Using BEA roll data for the period 2:10:07.5 through 2:10:45, the following graph describing the amplitude of the roll oscillation was prepared:

http://home.comcast.net/%7Eshademaker/RollAmplitude.jpg
The amplitude is the total roll motion in degrees following a reversal of the roll rate. It is obvious that he was beginning to get a handle on his roll control problem when the aircraft stalled and created a new set of control problems.

Machinbird,

Is it?

@machinbird


PIO
1 unintenditional YES
2 PF stears exact 180 deg out of phase
3 extension of the airplane’s operational usage into an area for which it was not intended, or following a failure, and is not the fault of the pilot
4 IMO .......software element upstream of a control effector.....???
5 divergent with time, after 2:10:07
6 number of cycles of oscillation ??? more than 5 ???
7 The most common frequency is in the range for pilot closed-loop control.... here it was 1/3Hz
8 1/3 Hz is not high frequency it was not "mild PIO"
9 roll ratchet...... >10 deg
10 Peak-to-peak angular rates are usually greater than ±10 degrees/sec, and control forces greater than ±10 lb, though rate limiting can attenuate the former and result in large increases in the latter.8 “Severe” PIO requires immediate changes to the airplane, and if it occurs in developmental testing the flight test program should be postponed or redirected until the corrections are made. YES we wait

This article seems to define the phenomenon as being anything that authors wish it to be. The evidence is shakey and in some places totally worthless and someone has clearly wasted money commissioning the article. Definitely part of the shoal.

I was expecting this type response. Typical hairy-chested "just fly the aircraft" comment of someone who has never encountered PIO because his aircraft experience involves highly damped flying machines.

My first knowledge of PIO was a news clip explaining how the Navy had lost a Sea Dart aircraft during a high speed flyby.
Later, while assigned to a Test and Evaluation facility, one of the engineers led me to the original full accident report on the Sageburner F-4 PIO accident.

I've personally never encountered PIO inflight, but have experienced roll PIO while flying an early visual simulator with a ~1/3 second visual display computational lag. Disconcerting to say the least. I had to go back to the flight instrument display to regain control. (Note: These were actual instruments-not on the visual display). Small motions did not trigger the PIO, but rapid-high gain lateral motions did. Until you experience the effect, you would have trouble believing it could happen. The onset is sudden. When it does happen, you tend to blame yourself because you are "in control."

The paper I referenced earlier has very little in new concepts. The new part involves the "pilot's mental model of the aircraft" wording. It does an excellent job of bringing together available information on the subject of PIO. The AF447 initial "roll problem" seems to fit the 10 PIO characteristics listed in the paper, but I'll let BEA make the determination, They have better versions of the data.

And for the conspiracy theorists, if BEA does not comment on roll PIO in any manner, either to affirm or deny, then you will have a red flag indicator.

Actually it is very close to 180 out most of the time until he gets it under control but it is converging, not diverging
If you look at the reversal intervals, PF starts out reaching his maximum control input shortly after reaching his roll max angle for a particular oscillation, and he is able to gradually gain on the oscillation so that he is actually leading the oscillation, at which point the amplitude starts to die down, only to have the oscillation flip phases on him. and go through another (smaller) cycle. At least, that is the way I read it.

Machinbird,
Thanks for the link!
A bit laborious, as articles go.... but it covered the subject quite well for this ancient flight control engineer (Rtd.), complete with Bode plots and suchlike, which tell the story faster and clearer to those who can read them, rather than long verbal descriptions.

And for those who've never experienced PIO : 'hands up' for those who've never experienced DIO either (driver-induced oscillations, speed or direction) after hitting a couple of pot-holes or speed bumps.....
Been there, done that (luckily on local country roads, without disaster ensuing).

Sure, it's not the same. But it gives you an insight into how a vehicle you are confident of being in control of (near perfectly) at the time, can suddenly acquire a mind of its own....

Machinbird
I have stated earlier that I see merit in your suggestion but that I see it on a mechanistic level - an explanation of how the phenomenon worked but not a casual factor. This is my main objection to the paper you linked. It was too vague and too inclusive. The phenomenon wasn't adequately defined (it could be anything seemed to be the message) and it seemed to want to attribute an overly deterministic approach to a pilots actions. In other words the pilot was not responsible for his actions and a helpless victim of PIO. One is forced into the question why have pilots then? Are they truly unable to take decisions and judge a situation? I tend to believe that a pilot has responsibility for his/her actions and that a statement like 'is not the fault of the pilot' (Conclusion No. 3) is just as dangerous and misleading as 'is the fault of the pilot'.

We end up returning to the human and cultural factors of training, CRM, SOPs, chain of command. You mentioned you experienced PIO in the simulator and how you solved it by using your instruments. This seems to have been lacking from the PF - as I stated before know your machine and trust your instruments. It's a training and cockpit discipline issue and the paper seems to make no mention of this. You yourself mentioned training and I would add practice - skills atrophy without use. Once again one is forced back to the conclusion that this was a poor crew who took a perfectly flyable aircraft and put it into a non flyable state. Whether they were a one off or indicative of a broader trend is open to debate. Of course the crew were poorly served by their employer - Air France; and the Air France safety audit indicates serious cultural issues developing in their pilot corps. One hopes that Air France are addressing these as a matter of urgency.

If BEA do not reference PIO as a factor it won't be because they have an agenda but because they don't consider it germaine. That too is a legitimate judgment.

OC, lets try the following concept on for size. Don't worry how the situation occurred, just how the pilot handles it once discovered:

As you lift off the ground, the aircraft rolls the wrong way in response to your roll inputs. If the pilot is not able to override his natural tendency to correct a roll to port by moving the stick to the starboard side of the cockpit, is it then his fault that the aircraft crashes? Shouldn't he be able to rewire his brain on a moments notice to reverse the response?:rolleyes: That is exactly the situation a pilot facing PIO encounters. His learned responses don't quite fit the situation any longer. If you encountered this type of situation, would you also be able to remember your aerobatic training to put the stick forward while inverted to keep from losing altitude? This is similar to the kind of control problem the AF447 PF may have faced (albeit a bit more extreme.)

The roll behavior after the autopilot dropped is extremely anomalous. If BEA does not address why it occurred, then they would be putting their heads in the sand. There would be a lot of people asking hard questions then.

This is the paragraph that you are objecting to. PIO really is a design problem and can be tailored out of the control system if known. If there was not a test point that stimulated the PIO tendency in that corner of the envelope, it may not have been uncovered during the flight test program and subsequent line flying. PIO is very dependent on pilot technique. For example, if a pilot is attempting to damp out a rate of motion, his control strategy is different than if he is attempting to hold an attitude.

Saying that PIO is not the pilot's fault is not the same as saying that PIO is not the pilot's problem. As you well know, when airborne, there is no one available to save you from your predicaments but you. By saying it is not the pilot's fault, the paper indicates that is up to the airframe maker and certifying authority to evaluate the problem and ensure necessary corrective action.

Machinbird
Sounds rather 'Camelish' (the said biplane used to pull to the right due to the torque of its Bentley engine). Are you saying that the control response is tardy and that the pilot's reactions are too quick? It has all the flavour of panic and forgetting how the machine actually flies. Those who have commented on flying the Airbus family particularly the A330 comment that it is a very stable aircraft in all aspects of its flight envelope. Therefore for your theory to work as a causal factor there would have to be a hidden design flaw which was not spotted in flight testing. I doubt this and fall back on the explanation that the PF (for some reason) lost it and overreacted terribly. The aircraft is going to respond to the pilot inputs and these are what caused the rolling - not the aircraft. A thorough rereading of the CVR transcript might help here. There is a disturbing lack of professionalism manifest throughout the sequence of events and the rolling is just a symptom of this.
What is missing from Conclusion No. 3 is the word 'can' because PIO can also result from a panicking pilot 'mayonnaise stirring' without the aircraft having any blame (as it were). However, I picked that conclusion out because it was an excellent illustration of the sloppy language used in the paper. What the PF needed to do in the AF447 situation was wait and analyse then act. He panicked and flopped around hopelessly and his colleague who could have taken command (as he seems to have understood the situation better) did nothing. No CRM, cockpit discipline, SOPs, chain of command. I keep on repeating this sorry to say but these factors are there for a reason - so that pilots do not get into messes when faced with unfamiliar situations. Simply a training and cultural issue - if you have the time take a look at Pan Am (late '60s early 70's) and Korean Airlines (1970s to early 2000s) for just how nasty these things can get.

OC,
Consider what percentage of the A330 flight time that has been accomplished has been in Normal Law, Now consider what percentage of that has been flown on Autopilot.

Then consider what percentage has been in Alt 1 Law and in Alt 1 Law with Autopilot.

Finally, consider what percentage has been in Alt 2 Law (Autopilot cannot engage)

Assuming manual control, does the aircraft feel the same way in Alt 1 Law as it does in Normal Law? I believe the answer is yes, just the protections operate differently.

Assuming manual control, does it feel the same way in Alt 2 Law as it does in Alt 1 Law? No. Roll response is different.

Other than the test flight program. I would be surprised if the aircraft has accumulated 10 hours of flight time in Alt 2 Law during its entire line flying lifetime.
But those that may know better should feel to correct any misperception on my part.

If I am correct, the bulk of A330 flight experience would not be relevant to AF447's loss of control in Alt 2 Law.:confused:

Machinbird
If you will forgive me the use of my favourite metaphor; that is a particularly juicy red herring. Just because most of the flying may be done in Normal Law doesn't mean that no flying is done in ALT2. It possibly is more than 10 hours but I don't know. However, be that as it may, a properly trained and conversant crew should have no trouble using the aircraft in ALT2 law. Those who have tried to fly it in such a state and who have posted say that it flies well. It was designed by Airbus to fly well - you can be sure of that. It would never have been certified if it was an absolute pig to fly without protections. Once again it's a training issue which should have been addressed in the simulator. If it wasn't then again it's a training issue. Pause, diagnose (using your instruments) then fly. But then I am afraid that this crew would have flown anything into the ground.

OC, I might share your faith in the reliability of the certification process except I have seen examples of the subtle ways things can sneak through, only to be found later, usually under adverse circumstances.
There is a reason that the referenced paper has this quote
PIO can be hard to reliably predict and prevent considering the various different control strategies employed by the pilots flying a particular type of aircraft. (But at least the autopilot should follow its programming in a reliable and predictable manner.)

Training can help pilots avoid unsafe control strategies, and can teach them what to do if they recognize a PIO condition. Has anyone received such training?

PIO recovery:

For example, in B type aircraft, the PNF can assist in breaking a PIO by helping hold the control wheel steady, but in newer A type aircraft, this is not possible.

In either type aircraft, PF can back out of the oscillation by loosening his grip on the controls, reducing the amplitude of his control inputs, and even releasing the controls completely until a PIO dampens out.

On either type of aircraft, exchanging roles between PF and PNF may change control strategy sufficiently to break a PIO. (This would have likely have been the best way to help in the AF447 situation).

Meanwhile I think we can collectively make some good use of your pet herring. I'll bet he's tasty.:}

“The design process of the airplane has matured, flight control systems have evolved, criteria and analysis techniques are available, yet PIO persists.”

Certainly it does but that is because it is pilot induced. It sounds a bit facetious - I am not trying to be so but point out that this is not nowadays a design issue so much as a human issue. There is nothing I can see in the accident which can be attributed to the aircraft. A different approach to training is probably the answer and proper CRM but the design oriented approach will not work in most cases because of the human factor. There will always be someone who finds a way to crash an aircraft in a totally unexpected way. In the end it still comes down to the man at the front.

You can train crew as many as you want
You can teach CRM as many as you want
Even if the crew of the AF447 was super trained to cope with all situations you can think about ... it was useless in their case .. cause they never recognized in which situation they were ...
They never understand what was happening .. so they were unable to apply any procedure .. learned or not ...
They were like children playing with buttons and levers .. and hopping something nice will happen ...

OC, as long as you hold that belief, you will have the PIO cause and PIO effect reversed. But you know that and in the big scheme of things it will probably make no difference- unless you encounter PIO yourself.

The training factors are significant in the failure of AF447's crew to recognize and declare a stall, but if they encountered roll PIO during the transition to ALT2 Law, that could be the reason that they did not/could not fly pitch and power successfully and lost track of their energy.

Remember this paragraph from the Aristotel report?
According to my decaying math skills, initial peak roll rate was on the order of 10 degrees per second for the first 4 oscillation half cycles but if someone would like to look this aspect over more closely, I would appreciate it. I can see evidence in the roll position record that PF's attention was heavily devoted to this problem. (Changing his strategy & adaptation.)

Machinbird

'throughout the flight, the movements of the elevators and the THS were consistent with the pilot’s input'
BEA Third Interim Report

It is important to recall that the pilot was the one who was making the inputs. This is where the Aristotel report falls down and badly in that it assumes that these inputs are a result of factors that can be designed out rather than factors that rest in human entities. One can almost say that it is written to the requirements of a pilots union. Rereading the 3rd Interim report we have a clueless PF and a PNF who doesn't feel he has the authority to intervene even though he seems to understand what is happening (as jcjeant succinctly notes). The more important document here is the Air France safety audit. It identified cultural issues that would lead to such a series of events. I'm not going to discount PIO entirely but it doesn't fit the circumstances of the accident and would not rate as a causal factor.

In other words, the motions of the control surfaces were consistent with the pilot's control inputs (i.e. no unexpected control system inputs)......but that says nothing of the dynamics of what the control inputs did to the aircraft. From the same report's data, it also appears to have set up a roll oscillation.

OC, What you do not seem to realize is that the Aristotel paper builds on a long history of professional thought on the causes of PIO. This is not a report that just "appeared out of the blue".

That is not an assumption that PIO can be designed out of a particular aircraft's control system-you can take that as a fact, but first it has to be recognized so that it can be addressed. Pilots who blame themselves for all aircraft handling problems are one of the reasons not all PIO problems are addressed.

I will concur that the crew of AF447 seemed to be clueless about a large body of fundamental aviation knowledge that night, but I suspect recognition of a PIO context for their initial manual control performance will explain how they lost control. It may even help explain why they failed to regain control, although the aircraft was then in a stall and no longer subject to PIO. But this area is one for the human factors experts.

180 deg is the way you move on the swing set if you will hold the swing-amplitude, if you will stopp you try to move in 90 deg (or 270 ???)
http://www.elsenbruch.info/ph12_down...e_Schaukel.gif



if I put together HN´s vertical wind velocity and the roll altitude, then both cange with the same frequency of 1/3 Hz

we do not know much about the turbulent air in this case, but it is truly not one uniform mass which moves up and down, it might be that it was one vortex with the dimension d +/- 800m...... if they flew cross through it, the vertical wind velocity is explicable...

but what will be if they flew alongside of some vortex with this dimension and this frequency? changing different AoAs at both wings with 1/3 Hz..... VIO

the PF did not beginn with this oscillation, with the stick he just helped to hold the roll-amplitude.... (and forgot to control the pitch....)


http://s1.directupload.net/images/11...p/yutzngap.jpg

I don't know if "forgot" is the right word. No matter how incorrect the pitch inputs were they were very positive, and way in excess of what should be expected at that altitude.

Even with protections out, the airframe itself is very stable - with 20/20 hindsight, the correct response should have been to understand what the turbulence was doing and very gingerly make small corrections once that was understood and a "feel" for the situation was gained. Instead it looks very much like every control input was reactive to each individual bump - possibly resulting in PIO in the lateral axis, but in my opinion there's not enough evidence to say one way or the other.

The main problem is that the response was very instinctive in nature, but not being trained in high-altitude handling the risk was that the response itself was likely to be inappropriate and excessive because the only manual handling the PF was used to was at low altitudes and commeasurately more extreme in terms of sidestick deflection.

As far as I'm concerned though, this is all by the by. The main problem was organisational in nature - Air France operating a type which was known to have potential issues requiring manual handling at cruise level (until fleet-wide repairs were effected), yet nevertheless rostering crews in such a manner that if such an event happened, the flight deck could potentially be manned by a crew without the required experience to recover correctly. That - based on the information we have so far - is the primary reason that control was lost and the aircraft crashed. The details of how that loss of control developed, while useful to understand, are at best a set of contributory factors.

Machinbird
I don't think we'll agree on this and to my mind it's because of a fundamental difference in the way we're looking at things. I am looking at the actions of the PF as those of a being capable of making independent decisions unaffected by external factors. Your approach seems to be more deterministic - the PF is subject to factors which force him to act the way he does. To a large extent he has no control over what he does.
Whilst both views have a measure of validity the (shall we say) free choice view is a far better and more realistic model for explaining things. The interesting paper you mention is problematic in that it reduces the human element to a 'cog in the machine' as it were but this is symptomatic of the whole PIO approach. It is logically flawed as a concept in that it assumes no choice of action. As I have mentioned, as a piece of research it is woolly and far too broad in its spread. Choices exist but how we exercise them depends on our training, professionalism or the culture we follow. But and this is the important thing - we always have the choice. This is the case with AF447 - the pilots had choices but ignored them.
Sorry for the philosophical digression but I felt it was relevant in this case.

OC,
You sound as if you have never experienced PIO (or DIO, as I mentioned earlier).
You have no 'choice' at that moment.

Yes, I agree wholeheartedly.

We are capable of making choices/decisions as reasoning beings, but in the heat of battle, it can be too late to make relevant choices. Much of what we do is pre-programmed (trained if you will) based upon earlier choices. When that training conflicts with reality, it can be too late to change your mind on your course of action, especially in aviation. That is what Christian was just alluding to, and what I was alluding to with the reversed roll control scenario.

Machinbird + ChristiaanJ
The choice is to act or to delay your action. There is a belief that by acting quickly you can deal with the problem (and this is indeed the case in some situations) but more often than not it is better to pause and evaluate. This is frequently the case with DIO. One thinks of the supposed Prius issue which turned out to be driver induced. Drivers panicked and blamed the machine for their actions where taking their foot of the accelerator would have solved the problem.
With aircraft a pause with a light touch works wonders. Of course I agree that sometimes it isn't possible but most of the time it is. In the AF447 example there was ample time for the PF to pause and evaluate. He didn't and so ended up in a stall. But what we do have here is a training and possibly experience issue not an aircraft issue. The aircraft did what the PF told it to do. If the pilot had left things, the aircraft would have most likely stayed in a stable condition within its flight envelope. A properly disciplined and non-panicking pilot would have paused, evaluated and then followed the SOP for UAS. He would have worked in concert with his colleague to find a solution. PIO isn't the issue here (except as a mechanical process) but the pilot's conduct is (I am sorry to say). A look at the Korean Airlines Flight 8509 accident shows how a competent crew dealt with a roll issue due to an aircraft fault (I am referencing the first crew not the second). But in AF447 we cannot escape the issue of crew competence or rather the lack of it.

OC
I'm not entirely rejecting what you have just said, I prefer the firm&positive well considered method of operating flight controls, but I do have a lot of frightening incidents engraved on my eyeballs that are visible when I close my eyes.
Sometimes you have to act NOW, because there is no time to consider. How does one figure out which is which? I think the answer is experience and exposure.

I do not place AF447 in that category, however.
It seems that PF on that aircraft went to full respond mode when he was roused from his relaxed cruise state. The initial control movements are far too large-for what he was up against. Maybe the cavalry charge music had something to do with it? ;)

PIO:s
 

The SAAB company took a patent may years ago on a method to prevent PIO (after the 2 JAS 39 Gripen PIO accidents), but normally this seems to be simply done by rate-limiting in the software. I don't know which method is used in the A330:ies.
I have been wondering if any such PIO-preventing function, which ought to be in operation in normal law, is still operational in alt law 2.
PIO can apparently also occur if the hydraulic system is overloaded by extensive control surface movements, especially shortly after a reduction in N1.

Keep up the interesting and good parts of the discussion.

Important information
 

Machinbird,

New Background Information on PIO

Excellent work on a fascinating issue,

Thanks, :ok:

OC, I don't wish to belabor this point unduly, but you really do not understand the problem of what PIO is. If we were to completely accept your viewpoint, we would throw the work of several generations of aircraft handling specialists into the dumpster as an unnecessary complication.

The roll oscillation on AF447 which I suspect may have been PIO was a converging oscillation. There are other oscillations that diverge and are nothing to be trifled with.

Take a look at this video clip of the Sageburner accident and tell me how well your strategy of deciding to do nothing would have worked. This video is a pale imitation of the original phototheodolite film. On that film, the photointerpreters could clearly read out actual stabilator position and thus infer stick motions.
F-4 PIO - YouTube

RR_NDB, I think we owe OC a vote of thanks for his reasoned challenge to my points.:ok:

Being forced to defend a concept requires both parties to explore their thoughts carefully and to develop them to a greater degree than if there were no challenge.

PIO or APC or whatever you wish to call it is a very interesting topic, and produces many surprises. I am pleased that others find it interesting too.

In the case of AF447, the initial roll oscillation stands out as a very strange thing. It will be interesting to see what BEA makes of it.

Machinbird,
I should have commented earlier. ...

I've read your recent posts with interest. Excellent work.

Thank you for bringing it forward, and thank you for your patience.

I mentioned this opinion before, that that the full set of technical elements involved in the AF447 (and other accidents), will be a reunion of those enumerated, and made public by BEA and those tacitly recognized and addressed by the manufacturer in improvements/enhancements coming with new versions.

We're talking about a heavy, inertia laden aircraft at 265 knots, which is decelerating, with an initial max available roll rate in roll direct of less than 20-25 degrees per second (max rate is available at about 320+ KIAS clean, less on down). Rate-wise even at full SS deflection the thing is a slug.

NOT, as fighters go, an inherently pitch sensitive aircraft doing 900+ mph at 125' AGL with a malfunctioning pitch damper.

A330 IS a 'just let go'.

Machinbird
It has indeed been a fascinating discussion but I would still question the involvement of PIO in this case. The sageburner accident is indeed interesting but is it relevant? A high speed jet fighter going for a low altitude speed record? You are almost certainly more conversant with the design philosophy of the F4 than me but I would have thought that it was designed to be very responsive to control inputs - more so than a civilian airliner. Maybe for the pilot to have stopped the control inputs would have helped but once again I suspect you would be more knowledgeable on this point. However, PIO seems to be a phenomenon which affects small manoeuverable aircraft more than civil airliners (referencing the database in the Aristotel article). But even so with a small fast manoeuverable machine it is often better to 'let go and hold back'. I fully acknowledge your point that sometimes you have to act quickly but for most cases this would not be my approach.
OK465, I think, hits the nail on the head. The A330 is not a machine designed to be flung around. It is rather an aircraft designed to fly in a stable manner. Leaving the aircraft alone was the correct approach in this case - it would not have remained in its unstable state. A light touch on the controls if it threatened to roll too far but the roll amplitude was not excessive or too radical. PJ2 who commented on the incident in I believe the third thread of this subject advocated this approach and I would bow to his knowledge. I still find myself coming back to the crew behaviour in this accident. The complete lack of CRM cannot be disregarded and this is a more significant factor than any supposed PIO (and we must be honest we have no evidence of PIO in this accident - we have hypothesis but that is all). Remember in your experience in the simulator you were able to overcome PIO by use of your instruments (and I would assume a pause but do correct me if I am wrong). The PF in this case did not pause (a cavalry charge as you say) and does not seem to have had a scan and crucially to have ignored his copilot. This is the crux of the matter - a seeming panic reaction by both the flight crew.

Address OC comments
 

Yes it is a very stately slug. The problem comes from the difference between expectations of the PF versus what the aircraft actually did.

At altitude, roll damping is lower. Did PF understand he was in roll direct? Did he have appropriate training in flying in a roll direct law? Even sluggish aircraft can be overcontrolled or oscillate, they just do it slower, but they still oscillate.

Whether fighter or transport, 900 knots or 300, these things are aircraft and aircraft oscillate if not properly controlled. For an aircraft the size, mass, and control power of AF447, the roll oscillation it encountered was surprisingly quick, but the roll did not reach significant angles until after the stall. This may have deterred PNF from intervening.

The difference between divergent and convergent PIO is the amount of damping available. If the oscillation is building energy, bad things are going to happen as they did in the Sageburner accident. At some oscillation frequencies, pilots cannot effectively intervene.

OC, we are in full agreement that PF came on too strong when he took control. The problem appears to be that his initial mistake was not easily reversed.

The one surprising thing I learned reading the Sageburner file was that the aircraft was headed for an 8 g peak when the pilot released the stick in an attempt to break the oscillation. The aircraft had been trimmed in the alignment turn, and the additional nose up stabilator motion caused the aircraft to breakup somewhere around 15 g.

FWIW, On my roll PIO experience in the visual simulator, the only pause was the minor delay in visually locking on to the attitude indicator.

OC:
How about this, then? A bigass Boeing:

PIO jet airplane landing - YouTube

Feedback Systems complexity
 

Feedback Systems are inherently complex. When you introduce human inputs specially of high amplitude the results can be dangerous.

Anyway when you don' t know for sure all the "inputs" the PF "received" it's risky to conclude.

We are talking of a complex scenario with a crew (PF/PNF) lacking the training for the situation.

I love the KISS approach but for this analysis we must consider everything plausible and PF was reacting to stabilize.

Unfortunately due CRM, "tunnel effect", difficulties due "auto THS", use of SS or just panic then the entire crew failed to timely act properly or even "understand".

I understand MB comments on oscillation as a possible complex factor. OTOH in general i agree with many points OC put.

PS

I tend to respect too much all kind of oscillations or "transients" leading to dangerous situations or crashes, mostly the ones affected by human beings inside the feedback loop introducing extra "inputs".

Remember me the "butterfly region" . I feel "butterflies" in stomach when imagining what can happen.

In general, "laissez faire" is safer, i agree. But in some cases you must act decisively.

Which ones? How to manage in "degrading modes" not perfectly timely understood.

Acting decisively avoided me two serious car crashes. And subsequently i had to stabilize the vehicle. And was very difficult and requiring extremely dangerous maneuvers. Full of adrenaline in the end.

May be applying precise and ABSOLUTELY NECESSARY inputs, proportional to the surprise in the beginning.

When confused, better to wait and see.

This remembers me about people*:

• Intelligent and active, no problem
  
• Intelligent and passive, no problem.
  
• Dumb and passive, no problem.
  
• Dumb and active, extremely dangerous...

:E


(*) A friend told me about people entering the Army.

Organfreak
..However, PIO seems to be a phenomenon which affects small manoeuverable aircraft MORE than civil airliners (referencing the database in the Aristotel article).

Machinbird
I do believe the PF understood he was in ALT2 - after all he calls "I have the controls" (which I interpret as an acknowledgment of the switch) but if he didn't that was also an indication of poor flight deck management and serious training deficiencies.
I think we are all in agreement that sometimes you must act and act quickly. Getting that right depends on your experience and training and here I think the latter let the flight crew down. I am afraid the PF's behaviour fits RR NDBs fourth category.

Personally I do not believe the PF's call of "I have the controls" (in French) was acknowledgement that he was in ALT2 - it was only acknowledgement that the AP had disconnected, and hence the PF has manual control. The CVR transcript shows the PF giving that call at 2:10.06 which is within 1s of the AP disconnect, so I do not believe that after this surprise event, he knew which mode he was in before he said that.

Approx 16s later the PNF announces "Alternate Law protections" but I've never seen any indications of acknowledgement from the PF, nor whether he really understood what that means about the available protections - which seems to fit with your second point above. However other things like cognitive overload were also well-argued in the past.

I think we all need to be cautious in evaluating this crew's personal characteristics.

We have the advantage on them of knowing how their efforts turned out.
They were humans like us and did not intend to have their efforts turn out badly. We make mistakes, we have training issues, and poor performance issues. The same weaknesses applied to them. We are only in the early phases of learning what they were up against. Hopefully BEA will be able to put this whole puzzle together.

If we are to be critical, let us be critical of their performance, not their persons.
There is still a lot we do not know.

@DW:
LOL!!!

Bonin had a little more room to recover, it has to be said. :eek: