  #431 (permalink)  
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RetiredF4;

Many thanks for your post. Machinbird, many thanks as well - as I say, I'm open to "PIO" explanations. I'll read the work at the link you've provided RF4, and am also searching / examining the papers extant and downloadable on the subject*. I'm not an engineer but flew the A330 1999 'til retirement, (as I believe you know) so all writing is of course from that p.o.v.

*Many papers require membership or attendance at the institutions publishing the papers. In my view, the advancement of knowledge and available peer review of SMEs who may not qualify under such narrow restrictions limits knowledge in exchange for the $20 bucks or so one has to pay for each paper. My views on patents are similar...
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Old 22nd Sep 2014, 20:37
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Because the two views – machine or human, are held by humans, then the human is held accountable – us, ourselves, how we think about the situation; the process of thinking.

This is not as philosophical as might first appear; consider the events preceding AF447.
A technical weakness was identified with the probes – a rare form of icing. Solution, modify the probes. Until this could be done, the risk of a multiple failure was mitigated by having at least one modified probe, but if this was not possible, the crew would be trained to manage the outcome of the failure - procedure.

This is a logical engineering (technical), machine view. However, there was a break-out point when considering the crew – not as a weakness which required additional training, but as an asset which could mitigate the threat.

The flaw in the engineering view (manufacturer and regulator) was the failure to realise that the threat was the ice crystal conditions, not the resultant of an icing encounter with deficient probes. The alternative realisation required a human, operational viewpoint.
Thence in true TEM fashion, avoidance should have been the primary human activity, supported by information about the threat and how to detect it. Avoiding Cbs involves a routine and already trained for-behaviour, with procedural backup in the event of mismanagement (error).

Re automation dependency; it’s not the pilots who are automation dependent, but all levels of the industry. Manufacturers and regulators have difficulty thinking outside of their numerical, probabilistic approach to aircraft design and certification, whereas the real world involves the indeterminate behaviour of humans interacting with a machine. If regulators become locked-in by a machine view then blaming the human is a logical outcome.

‘A problem to control, or a solution to harness’.
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Old 23rd Sep 2014, 19:10
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Info OSV

L'interruption de l'alarme stall ne signifie pas systématiquement la sortie du décrochage (sur Airbus)
The Interrupt of the the stall alarm does not automatically mean out of the stall (Airbus)
(On Airbus) how the pilot know that he is out of the stall ?
By putting his hand through the side window?
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Old 24th Sep 2014, 01:39
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Winnerhofer,

The quote "by Bill Palmer" is very good. Basically, I have the same perspective , Bill has better wording. One remark though… Instead of a piano player comparison, I would choose a Toyota Prius driver. I mean: Even with brake fully applied, the airspeed still builds up… "The experts are right." The driver needs recurrent training and practice for manual shifting in neutral... Is this right? or… Toyota has to change design!
Already in 2010, Prius was the safer car regarding the sudden acceleration issue
https://www.youtube.com/watch?v=IqG4mZbM9rs
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Old 24th Sep 2014, 01:46
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Vanity Fair article on AF447

There is an excellent article in Octobers issue of Vanity Fair called Human Factors. Written by a non-pilot but very well researched. A recommended read for all of us.

I hope you read it.
http://www.vanityfair.com/business/2...ight-447-crash

Last edited by 400drvr; 27th Sep 2014 at 15:44.
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Old 24th Sep 2014, 04:55
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Devil

Not again please with VF ad , many contestable assertions, manipulation
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Old 24th Sep 2014, 06:10
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More on AF447 PIO

The article posted by Retired F-4 draws heavily on the National Research Council book on PIO that I have recommended in the past. (National Research Council. Aviation Safety and Pilot Control, 1997) For one with an understanding of aviation and the concept of feedback loops, it is an easy read, and as a soft cover version, is very affordable.

I use the term PIO because that is what I am comfortable with, but I interpret it as Pilot in the Loop Oscillation. PIO cannot occur if you are not exercising direct control.

I recently had a message from a tactical jet pilot describing a PIO incident he experienced. He stated that he was too busy during the incident to communicate with his back seater in any meaningful way. The workload was so high that he had no spare capacity to communicate! Can you see the relevance to the AF447 cockpit scene?

Yes, AF447 was not in a PIO when it departed from controlled flight, however the PF had just been through 30+ seconds of hell that shook his faith in his aircraft's control system and fatigued his mind. At the same time, the PIO incident had set him up for a stall by stealing his airspeed and leaving him in a nose up attitude.

Why didn't he control the nose attitude you might ask. The simple answer is that he didn't have the attention to spare to adequately perform that task. He was concentrating almost exclusively on the roll channel and I believe was already tense and nervous before the autopilot dropped out which caused him to pull the stick back unconsciously.

In the main AF447 threads, a gent who goes by the handle "grity" prepared several charts of stick motion for the first few seconds after the autopilot dropped. The following chart is the best of those:

The numbers on the move lines correspond to the time in seconds after time 02:10. Bonin took control at time 02:10:07.

If you will notice, the majority of the first 11 seconds that the chart covers was spent in the 4 to 8 degree back stick range and only toward the latter part of the period does Bonin provide a couple of pulses in the nose downdirection. For the first 9 seconds he is just banging the stick from side to side while holding it fairly consistently in the 4 to 8 degree aft stick range.

Here is what these roll inputs did to the aircraft:

As expected, there is still much skepticism about what PIO had to do with the loss of AF447.
Simply, that type of input at cruise speed is overcontrol, not to be confused with PIO.
There is a simple difference between overcontrol and PIO. If you know you are overcontroling you can stop.
If you are in a PIO, you see the situation as the aircraft fighting your control and you cannot stop because you must keep the aircraft under control.
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Old 24th Sep 2014, 10:04
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Originally Posted by 400drvr
Human Factors. Written by a non-pilot
Aw, c'mon. You can say a lot of things about Langewiesche, and he's certainly never been an airline pilot, but he used to earn his living as a pilot for several years, before he became successful as a writer.

but very well researched.
At least he's been talking to a lot of people and has picked up some interesting observations along the way.
For example, from his visit to the BEA:
With most of the weather still lying ahead and an anxious junior pilot at the controls, Dubois decided it was time to get some sleep. The chief French investigator, Alain Bouillard, later said to me, “If the captain had stayed in position through the Intertropical Convergence Zone, it would have delayed his sleep by no more than 15 minutes, and because of his experience, maybe the story would have ended differently. But I do not believe it was fatigue that caused him to leave. It was more like customary behavior, part of the piloting culture within Air France. And his leaving was not against the rules. Still, it is surprising. If you are responsible for the outcome, you do not go on vacation during the main event.”
And:
Bonin didn’t just ease the stick back—he hauled it back, three-fourths of the way to the stop, and then he kept on pulling. Alain Bouillard, the French investigator, equated the reaction to curling instinctively into a fetal position.
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Old 24th Sep 2014, 13:19
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So we have full control inputs in a high altitude flight regime where the rule is to fly with a light touch. Had a conventional linked control column been fitted to the aircraft, the PNF would certainly have noticed the gross control movements and probably been prompted to intervene at a much earlier stage. A classic case of the left hand not knowing what the right hand is doing and vice versa. Sure, the crew weren't communicating with each other in identifying the problem, but the situation was greatly compounded by a control system and instrument layout that effectively hid each pilots' actions from the other. The cockpit design and control layout are not designed for instinctive responses in abnormal flight upsets. Flight control inputs can be summed or subtracted if both pilots grab the sidestick controllers at once without one of them pressing an override button. Either pilot can press the button without the other being aware in a high stress situation so you end up with an aircraft that has unpredictable responses and a crew that are fighting each other (and the aircraft) at the controls without being aware of the situation, which seems to be the case here for at least part of the descent.
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Old 24th Sep 2014, 18:03
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Originally Posted by G0ULI
classic case of the left hand not knowing what the right hand is doing and vice versa
That's the beauty of the SIDESTICK philosophy as Airbus elected to implement it ...
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