I believe it depends on the mode of icing - if the drain-holes did NOT become blocked and the forward opening DID, with the static ports unblocked, then the pressure within the pitot drops toward static, leading to a low speed (ultimately zero) reading. Given that pitot heating was ON, then icing of the leading port ONLY is the most likely scenario. Particularly given the fact that the speeds appeared to recover and read correctly a little later in the sequence (assumption being that heating led to the ice melting...).

Given that you note you have NOT read the entire thread (which is a task, but really the only way to avoid rehashing half-baked ideas), I'm loath to state anything more than you are quite a long way from the current line of thinking. There is little contention that the pitots iced, leading to AP and AT disconnect (per design) with the crew taking manual control in ALT law... it was uphill from there out.

:sad:

Thanks for the chart, it shows that there is feedback between sidestick position and force that is "local" but that does not provide tactile feedback to the pilot regarding the requested inputs affect on the aircraft.

In the "old school" derived from original direct cable controls (later emulated via artificial feel) the same chart would have opposing forces generated by "artificial feel", harder to push if speed higher or whatever.

I don't have an informed opinion on whether this lack of artificial feedback is a "good thing" or not, just wanting to be clear, in my own mind at least, on how it works.

Despite the lack of "informed opinion" I will guess that feedback might not be that helpfull since the relatively limited range of motion makes this as much as "force" sensor as position. That combined with different meaning of inputs across the laws would create yet another layer of possible confusion.

I cannot find the post of PJ2 from above in which he mentions a schematic and neither can the search facility.
I believe that with fbw we have created two classes of pilots.We have the old school who are probably better polers and have been brought up on tactile feedback through feel,and sound of their aircraft and those who have only flown an electric jet where the aircraft has never let them down.The latter have flown in alternate and direct laws only in the simulator and trust the automation implicitly because normally it always works.They are used to a low workload and probably the odd single failure not the multiple that would have been introduced by unreliable airspeed..
The former do not like the fbw as it does not fly like a proper aircraft,the tactile clues such as engine noise,pitch changes with large power changes ,the nose dropping in turns unless you put in a little nose up pitch are all missing.The thing they hate most is that you do not have a direct stick to control surface relationship and you cannot feel your colleagues inputs through the sidestick..who is the better pilot and who is better at dealing with unusual situations?
I believe that Airbus decided that the weak link is the pilot and they do not want you flying the aircraft.They also want to make it easy to use low experience pilots in their aircraft but this is fine until some real stick and rudder skills are required.What happens then if you never learned these skills?Perhaps the lessons of AF 447 will show us.

Dozy, I appreciate your stubborn defense of this design decision, but do not accept from that side of the rooom, as it were, that the decision necessarily allowed for the "right" balance between man and machine in the man-machine interface.

An assumption in most machine design choices is that (operators) pilots retain piloting (operating) skills as a step zero in the process. (You put an untrained machinist on a lathe, and watch the money bleed from your production via waste and lost). Without feedback, without tactile sense, your brain to muscle memory goes to hell and your piloting skills are less than 100 %, unless you train to a new skill set.

In three separate, and long threads, if appears that a non trivial number of the airline pilot community have deep reservations about the matched triplet of training, currency and proficiency.

Try this.

Teach someone who has never flown to fly VFR, to include stalls, landings, and spins. Then, for the first time, put him or her under the bag, zero visual reference, vertigo rampant, and have him or her, even with some sim training, try to fly instruments in mild or light turbulence, through climbs, turns, descents, power changes, and some unusual attitudes. The odds of overcontrol or scan breakdown, even on conventional controlled aircraft, are pretty high. (For your own amusement, I'd like to be able to transmit a video of my own first ever on instruments flight. A bit of a mess, that one ... as expected in most training scenarios). How do you overcome that? Training and proficiency.

Time and again people have pointed this out, in this thread and others ... how pilots fly is informed by all of their flying experience, and all of their training.

If one takes the tactile feel, which at this point in aircraft design has been "manufactured" for a generation, (to include the helicopters I've flown) out of the loop, you have robbed the pilot of a standard tool to use (working around a trimmed position, or a null position, using vestibular and tactile sense) in making sense of his situation -- hence the term situational awareness -- and making the plane fly as he or she wishes it to.

That is what flying is. You make the plane (within its physical design capability and limit) do what you want it to do.

That said, the Captain from the AvWeb article knows how to fly the 330, and has some advice on those who wish to do it well. He's pointing out that the design has in some senses (hardly all) vacated the above assumption. What is apparent is that the new assumption has not necessarily been trained and embedded into the pilots who fly it. (Again, 99+% of the ones that take off come back down, standard day at the office, the pilots and their machine interface just fine).

Go back to our novice on his, or her, first instrument hop.

The novice pilot has to have the vertigo resistance trained into him, or her, so that when that distraction arises, an appropriate response is made, and the machine is obedient to the pilot's will.

Mayhap the captain's point is that retraining, and proficiency, in the "play it like a video game" approach needs to be incorporated into the training and education scheme better than it has been to date.

If, like vertigo resistance, you have to be trained and taught no to rely on stick feel, on vestibular and tactile sense, then train to proficiency, educate to understanding, then rinse and repeat until it's as embedded as "pull stick pack, cows smaller, push stick forward, cows bigger."

Control inputs and feedback
 

Salute!

Hmmmmmm, PJ's post was there, but I can't find it now. Good charts.

So I shall post two graphs of another FBW stick inputs from my personal Photobucket albuyms that I made myself from data and an Excel spreadsheet. Will they disappear as well?

All inputs were force and not stick movement. As with the Airbus, there was no feedback as to how much you were commanding, just body rates and gees that you felt in the seat of your pants.

Roll command:
http://i120.photobucket.com/albums/o...s/roll_cmd.jpg

Pitch command:
http://i120.photobucket.com/albums/o...gums/pitch.jpg

The tactile feedback most pilots here talk about is actual or synthetically-generated pressures on the stick from the control surfaces ( not spoilers or flaps). So a high speed aileron flutter is easily felt, as the stick is vibrating left-right. At high AoA, the stick gets "mushy" ( real technical term we used as instructors, heh heh). i.e. you could move it rapidly but nothing happened and you kinda knew that the elevator or ailerons had no meaningful effect. Then, at high speed, the stick became "stiff", and required more force to get the control surfaces to move than when in a stall or approaching a stall.

So I agree with the folks that talk about a giant video game.

Well, I'd like to hear from "gums" on this one - the Viper has no feedback per se for the sidestick - it is a force sensor (for want of a better description).

Much of this discussion lately seems to operate on the assumption that the control 'stick' of the 50's is the 'right stuff' and any other way of doing it is somehow bound to fail.

However the current generation have grown-up using joysticks and control inputs such the Wii controller, etc, and have 'learned' very differently from days of yore... Having been involved in a number of UAV programs, you only have to see the control stations for these aircraft to understand that the "pilots" (go with the flow...) are a different breed. Are they so different from the 'bus pilots?

If the slate were entirely blank and we were tasked with developing a control system for a new cockpit what would it look like? My guess is such a design would be rather different if you happened to be age 24 versus age 54.

'different' is not 'wrong', necessarily. Attack, defend, ad absurdum.

Different has challenges that fairly speaking, need addressing. Or, redefine the operator syllabus, and accept problems that appear in transition. Too much PE lately, of all description. Where it can be identified, it needs to be corrected.

The pilots first wanted a window, then a Stick, then some Press (Mercury).

This debate has become tiresome, and actually forecloses progress toward that which is all important

Airbus feedback?
 

Where does this idea that there is no feedback on the Airbus control system come from? the side stick itself resists input via a spring so that a certain force is needed to move it through a certain deflection, and then that deflection commands (initially at least) a normal acceleration which is constant over most of the envelope in all laws except direct, as I (mere Boeing pilot) understand it. I got the following from a 1992 paper which I assume is still roughly right:

Limits:

Pitch
Max. load 10 daN
Threshold 0.5 daN
Deflection +-16 deg.
Orientation 20 deg fwd.

In non engineer units doesn't that mean you need roughly 10kg or 23 lb to demand the maximum allowed normal g of 2.5. The feedback is firstly the spring rate of the side stick, and secondly the response of the aircraft, what more should one want?

I would still like to understand why the first two stall warnings were generated before everything went pear shaped, doubtless the full BEA description will clarify that, but it would seem that when the PF took over he put in a mighty demand for no very obvious reason

I'm painfully aware of that, and if you think I'm being blase or somehow dismissive of tactile feedback in it's place I promise you I am not. However, when I talk about these things I am talking with my "engineer's hat" on. As I've said countless times before, there are failure modes of a backdriven system that are distinctly non-optimal, as well as the consideration of extra complexity.

The "feel" that a pilot gets back through the yoke from the Comet onwards has been mechanically interpreted. You are not "feeling" what the aircraft is doing, you are merely feeling what the artificial feel system thinks you should be feeling based on the input parameters it is getting. In the Comet up through the 767, what you were feeling was mechanically driven. The A320 and her descendants dispensed with it entirely and the 777 actually had that feedback response programmed into the computers. That was a design choice, and while a non-trivial number of pilots have reservations about the fact that Airbus dropped it, it is also true that a non-trivial number barely missed it at all. It is therefore a matter of personal preference. Dealing with the visual-only feedback channel is a matter of training.

We don't know whether the PNF spoke up about the strange attitude or not at this point, so any argument over backdriven sticks is basically irrelevant to the subject at hand. We *do* know that when whoever was in the LHS tried to take control, the PF spotted it and handed over without a fuss. In the stick-shaker regime, connected control columns did neither Birgenair nor Aeroperu's crews any good, as the cacophony of lights, sounds and warnings made problem-solving practically impossible. This was a nightmare situation that would test even the best pilots no matter what aircraft they were flying.

According to an earlier BEA report on a different incident (I'm still trying to track down the original research - any help much appreciated), tests indicated that in a panic situation 80% of pilots would instinctively pull back on the stick. I'm not saying that's what happened here, but it's definitely one of the possibilities.

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.


If my English reading skills are ok, capt is saying that, if Autothrust trips (due to UAS, or any other cause), engines go to CLIMB power without crew intervention!!!

And, at cruise setting, the inference is, AT trip will likely induce pitch up in A330 as consequence of thrust increase? :eek:

So AF447 likely to had pitch up produced both by thrust increase PLUS induced by PF sidestick :sad:

Is it possible they suspected the tailplane (only) was stalled? Perhaps due to ice?

On other aircraft I understand the standard proceedure for recovering from a tailplane stall is stick back and reduced power. I believe the thinking is that increasing the camber lowers the stalling speed.

Bovine scaling
 

.... then rinse and repeat until it's as embedded as "pull stick pack, cows smaller, push stick forward, cows bigger."

Perhaps better expressed in this instance as "push stick forward, cows bigger - pull stick back, cows smaller - keep pulling stick back, cows get bigger again......

No, he's wrong. When autoflight trips out, the trim and power settings remain at their last assigned setting. Thrust will not change from that setting no matter what detent it was in until one of the pilots manually moves those levers.

This makes me highly suspicious of his credentials - if he's flown those thousands of hours in an A330 and doesn't know that then I'd be a little leery of getting on his aircraft.

THS trim law
 

Hey, DOZE!!!!!!

Can you show us the law for the THS trim position? Would help a lot of us to understand the first minute or so of the accident.

For example, if I hold a slight back stick to command a slightly higher gee ( a gee command plane, right?), then does the THS move to "help" me achieve the gee?

Secondly, is the THS law related to airspeed/mach?

In short, how does that sucker work?

Dozy, thanks. It does not matter one whit that "since 1950" the force gradients and feedback mechanisms have been added ... they were necessary due to the magnitude of control forces as planes flew faster, and in part due to the undesirability of direct feedback heading back down the pipe into the cockpit.

What evolved was the concept of the "trimmed position" which is a null point about which correction is made. Many of the advances since just after Wilbur and Orville hung up their cleats amount to is ways to aid and abet the standard task loop of flying, and to do so from around a known "neutral" position ... not of the airfoil, but of that which controls it.

Set condition (what you want the airplane to do) via control inputs (which
includes power, we'll leave gliders out of it, yes?) and then check to see if it does what you want it to, or not. If yes, hold, and then trim, that condition until you want to change. If no, change and retrim until you get to your yes ... and you are in a steady state climb, level flight, turn, descent, or combination thereof.

Again, there was good reason, both behavioral and psychological, to retain the use of tactile sense in the control loop as an error detecting input.

I disagree with your attempt to dimiss it in this little throwaway.

I disagree with your merely. The point is to scale it so that what you feel is a tactile representation of what the aircraft is doing. (Good example is nose trim: "I gotta push to keep the stick outta my lap, nose is in, and trimmed in, the wrong place for this flight condition.") That feedback system is useful for pilot decision making. The art and craft of feel and feedback developed over some years. It allows you to add the tactile sense to your suite of tools, rather than limit it or even eliminate it.

Consider the training that gums and his comrades underwent on a continuing basis. (The USAF is nothing if not zealous about training).

Your operator is a necessary element of the control system.

I was hoping you'd see the link, and that I was pointing to the underlying issue: you have to train to proficiency. Since most people don't begin flying in FBW, and do begin with an ergonomically sound, and proven, method that applies the tactile senses to the system (man and machine in the gestalt ... ) you have to pay attention to how you do your transition training, and your proficiency and habit building. If you design your system with erroneous assumptions on that score, you open up a nice can of risk whoopass.

I am done with that, thanks for your insights.

Note: thanks to poster who explained better the feel system in the Airbus design.

tubby, others, I deleted the post temporarily as I was unhappy with it. Sorry for the loss of signal. This stuff has to be done so carefully so as not to cause wrong understandings and lead others down blind rabbit trails! - pj

The following schematic may help:

http://www.smugmug.com/photos/i-h43b...-h43bMqh-L.jpg


Machinbird;

Re "one of the most experienced A330 pilots"...Perhaps so, perhaps not.

We have to approach this article with the same caution as any which "arrive" in the publice venue.

We have absolutely no way of verifying that this is from an A330 pilot.

As with the comments from a Professor Hüttig last week, (who I do not believe was "an Airbus pilot" because he doesn't tell us what exactly his Airbus/airline experience is), we have no information on this author who claims to have 4500hrs on the A330. Probably does but the stakes are far too high, the desire for accurate information too great, to expect others will take an internet posting as the truth. Establishing credibility takes time, discussion and a good smeller.

Whoever he is, I think he's wrong on comparing the airplane to a video game and he's wrong on the artificial feel matter; the non-moving thrust lever item has been around for decades and won't be resolved by his or any others' comments; they are, for the many who are experienced on the airplane, a non-issue.

The A330 is what it is in these specific respects and I think it is reasonable to state as an experienced airline pilot that after one is trained and finishes an informal "apprenticeship" in real airline operations one gets accustomed to one's airplane, especially after 4500 hrs on the machine. One gets used to "what is" and, as a professional, maintains a regime of continuous learning by staying in the books and practising one's craft by hand-flying including disconnecting the autothrust.

In reference to the article, it is worth asking oneself the question, Why are people saying the things they are saying? Motivations are numerous and very complex and no question, no comment is "innocent". Do we follow the money, the ethics, the lofty goals of learning? All are choices which we make, for the most part, subconciously, when something either feels right or smells a bit. Why would someone "go public"? Attention?, setting the agenda?, enframing the discussion? We are not told who wrote the article. We are free to judge that for ourselves. Is that intentional or done naively unaware that others would ask such impolite questions?

How many who continue to pronounce on "the dangers of Airbus" and the "confusion of laws" have ever flown any airplane at all let alone the A330? How many here have had the A330 Course and flown it in-service in real life?

I submit that the act of summarizing the details of the A330's AFS laws and trying to make academic sense of them either to oneself or others is the same kind of cognitive act as trying to describe to someone exactly which specific muscles to move, and when, to walk up a flight of stairs. One googles "smart-cockpit" and like so many who use the internet for personal qualifications, consider themselves sufficiently knowledgeable to actually say something about the airplane without ever having flown it. If it were that easy and that simple, we wouldn't need the training and checking regimes that regulators require and airlines routinely provide.

That the design and execution of the design most definitely deserves comment and critiquing. There are some serious questions to be asked.

Dozy...re, "No, he's wrong. When autoflight trips out, the trim and power settings remain at their last assigned setting. Thrust will not change from that setting no matter what detent it was in until one of the pilots manually moves those levers.

This makes me highly suspicious of his credentials - if he's flown those thousands of hours in an A330 and doesn't know that then I'd be a little leery of getting on his aircraft. "

Yes, exactly. He may be who he says he is; doesn't matter. THR LK has been around a long time, but not forever. I flew the A320 without thrust lock. One remembers very quickly how to disconnect the autothrust. But when the engines went to the donuts, it was a non-event...an embarrassing cause for questions from the back but nothing beyond that.

For those who seem to believe that CLB or even MCT at FL350 on the CFs or RRs is cause for a huge pitch-up followed by an immediate overspeed or an uncontrolled climb for the A330, it needs to be understood that there is not much residual thrust remaining and the aircraft response from what "boost" there is, is emminently controllable. On the A340 one could likely leave the CFM-56's in TOGA and you'd take all day to overspeed the airplane...they didn't call them hair-dryers for nothing.

THS trim law
 

@ Gums:

There isn't a separate THS law.......there are pitch laws!

In manual mode (Side stick control) short orders are handeld by elevator deflection.
Long term orders by THS. (autotrim)

Just like any other design.

The gains depends on Vc, CG and Flap/Slat position.

I presume you are just trying to be facetious ?
Otherwise your post makes no sense.

@gums

There's a useful document here:

A330 Flight Controls

But as I understand it, it boils down to "if the pilot is still holding the stick back at the limits of elevator authority, trim nose-up to assist until the pilot stops issuing the command". This should hardly ever be necessary, as it is intended to escape from extreme attitudes only, but it is there.

@Lonewolf_50

I *know*, and I know that many pilots agree that the loss of tactile feedback was a mistake. I do not "dismiss" anything and I do not reduce pilots to "operators". I think we're poking at cross tortoises here. Airbus aircraft do retain a degree of artificial feel to allow the pilot to know what the *aircraft* is doing, but what CONF and the others are banging on about is the fact that on the Airbus you can't directly feel what the other *pilot* is doing. That's the issue, and that's what I'm talking about when it comes to back-drive.

Dozy, thanks, sorry I beat that poor horse into glue. :O

@ twistedenginestarter
 

You are not alone here. It all looks strikingly similar to Pulkovo 612. And there is a proven fact of vicious vertical air movements - they had pitch angle = aoa in horizontal flight at FL 380 which has no other explanation than downward wind strong enough to change aoa by about 4 degrees.

twistedenginestarter,

There are several BEA reports to read:
The first BEA Interim report you can find here:
http://www.bea.aero/docspa/2009/f-cp...90601e1.en.pdf
It speaks of pitot tubes and gives the information on how they function and how they are connected to the flight system.

The second BEA Interim report you can find here:
http://www.bea.aero/docspa/2009/f-cp...90601e2.en.pdf
This report gets deeper into the pitot tubes. It discusses how they are certified and examines the experiences of pitot tube icing and observed differences of icing between pitot tubes manufactured by Thales and those manufactured by Goodrich on Airbus aircraft. Refer to Appendix 7 for a listing of events. I think the BEA is very suspicious of pitot tube icing at the time of this report as Thales pitot tubes were the installed on AF447, which were to be replaced by a EASA AD, but were not yet changed out on AF447.

The most recent BEA report is an Investigation Update you can find here:
http://www.bea.aero/fr/enquetes/vol....mai2011.en.pdf
It makes no mention of the pitot tubes, but gives some information from the FDR and CVR regarding the last moments of the flight.

Hope this helps your understanding.

You are misinformed. Pitch angle is between longitudinal axis and the horizontal plane. Airplane AoA is the angle between longitudinal axis and airspeed vector. In horizontal flight in still air the airspeed vector is horizontal, therefore pitch = AoA. EDIT:: IOW, pitch=AoA implies zero vertical air movement.

Do not confuse airplane AoA with the local AoA of a wing section at any spanwise station, which varies considerably between wing root and tip.

THS autotrim mechanization
 

Thanks for the reference, Doze. Already had same for another 'bus variant, but nice to read the real deal.

I still can't see a diagram of how the THS moves with respect to the pilot or autopilot inputs to the "system".

I don't like the term "autotrim", BTW. We tried to eliminate that term in the Viper, as all it meant was the jet would try to maintain the last TRIMMED gee command. Unlike the 'bus, we could trim the gee with the hat switch on the stick or the roller gizmo like the 'bus has. If we had trimmed for zero gee ( some guys did that for air-to-air maneuvers so all they had to do to get energy in a hurry was relaz pressure on the stick), the thing tried to get to zero gee when you let go, duhhhh? We did not have the pitch attitude correction or the bank angle correction - a stable 30 deg climb only required about 0.87 normal gee, for exampl. So our jet would continue to slowly pull up if you let go and it had been trimmed for one gee. As with our little jet, the Airbus is not an attitude command system.

So what gee does the Airbus try to reach when I let go of the stick and the THS is at 10 degrees or 2 degrees or....??? The jet is a gee command as the basic Viper is, and has different gains and rates and such, but it is not an AoA -gee system like we had. Ours gave you 9 gees at 15 degrees AoA, then the gee went down until 25 degrees AoA and it was one gee. Our manuals showed this and we demonstrated it first hop with student studly.

So what does the THS do if I have a constant back stick that moves the elevator beyond "neutral"? Another post implies that the THS does not move unless the elevator is something other than the "neutral" position. Surely someone here can show how the thing works.

Inquiring FBW pioneers wanna know!

That may be true DW, however we don't know what pitch & power (therefore energy) direction George was trending in prior to the disconnect. That, along with scores more information have been unfortunately left out of the BEA report.

By the way, the Braniff example you just cited was not true. A Boeing pilot was in the seat, but not at the controls and it was not a developmental test flight. The Braniff pilot managed to remove 3 engines before they had to crash land the aircraft. In the sense of flying a 707 with 1 engine, that surely would have been in the realm of a flight "test. "

;) cheers!

Side-stick Position
 

Having noted a few comments about the PNF not knowing what the PF is doing with the side-stick, it is worth noting that in the Ground Mode after start-up the side-stick position is shown on each PFD.

http://oi55.tinypic.com/fejx9t.jpg

My suggestion is that in Flight Mode that this option is selectable, and when in other than Normal Law and on auto A/P disconnect, that the side-stick summed position be shown automatically on both displays. Both pilots and the 3rd or 4th seat occupants will also see what is happening.

DW:
What is the nature of the artificial feel you mention?

If not to the sidestick then where?

Lack of back drive (what the other pilot is doing) is a seperate issue than tactile feedback (what the airplane is doing) to the controls.

The lack of "what the other pilot is doing" feedback seems to me to be more questionable than "what the airplane is" doing since that data is available in many other forms but the PNF appears to not have a way to tune in to "input vs response" of the aircraft.

ChristianJ.. The artificial feel built in to the Boeing flight control needs speed input and from memory it used a different set of pitot tubes for that. It did not use the regular pitot information provided to the flight instruments. Those tubes were also heated, but my suggestion is that if the flight instrument tubes iced up, then the feel system pitot might also be iced up, thus causing the feel to be incorrect. Hence the feel might be wildly inaccurate under those conditions.
I am not aware of any way to turn this system off, but in the old 737 you could turn off the hydraulic system that powered the feel and it was a strange experience to fly an airplane without any feedback. As some have said, like a video game. I never did hear of any problems with the feel system on the Boeing, but it might have had some effect on the two 757 accidents. Since the 'Bus does not have the system it would not matter.

The Boeing checklist has a table of thrust and attitude for various configurations and speeds, to cover this type of emergency. Does the 'Bus have that, and is it accessible in flight? (paper or plastic)

Would the crew have been trained on this?

Of course. It's in the QRH.

PJ2,

PJ2's quote:

I agree, there isn't much left to go relative to thrust! A couple of questions:

1. What would be the N1% at cruise at 35K for the CF6-80E's at Mach 0.83?

2. What would it be if the Mach was reduced to 0.80?

Also, I noted the BEA changed the estimated COG to 29% aft from 38-39% aft on AF 447 at the time of the incident. If true, what does that do to N1% as I would think the N1% required would increase to maintain speed due to more drag?

Your thoughts? I am interested in this among other thing I am not familiar with.

Possible Updraft Effects
 

There are a number of unresolved (at least for me) queries based mainly on the information in the BEA Interim Report 2 and the Update on Investigation report of 27 May 2011. A possible scenario that might answer these queries is rather than one of blocked pitots, instead a moderate to severe updraft.
Queries:-
a) A/C rolls to right: The “go left a little” at 02:08:07 would put the turbulence to the right of a/c, with the a/c flying at a tangent to any column of rising air. A moderate to severe updraft under the right wing would probably then cause EFCS to respond with right wing down.
b) PF inputs left and nose-up: In an Updraft air is being forced up by the air beneath so static air pressure would increase. This would cause Baro Alt to very rapidly decrease, giving the impression the a/c was descending, possibly then causing the PF to pull the nose up. Also a “barometric vertical speed higher, as an absolute value, than 20,000 ft/min”would cause the FPVs to disappear.
c) TCAS fail: this could be due to failure of the altitude credibility check
d) A/S "sharp fall" from 275 > 60kts Captain's PFD: In an updraft the raw reading of dynamic pressure would be affected(as the airflow would be partially across the end of the tube) by cosine of AoA plus any venturi effect. Also in an updraft, with a rapid increase in local static pressure, calculated AS would rapidly decrease. The subsequent calculations of AS would be affected by the various changes in AoA and static pressure causing a number of fluctuations. Other air speed related faults could also be due to the effects of an updraft, e.g. ISIS and ADIRU.
e) PRIM 1 and SEC 1 fault:Possibly the PF turns them off in desperation, believing that the apparent erratic behaviour of the a/c was because the EFCS was faulty.

No problem, thanks for the correction. However part of me suspects that if PPRuNe had existed back then, we'd have heard all about how Douglas had never lost a civilian test pilot in the same amount of time, how Boeing was messing with time honoured pilot tradition with these jet aircraft, and just what the hell was wrong with good old propliners anyway?

;)

No worries. Funny stuff no doubt re: a PruNe back in the day! Would have also been nice to read what some of the craggy faced "king of their domain" old timers had to say back then on CRM when that newfangled idea came onto the scene some few decades afterwards.

pj2

very nice post and you,re right ! on an anonymous forum its hard and sometimes dangerous to follow expreriences from self named experts.i can remember an another discussion and dangerous hints from a now banned member...

well,i am not an airbus pilot, but discussing terms like moving/non moving throttle levers for real life is silly. it is a non event for anybody who is REALLY rated on this plane (and not a computer game) . people need to understand that this planes fly everyday and all we need is the understanding that you "notch"the levers for a certain part of flight and let the computer help you. every truly real pilot will understand that in times where you deal with several other things like ATC, delay problems , unexpected route changes especially at a complicated departure, the computer will help you, not harm you, but the plane still will be limited to physical rules. the same applies to the migty TOGA. i wrote like you also several pages before that toga in fl 350 will not give you such a burst that its in regards to trim its an event.

well. the critical question for all this discussion, on an open forum like it seems not very sufficient discussion, is what happened and what can we learn?

it seems strange for me that he pilot climbed out and stalled ( in alt law) until impact. even when airbus is blamed for an failure on IAS indication... keeping power and pitch could help. maybe it was like many incidents: a massive pilot error who wasin panic. this happens, and every time it happens it is sad.

best regards to all !

HazelNuts

I think you might find a common definition of AoA is freestream vector Vs Wing Zero Lift Angle, not fuselage axis datum

or even, Vs Wing Chordline Datum

After all, when w/t testing wing sections, there is no fusleage or wing chord datum setting angle to refer. to

Turbine D;

I don't have the numbers for a CF installation on a 332. The Trent installation on a 333 requires a cruise N1% of 78.1, with a CG of 37% - the chart doesn't provide for corrections but I think your observation of a forward CG requiring a bit higher N1 is sound...certainly it would again be a bit higher at M0.83, and quite a bit less (in terms of fuel flow) at M0.80). Max CLB might be 83-87% N1, MCT might be around 92-94% N1. As a good friend described it, the L/D curve is like a marble on a plate...

My personal experience with the A340 (CFM-56s) was a much higher fuel flow required at M0.83 than M0.82. We could often save 3000kg on a ten-hr flight by bringing the Mach back by .01, (about 8-9kts), with ATC clearance. M0.80 wouldn't normally be filed of course as that's quite slow on either ocean but that's the Turbulence Penetration speed, so used as needed. Perhaps someone here might have those exact numbers for you.

Way back on page thirty-something, it was theorized that none of the three pilots recognized the stall because none of them said anything about getting the nose down.

I have been in a full stall in a swept wing narrowbody (MD80 on a post m/x flight check) and I can add my agreement to that theory. In my case, I was the pilot monitoring the system (stall warning) and was surprised by the unexpected break. Rest assured that I immediately started yelling "PUSH" at the top of my lungs.

To all: As a current A320 Capt, these threads on PPRuNe have been a valuable learning experience. Thank You to everyone.

PS. My carrier produced and trained a fine scenario for Sim Tng of the UAS scenario. But it was based on ADIRU issues not external issues that could cause confusion in the FBW system. This forum has added far more to my knowledge of UAS issues than the airline tng ever did. Thanks again to everyone.

Altimeter Data Available?
 

Have not seen much mention if any of whether altimeter data was available. It appears to me from looking at the releases that it should have been there, and would have been unreeling downward and would have been part of the instrument cross-check. Anyone knowledgeable on the -330 want to comment on this?

alex_brin, relax a little and consider your sources. He who lives by the news media dies by the news media, or something like that.

The news media is in business to make money. "Extrapolating" and outright "lying" make money.

The "I do not understand" quote does not exist in the BEA report. The closest it comes is this: The plane's systems were feeding them gibberish for data is what they seem to be saying there. It also implies that at that time they both saw the same thing and were concentrating on their training, which at that time suggested some stall warnings were spurious and in any case recovery meant applying a little more power. We really do not know what data was presented to the PF. He was apparently sitting on the right hand side and the RHS sensors were not recorded the way Air France had the FDR setup.

We can infer from the data presented that a cluster of deficiencies all got together to conspire to bring this plane down. That's not fact. It's simply extracted from the data. Pitot tubes can ice up under conditions they experienced and display false, very low, values. The conditions do not turn up on radar which works best with water and works poorly on frozen water. The pilot training left out some critical "complexities" about high speed stalls and trim tabs. The warnings presented to the pilots MAY not have distinguished between "about to stall" and "stalled" which CAN but don't necessarily have differing recovery modes. The software presumed at 60 knots the aircraft had to be on the ground so stall warnings are superfluous, even at 37,000' indicated altitude. This is not quite accurate as this flight shows. And the pilots seem to have done inexplicable things given the data cluster fed to them when the auto-throttle and autopilot both disconnected.

The above list includes hardware, training, and software design deficiencies.

Regarding the software deficiencies no coding or programmer errors are evident here. They built the design given to them very well. And the particular design decisions may represent engineers getting overruled by management.

So there are enough issues here that courts are going to have a field day trying to affix blame. And some aspects of the plane and training probably should get revisited. How much is a good question. Perfect safety requires infinite effort which requires infinite knowledge and infinite money, none of which exist. And this plane is also far more reliable and safe than prior choices such as the DC-6s, Connies, and 707s I rode on as a child and adolescent. Major improvements may be difficult and, frankly, cost more than is sustainable for either AirBus, Boeing, or the airlines involved. (Some of these issues no doubt infect Boeing aircraft, too. Perfect is for God. All mankind can do is strive for perfection within our limitations.) Simple things like modifying training and using two different types of pitot tubes on the same plane may help. Modifying the software is a very expensive and finicky process. That may not be possible and training extensions to cover this may have to take place.

All of this is without the extended analysis I expect BEA to make. These are my relatively untutored observations with a subset of the data BEA has. I am willing to stick my neck out and suggest if it is pinned on the pilots that will implicate deficiencies their training.

And I've rattled on long enough so it's time to quit with a little observation to another member here (who knows who he is) that the Vertical Stabilizer appears to have really been a part of the plane affixed to the plane until it interfaced with the ocean. And note that I'm trying to determine potential causes and in no way apportion blame.

Does the FBW system know whether the symptoms of Unreliable Airspeed are caused by pitot tube failure (icing) or caused by ADIRU failure?