How to have an accident in a fly by wire aircraft (X-31)
 

This link has probably been posted before on one of the AF447 threads, but I didn't find it in a quick search.
http://pbma.nasa.gov/docs/public/pbm...m/x31_sfcs.pdf
Not an exact model for an AF447 loss of course but it shows how dynamic instability can be caused in a FBW aircraft.

Do the PRIMs adjust control system gains based on airspeed? It would seem logical that they would. This would be mostly relevant to flight prior to the first ACARS message. Wouldn't control gains increase at lower speeds to compensate for decreased control effectiveness at lower dynamic pressure?

The material mm43 and others have published is both astonishing (for a layman like me, just a humble PPL MEP) and complex.

This complexity is further complicated by facts coming to surface along a time line.

I have read every single post in this thread but even then sometimes I "loose" things. Things not being in my native language sometimes complicate things. I am sure some French people follow this thread and struggle even more.....

Valid comments were made about new participants needing to read the entire thread before commenting and/or things being done again and again (discussion with Bearfoil esq.)

Perhaps mm43 could or someone else could make a synopsis of the pprune analysis so far and post it via a link every so often? Once a month?

Just a suggestion.....

Thank you for you great work all! :ok:

Surface drift
 

Thanks for this information mm43.

A few thoughts:
1. A human body in the water will drift with the water current much more so than it will be "blown" through the water by wind. Bodies are mostly water, have a density just a little greater than or just a little less than water (hence some sink and some float), and there is little above the water to catch the wind. So the drift of bodies predominantly reflects the effects of water currents.
2. Other materials found will drift with a hybrid of water current and wind - depending on their density, the shape, and the proportion above the water to catch the wind.
3. Kerosene floats on top of the water and hence its drift will be significantly wind effected - far more so than bodies. We don't know if the pollution was Jet A1 or not. Was it ever tested to determine its nature? - I imagine that oil from a ship would be much heavier than Jet A1. Is such testing even reliable after some days? - have the lighter fractions evaporated and hence is it possible to determine the nature of the fuel? If the fuel was from AF447, the ENE winds suggest the impact was upwind of this. That is hard to reconcile with:
a) bodies drifting in a sea-current to the NE and then the N, suggesting the impact was further west
b) where the authorities have searched so far
So how certain are we that the sea current was initially NE?
4. We know that the bodies all entered the water at the same time, and likely close together (barring airborne breakup of the plane). Those bodies found were always afloat and hence all were subject to the same surface current.
5. From when the bodies were found, they seemed to have been drifting pretty much due north - perhaps slightly west of due north. Of course the current may have changed over time or distance or both, and equatorial currents are especially fluky. So there is plenty of guesswork here. You can't simply extrapolate back southwards til time zero.
6. Of course if the current had been constant (and I am not sure that we know it was not), then the bodies track back pretty much exactly to a point 1-2 days wind drift ENE of the "pollution" spot.

So did the plane turn to the right (and not the left) after encountering severe turbulence beyond the last known point? What do the pilots here think?
a) We believe that the Captain was not on the deck at this time. If the two pilots flying at that time decided to divert around weather but still keep going to Paris (ie not return to Sth America), then which way would they more likely turn?
b) Faced with severe turbulence requiring a change of course, would you chose to get closer to land rather than turning left towards the middle of the north Atlantic?
c) Would the recent communication problems with Africa mean you would tend to turn towards Africa (expecting that communication would improve) rather than further away?

Hi,

This sentence is very interesting ..
For the passenger perspective:
The passenger has no right before boarding to learn about the experience of the pilot(s) in charge and therefore can not refuse to board if it deems that this is insufficient experience
On the other hand, an airline must (should?) ensure that all pilots she hire have sufficient experience to cope with all situations and the plane is technicaly fit to fly safely.
It is incomprehensible (always at the point of view passenger) that some accidents (with the same cases) have happy endings and other evils .. and it was due to a difference of experience ....
The recent A380 case seem's to fit ... :)
Until these problems are not resolved to fly is always a gamble despite all the propaganda was made about the increased security .. aircraft safer .. etc. ..

Way back in the original R&N forum thread, I posted these images of the currents.

Five days centered on May 28
http://i136.photobucket.com/albums/q...NAG-0290-1.jpg

Five days centered on June 2
http://i136.photobucket.com/albums/q...NAG-0289-1.jpg

Five days centered on June 7
http://i136.photobucket.com/albums/q.../SNAG-0291.jpg

From recollection, I believe I placed the dot on approximately where the first body was recovered. If the dot position looks to be in error, I am certain mm43, whose knowledge and expertise far exceeds mine, will correct.

http://i136.photobucket.com/albums/q...SNAG-0289A.jpg

The surface currents argue against any turn to the right of the track.

I am interested in whether the new search will re-examine some of the area previously searched with either new technology and/or new methodology, or will focus exclusively on areas not previously searched.

jcjeant

Along those lines, Qantas 380 has five Captains on the flight deck, encounters an emergency fifteen minutes after launch, in daylight, VMC, with four engines, (make that three), etc. etc.

447 has two 3-4k hours pilots on the flight deck, with two engines, very dark, in severe turbulence, and the panel goes South.

Crap roll? If passengers were actuaries, (some are), they would perhaps flock to the 340/747 for long flights?

PanAm brought back furloughed white hairs when the 747 was introduced. They had been furloughed when the 707 debuted, they were "not up to the new technology". The senior Captains were back on flight status lickety split when the PR people reckoned the passengers would feel more comfortable with gray hair instead of young uns up front.

Sell the "sizzle" not the "Steak"??

bear

slats11
Fat people have greater buoyancy than thin people, i.e. the density of fat is less than water. Decaying bodies create internal gas which causes bloating and increases the buoyancy and therefore their freeboard (the area subject to windage). Sea water temperature of 29°C accelerates this process.
The galley cabinet, Vertical Stabilizer, seat cushions etc.. are items that were subject to significant windage. The V/S presented a difficult case, as its rudder was hard to starboard (35°) due to the center of buoyancy and the attitude adopted in its floating mode. The V/S not only exibited leeway due to windage, but it was quite capable of "tacking" (to use a nautical term) in certain wind conditions.
Wind friction on the sea surface is only a fraction of that exerted on an object 2m above the surface. However, you are right, the oil floats and its adhesion to the sea surface is the only dampening factor when confronted with wind on its top surface.The Pollution Spot was identified by satellite radar imagery 30 hours after the suspected crash. It was only seen once due to orbit geometry. The satellite evidence was only found following extensive research well after the event, consequently physical examination was not possible.Jet A1 has an SG in the range of 0.78 ~ 0.84, Marine Desiel / Gas Oil is 0.84 ~ 0.92, and Bunker Fuel / Heavy Oil 0.92 ~ 0.98 subject to temperature. SaturnV has re-posted data from the NOAA-OSCAR project, and coupled with QuikScat satellite 2m wind data, it is/has been possible to backtrack to the south and west of where the bodies were initially sighted.I don't think anyone is extrapolating on a constant time versus distance basis. There has been plenty of detailed work presented in this thread and in the old AF447 thread (about 6,900 posts) which covers backtracking based on the limited information that is available.FluidFlow demonstrated mathematically that the Pollution Spot was a position of interest, but as you mention the vagaries of the North Atlantic equatorial currents and winds tend to make that assumption purely theoretical.Not actually relevant, as evidence has been presented by the BEA that proves that other aircraft flying the same and an adjacent airway that night took the appropriate wx avoidance after observing what was ahead on their wx radar. Some went left and some went right, and I don't think that where the nearest land was or comms difficulties with Dakar Oceanic or Atlantico made any difference.

Finally, I've gathered a lot of data from varied sources on the Equatorial North Atlantic surface currents, and can without doubt state that giving a Chimpanzee a pencil and asking him to write his name could possibly reveal where the surface current had been previous to the first sighting on 05 June back to around 0215z on 01 June 2009.http://images.ibsrv.net/ibsrv/res/sr...s/badteeth.gif

mm43

PanAm brought back furloughed white hairs when the 747 was introduced. They had been furloughed when the 707 debuted, they were "not up to the new technology". The senior Captains were back on flight status lickety split when the PR people reckoned the passengers would feel more comfortable with gray hair instead of young uns up front.

-----------------------------------------------------------------------

Huh? Furloughed when the 707 debuted? So the union just stood by while former pilots were put back on the seniority list? Removed because they can't handle the 707, but a decade later they're the sharpest guys Pan Am can find? So Pan Am recalls them and makes them 747 Captains?

And you think Pan Am had 'young' Captains that were senior enough to fly the 747 when it first came on line? How young are you talking about?

I'm curious, where did you get these 'facts'?

Your point about the captain being "in the back" is complete supposition. This has not been established in any way shape or form other than speculation.

The problem with these surface current graphics is that they don't seem to reconcile with what we see. These graphs show that the current was predominantly to the east (maybe NE) at 3 North . However we have a line of bodies arranged roughly North-South, separated along this axis, and drifting approximately North. From memory, the separation was greater NS than it was EW. We know the current was to the north when they were found. However this suggests that it was also to the north for some time prior to discovery. The significant separation along this NS axis is what you would expect with a group of bodies drifting in a current to the north (different bodies will have different drag coefficients according to clothing etc, and hence will vary in how well they are carried along by this current).
Obviously they will appear separated NS when plotted on a graph due to discovery at different times. However the separation seems greater than that due to drift while they were still being discovered. They were separated NS well before any were discovered. Bodies were found on the 6th to the south of those found on the 5th. Clearly they were drifting north (rather than east) at different rates - suggesting the current was predominantly to the north.
If they had been exposed to a significant east component, then there would have been more scatter in their longitude when they were discovered.

I have followed much of this thread including the extensive drift analysis. However the aircraft was not found where this suggested that it could lie. Maybe we missed it. Maybe we were not looking in the right spot.

A turn to the right rather than the left would be pretty relevant regarding where to look. Most of the search has been to the west implying a turn to the left. Again, maybe we have looked in the wrong place. A turn to the left also excludes this pollution spot. A turn to the right could include it.

BEA PR/Transparency
 

As I complained on the original thread a year ago, BEA's attention to the public interest regarding information about the search for AF447 is about 2 on a scale of 10. The promised assessment of prior and future search phases, supposedly to be announced in October, has never arrived, though decisions are clearly being made that reportedly lead to a February 2011 Phase 4 startup. Sources are news outlets; BEA is silent.

A great deal of work went into BEA's "Drift Report" last year. I'm certain a great deal of work has gone into this latest assessment, too: How can you book or contract AUVs and ROVs only 60 to 90 days out without a plan and defined area(s) to search? It will be interesting to see where they choose to search More interesting would be a report on WHY they decided on those places.

Feels like a gang of school children playing marbles, but the fellows with the big marbles won't share, so the rest sit around and watch and get pis sed off. Is the silence because there are lawyers, corporations, and vested interests in the game, and information needs to be carefully groomed and each step carefully staged? Where is the transparency and openness? The search for the truth? Why adversarial instead of collegial? I'm not a conspiracy theorist, but I do hate sitting around waiting for groomed data and pablum... In the Internet age, there are only poor excuses for not sharing.

GB

slats11
That's where the Chimp comes into play! We don't know that the one of the bodies recovered on the 6th wasn't in fact one that was sighted by a passing ship the previous afternoon. What I am saying is that just because we know where bodies were when they were found, it doesn't necessarily follow that joining the dots represents where they had been.

Hypothetically, consider that the first sighting was in fact a body that was recovered the following day, then the drift (current plus leeway) was to the WSW and the bodies were actually carried round in an anticlockwise eddy and in the process fanned out as the current vectored back to the north. This is simulated in a graphic below, where the NOAA-OSCAR smoothed current is depicted in red, and the drift of 2 bodies is shown. A cyan line represents one and the dotted magenta line the other. As they start to separate, they are subject to differing current/windage effects, and as portrayed, they eventually finish up taking different paths.

http://i52.tinypic.com/r0tg79.jpg

Say the position on the 5th is the same body shown on the 6th, then it can be assumed it followed the cyan track and that shown on the 7th followed the magenta track. Now you can clearly see that without knowing which tracks they took, the above is just an assumption.

All I am saying is what has been depicted in the graphic is not unreal, and many similar drifter tracks have been noted in this area of the Equatorial North Atlantic. A line drawn south through the 7th and 6th positions may lead to the Pollution Spot, but a line drawn through the 6th and 5th positions clearly doesn't.

The surface currents in this area are subject to very small changes in true sea level and barometric pressure, which can be exacerbated by small shifts in wind direction and speed. On top of that there are the solar and luna tides. In other words, the whole area is like a badly wired telephone exchange - you'd be lucky to get the same number twice.http://images.ibsrv.net/ibsrv/res/sr...lies/wink2.gif

mm43

Great Bear

Transparency? Isn't that what Alice found when using the "Looking Glass"?http://images.ibsrv.net/ibsrv/res/sr...ies/boohoo.gif

mm43

GB, I'd agree with you except that I take these two threads here as evidence that a premature partial release of "everything" would likely be very harmful to a effort to realize a dispassionate explanation of the crash.

Now, when this is over if they do not reveal everything that's not subject to privacy laws I'll be looking for a pitchfork and/or a torch.

But the fat lady is not even warming up in her dressing room, yet.

slats11, I am not going to re-post the Brazilian search grids for June 2-5, but the focus was on areas to the right of the track. I think it a fair presumption that if AF447 had deviated right and crashed, wreckage and bodies would have been discovered earlier, given that was the area being overflown in the initial search days.

Look back at Takata's post #2050 on 21st June 10 in the original thread. The bodies are all clearly in a NS line drifting north over the period 6 through 10 June. Despite the surface current charts for that time and that location showing that the current was somewhat N of E around 3.5 degrees N, and then less strong and probably E of N around 4.5 degrees N.

So do we believe the recorded positions and times that the bodies were recovered? Or do we believe the surface current charts. Because it does not appear that both can be correct. .

If the bodies did not drift in accordance with these charts when they were being discovered (6-10 June), then how can we be sure they did for the first 6 days? A lot has been made of a presumed eastward as well as northward drift of bodies. All I am saying is that I am not sure this is correct. They were drifting north when they were found. Maybe they had been since impact.

These charts are very low resolution. Maybe 180,000 square miles. Summarized by 50 average vectors. I am not sure that these charts are that reliable at the scale we are trying to use them.

The most similar objects in the water were all the bodies. Pretty much the same size, shape and density, and all pretty much the same balance of current and wind affected drift (mostly current). The bodies therefore are the signal. The other wreckage is all dissimilar and the relative proportions of wind and current effects will differ significantly. This wreckage is the noise.

mm43, I get your example with 2 bodies. Eddy currents could do anything with just 2 bodies. But 20 or so bodies as in Takata's map? That is a pretty impressive line.

On a separate question, I think most of us would agree that we really have no idea where inside (or even outside) the circle AF447 lies. Is any area really more likely than another? The search to date has been in accordance with the accepted theories as to where it is most likely. Either it was missed, or it is elsewhere. As we enter phase 4, maybe each point has a similar probability. Given the heterogeneous nature of the terrain, perhaps the best chance is to focus on the relatively flat areas and hope we are lucky. If the search experts estimate that the chance of finding given wreckage in a fairly flat area was 2 x (or 3 x, or 4 x) that of finding the same wreckage among mountains and ravines, then maybe this weighting is more important than any particular theory as to where it was more likely to be.

mm43

Thanks very much for the graph you posted, so with regard to all the great science that has be presented on this forum over the last year or so, i wonder if you guys wouldn't mind marking just where on the last graph you think the aircraft entered the water, for me it would just be a case of a tracking line from either side of items and bodies found and where they intercept start looking. Now i know it's not that easy but its not been found anywhere else so why not. So where do the rest of you think it is? perhaps letting other see this and then comparing it to what BEA come up with might, just might give some idea as to what there thinking is.

New Search
 

Apparently a meeting was held today 11/29 with the families. A very little bit more information about the proposed search has appeared here:

Rio-Paris : Quatre mois pour retrouver l'pave - Monde - Actualité Challenges.fr

I will not repeat Google's translation, but leave interpretation to those with a working knowledge of French.

Google's translation of this article:

Secretário francês dos Transportes se reúne com familiares de vítimas | RFI

Says: "Details about the new phase of the search will only be announced on December 13, in another meeting which will be attended [by] BEA..."

The reported meeting between the "families of victims association" and the Secretary for Transport is translated below, and as reported in the Brazilian media and in this thread a few days ago, a further meeting on 13 December of Brazilian and French officials will outline details of the proposed search.

A translation follows:-
mm43

slats11
Maybe that is true, I don't know and I doubt if anyone else is in the position to positively identify where they drifted from.

The area in the immediate vicinity of the Pollution Spot is, as I have said before, a good place to start. However, with more precise interpretation of sea levels, winds and shear effects, I would not be surprised if a model has not come up with something that supports a viable starting point. We shall wait and see.
My best estimate is that the wreckage will be confined to an area within a radius of 400m. Even if some is down a steep ravine and gets missed in the sidescan survey, something else will be found. It only takes the finding of one piece of debris on the bottom, and the rest will follow.

mm43

I am lost when it comes to currents and winds affecting the bodies. I am not even sure if the indexing of each victim is by date found, or some extrapolation. It does seem to me that the first body found would be closest to the wreck, and all current analysis must start the "backcasting" there, on that spot? Whatever distance separated the victims at water entry was simply expanded, and as Slat11 has said, a funnel shape should point to the impact point. That is the simplest and most direct process, imo.

The pollution spot, with its "forks" seems to be explained best (HN39?) in that the point may be impact, and as the fuel sank with the wreckage, it floated in an ever increasing fan up to the surface. The impact loss of fuel would have started drifting right away, and the sinking fuel would have remained somewhat "localized?" If the HS and Tail Tank drifted in another direction, but provided fuel for the upward flow, would not the bulk of the surface fuel be closest to the impact point? (The bottom of the inverted "V", left). This is simplistic, naturally.

I want to continue to remind us that a very large body of evidence has not been made public. The families, to include the Brazilians, have 'partnered' with the BEA now. I don't know how the French do it, but without subpoena, or pending Court action, an American group might be told to "Just Wait for The Final Report!!"

With the Families in the 'group investigating', and BEA's seeming unwillingness to make public their plans, one suspects that BEA were......"encouraged". Court records in the US are almost always "Of Record", "Open".

bear

slats11, perhaps mm43 has the data, but I have not seen it. The data being:

a.) the daily boundaries of the aerial search grids flown after June 7.
b.) the day, time, and location of wreckage and/or bodies as initially spotted daily in the searches flown in a.).
c.) the correlation between b.) and the day, time, and location of the retrieval of the spotted wreckage and bodies by surface vessels.

c.) ought give you some approximation of the current and windage at least during the period between events b and c.

takata was hypothesizing early on that the flight deviated right, and possibly had reversed course and was headed toward St. Peter and St. Paul when it crashed.

There are a lot of variables that might explain the Brazilian military failing to spot bodies or much of the floating wreckage in the search grids that were flown June 2-5, but it would be a pretty incompetent search if something as large as the VS was missed in the area searched on those days.

SaturnV
I think you have "hit the nail on the head" - as much of the info I have seen was related to grids prepared for searching, but no confirmation that they had ever been flown. This I believe was due to miscellaneous flotsum and so-called oil slicks being sighted well to the SE of the Last Known Position. The "focus" of the search became "blurred".http://images.ibsrv.net/ibsrv/res/sr...ons/icon13.gif

With regard to individual items, I will give you an example of the Outer Spoiler located about 42NM to the N by E of TASIL on 13 June. Between the time it was first sighted and its actual recovery, it drifted to the WSW at a speed of 0.5m/s (1 knot).

mm43

Hopefully in the 8 months between phase 3 and 4, those responsible have started from scratch. If there were some false assumptions and conclusions directing the earlier searches, then hopefully these have been identified and eliminated. The best way of doing this would be to bring in some new people. Otherwise it is all too easy to keep "confirming" previous errors.

It is important to know exactly what areas were searched initially (as opposed to what had been planned to be searched), as well as the meteorological conditions that may have impacted on these searches. If there was low cloud or rain or even haze, then lots of things would have missed by relatively fast moving fixed wings at 1000-1500'. Bodies most definitely would have been - they are difficult enough to see even with good visibility from a helicopter at 500-700'. Think how small people on the ground look from a 10 or 15 level building. And that is looking at the entire person - not just that bit above the water.

The other thing to consider is how many white caps there were on the waves. If there were lots of white caps, it can be hard to see light colored objects. Even a VS. All you see are hundreds of white caps in all directions - and you try and look to see which ones persist and may be something, and which ones disappear and are just breaking water. You can't keep asking the pilot to go back and circle every possible piece of debris or else you will never complete the assigned grid.

I suspect that air searches sound most easy and reliable to those who have never spent hours staring out over lots of empty water. If you listen to the accounts of survivors at sea, a common statement is how many aircraft flew over them with out seeing them.

I can only assume that they have established what areas were searched in the first few days, and the degree of confidence that can be attached to these searches.

Is it partial or is it everything ... ?

Here is a poor argument to justify a need for only limited transparency.
It is not a time to definitely explain the crash, this is the time to explore any possibilities and for that, the more heads the better, but transparency is crucial.
Passionate/Dispassionate ... what's the problem ?
Harmful to whom ?

Well, only four main players - picking one, or two, or three which would be easy. The fourth, only aviation.

In Politics, it is always toxic to try to "hide" information. For once, Politics is in there next to reality; the reality Leopard is lurking, and there will be losses. As wes says, the biggest loss will be to Aviation. The unmitigated hubris is starting to bloom, in public. (imo).

bear

I know the location of the captains body being found away from the FO's makes it speculation that he probably wasn't in the cockpit. A previous post stated that and it may or not be true. If the flight is more than 8 hrs each crew member is required to be off duty to make the flight legal. Usually it is divided up evenly so everybody gets a couple hours rest. Look at the recent Air India incident when the captain went back to pee and the FO pushed on the control column adjusting his seat and went into a high speed dive because he was inexperienced and in that case incompetent. Sometimes you have to use what you have left to keep control. I'm not saying holding attitude and gps ground speed would have worked but it probably was all they had. Hopefully they will recover the black boxes but doubt it will happen.

In the very early days of the original thread (now in Tech Log) it was reported that the body of the CA was one of those recovered. The others were pax and FA(?). None were the other two pilots. Posters familiar with the AF crew rotation routine on this RIO-CDG route and the timing of the events indicated that the CA would likely have been "in the back". Recall also that a section of a "crew rest" module was among the aircraft parts recovered. There was supposition that the CA may have returning to the FD as a result of the turbulence.

Kappa

Captain Dubois (Marc) was found among the other passengers, and it would have been unlikely for him to have been in the Rest Module. Captains rest is just aft the cockpit, a cot and a curtain, as I understand it. No ID was forthcoming as to his injuries, I believe the "Seated" pax were described as having injuries consistent (patent) with those in seats at impact. He most likely would have been unbelted or loosely restrained? As it happens I believe his rest was up at 0200, the time of beginning of upset? He likely took off, captured cruise, and left the cockpit, first rest. He was due back in the cockpit at 0200, as described by other AF crew familiar with procedure on this flight, as I recall.

cheers

bear

Bear, I'll accept your memory. I just wanted to respond to Tokyo Geoff that there was reasoning behind the "supposition" and "speculation" that preceded the recent post in this thread by p51guy.

I just modified my post to refer to the original thread now in Tech Log.

kappa

got it.....:ok:

How did lack of airspeed data cause AF-447 to enter an unrecoverable stall?
 

The most likely theory for the crash at this time seems to be that the aircraft entered a violent storm, the pitot tubes froze over, and the pilots stalled the aircraft b/c they didn't have reliable airspeed data. I don't really understand why a lack of airspeed data could lead to a stall. I fly hang gliders and have no indication of my airspeed, yet I can still keep it from stalling - because I know that if I shift the CG back to a certain point it will stall so I never exceed this position. Now, I'm sure the handling of an A-330 is very different from a hang glider, but why do you need reliable airspeed data to keep from stalling? To my understanding, a stall occurs when the AoA exceeds a critical value causing boundary layer separation on the top surface of the wing and loss of lift. And as far as I know, AoA is controlled solely by the trim of the horizontal stabilizer. And a sensible pilot or flight computer would not trim the aircraft past the critical AoA. I see how a powerful updraft or tail wind could cause the wing to stall before the attitude can adjust, but couldn't that happen regardless of whether you know your airspeed or not?

I am aware of all the speculation - it is precisely that.

No evidence at all, and there could be hundred and one other reasons for the Captains body being recovered without the pilots.

You're right. Theplane will stall once it AoA was exceed.
But for the aircraft at cruise, in order to maintain the level altitude you need a
constant lift to counteract the weight.
So, if the pitot tube is frozen and send the data to the autopilot and
auto throttle that the airspeed was way to much higher the autothrottle will
decrease the throttle which slow your airplane down. Normally, when the aircraft
slowdown it want to go down. However since autopilot want to maintain the
altitude that pilot dial in or FMC, the autopilot will pull the nose up which increase
AOA. So the aircraft will continue to slow down and pitch up untill it stall and
then crash.

This is how I think it was work. However, may be the ice might form on the wing
and make the aircraft stall faster too.

Best regard

Thanks for the reply, that makes sense. But why would the autopilot be so stupid as to exceed the critical AoA? I can't imagine that an interlock is not in place to prevent that from happening. Isn't that the whole Airbus flight control philosophy after all? And I would hope that the pilot would be smart enough not to do that either if he were flying manually.

Wing icing at that altitude is fairly unlikely because of the OAT.

The autoflight & FBW systems most likely got into an ever worsening feedback loop and possibly exited that loop in direct law with a compromising attitude and speed. I feel fairly certain that had this happened during daylight hours, the pilots may have been able to successfully recover control of the aircraft.

AFAIK, the Airbus still flys under the old mantra "power + attitude = performance".

Now I simply cannot believe that the pilots of this aircraft were a bunch of dopes, so there was some other major problem preventing their setting power and attitude to maintain a survivable speed.

So, what went wrong??? The info out there in the public domain suggests that they had valid attitiude, where were they mislead into a fatal series of errors? More importantly (to me) how can I recognise a similar chain of events setting up to hurt me???

bearfoil, "In Politics, it is always toxic to try to "hide" information."

I believe a fellow named Assange is proving that sentence is dead wrong. Shame on you.

I think if you add in severe turbulence, multiple systems failure warnings, possibly a wing drop stall and g forces you will fast find task saturation and loss of situational awareness would hamper any crews recovery.