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AF447 Thread No. 3

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AF447 Thread No. 3

Old 6th Jun 2011, 14:22
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The MD-80, fus 909, improperly flown by an FAA pilot, was repaired, used again in flight test, then sold to an airline.

The 757 pitot static accidents would have had exactly the same outcome with any other airplane, and not the fault of the 757. All the Birgenair Capt had to do was reach forward, and rotate the AIR DATA switch from NORM to ALT. These were not accidents during flight test.

No doubt the A330 design team learned from their flight test accident, but comparing it to AF447, I'm not sure what they learned.
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Old 6th Jun 2011, 14:49
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Originally Posted by Graybeard
The MD-80, fus 909, improperly flown by an FAA pilot, was repaired, used again in flight test, then sold to an airline.
If that damage had happened on the line, it would have been written off.

The 757 pitot static accidents would have had exactly the same outcome with any other airplane, and not the fault of the 757. All the Birgenair Capt had to do was reach forward, and rotate the AIR DATA switch from NORM to ALT. These were not accidents during flight test.
As I understood it, prior to Birgenair that option was not easily available. The AIR DATA switch was retrofitted afterwards.

No doubt the A330 design team learned from their flight test accident, but comparing it to AF447, I'm not sure what they learned.
The only way that's relevant is if you assume AF447 to be a mode confusion accident, which isn't supported by any of the evidence we have so far. Losing Nick Warner and the other test pilots was a tragedy, but as SLF I'd far prefer such things to be found in testing than on the line.

While I'm on the subject, Boeing lost a 707 on a test flight with a Braniff crew (with a Boeing test pilot at the controls). This is not a Boeing/Douglas/Airbus competition, we want all the aircraft to be safe, and no amount of transatlantic sniping is going to help that.

Last edited by DozyWannabe; 6th Jun 2011 at 21:00.
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Old 6th Jun 2011, 15:27
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Originally Posted by rudderrudderrat
I think it's a pity that the PNF was unaware of the stick inputs being made by the PF (due AB design). If they had control sticks which moved in response to the the other stick input - maybe the PNF would have recognised the stick full back requests?
Correct. Even better with the usual control column, the Captain standing behind could have also contemplated what kind of inputs were applied ...

Graybeard,
Is the Toulouse A330 accident report on the BEA site ... ?
At 23% the take off CG was very much FWD for AF447.

alex_brin,
You can quote as many newspapers as you like ... what does it worth when they all refer to the same single source France-Inter ... !?
Data belong to the BEA ... well, where are the 'leaks' coming from ... ?
If Polaco has privileged information, why don't the BEA just include it in its public note ... ?

Machinbird,
There is absolutely no demand for the report right now, the BEA will take the time necessary.
There is a request for the data, nothing more, and certainly not that pseudo communication.
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Old 6th Jun 2011, 15:32
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Dozy:
As I understood it, prior to Birgenair that option was not easily available. The AIR DATA switch was retrofitted afterwards.
You understood it wrong. On every 757/767, there is a row of five switches just outboard of each pilot's EFIS with NORM/ALT selections for IRU, A/P, ILS, EFIP and Air Data. The EFIP is the symbol generator for the EFIS. The ALT selection engages the third set of Autoland Critical items. Air Data is not Autoland Critical, so there are only two ADC.

Going back to my original question: "When was the last time an airliner was lost in flight test? There haven't been an A300, A310, A320, A340 or A380, have there? You have to go back to the 707 or BAC1-11.

You don't like the A vs. B comparison: how about A vs. Fokker?
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Old 6th Jun 2011, 15:40
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Post on Avweb

There is an interesting letter from a confirmed but anonymous A330 pilot on this weeks AvWeb , it's about halfway down the page below the podcast that refers to 447.
Sorry I can't link directly to letter
AVwebFlash Complete Issue
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Old 6th Jun 2011, 15:50
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Originally Posted by Graybeard
Going back to my original question: "When was the last time an airliner was lost in flight test? There haven't been an A300, A310, A320, A340 or A380, have there? You have to go back to the 707 or BAC1-11.
Yes, because both were significant advances in technology and design (swept-wing jet transport in the case of the former, early T-tail design in the case of the latter). Boeing basically rested on their laurels and designed more-of-the-same-only-slightly-different right the way up to the late '70s, and even then the 767 and 757 were slight evolutionary changes. The gradient from that to the A32/3/4/80 was as much of a leap as the 707 was over the Stratoliner in many respects. Boeing's engineers themselves admitted that had the Comet not blazed the trail, they'd have probably made the same mistakes with the overrotation and metal fatigue aspects of the design with the 707. It seems every manufacturer learns the hard way at least once and Airbus is no exception.

But again there is no evidence that sidestick philosophy or mode confusion played any part in AF447, despite the number of people wishing it was so (I note CONF again forgetting that the PF was well aware of the occupant of the LHS taking control, which is one of the few things we do know about the flight deck atmosphere), so all we're doing is rehashing old arguments that are essentially a matter of personal preference and have no relevance to the subject at hand.

In fact, with the autopilot known to be offline in the case of AF447, it is a certain fact that the A330 test flight accident has no relevance, as it was an autoflight mode confusion problem - and one that was remedied long ago to boot!
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Old 6th Jun 2011, 16:10
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Confiture:
quote:
Originally Posted by rudderrudderrat
I think it's a pity that the tPNF was unaware of the stick inputs being made by the PF (due AB design). If they had control sticks which moved in response to the the other stick input - maybe the PNF would have recognised the stick full back requests?
Correct. Even better with the usual control column, the Captain standing behind could have also contemplated what kind of inputs were applied ...
No need for mechanicall movement to keep PNF aware of the control inputs, a vector display would work well. Lenght and direction of vector (line from a central "0" dot) would show the inputs.

Dozywannabe:
But again there is no evidence that sidestick philosophy or mode confusion played any part in AF447, despite the number of people wishing it was so (I note CONF again forgetting that the PF was well aware of the occupant of the LHS taking control, which is one of the few things we do know about the flight deck atmosphere), so all we're doing is rehashing old arguments that are essentially a matter of personal preference and have no relevance to the subject at hand.
This is not about "awarenes" of who has control, it is about the PNF being able to follow what is going on, without knowledge of the control inputs in the several minutes before taking control he may not have been aware of the (almost) constant NU input.
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Old 6th Jun 2011, 16:20
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What part of "pilots were in the loop during requirements gathering" are you failing to understand?
DW, you don't need to use that as an excuse: engineers did a very good job building the A320.

On the pilot side however, how deep "in the loop" or enthralled they were is questionable. They missed some important details and some of them had to be corrected later.
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Old 6th Jun 2011, 16:24
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Avweb.com A330 Article

Here it is, posted for you to read. Source is Avweb.com. Hope you guys flying the 'bus are on the top of your game.
Letter of the Week: Airbuses Fly "Like a Video Game"


I would like to offer my comments and perspective with regard to the Air France Flight 447 accident. I have been a A-330 captain since 2003 and have over 4500 hours in the aircraft. While many A-320 pilots undoubtedly have more series time, I believe this probably makes me one of the most experienced A330 pilots in the world.

When asked how I like the aircraft, I tell people that there is likely no easier airplane to take over an ocean, and that the systems design and presentation is superb. That said, the automation is more complex and less intuitive than necessary, and the pilot-aircraft interface is unlike that of a conventional aircraft. Most important with regard to this accident is the fly-by-wire sidestick control. The sidestick itself has a very limited range of motion, making inadvertent over-control very easy. Of even greater significance, the stick itself provides no "feel" feedback to the pilot. That is, unlike a conventional aircraft, the pilot does not get a sense through pressure of how much input is being sent to the control surfaces. The most important advice I give to pilots new to the Airbus is to treat the aircraft not as an airplane, but as a video game. If you wait for the sidestick to tell you what you are doing, you will never get an answer.

Taking into consideration that Air France 447 was at FL 350 (where the safe speed envelope is relatively narrow), that they were in the weather at night with no visible horizon, and that they were likely experiencing at least moderate turbulence, it does not surprise me in the least that the pilots lost control of the aircraft shortly after the autopilot and autothrust disconnected.

Let's keep in mind that these are not ideal conditions for maintaining controlled flight manually, especially when faced with a sudden onslaught of warning messages, loss of autofllght, confusing airspeed indications, and reversion to "alternate law" flight control, in which certain flight envelope protections are lost.

A very bad Airbus design feature is thrust levers that do not move while in autothrust. They are instead set in a detent which would equal climb trust in manual mode. If the pilots did not reset the thrust levers to equal the last cruise power setting, they likely eventually ended up in climb power, making it difficult to reset the proper cruise power setting and adding to what was likely already a great deal of confusion.

But the real problem probably occurred immediately after the pilot flying grabbed the sidestick and took over manually. Unfortunately, airline pilots rarely practice hand-flying at high altitude, and almost never do so without autothrust engaged. As a result, we forget that the aircraft is very sensitive to control inputs at high altitude, and overcontrol is the usual result. Because the Airbus sidestick provides no feedback "feel" to the pilot, this problem is dramatically compounded in this aircraft.

I believe the Air France pilot grabbed the sidestick, made an immediate input (because as pilots, that's what we tend to do), and quickly became quite confused as to what the aircraft was truly doing. This confusion likely was exacerbated by fixating on airspeed indications that made no sense while trying to find a power setting with no airspeed guidance.

When transitioning from autopilot to manual control at altitude in the Airbus, the most important thing to do at first is nothing. Don't move a thing, and then when you do, gently take hold of the sidestick and make very small inputs, concentrating on the flight director (which, in altitude hold, should still have been providing good guidance). Of course, this is much easier said than done with bells and whistles going off all over the place, moderate turbulence and a bunch of thunderstorms in the area. As I said before, treat it like a video game.

So why did the Air France pilot find himself at the limits of sidestick travel, and then just stay there, maintaining a control input that simply could not logically be correct? When things go really bad and we are under intense pressure, it is human nature to revert to what we know from previous experience. Remember, the Airbus flies like no other aircraft in that the sidestick provides no feedback to the pilot. It is a video game, not an airplane.

I believe the Air France pilot unintentionally fell back on all of his previous flying experience, in which aircraft controls "talkedF" to him when he moved them. Distracted by many confusing inputs, he instinctively expected to be able to control the aircraft by "feel" while dividing his attention to address other matters. I've seen it happen in the simulator, and in an Airbus this is a sure way to lose control of the aircraft and is possibly the most dangerous aspect of Airbus design philosophy.

One last note: Airbus pilots often claim that the aircraft "can not be stalled." When the flight controls are in "normal law" this is a reasonably true statement. However, in "alternate law," as was the case here, stall protection can be lost. If we ever practiced this in the simulator, I don't remember it.

Lest anyone think I am blaming the Air France pilots for this accident, let me be clear. Despite all of my experience in the aircraft, I am not the least bit certain that I would have been able to maintain control under the same circumstances. I do feel certain that were you to spring this scenario on pilots in a simulator without warning less than half of them would have a successful outcome. Safely flying the 320, 330 and 340-series Airbus requires something of a non-pilot mindset.
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Old 6th Jun 2011, 16:43
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How accurate is the statement that this captain made regarding his time in the A330? 4500 hours in this aircraft would make him/her one of the most experienced pilots in the world on the A330?
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Old 6th Jun 2011, 16:52
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"Lest anyone think I am blaming the Air France pilots for this accident, let me be clear. Despite all of my experience in the aircraft, I am not the least bit certain that I would have been able to maintain control under the same circumstances. I do feel certain that were you to spring this scenario on pilots in a simulator without warning less than half of them would have a successful outcome. Safely flying the 320, 330 and 340-series Airbus requires something of a non-pilot mindset.Lest anyone think I am blaming the Air France pilots for this accident, let me be clear. Despite all of my experience in the aircraft, I am not the least bit certain that I would have been able to maintain control under the same circumstances. I do feel certain that were you to spring this scenario on pilots in a simulator without warning less than half of them would have a successful outcome. Safely flying the 320, 330 and 340-series Airbus requires something of a non-pilot mindset."

Vett this or no, this states the challenge in basic terms. "Informed Perception", or one could say, "Intuition". The conflict was historical in 1960, When Mercury saw the astronauts lining up on the side of the "sticks" or the engineers.

Airbus brought this conflict to the fore, right or wrong. In building an a/c that embraces the left brain approach, aviators took a second seat. Now call this parochial or ego driven, there is a "Factor of Flight" in play.

On the one side, folks can recall the "record". This, to me, is missing the point.

Without a definition of the challenge, anecdotalism merely muddies the water.

I note a very astute gent here who argues well his points. With respect, I note how utterly blind is this man to the fundamental challenge. On t'other side, the old "sticks", who seem to be immersed in nostalgia.

This is NOT "preference", this is brain architecture. I am amazed at my son and his friends, who, after gaming one game for some time, know it completely, beat it completely, and then look for a new game. These are the future pilots, imo. As long as the game doesn't glitch, all are happy.

Problem solving? IMO the really good players can't do math, and cannot perform without "rules". If the game goes south, they get furious, immediately. "something's wrong with the game".

Last edited by bearfoil; 6th Jun 2011 at 17:06.
 
Old 6th Jun 2011, 17:04
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Notwithstanding the thousands of words that have been written in Pprune about the AF447 crash, its causes seem reasonably clear, at least to me. I would suggest the following:
  • Cause No 1 - A failure of navigation by the crew in allowing their aircraft to fly too close to, or through, dangerous Cb systems.
  • Cause No 2 - Icing up of most, if not all, of the aircraft's pitot heads leading to the flight computers and flight crew having no source of reliable airspeed measurement.
  • Cause No 3 - Based upon the information released so far, by the BEA, the flight crew did not appear to have a proper understanding of their flight situation after the automatics disconnected and hence, did not apply the right corrective actions (flying with appropriate pitch/thrust settings) which would have prevented their aircraft from stalling into the ocean.

There has been some discussion in this thread about what might be done to overcome pitot icing problems. An idea (probably crackpot) occurred to me of a pair of extra retractable 'standby' pitot heads, normally housed within the fuselage in a heated compartment, which could be deployed in the airstream in the event of the normal pitots icing up. Even if these 'standby' units only worked for a few minutes, it might be long enough for a crew to recognise that their actual airspeed was OK and that they should fly appropriate pitch/thrust settings. Also, iced 'standby' pitot heads could be retracted and warmed/de-iced within the fuselage before further deployment into the airstream.
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Old 6th Jun 2011, 17:10
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Originally Posted by Machinbird
Here it is, posted for you to read. Source is Avweb.com. Hope you guys flying the 'bus are on the top of your game.
Interesting article, I admit, since it's not from a flight simmer but an A330 pilot.
Thanks, Machinbird !

Of even greater significance, the stick itself provides no "feel" feedback to the pilot. That is, unlike a conventional aircraft, the pilot does not get a sense through pressure of how much input is being sent to the control surfaces.
Correct me if I'm wrong, but hasn't "artificial feel" been around for a very long time for conventional powered flying controls ?
And isn't that "artificial"? I.e., it bears no direct relation to the "input" to the control surfaces (or the control surface hinge moment, if you prefer)?
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Old 6th Jun 2011, 17:23
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Originally Posted by ChristiaanJ
Correct me if I'm wrong, but hasn't "artificial feel" been around for a very long time for conventional powered flying controls ?
And isn't that "artificial"? I.e., it bears no direct relation to the "input" to the control surfaces (or the control surface hinge moment, if you prefer)?
You're exactly right - if I may betray just how much of a nerd I am, I believe the phrase is "The yoke is a lie".

@MurphyWasRight - I know what you're saying and I agree, however who was doing what and when is not known at this point and what we have is a bunch of people who are trying to hammer this incident into a shape that follows their particular bugbears with the Airbus FBW system.
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Old 6th Jun 2011, 18:07
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ChristiaanJ:
Quote:
Of even greater significance, the stick itself provides no "feel" feedback to the pilot. That is, unlike a conventional aircraft, the pilot does not get a sense through pressure of how much input is being sent to the control surfaces.
Correct me if I'm wrong, but hasn't "artificial feel" been around for a very long time for conventional powered flying controls ?
And isn't that "artificial"? I.e., it bears no direct relation to the "input" to thecontrol surfaces (or the control surface hinge moment, if you prefer)?
The difference here is not between direct (cable to surface/C172) or artificially generated (input/airspedd/some function = force) feeedback but between tactile feedbback and NO feedback at all.

If I understand correctly the Airbus sidesticks do not provide any feedback, they are "input only".

Last edited by MurphyWasRight; 6th Jun 2011 at 18:13. Reason: Fixed nested qoutes that scrambled meaning.
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Old 6th Jun 2011, 18:17
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@MurphyWasRight - Yes, but there are solid design decisions behind them being that way.
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Old 6th Jun 2011, 18:24
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DW: @MurphyWasRight - Yes, but there are solid design decisions behind them being that way.
May well be, any isolated design decision considered without the full context can often appear sub-optimal.

I was just pointing out no matter if "right or wrong" (given full context) that the lack of feedback is a significant departure from other designs.

The step from direct to "generated/artificial" feedback is minor compared to "from feedback to no feedback".
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Old 6th Jun 2011, 18:37
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The old-style control column provides feedback, but that is dependent on a separate set of pitot tubes. If those were to ice up the feedback could well become incorrect as well. However it is easy to see what is happening, and to determine how much the control column/engine controls have been moved away from neutral. For example if you had full back stick with a conventional control or full thrust with conventional throttles, you would see/feel it straight away. That makes it easier to decide if the airplane is working as it should, and you could fly it even without instrument indications. Take for example a spin; if you neutralise the controls and close the throttles you could reasonable expect the airplane to recover. The Vampire had a white line painted on the instrument panel to align the stick in the event of a spin recovery, since the stick was offset a little with wings level. How would you do that in a 'Bus?

The 757 accidents were caused by, in one case, tape over the static ports and mud wasps in the pitot tubes in the other. In both cases the airplane was flyable, if the crew had used the inoperative pitot/static checklist and procedures. Poor training perhaps? They both had GPS speed and heading, attitude etc. Altitude was not available for one of those crews but depressurizing would give them an independent altitude from the cabin altimeter. Smashing the glass in the standby altimeter perhaps would work as well after depressurising?

Why did this AF crew not know what was going on and what to do about it? If we could know that we could stop a similar accident in the future, but perhaps it should now be expected that a crew will not be able to handle an all-automatic airplane without those automatics. Some fighters are designed that way but they have ejection seats.

I never did acept that easy means better, when it comes to airplanes. I relish the chance to do something that is harder than it maybe needs to be, and look forward to approaches at minimas or takeoffs at high weight/density altitude. I like to fly floats, skis, night VMC etc and cannot understand the delight the 'Bus pilots take in their fully automatic machines, with a lunch table instead of a stick.
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Old 6th Jun 2011, 19:00
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Originally Posted by MurphyWasRight
I was just pointing out no matter if "right or wrong" (given full context) that the lack of feedback is a significant departure from other designs.
But the other designs were based around trying to mimic the behviour of flight controls as they were in the '30s and '40s. At some point you have to start with a clean sheet of paper and go "what do you really need to fly this aircraft?". I think the Boeing back-drive system as used in the 777 is a marvel of design, but in raw engineering terms it adds a level of complexity** to the implementation that it seems the Airbus guys felt wasn't warranted (Let's face it, applying FBW - space-age control systems* - to an airliner was enough of a jump in complexity to start with).

The step from direct to "generated/artificial" feedback is minor compared to "from feedback to no feedback".
To be more precise, it's going from "visual/tactile" feedback to "visual only". And yes, that has some drawbacks, but it's not the danger some like to paint it as. The fact is that since the '50s airliner design mandated that cable controls were no longer sufficient to move flight surfaces, and what you've had since is a plethora of mechanical (and in the case of the 777, software) devices to replace that feedback loop artificially.

Now, in a trainer, where you need to feel what the other person is doing that feedback loop is necessary. In an airliner with manual reversion (of which - excluding the 737 - there aren't many flying these days) then the combined pull on the columns can gain you extra leverage, so it's necessary. In a modern airliner where the flight controls are fully hydraulic and/or electronic then that feedback channel serves little or no purpose.

No-one knows at this point what the PNF was thinking, we also know very little of what he said. He had an ADI in front of him that would have been telling him that the aircraft was going nose-high. Surely any pilot in that situation would turn to his or her colleague and say "are you doing that?". The fact is that we don't know - and these endless rounds of speculation are for the most part just people with grievances against Airbus giving them a kicking.

[* - Did you ever hear Buzz Aldrin complaining that he couldn't feel what Neil Armstrong was doing on his sidestick? I'd like to hear some of the naysayers try to relegate those guys to "systems operators" ]

[** - In engineering terms "complexity" = "more components that can go wrong" ]
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Old 6th Jun 2011, 19:09
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Sorry - Any evidence of Pressure Sensor Icing?

I do apologise for not reading more than a few pages of posts. But maybe a few other latecomers will also not pick up what the general feeling is at the moment

I was re-reading the BEA report and I can't see any evidence whatsoever for pitot etc icing.

The computers seemed to be experiencing wild fluctuations in speeds. When the speeds became very low, the computers marked them as unreliable. But they were consistent. Surely icing has the opposite effect - readings would be very slow moving, and inconsistent (- why would two sensors fail simultaneously) ?

So what I'm thinking is, at the time, we saw the automatic reporting messages mentioning invalid speeds and we all thought it must be icing. Now we see all this stalling and people are still clinging on to the speed indicators being incorrect.

What is the current feeling? - it looks to me as though the pilots had the instruments working most of the time.

Did vicious vertical air movements trigger an upset which the intended behaviour of the computers unfortunately led to the crew getting disoriented?

Is that where we are at the moment?
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