That is correct as far as the voting system goes. Once voted, the "polled" value is used by the PRIMs in performing their function. The voted value triggered the monitoring process described in BEA's discussion of the PROBE PITOT fault message, and its downstream conditions such as AP off, A/THR off, Alternate law (prot lost), etc. The voting system resulted in the ADR DISAGREE message that occurred much later.

Hi PA 18 151
My understanding of the ALT2 being latched is that as soon as you've got an ADR disagree, the system cannot be sure that the equation you write above is true.

Why ? Well, imagine an aircraft in an ash cloud :
- at first, pitots (front end) are clogged => speeds decreases, but not exactly at the same time => ALT law
- then, out of the ash cloud, the ashes move in the pitots. The front end became unclogged, but then the remaining ashes clogg the drain hole of, say, two of the three pitots => those two pitots give consistent and valid speed. But that speed is uncorrect (too high, because of the drain hole clogged).
If the system goes with this (incorrect value) to revert back to normal law, it's kind of dangerous, cause it may trigger the overspeed protection (climb order) when not needed/relevant.

Therefore I think the logic is to latch the ALT law, until the aircraft/system (probes, computers...) can be fully checked, on the ground.
The rule would be some kind of : ("you" being the computers)
"As soon as you've got a problem with the probes/ADR/speed calculation, you cannot be sure the speed you sense/vote/choose/know is indeed correct. Then you have to let the human crew in unrestricted control, via the ALT law being latched".

Hi AlphaZuluRomeo,

Yes I think that is a good explanation for why ALT 2 should be latched. I suspect Airbus should take a look at this again and I am sure they are doing so. Icing conditions are more frequently encountered than ash cloud conditions and the ice didn't hang around for long at all.

There was an inconsistency between the speeds displayed on the left side and the integrated standby instrument system (ISIS). This lasted for less than one minute.

In this situation. The aircraft knew it was stalled, knew it's pitch angle, and had consistent and valid airspeeds. What more info do you want before you start to lower the nose?

And you are correct, the vast vast majority of airline pilots could correctly manage the pitots icing, unreliable airspeed, any subsequent change of flight law, and the safe conclusion of the flight (and recovering from a high altitude stall without thinking about it). I think those who say they would also be in trouble are just being melodramatic, if not they should disqualify themselves.

- I feel that 'vast' is being overly optimistic, but whatever - what you are effectively saying then is that these two AF pilots were (surprisingly) NOT so able and that there was no further complication? Case solved, matter closed? Hmm. Maybe. Maybe not.

BOAC,

My comment was to AlphaZuluRomeo wrt ALT 2 being latched and letting the pilots take over from there.

But if you don't think all crew could manage this event then why are you so convinced the aircraft is at fault? You demand evidence for CB penetration but are not so picky when looking for evidence the aircraft caused this accident.

Case is not closed. We don't know all the contributing factors.

A33Zab;

Your "Chronology of events @ 5 sec interval." has a column headed "STALL AoA". I presume that is 'alpha-max', which is not stall AoA but somewhat less. Alphamax varies with Mach number as shown on a graph posted a few days ago. For the Mach numbers in your table:

Mach ... alphamax

0.8 ......... 5.2
0.68 ........ 7.1
0.64 ........ 7.7
0.59 ........ 8.1

AZR: Except, in this case, they didn't have unrestricted control. The flight control system kept changing the pitch trim. While this was result of an inexplicable nose-up command on the side stick, the pilots apparently didn't notice it. As I've said several times before, when the system gives up, it needs to turn off autotrim along with the autopilot. :ugh:

- then we agree on that! . I "demand evidence for CB penetration" simply because we have none although it is an oft-issued 'fact' on here. I am pretty certain "the aircraft is at fault" since I believe if the pitots had not failed the accident would not have happened, nor, I personally believe, would it with iced pitots with a 'conventional' FCS, but am keeping an open mind on the rest - and am yet unconvinced either way due to the paucity of information from BEA.

For Smilin Ed - I agree, and feel that Dozy's proposition a while back of a reversion to Direct Law in such situations would be a good idea, although an anathema to the FBW world. Assuming also, of course, that the crews are trained to....................etc etc.

The accident (as we know it) would not have occurred if autotrim had frozen when it left Normal law.
Maybe Alt 2 law has some issues. Hopefully BEA will get to the actual bottom of the crew's control problems.
Gotta go with what Ed said.:ok:

Sub heated Pitot´s in a flawed design (in respect to air speed measurements)
 

:ok:

1) Pitot´s presented intermittent failure (a fact)
2) The implemented redundancy proved to be useless in this case (a fact)
3) The implemented redundancy is flawed? (when using these AS sensors)

And if other factors (a/c Systems) are also related to the LOC we would see another, more serious, design flaw(s) and the crew as "probable victims" of a K.I.C.S. System.


C.= Complex


We are realizing how serious was the first Leak (LF).

Er, I'm pretty sure this was discussed on the previous thread - some time ago they not only "admitted" that it was a problem, they changed the behaviour so that when A/THR kicks out, the thrust remains at the last setting the A/THR commanded. The thrust setting does not change until the pilots touch the thrust levers.

As it is we seem to be discussing three scenarios here. Note that what follows are largely my opinions, for what they're worth.

Svarin postulates that some hitherto undiscovered software bug caused the FCU components to slip in and out of Normal Law, causing intermittent activation of protections forcing the aircraft nose-up. Personally I find this the least likely explanation, based on the specification and design of the systems as I understand them, coupled with the fact that the A330 has been flying for nearly two decades without such a scenario presenting itself, despite numerous documented failures of the pitot system. I'm not saying it's impossible, just pretty remote based on the information I have.

Chris Scott wonders if the "G-Loading" mode of the FCU would have ordered up elevator and consequent nose-up THS movement via the autotrim system. Personally I think this scenario slightly more credible than Svarin's, because it is more of an edge case in terms of specification and design. That said, I'd be very surprised if the engineers overlooked this consequential failure mode given how thorough they were with everything else.

Finally we have the scenario I consider the most likely, which is that the autotrim was responding directly to the pilot's consistent nose-up sidestick commands, but this in itself opens a can of worms because it is perceived in some quarters (incorrectly IMO) as an attempt to "blame the pilot" and get Airbus/AF off the hook. For a start, Airbus and AF are already on the hook to some extent because of the known pitot problem, and AF's response to the service bulletin not being expedited in the wake of the numerous cases where these failures led to near loss of control incidents. The old aerospace chestnut of a "failure of imagination" comes into play here, because most of the previous events occurred in daylight, where pilots had an external reference from which to aid their recovery of the aircraft. Prior to the accident, few seem to have taken into account how much more dangerous a failure of this nature would be in adverse weather conditions in the dark hours of night, which would suggest that the lessons of Birgenair and Aeroperu were not heeded as well as they should have been.

For my part, I agree with PA 18 151 in the sense that this case is far from closed and we should respect the abilities of the investigators to get on with it. To clarify my position as referred to by BOAC, I mentioned that another poster (I believe it was Smilin'_Ed) seemed to be proposing a drop to Direct Law in the case of air data failure, and bypassing Alt 2 entirely. Indeed, it would appear that is indeed what Smilin'_Ed is proposing ginven his recent posts. Personally I disagree and think that Alt 2 has a purpose in this kind of incident, although it can be argued that the outcome of this particular scenario doesn't reflect well on the design. As I've said many times before, the ability to manually control trim is available in any law, including Alt 2, provided via the trim wheels sitting right next to the inboard hands of both pilots. Indeed I think it was PJ2 who stated that as part of his training he was required to land the A320 simulator using rudder and pitch trim only.

BOAC, I find it interesting that you acknowledge that your background information on FBW airliners is limited, yet you feel qualified to state that a drop to Direct Law is "anathema to the FBW world", by which I presume you mean mentality. I think that this is a fundamental misunderstanding. Part of the FBW rationale was certainly to reduce the cost of operations by using lightweight componentry in aircraft controls, however another purpose of the design was to assist pilots - not hinder or eventually replace them, no matter what some of the more lurid scaremongering on this forum from time to time suggests. The designers and engineers asked pilots what they wanted when the requirements were gathered, and built a system that implemented the specification drawn up from those requirements. The whole idea was to build something that *worked*. If the decision is taken that a drop to Direct Law in this scenario would be preferable, then I'm sure they will make that change.

As I stated, I'm of the belief that Alt 2 serves a purpose, and that a lot of thinking will be done based on the evidence gathered in the investigation of this accident. I'm sure that scenarios were considered that make Alt 2 a much better fit than Direct Law in this set of technical circumstances, and eventually they will have to weigh up those hypothetical scenarios against this real one before they make that decision. Birgenair proved that a more "conventional" FCS is no protection against the "loss of air data" scenario, and just for the record on this thread I will state again that the Birgenair Captain was a *highly experienced ex-military pilot* and even he was thrown (even as his two F/Os were repeatedly feeding him suggestions that might have helped). He didn't seem aware that the situation was being made worse by the actions he took all the way down to the ocean.

There seems to be an undercurrent on here occasionally that some pilots are not only distrustful of technology, but also have a dim view of the engineers that built the aircraft they are flying - seemingly thinking that because the protections were implemented by engineers, therefore the engineers must in turn have a dim view of pilots' abilities. I can't speak for engineers in general, but I must say that I think this view is blinkered. It is in the interests of pilots and engineers to make aircraft as safe and as comfortable to fly as possible. Ultimately pilots are responsible for the lives of everyone on the aircraft with them and additionally pay the price if something goes wrong. But another way to look at it is that engineers are responsible for *every* person riding on the aircraft they design, *every single time* one of those aircraft takes to the skies. Think for a second of the Boeing engineers that carried out the faulty repair on the aircraft that became JAL 123. Think of the price that the JAL engineer who signed off that repair paid (I believe he took his own life).

Thinking in these adversarial terms is not only counter-productive in my book, it is also dangerous. We are all in this together in a very real sense - I may not agree with what Svarin, Chris Scott, BOAC and some others are saying, but it would be churlish and short-sighted of me to not take it on board and at least accept that there is a possibility they're right. I think any engineer worth their salt would feel the same way, even if only to provide the data that contradicts (or even backs up) the theories and ideas put forward. At this point I am out of data, so I'm back-seating this for a while and hoping that the report when it comes is thorough and well put together.

Let's be safe out there, people.

That would be in Mechanical Law. The last ditch bring it back mode of control.

I hope you are correct, and indeed if you are, I am more than willingly to retreat.

Looking at post #379 and that graphic, it seems to show that that thrust went to TOGA @ 2:10:51.

Then again the handling pilot may have selected TOGA rather than AT logic.

Time will tell.

At 2 h 10 min 51, the stall warning was triggered again. The thrust levers were positioned in the TO/GA detent and the PF maintained nose-up inputs.

Clearly PF induced.

BOAC,

Imagery from 02h07. Position (square box) is the 02h10 ACARS position.

(Source Annexe 1 of the French version of the first BEA interim report.)

Temperatures above -50C

http://i136.photobucket.com/albums/q.../SNAG-0311.jpg

Temperatures above -75C

http://i136.photobucket.com/albums/q.../SNAG-0312.jpg

Would appear to be rather close to a Cb.

From Tim Vasquez's June 1 2011 re-analysis, his worst case scenario, and general conclusions.

Air France 447 - AFR447 - A detailed meteorological analysis - Satellite and weather data

Hi,

1 Well if I refer to the 1 quote .. it's seems they already overlooked one problem .. so why not some others despite how tourough they were....


Due to the last BEA note from 27 May 2011 and how reported in the newspapers (after all ... the general public is also concerned and can have some opinions) the direction of pointing fingers his obvious ....
After all .. who was in command of the AF447 ? .. the pilots .. or (in France) the sleeping enginneers .. softwares dev of Airbus or AF management people that night ?
We have the scene of the crime (35.000 feet and icing environment) ... the perpetrators (the pilots) and the weapon (the plane)
It's just we have not yet a reason for why the crime was perpetrated ...
Very sad that Peter Falk just left us days ago .....

- re-phrase that to "Would appear to be rather close to a red blob" and I'll agree.

You have provided your own answer to your earlier question - "METEOSAT measurement shows that cumulonimbus overshoots reached at least 6,000 ft above the tropopause." - I'm sure if you were to Google the height of the trop in summer in the tropics you will be complete.

Note the conclusions:
"Air France Flight 447 crossed through an area of tropical showers and/or weak thunderstorms with weak to moderate updrafts and a high likelihood of turbulence.", and also the last paragraph in your quoted piece.

Yes, they MAY have flown too close to the active part of a CB or even into one. They MAY have not used the radar correctly. At this time we can only surmise. I expect the CVR will tell - I understand there was little evidence of pax being strapped in?.

DozyWannabe: +1:ok: well said

Anyway, the fact that a change to the A/T behavior WAS implemented should be a affirmation of a lack of arrogance on their part: "we got this wrong, we fixed it...". That does NOTHING to confirm or infer there are other alligators hidden in the lake.

Ultimately the piece of the jigsaw with the GREATEST variability and uncertainty with respect to predictable behavior IS the chap with his hands on the controls. Let's be brutal here - ANY aircraft can be driven into the ground with the wrong pilot input, FBW, flight control computers, PRIMs be damned. Clearly that is inciteful and I am NOT claiming that there was any intent related to AF447. But once the auto-everything lets go the PF needs to get on with the program pretty damn quick.

Unfortunately in this case, I have a great fear that the sudden delivery of the aircraft into the PF in this case was entirely unexpected and the actions in the first few seconds were, (how can put this?), less than optimal. The game was not over, but little of what followed appears destined to recover the aircraft.

A fairly benign UAS event became a fully developed stall in less than 60 seconds or so. If THAT is what happened, then all this Airbus bashing seems out of place. That is not to say Airbus and the BEA will not find recommendations to ASSIST the pilot in such a situation, but I'm betting a buck it won't be a drop to Direct Law or elimination of the THS trim function in Alternate.

@Dozy: As I have said before, there is not necessarily only one cause of this accident. It appears to me that both the pilots and the aircraft have shown some deficiencies. Ascribing some of the blame to the pilots will not get Airbus/AF off the hook.

@Dozy: [quote] To clarify my position as referred to by BOAC, I mentioned that another poster (I believe it was Smilin'_Ed) seemed to be proposing a drop to Direct Law in the case of air data failure, and bypassing Alt 2 entirely. Indeed, it would appear that is indeed what Smilin'_Ed is proposing ginven his recent posts.[QUOTE]

From a pilot's perspective, if someone hands me the controls and says "You have it." I want him to keep his hands off until I hand it back to him. I don't want him to touch the trim unless I ask him to do so. Maybe not all pilots agree with that but I was trained to evaluate the "Flying Qualities" of aircraft. I made my living doing just that and my opinion is that the autotrim needs to come out when the confusers get thoroughly confused and give up trying to fly the aircraft.

@Dozy: Yes, the ability to manually control the trim is there but they didn't use it. We don't yet know why but it is clear that they let the system trim them up into a stall. In the world of pilots, that is a big no no.

@Dozy: But, in this case, the system did hinder the pilots. The pilots were remiss in not catching the fact that trim had run full nose up, but the system put it there when it shouldn't have, reducing their ability to fly it out of the stall.

In every fixed wing aircraft that I have flown, directional stability and pitch stability are positive and only lateral stability is neutral. The Wright brothers initially thought that they wanted neutral pitch stability but after a couple of flights, they began to realize that pitch stability had to also be positive. If not, when they pulled the nose up, it would stay there until the aircraft stalled. That's when they changed their design to positive pitch stability which brought the nose back to the trim speed when they let go of the controls. Having the autotrim follow the sidestick commands essentially gives the aircraft neutral pitch stability. Neutral pitch stability is fine as long as the autopilot is functioning properly, but when it quits, you really need it to be positive when you are hand flying.

The Wright brothers were smart people that designed a stable aircraft after a few tries. Airbus found a way to make an airplane fly like their first one before they corrected it. Neutral pitch stability might make flying easier when things are working right but in this case it helped seal their fate. Some day in the future we might have all the data to see why a perfectly good airplane with a minor airspeed problem ended up 13,000 ft below the Atlantic.

Deviation - too little too late
 

BOAC
Quote:
Originally Posted by OC
BOAC - Apologies for the slow reply. Details of other aircraft deviating round the weather front can be found in already released BEA reports and in various posts in the threads on this subject. I am sure that if you look you will come across them.

- is it perhaps that you have missed the 12 deg deviation of AF447 in the report? As far as I know there is no evidence that they 'flew into a CB'.

There is nothing but evidence they flew into a CB.

But I want to add what we know and what we don't about this.

First the mission of the BEA, or any modern country’s investigative body’s is to assess the facts, try to make a determination of Probable Cause, and make recommendations for corrective action. Or lessons to prevent it from happening again.

It sometimes is implied that they “will leave no stone un-turned to arrive at a resolution.”
That is incorrect and is used when there are reasons for the outcome to be delayed.

In the Air Force where I served as an accident investigator for fighter squadrons, the mission was slightly different. And we had many more accidents to deal with. The AF did not have the luxury of waiting for the up to two year time lag waiting for results, as national security was at stake. Thus their mission was a Safety Investigation. All of the parties were immune from prosecution, legal suits did not apply, and the object was urgency, so that we could get back in the air again. Their goal is to make a determination of Probable Cause also and make recommendations to avoid or prevent.

The definition of probable cause is simply, more likely than not. Or technically 50.1% versus 49.9. A very low level of certitude, but considering all of the many unknowns very practical.

Here we know some things for sure, many many more we know literally nothing about.
1) We know: thunder storms along the track. No one knows how severe.
2) We know there are severe up and down drafts in them.
3) We know all 3 pitot tubes iced up. No one knows precisely why.
4) We know critical airpeed indicators went out.
5) Auto-pilots failed.
6) Auto-throttles failed.
7) Uncommanded 7000 fpm climb. Despite the plane being at it’s maximum cruising altitude. Evidence of 60-70 kt updrafts according to meteorological analysis.
8) Airspeed falling to below 60 kts.
9) Flight controls ineffective below 120 kts.
10) I know, you cannot control an airplane with trim alone.
11) No one knows for sure what a plane will do in a deep stall.
12) No one knows for sure whether a plane can recover from a deep stall especially with limited flight controls.

Questions I have:
Why was the flight dispatched into a known line of thunderstorms?
Why is there so little concern about the effects of flight into thunderstorms?
Despite all of the warnings on the subject?

To me there is no mystery.

wallybird7: The ITCZ is a well understood area, that routinely presents challenging weather conditions. However EVERY flight traveling North<>South in this region of the World will transit the ITCZ. So your question "why were they dispatched into a known line of thunderstorms?" is rather misrepresenting the situation. This area of weather is not a rare occurrence, more so a common situation, and in fact the conditions that night were NOT particularly severe, with the term being "moderate thunderstorms" being the one most often applied after skilled analysis.

There were many other flights that passed through the SAME weather system, however the majority applied some diversion to a much greater extent than anything AF447 attempted. THAT to me is the most problematical concern of mine - WHY didn't they divert around the system?

Hi Smilin_Ed
I must disagree with your first sentence. If the auto-trim followed the crew's orders (via the sidestick) then the crew had unrestricted control.

Perhaps you interpreted "unrestricted" as "full manual" ? That's not what I meant. For me "unrestricted" means just that : the planes follows the crew's inputs, and the computers don't prevent manoeuvers because it "thinks" they're of no good.

Maybe a full manual reversion (direct law, no auto-trim, as you promote it) is easier to understand. But IIRC, on the A320 which crashed near Perpignan, the trim was manual (only) ; the crew didn't notice it either, and the plane crashed.

-----------

@ DozyWannabe (post #406) : :ok: :D Sir.

DEVIATE
 

GarageYears

Yes a slight misrepresentation -- and yes I know CB's are common. But every other flight deviated. Perhaps 447 did not deviate enough. But with all the glitches to me crystal clear the thunderstorm probably had "something to do" with the entire chain of events. The icing, the updrafts, the out of control climb. Something.

Every pilot I know says the same thing. Deviate, a lot.

I do not understand the casual dis-respect for the power of a thunderstorm.

BOAC,

From the BEA reports to date, it would appear they did not perceive the Wx ahead to be extraordinary.

While the BEA report does provide the number of rotations each of the pilots had flown on South American sectors, it does not indicate when these rotations were flown, and on what sectors. So their actual experience in transiting the ITCZ over various seasons is yet to be revealed, and may never be.

If the time had been daylight, and they had seen a Cb towering 20,000 feet above their FL ahead on the airway, I suspect they, like nearly every pilot, would have deviated off the track, and put their plane at a safe distance from that cell. What might be the appropriate, one adjective characterization of a pilot who would fly into a Cb whose top is 15 or 20 thousand feet above their FL in the cruise?

I don't know whether the BEA will ever provide more information on AF459 following on the same airway 35 minutes behind, and compare the reaction and response of the AF459 cockpit to that of AF447. It might be quite telling.
________________________

Given the relatively higher percentage of cabin crew bodies recovered floating, unless they were in crew rest modules, it would suggest that the cabin crew were not instructed to take their seats and tighten the straps. More about this will be known once the autopsies and identifications are completed on the 100+ bodies retrieved in their seats.

Restricted control
 

AlpaZulu

I must disagree with your first sentence. If the auto-trim followed the crew's orders (via the sidestick) then the crew had unrestricted control.

Auto Trim is not a primary flight control. Therefore the crew's control was restricted. You cannot recover an out of control plane with trim alone.

Ah, then wallybird7, you and I ARE on entirely the SAME page then. Because that is the root of the mystery here - why didn't they deviate? Everything that follows is a consequence of this fundamental issue. And we can postulate alternate trim functionality, this law or that, until we are blue in the face, but were it not for a simple 100nm East or West (name your distance/direction), we would not be having this discussion, which makes this all the more sobering.

CB's Respect
 

GY

So very true!

"unrestricted" vs "full manual" ?
 

@AZR: OK, AZR, I yield to your semantics.

But I hope the pilots did not really intended for the trim to go full nose up. I don't like to use the word panic to describe the situation but things sure are pointing in that direction. That's what happened in Buffalo and it was 100% fatal there too.

True, but it is possible to use the trim manually in any law. Manual Trim has priority, and when manual trim commands cease, autotrim will function again. I misinterpreted that earler, thinking that manual trim activation was a one-shot action which disabled autotrim for the duration. That said, if the pilot doesn't like what autotrim is doing all he or she has to do is keep their hand on that trim wheel.

Agreed. I think we're on the same page

That's a good point, and I'm sure that will be taken into consideration. Having said that I think your use of "confusers", while amusing, is an example of the adversarial attitude I was talking about earlier and undermines the very salient information you provided above.

Now this is the point when things get tricky. What you perceive as "the system" trimming them into a stall could equally accurately be described as the PF inadvertently trimming them into the stall by his direct actions, if indeed it turns out that the THS movement was sidestick-induced.

This is why I try to be really careful with language here because I don't want to give anyone the impression that I'm disrespecting the piloting profession when nothing could be further from the truth. We all make mistakes in our day-to-day lives, some of which have more far-reaching consequences than others. Being in charge of a two hundred-ton metal tube moving through the sky just below the speed of sound with a couple of hundred people behind you means that for line pilots, those consequences tend to be more far-reaching on an almost constant basis. When I hear the phrases "I don't believe a pilot would do that", "No pilot in his right mind would do that" or "A pilot would never do that" I get a sinking feeling (with no instruments to reference to confirm my physical perception ;)). This is because we're all human, and pilots - some of whom were below average, but many of whom were experienced, skilled and respected - have nevertheless done things like attempting a take-off without clearance/in snow conditions with engine anti-ice off/with high-lift devices not extended, shut down a working engine leaving the aircraft to fly on the damaged one, pulled back on the control column turning a stall warning into a full stall... the list is a long and sad one.

To be clear, I'm not bashing pilots here - I'm simply stating that the consequences that the men and women of the piloting world face for the kind of momentary lapse in judgement that would be easily resolved in almost any other workplace are far more severe, and that's why I personally have a lot of respect for all of you. But being almost hair-trigger defensive in the way that I see sometimes on here does you a disservice, when what I'm sure engineers all want is to make your (and our) lives as easy and safe as we can.

Right now we're speculating on information that was barely more than a press release. The people that designed these systems weren't stupid, and I'm sure there are very logical reasons for the system being designed the way it is. Remember that this was designed to be the next generation of flight controls - doing things a certain way because that was the way they'd been done since WW2 (or even beforehand!) wasn't a valid design input. Being as friendly and logical to the pilot as possible certainly was, the only problem with that being that some pilots prefer different things.

I'd need someone like PJ2 or Chris Scott to provide the data, but I'd be very surprised if they didn't factor that basic aeronautical knowledge into the design somehow (I'm a logic guy, the complex maths isn't my forte). We're not going to know exactly what the inputs were until the report is released, so I think we're going to need to keep our powder dry until then.

The crew obviously didn't just fly through a CB. Every crew finds their own way around them. No evidence of any major turbulence is reported in the BEA report. They iced up as had many Airbuses prior to this event. All indications are they lost airspeed indications and for some reason pulled back on the side stick until they went into a deep stall. No reports of severe turbulence or vertical drafts. I think it best to wait for the report rather than add personal concepts of what might have happened. The BEA report has nothing to report of any significant turbulence.

Hi,

They don't report .. ? .. but the pilot report ...

BEA 27 May 2011 note

And ..

Now of course .. are they warning CC of significant turbulences .. when they add "you should watch out" ?

Other than the inconsistent airspeeds that began this waltz ...

You have returned us to the issue of not knowing the AoA.

If the aircraft "knows it is stalled" but the pilots don't, what are your suggestions?

Follow on to that is: what were they trained to do in the case that they had stalled the aircraft?

There was posted either in this thread, or in the one at Rumors and News, a graphic depicting a 16 deg nose up on a display. You might see that on a departure climb, but how often in cruise?

This takes me to BOAC's question about a crew allowing their aircraft to head into orbit: what airline pilot, flying at altitude, would find a 16 deg nose up attitude something other than abnormal?

Why would either let that nose attitude sustain?

This goes back to what may not be answerable: what did each member of that cockpit crew see in front of him, and what was he paying most attention to?

This is where (and why) I keep going back to Birgenair - where a very experienced pilot stalled and span his 757 despite the fact that the only fault on the aircraft was a single blocked pitot tube. It is impossible to know what was going through his mind, but nevertheless - even with both his F/Os calling "ADI" and "Stall" repeatedly, he apparently did not process the information that the ADI was giving him - that he was excessively nose high for the phase of flight he was supposed to be in. Attempts to remedy the other factors in that accident have been included in pilot training and bulletins from the manufacturers (and indeed a design change to the 757) over the years, but the fact remains that psychological factors in an incident of this nature are possibly not as well understood as they could or should be.

BOAC
It may be losing sight of the wood for the trees but to dismiss the aircraft entering turbulent weather as not relevant is rather rash. The fact that the crew of AF447 did not deviate round the weather front is highly significant. The pitot tube failure whilst clearly a contributory factor is not the reason for the accident. The actions of the flight crew in responding to the situation and entering the thunderstorm when others didn't are. I am not assigning any value judgment here just noting an event.

Hi,

I wonder if it's not a usual behavior of some AF pilots to take at least some risks on this route or in case of similar weather ..
It's to remind sometime after the AF447 disaster .. the AF445 "mayday" on same route and somewhat same conditions ...
It was "apparently" a non event (but passengers were strongly shacked for longtime .. big turbulences) and plane lost altitude (was it stalling also ??) .. but happy end ..... in this case .
We will never know what really happened as the recorders were erased or datas convienently missing ...
Another "cas d'école" .........

Go figure .......

DW: What design change? Are you still hung up with your misinformation that the Birgenair Capt didn't have an AIR DATA: NORM/ALT switch on the panel in front of his left knee? That switch was there from the beginning of production of the 757/767.

The Capt. cocked up, that's all. DW, why are you trying to blame the 757, and let the A330 off free?

As for CB, thousands or millions of flights have successfully negotiated the ICTZ at flight levels since the day of the 707, with Wx radars far more primitive than what AF447 had, yet how many crashed?

Graybeard:

I think you'll find that you've missed the point I was trying to make. This isn't about A v B, USA v EU, pilots v engineers or any of that rubbish.

There seems to be a point at which the human brain can only process so much information. In the case of Birgenair it seems that the PF was unable to determine from the ADI that he was nose-high and stalling because he was still focused on the initial false overspeed warning. In the case of AF447 it appears that the PF repeatedly pulled back on the stick despite this being the precise opposite action to what was required for recovery - his ADI was right in front of him and presumably working throughout. If this is indeed the case why does this happen?

(The information that the 757's design was changed to make it easier to switch air data after the Birgenair crash comes from the ACI/Mayday episode on the subject - it is possible they got it wrong...)

From a pilot's point of view, I can understand loosing time or even being fixated and not physically doing what I'm supposed to do. In the case of AF447, however, BEA report suggests a persistent positive action from the PF. An action that is bewildering given the circumstances.

I'm with Savrin here. The a/c systems need full scrutiny, if only to understand what made the pilots react the way they did. The problem with explaining away PF action is that it is just too persistent.

Hi,

I hope that after your explanation above .. you do not more critisize my informations sources .. because it seems that your sources can not be described as more serious than mine :ok: