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AF 447 Thread no. 4

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AF 447 Thread no. 4

Old 4th Jul 2011, 18:40
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takata,
Thanks for your very careful explanation. It was the word "leg" that I needed to be clarified. Anglophone crews usually use it to mean "sector", i.e., the whole of a flight.
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Old 4th Jul 2011, 19:14
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P3s

I was a CRP of sorts or a P3 on Yorks in the 1950s. We had to have 4 on the flight deck for our trooping contract, for 40 Troops and one RAF AQM. After 230 hours as the fourth man, I did my "Legal Six " T/O and landings with the Chief Pilot. I was promoted to F/O. I must have been good, or impressed, because it was another 600+ hours world wide, from KIN to BKK, as the only other pilot on board, before I did another one ! (I had flown for a longer flight in a glider before my first flight in a York.)
Modern simulators must be better than the Link D2, or earlier, the Ryper Simulators I was trained with, (they were close to the present Control Tower) at Farnborough in 1945. I do not know how much they cost to run, once you have one, as opposed to what is charged per hour.
The early post war civil aircraft were "cheap to buy and dear to fly" ( Sir George Edwards said that he had sold a Viking for £ 35,000.) Now the pattern is reversed - dear to buy and cheap(ish) to fly.
Our passengers paid £75 (1952 pounds) from KIN to UK.
One of a number of French National Gliding Centres used to be between Toulouse and Carcassone. They used to be run rather like an Outward Bound set up, helped by the French Government, to encourage air mindedness...

I am impressed by the amount of ordinary Traffic which had to be available before anything had happened to AF447.
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Old 4th Jul 2011, 19:18
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Originally Posted by Mr Optimistic
What does 'twice in a row' mean - why not continuously ? Doesn't the warning continue until the a/c is unstalled
Stall warning means that the AoA has exceeded a threshold that is several degrees below the AoA at which the airplane stalls. Stall warning continues until the AoA is below that threshold value. IMHO 'twice in a row' means that AoA was just below that threshold, and small 'bumps in the road' caused brief exceedances.



Originally Posted by RetiredF4
2:10:05 - 2:10:20
(...) AOA being 4° at the beginning, raised quickly to above 10, triggering the stall warning (yes, i think that was a valid stall warning). (...)Only 15 sec passed, we are now at FL375 and Pitch is 10° AOA not known but somewhere around 10?
The AoA in level flight at FL350/M.81/275kCAS is 2.55 degrees. 4 degrees is the stall warning threshold at M.81 and would produce about 1.42 g normal acceleration. I don’t think “gee” exceeded approx. 1.4 because it then becomes rather difficult to match several constraints imposed by the FDR data released in the BEA Update. At 10 degrees AoA, M.81 the airplane would be fully stalled, but that didn’t occur here but much later. According to the BEA, “pitch attitude increased progressively beyond 10 degrees” between 2:10:05 and 2:10:50. Therefore I think that the ‘mean’ AoA got close to but did not exceed the S/W threshold at this stage, i.e. the triggering of S/W “twice in a row” was probably due to ‘light chop’ causing some AoA fluctuations between 2:10:15 and 2:10:25.
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Old 4th Jul 2011, 19:26
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Originally Posted by Chris Scott
Not sure exactly what you mean by "calculate", but if not fully capable how could it offer Pitch-Alternate Law?
Hi Chris - what I'm saying is that your initial suggestion was that the "G"-loading system would possibly trim the aircraft nose-up at stick neutral as the speed appeared to decay. What I mean by "calculation" is that if the aircraft systems know that there is an double or triple erroneous airspeed indication, it drops to a mode whereby any protection or flight logic relying on airspeed is disabled. Surely this should be the case with the scenario you're describing - while "G" measurement itself is independent of the air data (thanks A33z), the logic you describe requires that data to work. So without airspeed data, how would the FCUs know to trim the aircraft nose up to maintain "G"?

Originally Posted by vbp.net
To DozyWannabe #657. OK, AS is derived from 3 pitot tubes that could lead to problems if two of them are wrong but close enough to be taken as valid. Then why not compare AS history with GPS derived speed (history) together with thrust/attitude. I mean : compare the trends. If the plane is level flight, if thrust is not changed (even in turbulent weather) and a dire discrepency is noted (IAS significantly increasing/falling while GPS speed no change) wouldn't that be the case that AS should be highly suspected to be wrong ?

I don't mean the A/C should do something with that ! But the pilots might be warned.
Hi, and welcome.

The problem with what you're describing - as with any extra logic - is that you get into the engineering reliability maxim, which is that the more complex one makes a system, the probability of introducing errors also increases. The pilots are warned with the current system - an ECAM message "ADR DISAGREE". It's easy for such messages to get lost in the heat of the moment when things start to go pear-shaped however.

Originally Posted by Smilin_Ed
Why didn't they notice it? It wasn't in their scan because they apparently were trained not to touch the pitch trim wheel(s) since pitch trim is always automatic and since it's automatic, why would you care?
Surely an attitude indicator displaying mostly blue would be a hell of a hint, however - and if you're trying to tell me that the ADI was not part of their scan, then that would highlight a terrifying oversight in their training (I suspect that isn't your position, however).

Also, at present we do not know AF's policy regarding training on the trim wheels. Svarin said that his current airline discourages their use, but he does not - as far as I know - fly for AF.

Originally Posted by bubbers44
I think the inexperienced Colgan pilots resorted to a previous aircraft the captain had flown that had a tailplane stall recovery procedure that was opposite of wing stall recovery. This wasn't a problem in their aircraft and all pilots are taught to lower the nose in a stall, they raised it causing the crash.
That explains the Captain's reaction, but not that of the F/O, who I believe came straight to the Q400 and did not spend any time on the Saab. They both pulled back hard almost simultaneously. It's a well-known tendency for new pilots to instinctively pull back on the stick when receiving a stall warning (or indeed any unexpected shock) and is something that has to be trained out early on. As I recall the inference from the NTSB report on human factors suggested that fatigue and exhaustion may have caused this instinctive reaction to take over.

Something motivated them to pull back and all I can think of is an overspeed warning that was false.
I think if it was as simple as that then that information would have been released in the press note and the report would be coming along a lot sooner - along with a service bulletin or AD relating to the warning systems in the A330/340.

The fact they are holding all the pertinent information back that they have makes me think we will have some big surprises when they finally have to reveal it to the public.
I suspect that the BEA are in the process of a long drawn out human factors investigation to answer that question - these things take time. I don't think they're holding information back any more than any other investigative agency would at this stage, certainly not for any nefarious reasons - I think they honestly don't know (or didn't know at the time of the "note"'s release) why the PF reacted in the way he did. So in answer to your later question (paraphrased) of "why haven't they released the final report?" the answer is simply because it is not ready yet. I've already said several times that I doubt the NTSB or AAIB would be under so much pressure to release information early from some quarters on this board in the way the BEA currently is. Why is that, do you think?

Originally Posted by RR_NDB
And the growing complexity concerns me.
Yet you're still advocating more technical solutions to implement in the design - surely if you were *that* concerned about complexity this would not be the case? The logic implemented in these aircraft (and those FBW airliners from other manufacturers) is actually pretty basic in modern computing terms. Asi I've said many times before it also uses obsolete technology (and always has) because the characteristics of obsolete hardware were already well-understood.

Originally Posted by BOAC
Folks - why waste time on speculation? It is not rocket science to find out who was in the RHS. I guess that IF we need to know BEA will tell us. In any case, does it really matter?
With all due respect (and I do respect you - I remember you may well have "flogged [me] round in a Chippy" in my youth. For this and other reasons I will always think very carefully on the knowledge you share about aviation-related matters) - that's a bit rich.

We've had four threads and hundreds of pages, largely of speculation from people - some of them pilots - who nevertheless either do not/have not flown the Airbus FBW aircraft and/or do not understand the systems - including what they can/can't/will/won't do. These speculations have involved - among other things - wild theories about the computers going haywire due to a lightning strike, long-hidden software bugs coming out of hiding to neuter the unsuspecting pilots' authority and software designers and engineers wilfully ignoring pilots' input and building a confusing system out of hubris and a sense of superiority just for starters. Then we move on to the more subtle, but still noticeable digs at the technology - e.g. "confusers", "HAL", that old chestnut "Airbus one man/one dog flight deck" and an intent on the part of engineers to "reduce pilots to systems operators and monitors".

I realise that it is a privilege to talk with you all as a non-aviator myself, but if you can find me an aeronautical engineering forum where an undercurrent of disrespect towards pilots of that magnitude exists, then I believe you would consider it the height of rudeness and complain vociferously. Taking this attitude on the chin is IMO a small price to pay for what I get out of the time I spend on here, but I do ask that you think about what you're saying sometimes.

For the record, at present there is *no* evidence that the pilots were ever "confused" by what they were presented with. Alarmed, certainly - and with good reason - but not confused. There is also no evidence of any overspeed indication, no evidence of software-commanded flight controls outside of what was coming from the PF's sidestick and no evidence of any departure from their intended flight path which caused surprise. When the report arrives, we'll know better. It's also worth remembering that while we pore over the ACARS messages and the apparent crew actions, that the crew were not trying to diagnose the situation based on ECAM messages alone, but with a full set of available and functioning instruments with the brief exception of airspeed. I'm pretty sure that the "WRG" message, as I said before, was simply the FCUs playing catch-up with the already-triggered pitot data failure message, which would have led to the "ADR DISAGREE" message appearing on the flight deck. We're talking seconds and fractions of seconds here - in human terms, the computation delay was minimal.
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Old 4th Jul 2011, 19:37
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HN39, OK but eventually the AoA went well over and the aircraft stalled. It is inconceivable that somehow the fwd speed got to 60knots unstalled, so at some stage it should have been continuous until the fwd speed did indeed reach 60kts. One can only surmise that knowledge of previous false stall warnings in UAS conditions were somewhere present in their minds but if the plane was flown upto and into a stall wouldn't the warning have been somewhat insistent ? Is there some other condition of validity which would silence it ?
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Old 4th Jul 2011, 19:37
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Searching

PJ2
You may find Google more effective in searching PPruNe.
A search on "pprune pj2 rr-ndb" will show all your posts in which rr_ndb is mentioned and conversely all posts from rr_ndb in which pj2 is mentioned.
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Old 4th Jul 2011, 20:19
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Originally Posted by Mr Optimistic
OK but eventually the AoA went well over and the aircraft stalled. It is inconceivable that somehow the fwd speed got to 60knots unstalled, so at some stage it should have been continuous until the fwd speed did indeed reach 60kts. One can only surmise that knowledge of previous false stall warnings in UAS conditions were somewhere present in their minds but if the plane was flown upto and into a stall wouldn't the warning have been somewhat insistent ?
About 40 seconds later at 2:10:51 the stall warning was triggered again. The airplane probably stalled between 5 - 10 seconds after that, just before reaching its apogee of FL380 at 2:11:06. The airspeed probably remained above 120 kCAS during the descent. The low indicated speeds of 60, then 30 kt were caused by pressure disturbances at extreme AoA - the pitot pressure being lower than the free-stream total pressure and the pressure at the static source being higher than the ambient pressure.
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Old 4th Jul 2011, 20:19
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Originally Posted by Chris Scott
what topics YOU THINK are relevant
- well, in respect of this thread, this one of yours is not.,
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Old 4th Jul 2011, 20:27
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Hi DozzyWannabe,
Then we move on to the more subtle, but still noticeable digs at the technology - e.g. "confusers", "HAL", that old chestnut "Airbus one man/one dog flight deck" and an intent on the part of engineers to "reduce pilots to systems operators and monitors"….. but if you can find me an aeronautical engineering forum where an undercurrent of disrespect towards pilots of that magnitude exists
Will this do?

"Flying for the airlines is not supposed to be an adventure. From takeoff to landing, the autopilots handle the controls. This is routine. In a Boeing as much as an Airbus. And they make better work of it than any pilot can. You're not supposed to be the blue-eyed hero here. Your job is to make decisions, to stay awake, and to know which buttons to push and when. Your job is to manage the systems."
— Bernard Ziegler, former Airbus Senior Vice President for Engineering.
Great Aviation Quotes: Piloting
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Old 4th Jul 2011, 20:44
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Originally Posted by rudderrudderrat
Bernard Ziegler
*sigh*

We've already dealt with Ziegler on this very thread and others, at great length. An intelligent and gifted pilot with a flair for communication certainly, but some of the things he said weren't very diplomatic or clever*. Airbus has long since adopted a very different line, and dragging that old quote up is not unlike us software folks having a giggle at Bill Gates' alleged "640k should be enough for anyone" statement in 1981 - by which I mean it's an entertaining and valuable lesson in hubris from a point in history, but in no way relevant to the current state of affairs.

He was there to make headlines to support sales, not determine engineering practices, and as such I'm also pretty damn sure that there were Airbus engineers just as mortified by some of those statements as some pilots were.


* - As has also been stated, he is now a very elderly and frail man, so I have no wish to haul him over the coals again.

Last edited by DozyWannabe; 4th Jul 2011 at 21:21.
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Old 4th Jul 2011, 20:47
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All the required data is available with current FDR´s?

Hi,
DW,
Yet you're still advocating more technical solutions to implement in the design - surely if you were *that* concerned about complexity this would not be the case? The logic implemented in these aircraft (and those FBW airliners from other manufacturers) is actually pretty basic in modern computing terms. Asi I've said many times before it also uses obsolete technology (and always has) because the characteristics of obsolete hardware were already well-understood.
The use of the "obsolete" building blocks is not a reason to allow a simpler analysis, as you know. My concern is if we really have a "sufficient recording" to understand EVERYTHING that (possibly) happened during certain moments. Suppose during a glitch (a time dependent failure, not stable). Like the one Svarin discussed or other possible reasons that could affect the "output" of the "engineering black box". The always concerning, Testability issue.

I am thinking on that and preparing to answer PJ2 and to CJ post.

I hope i am wrong with this suspicion. If wrong will be better. My objective is to raise only important and relevant issues.

I am busy during this week but "in parallel" watching the thread, posting when possible after considering useful.

Last edited by RR_NDB; 5th Jul 2011 at 09:48. Reason: Text impvmt
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Old 4th Jul 2011, 20:49
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One mo'time

Salute!

First, I'd like to address the concern/question by Doze.

You do not need "q" or total pressure to trim the jet for a gee ( Nz). And it is disturbing to find from A33Z that the FLCS uses the same attitude reference system that is displayed to the crew. Hence, I continue to question some basic design implementations for the 'bus. It is too easy for the FLCS to have internal accelerometers and rate sensors and even air data sensors besides those the displayed to the crew. A layer of redundancy and a "core" system we humans can rely upon. If those embedded sensors go to "east jesus", then we're flat-a$$ outta luck. Sierra happens.

There are too many autopilot and "convenience" features that degrade one by one until in the "direct law". TOGA for engines and FLCS, "flare", Alt 1, Alt 2, sheeesh!

Once there's a problem, the basic flight control laws should be very clear from an aero aspect and a crew aspect. We don't need bank angle "protection"/overspeed "protection" and such in various modes. What we need is a well-designed plane that has basic control laws that 99.9% of the pilots can fly using basic airmanship. And not be concerned with losing one thing or the other along the way.

The 'bus looks to be a very well designed jet, or you couldn't have a "deep" stall, or a deep stall, for over 3 minutes without going into a spin or worse.

So I will continue to advocate a very straightforward system that has a myriad of autopilot functions as "inputs", not "protections". Once the A/P disconnects, the jet reacts to pilot inputs in a very straightforward manner. I fully understand control surface deflection rates, aero gains, etc. I fully understand why the THS trims to retain elevator effeciveness ( will be a contributing factor in final report, IMHO). I would not want to fly a jet that moves the elevator or commands spoilers and ailerons at the maximum possible rates regardless of the "q" or mach. But when those values are unreliable, the jet must still be flyable and not have all the "protectons" commanding stuff that we pilots don't want or need at that moment. Just let us fly the basic plane!!!

sorry for the rant. ....

Last edited by gums; 4th Jul 2011 at 20:54. Reason: added stuff
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Old 4th Jul 2011, 20:50
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Moore ´s law affecting all designs

Hi,

DW
Bill Gates' alleged "640k should be enough for anyone"...
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Old 4th Jul 2011, 21:02
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Now it has quietened down again, can I ask if anyone knows exactly which other bits of RHS 'important' data (apart from IAS) are not recorded?

Thank you, Gums.
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Old 4th Jul 2011, 21:13
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K.I.S.S. plane behavior in all situations

gums

What we need is a well-designed plane that has basic control laws that 99.9% of the pilots can fly using basic airmanship. And not be concerned with losing one thing or the other along the way....So I will continue to advocate a very straightforward system that has a myriad of autopilot functions as "inputs", not "protections". Once the A/P disconnects, the jet reacts to pilot inputs in a very straightforward manner. I fully understand control surface deflection rates, aero gains, etc. I fully understand why the THS trims to retain elevator effeciveness ( will be a contributing factor in final report, IMHO). I would not want to fly a jet that moves the elevator or commands spoilers and ailerons at the maximum possible rates regardless of the "q" or mach. But when those values are unreliable, the jet must still be flyable and not have all the "protectons" commanding stuff that we pilots don't want or need at that moment. Just let us fly the basic plane!!!

Perfect!

Or a plane (a/c+crew) that never do K.I.C.S. things sometimes.

C.=Complex
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Old 4th Jul 2011, 21:14
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Originally Posted by gums
But when those values are unreliable, the jet must still be flyable and not have all the "protectons" commanding stuff that we pilots don't want or need at that moment. Just let us fly the basic plane!!!
Again, gums, where is the evidence that the flight computers did anything they were not commanded to by the handling pilot? The whole point of the graceful degradation in laws is that the guy in the seat notices as little difference in how he was handling the aircraft before compared to how the aircraft handles if something has gone south as possible!

You've basically just described the A330 (A320, A340, A380) and B777!
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Old 4th Jul 2011, 21:21
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Along the lines of what Gums is talking about, It should be possible to measure roll rates achieved for small control deflections and then properly set roll gain after a loss of airspeeds thereby avoiding having to go to a roll direct law (Alt 2). Subsequent control inputs would update the gains. If in dead still air, the system could periodically recalibrate with small doublet inputs.
If wing flexibility causes delays in sensing, you could put accelerometers in the wings to get more timely information.
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Old 4th Jul 2011, 21:22
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Originally Posted by DW
Again, gums, where is the evidence that the flight computers did anything they were not commanded to by the handling pilot? The whole point of the graceful degradation in laws is that the guy in the seat notices as little difference in how he was handling the aircraft before compared to how the aircraft handles if something has gone south as possible!
- may I (as an aeronautically trained engineer, of course...) ask you

Where is the evidence it did not? and

is not the second part of your para the whole nub of the accident? They would 'appear' not to have noticed.

Machinbird - yes, let's put even more electronics and gizmos in the loop to go wrong. Look! We can have a whole extra page of ECAMS, bells, whoops and God knows what. What gums and I and a few others want to see is a stick that just moves the ailerons, and pilots who can use it..
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Old 4th Jul 2011, 21:41
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Originally Posted by BOAC
Folks - why waste time on speculation?
BOAC, sir, I'm getting mixed signals from you.

I took this post of yours as a well-intentioned move to stick to the evidence at hand, and when I ask a reasonable question of gums - namely whether he has any proof that the aircraft did not do exactly as the PF commanded (suspecting that he has no more evidence than I), I get a dose of whataboutery from your good self!

I want to make it crystal clear that at no point have I directly speculated on the actions of the crew. I can assure you that any refernce I have made to other accidents such as Birgenair and Colgan Air have been purely for the purposes of providing background information. Am I now to understand that speculation on possible mishandling by the crew despite a largely functioning airliner is beyond the pale, yet myriad speculatory accusations of poor design and engineering practices putting the helpless crew in an aircraft that was, for want of a better phrase, trying to kill them is somehow tolerated?

Talk about your double standards...
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Old 4th Jul 2011, 21:46
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Re HazelNuts39

Quotes all HazelNuts39
The AoA in level flight at FL350/M.81/275kCAS is 2.55 degrees.
The speed was .8M for turbulence, as the crew stated. Or do you say, they where still in decelerating mode? The AOA value was reached by the sudden pitchup to 10° pitch, which needs an acceleration and changes the stall AOA significantly. I cant tell you the numbers for the bus, but an AOA gauge in front of my nose taught me that over a considerable flying time.

4 degrees is the stall warning threshold at M.81 and would produce about 1.42 g normal acceleration. I don’t think “gee” exceeded approx. 1.4 because it then becomes rather difficult to match several constraints imposed by the FDR data released in the BEA Update.
Which one, please elaborate.

At 10 degrees AoA, M.81 the airplane would be fully stalled, but that didn’t occur here but much later. According to the BEA, “pitch attitude increased progressively beyond 10 degrees” between 2:10:05 and 2:10:50. Therefore I think that the ‘mean’ AoA got close to but did not exceed the S/W threshold at this stage, i.e. the triggering of S/W “twice in a row” was probably due to ‘light chop’ causing some AoA fluctuations between 2:10:15 and 2:10:25.
On what fact do you ground your statement?
The speed sure as hell was already decreasing after the initial exaggerated pullup, so it was not .80 Mach any more after the start of the pitchup. At 02:10:20 FL 375 was reached graph from A33Zab, at 02:10:55 TOGA was selected and at 02:11:00 FL380 (apogee) was reached. That is a 500´feet altitude gain in 40 seconds. Its prudent to assume, that the initial climb rate was higher, decreasing to zil, and increasing again after TOGA selection (02:10:55 TOGA, 02:11:07 the speed was 185 valid and pitch and AOA 16°. So most of the beyond 10° pitch in that timeframe produced only AOA and not much climb at all.(Aircraft level flight at 10° pitch resembles 10° AOA. And yes, it was stalled, therefore the stallwarning was present and then TOGA selected.

It does not make sense to compute the angle of attack under steady and unchanged lab conditions. The ship was handflown with changing speed and pitch and later on power in unfavourable WX conditions with limited or no protections in an altitude they couldn´t reach just one minute before. Any change of pitch first adds to the AOA. and only leads to change of climb rate (and therefore flight path vector, which influences AOA) with a delay, if the lifties say "Yes" to the pitch change.

Last edited by Jetdriver; 4th Jul 2011 at 23:05.
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