AF 447 Thread No. 5

[ChristiaanJ]

A33Zab,

Let's not confuse the issue.

IIRC, the AB SS provides a 'proportional' signal, from either pots or resolvers, and NOT a 'toggle' signal like the ancient Atari joysticks (LOL).

So your graph and post may be somewhat misleading to the uninitiated....

[Lyman]

CJ

Thanks, that was close call. I came very close to almost understanding what he wass saying.

[DJ77]

@DozyWannabe.
DW, I understand your point that in ALT2 the computers are missing some handles but to lose s/w would require triple AoA sensor failure or triple ADR failure or double FWC failure (and btw the UAS check list asks to respect stall warnings) so I still cannot see in what way preventing up-trim based on s/w AoA could be harmful.

[wallybird7]

PuraVida post # 1726

Perfect analysis! Totally agree.

[A33Zab]

Let's not confuse the issue.

IMO a non A. FBW and even the FBW insiders are already confused.

Sometimes a simplified approach can explain a lot i.s.o. confuse.

I know there are potmeters involved (hey, did post the SS diagram myself)

BTW, the graph is from A330 FCTM...surely not intended to confuse the Flight Crew.

The related text:



As the flight mode is always aiming to achieve the selected flight path, avoid the
temptation to over-control. The recommended method to avoid over-controlling is
to make a small sidestick input, hold for a short period and then return the

sidestick to neutral. Even in turbulent conditions, the control law resists the

disturbances well without pilot inputs. The pilot should try to limit his control
inputs to that necessary to correct the flight path trajectory and leave the task of
countering air disturbances to the flight control system. If the pilot senses an
over-control, the sidestick should be released.
In climb, cruise, descent and approach, all these basic rules remain in effect.









How much time was the SS released to give the flight control system the
opportunity to stabilize the upset?

http://i474.photobucket.com/albums/rr101/Zab999/SSGraph.jpg

[Smilin_Ed]

Dozy: Fair enough, that's your opinion - but have you ever actually flown a FBW Airbus? Plenty that have state that the autotrim is completely unobtrusive when hand-flying and that the aircraft as a whole handles rather well.

No, I have not flown an airbus. My problem with autotrim when hand flying any aircraft is that I may not want it to follow my control inputs. Unfortunately, this crew seems not to have known anything about trim. Maybe having the trim announce to the crew that it is moving would have been a wake-up call and someone would have said, "oops we don't want that," but I doubt it. It certainly would have got my attention. Sadly, the men seated in the cockpit were completely out of their element.

Quote:
You have stated that there are good and sufficient reasons for the design of the software in the hand-flying mode, but AFAIK you have not offered any reasons why that design is preferable to my reasons for disconnecting autotrim when hand-flying.
In fact I did, but it's several threads back - one of the reasons was the ability to have hands on throttle and stick in a pilot incapacitation scenario.

Pilot incapacitation is not much of an issue in a multi-seat cockpit. Trimming is not difficult and, for a pilot worthy of being called a pilot, it is a natural activity which is so routine that it is done almost unconsciously. I have flown aircraft with the pitch trim on the yoke, on the stick, and on the console. I never found it a burden to activate any of them. I prefer it on the stick or yoke since that does free up the other hand, but the difference is really not material. What I don't want is having the system changing the trim when I want to remain trimmed for a particular speed or AoA. In the case of AF447, the system gave up and turned it over to the people seated in the cockpit, except they didn't turn over everything and I believe that situation makes it more difficult to hand-fly. Autotrim has its place, but not in my cockpit when I am trying to hand-fly.

[Lonewolf_50]

airtren, you can lose lift without stalling.

Try it sometime.

Fly along with your flaps down. Then, raise the flaps. You'll lose lift, but you don't necessarily stall. You'll probably also descend, if you were flying level previous to the flap raising, unless you take the time to also add power ...

[bubbers44]

You only lose lift if you maintain attitude. If you pitch up with flap retraction you maintain the same lift until you stall.

[infrequentflyer789]

I get your point.... but as I said, I can't remember any serious issues with the mechanics of the Concorde artificial feel, which was a lot more complicated than the force feedback on an MS joystick.
My point being, really, that implementing reliable force feedback on an aircraft sidestick is no more difficult than what we did over 40 years ago.
And if one 'dies', there's always the other side.....

Did the artificial feel include airspeed as input ? - intuitively I feel it must do (and I believe B777 does), but deltas are very different so maybe it wasn't needed ?

If so, what did the system use in the event of uAS ?

On a vaguely related note, did Concorde ever suffer from pitot icing / similar uAS or at FL60+ was it simply not a problem ?

[infrequentflyer789]

@DozyWannabe.
DW, I understand your point that in ALT2 the computers are missing some handles but to lose s/w would require triple AoA sensor failure or triple ADR failure or double FWC failure (and btw the UAS check list asks to respect stall warnings) so I still cannot see in what way preventing up-trim based on s/w AoA could be harmful.

S/W can be spurious, particularly in uAS, but also, I believe, with one AOA broken (it would be outvoted by the other two for the PRIMS, but would still trigger SW - think Perpignan but other way round).

Stall warning is a warning to the pilots to asses the situtation and take action. It is not a certainty based on which the plane itself should take action or restrict the pilots action - the FBW Bus has all that in normal law, but if you get as far as s/w then this has already failed. Or in other words, if you get a s/w on a bus, the plane is already uncertain of its data.

The logic running through is that automation doesn't act (or restrict pilot actions) on known-bad data - but it may still warn pilots. Sadly in this case, I think the pilots believed the stall warning to be spurious due to uAS, and possibly believed they were overspeed and acted to correct that instead.

[Bill G Kerr]

I'm having a problem keeping up with the volume of posts, but I don't expect anyone has suggested this:
Hang glider pilots often tie a ribbon to the down-tube.
Maybe something that could be seen from the cockpit, but slightly more robust than a ribbon could work?

[infrequentflyer789]

Dozy, it you have relevant arguments on why autotrim should not drop out with the autopilot, I will be glad to consider them.


Can't speak for Dozy, but two relevant arguments that come to mind are Schipol and Bournemouth. The 737 autotrim does drop out with a/p - and the consequences when pilots didn't immediately realise weren't pretty (although at Schipol it was probably a minor contributor with not watching the thrust the major one).

The common thread to me is not that A control laws are better than B, or visa versa, but that pilots should be properly trained to fly the a/c they are flying, including stall recognition and recovery. It appears that this has been lacking across the industry for a while, hopefully now in the process of being fixed.

[ChristiaanJ]

I'm having a problem keeping up with the volume of posts, but I don't expect anyone has suggested this:
Hang glider pilots often tie a ribbon to the down-tube.
Maybe something that could be seen from the cockpit, but slightly more robust than a ribbon could work?Bill,
Something "slightly more robust" already exists. It's known as an AoA vane (sensor). There are a couple of those fitted to the nose.
Your ribbon is no more a 'stall indicator' than the AoA vane (or indicator), unless you know the stall angle of attack....
And there is no indication so far that the AoA sensors had any problems (unlike Perpignan).

[CONF iture]

And there is no indication so far that the AoA sensors had any problems (unlike Perpignan).
But what about number 1 stuck at 2.1 deg ?

[infrequentflyer789]

Been a systems engineer for almost 30 years now, and I've never heard of a signed 16-bit implementation different from the traditional -32768 to 32767 that has exactly one representation for zero (what you call "minus zero" actually being -32768). Any reference to this particular implementation you're mentioning?

Old engineer as well.

Ones complement and sign-magnitude both do this.

Not sure how much either is still in use though - not a lot, most things are twos complement, but maybe in some niches.

I have a very vague (and probably wrong) recollection that fixed-point datatypes in Coral66 and maybe ADA (not used that much) might have used ones-complement magnitude under the hood. On some hardware. Coral was definitely used in aviation (maybe still is, I haven't worked with it since the 80s) as is ADA.

[ChristiaanJ]

But what about number 1 stuck at 2.1 deg ?Missed that, you got a link?

[takata]

Hi Christiaan,
Missed that, you got a link?
Yes, Confiture is right.
See for example longitudinal axis simulation graphs p.44, incidence notes on detailed flight parameters p.30-33 (French report), as well as other graphs.

Below, "incidence IRS1 [DA] (FDR)" is showing a value for alpha probe #1 which remains blocked at 2.1° until after 0210:50; later, it follows other probes but its output is under-reading.

http://takata1940.free.fr/longitudinal.jpg

[TyroPicard]

Smilin-Ed
Autotrim has its place, but not in my cockpit when I am trying to hand-fly.

Only one question: In a FBW Airbus how will you as pilot sense which way to trim?

[Lyman]

Explain why Trim needed when trying to recover, Loss of Control? Autotrim is like the co-pilot moving the wheel, but in secret? No bicycle bell, or Clacking?

[ChristiaanJ]

takata,
Merci pour le lien.
I admit I missed that.
Not sure from where the FDR takes the "incidence IRS1 [DA] (FDR)" signal (I somehow doubt it's the 'raw' AoA vane signal), but I agree it further complicates the issue.....

[glad rag]

but I agree it further complicates the issue.Perhaps.
Perhaps it points towards the amount of ice on the airframe??
Perhaps not.

[gums]

Many previous planes had "beeps" or other indications that the autopilot or the "autotrim" ( hate that word) was moving the HS. In fact, an infamous crash near Indianapolis caused by LOC and ice building on the HS has a "whoof" sound on the CVR indicating that "otto" was trimming. When the crew disconnected the AP, shazam! Other big time problems with that incident, for another thread.

The huge HS can easily override the relatively small movements of the actual elevators. Just think about the area and remember the real "law" about rho vee squared times Cl times surface area. Then there's ol' mach. So near the critical mach, the elevators at the rear of the HS can become ineffective, hence the "all moving" stab on all fighters and some commercial planes since 1950.

The problem we dinosaurs have with some FBW implementations ain't the fact that electrical signals go to the actuators versus cables, pushrods, or hydraulic lines. Pure hydraulic pressure controlled from the stick/yoke valves that have been around for 60 years. The problem is that the engineers and maybe some pilots added "features", "protections", etc. that get in the way of hand flying when various components so to lala land. No commercial plane I know of is certified if it's basic aerodynamics are not up to spec.

Because we dinosaurs are used to trimming the pressures off of the stick/wheel/yoke, we expect things to remain relatively calm after a bump in the air or completely letting go of the controls. And if we were using otto, we expected some indication that otto had trimmed the plane versus us. So any reversion from automated flight to manual flight should not require instantaneous analysis of what the hell is going on.

I repeat for the nth time........ You can build and implement a FBW airplane that flies exactly like those of yore. Replace the tubes, cables, etc. with electrical wires and no big deal. It's only when many "features" and "protections" are added that you have problems with the training and competence of the crew. I only flew one state-of-the-art high performance jet that had a decent artificial feel to the stick, and it was a bellows doofer connected to the stick thru a pneumatic line that made it harder to pull/push when the airspeed went up. So the idea of force feedback to the FBW stick would be nice, but not completely necessary. In fact, it would be veeeeery nice as long as we had an indication other than our seat-of-pants that it was inop.

The basic rules are still applicable when a lotta electronics and such go away - pitch and power for last known condition, then go as gently as possible from there.

[CONF iture]

Perhaps it points towards the amount of ice on the airframe??
But Ice Detectors 1+2 didn't detect any (P110 EN)

You can build and implement a FBW airplane that flies exactly like those of yore. Replace the tubes, cables, etc. with electrical wires and no big deal. It's only when many "features" and "protections" are added that you have problems with the training and competence of the crew.
... but also problems with sensors and probes and everything that has to process their readings ...

In the meantime, when everything is by the book, it is Fantastic !


I admit I missed that.
Question is why BEA 'missed' it too ... ?

[takata]

And if we were using otto, we expected some indication that otto had trimmed the plane versus us. So any reversion from automated flight to manual flight should not require instantaneous analysis of what the hell is going on.
Look at the graphs cyan curves I posted above: graph 6 "Position PHR" = THS setting, and graph 7 "Position gouverne de profondeur gauche" = Left Elevator setting. Now, compare them.

As expected, THS is not following short term g-load elevator demands. During the whole sequence, 0209:40 - 0210:54, THS setting is changing from -2.8° to -3.4° (negative = NU)... hence a maximum variation of less than 0.6° in 1.14 minute. During this whole sequence, the long term pitch demand increased from about 3° NU to 11°NU, with up and down in between.

Stall warnings, sounded at 0210:51 and stall followed 10 seconds later. From this point, the large NU demand was confirmed both in amplitude and in duration by elevator ncrease up to Max NU deflection, and they were mostly maintained here during the following minute. Consequently, THS followed its order by moving in the very same way up to Max NU deflection.

There is absolutely no mystery about that: OTTO had NOT trimmed the plane versus pilot demand !!
- OTTO only did what it was asked to do!
Of course, this end result, with hindsight, is contrary to the good setting for a rapid recovery action... but nobody really wanted to recover from this situation at the first place!

[Lyman]

If this pilot is pulling, He has help from this THS. So he must take the timing of his pull, rmember how long, and hold down the same amount when he wants the nose to go lower? This pilot has not remembered some things, how will he know what to push? Is pushing also harder than pulling now, it gets less nose move?

You say loudly the trim is because of the pilot, but not the other? The pilot is not doing what he is to do? He does not know this trim, even if he remembers the airplane actions from gthe training? The THS knows, why not tell the pilot also?

What, you say noone wants the recovery? Also that the airplane in this shape is too slow for r4ecovery? What is this?

[ChristiaanJ]

Did the artificial feel include airspeed as input ? - intuitively I feel it must do (and I believe B777 does), but deltas are very different so maybe it wasn't needed ?Sorry, I'll have to pull out the doc... artificial feel was not "my" system. But yes, I agree, I would think "q" was definitely one of the inputs.

If so, what did the system use in the event of uAS ?
I can't remember any UAS incidents ever being mentioned.

On a vaguely related note, did Concorde ever suffer from pitot icing / similar uAS or at FL60+ was it simply not a problem ?Concorde went above Mach 1 at about FL350. At cruise altitude (FL500 to FL600) and Mach 2, TAT was in the order of +120°C, so icing was not really a problem then. And yes, at that altitude, Concorde was basically 'above' the weather, including the ITCZ..

[gums]

You are correct, TK.

And seems to me that the 'bus AP disconnect is very benign.

The problem we dinosaurs have is we still see things like "overspeed/mach" inputs and such versus simply letting the crew fly a fairly good aero design with appropriate warnings that they are going too fast, or getting too slow, or exceeding some AoA values, and so forth.

CONF has brought up a good point. My discourse on the FBW design concepts was to illustrate that we don't need an awful lot of sensors to fly a plane with a good, basic aero design. After all, we're not talking the F-22 or Eurofighter or Viper. Basic aero laws will provide static and lateral stability. But if we fool with "Mother Nature" by flying with an aft c.g., we can get into trouble. For the AF447 incident, looks like c.g. was not as far aft as would be normal for that phase of flight, so I rule out a serious static stability problem due to the c.g. One of the only reasons we didn't have a "direct" law in the Viper was the thing was intentionally designed and flown with negative static stability until above 0.9 mach or so. During the flyoff with the YF-17, the performance difference was dramatic. You can still see the difference when the Blues perform, or a Super Bug does a demo flight. That critter is very comfortable at extreme AoA because it is a conventional design. End of war story.

[Diagnostic]

{New here - Hi to all :)}

That initially "stuck" reading (according to the FDR) from AoA sensor #1 is interesting, isn't it. Presumably its output got voted out of being used, due to the discrepancy with the other two sensors, but the fact that it was different doesn't seem to be explained in the BEA report.

But Ice Detectors 1+2 didn't detect any (P110 EN)

Understood, but that lack of report from the detectors, doesn't prove ice wasn't present ("absence of evidence" and all that...), especially since there seems to be evidence of ice in that CVR noise noted by the BEA (page 73 English version).

What else could be the cause? Could the lack of report from the ice detectors be due to a different type of ice being present, than they were designed / able to detect? Being only a GA pilot, I have no idea how the ice detectors on an A330 work - any pointers?

After the logged AoA sensor #1 value gets "unstuck" from the 2.1deg value (thanks takata for that), at around 02:10:52, note that its value then gets "stuck" again for a while, but this time at a much higher value (> 40 deg) at around 02:11:45, when the other two AoA sensor values dip below 40 deg (page 107 English version).

My overall view is that there is a general "stickiness" to that sensor, and that's telling us something - whether it's affected by ice (of a type / amount / location not picked up by the ice sensors), or is a faulty sensor (lack of effective heating?), or ... ?

As I said, I hope the AoA #1 output wasn't being used due to earlier discrepancies, but I haven't seen that confirmed anywhere (I'd be very happy to be corrected on that!).

[sensor_validation]

Has it been confirmed what AoA sensors were fitted?

Pretty likely the Thales C16291AA given the choice of Pitot tube, if so one could have been suffering an extreme variation of the known fault at low temperature:-

EASA Airworthiness Directive (http://ad.easa.europa.eu/ad/2010-0016R1)

Note that the use of 3 sensors means that a single failure can be accommodated - but surely there should eventually be an ACARS maintenance warning to get the probe looked at?

[mm43]

There was a direct relationship between the rolling and pitching moments and that is best illustrated by superimposing the rolling data over that of pitching. Also remember that at all times the yaw damper continued to work and the rudder was being deflected up to the maximum of +/-7.9° allowed by the RTLU. Worth checking is the Normal Acceleration [g] to which has been added a smoothed line (red), and observe the 'g' recorded during the period of the THS movement.

The graphic below is a rejigged composite of those presented by the BEA, with the exception that the topmost section shows CAS as calculated (https://docs.google.com/leaf?id=0B0CqniOzW0rjNjAzMGRkYmUtZjMwNy00MzBmLWJmMzQtMzIwZjg 2ODYzZDlm&hl=en_GB) from BEA data by HazelNuts39.
http://oi51.tinypic.com/3097cs2.jpg
The sections covered by a pale yellow background are related to the period in which the THS moved from 3°NU to 13.6°NU, and the sections with a pale green background draw attention to the effect of a reduction in thrust.

During periods of prolonged right rolling/banking, the nose dropped in unison and the heading changed.

If the situation had been understood by no later than 2:12:10, there was a very good chance that the ND bank then taking place could have been converted into sufficient airspeed to allow a coordinated recovery. It didn't happen, as continued NU inputs and application of TOGA thrust saw to that.

[A33Zab]

Good observation!:ok:

Thx for the effort to make this clear.

@Diagnostic & sensor_validation:

so AOA#1 could be effected, however didn't had any influence.

FCPC using median AOA (or outvoted AOA#1), AoAsw using highest AOA value.

[Diagnostic]

@sensor_validation (re post#6628318 (http://www.pprune.org/tech-log/456874-af-447-thread-no-5-a-89.html#post6628318))

Very interesting AD, thanks for the link! I haven't seen any mention of the specific fitted AoA sensors, but that AD would certainly explain AoA "stickiness" wouldn't it.

It's a relatively recent AD (originally issued Jan 2010), but they are not limiting the list of potentially affected Thales p/n with any specific manufacturing date range - so perhaps that AD could apply to the AoA #1 sensor on AF447, if those Thales AoA sensors were fitted.

(IMHO it also goes to show that any AoA display should display the measured values for all 3 sensors, to allow the crew to take a decision abut which are most believable, in case of discrepancies - it must not display a single computed mean / median, as that calculation could be wrong, as the AD points out.)

@A33Zab - Many thanks for confirming that this erroneous AoA #1 value wouldn't have been used by the FCPC. We seem to be lucky that only 1 (and not 2) AoA sensors were producing erroneous values here - otherwise there's obviously a potential risk of another Perpignan-type situation, where the one "correct" AoA value gets voted out :uhoh:

[deSitter]

Smilin_Ed said

Trimming is not difficult and, for a pilot worthy of being called a pilot, it is a natural activity which is so routine that it is done almost unconsciously. I have flown aircraft with the pitch trim on the yoke, on the stick, and on the console. I never found it a burden to activate any of them. I prefer it on the stick or yoke since that does free up the other hand, but the difference is really not material. What I don't want is having the system changing the trim when I want to remain trimmed for a particular speed or AoA. In the case of AF447, the system gave up and turned it over to the people seated in the cockpit, except they didn't turn over everything and I believe that situation makes it more difficult to hand-fly. Autotrim has its place, but not in my cockpit when I am trying to hand-fly.

This is just conclusive. There is nothing else to argue about. I don't know why the apologists for automation cannot simply admit that they are wrong, or at least to admit defeat and claim that they are right anyway, as a face-saving maneuver.

[Mimpe]

great diagram mm43.

The thing that really gets to me about the graphic is the intensity of the initial zoom climb and the associated g forces....you cant really call that an appropriate hand flying response to autopilot drop out and speed indication failure by any conception..

I just wonder if the poor sod simply freaked out at all the alarms...tragic if the warnings of irrelevant failures ( irrelevant that is to the important task of of maintaining constant pitch and attitude) ended precipitating a bigger failure.

I suppose you could have some nice relaxing ladies voice saying " pitot failure...then a softly spoken expletive....its your aircraft now..we cant help you anymore...maintain constant attitude and thrust...please check the auto trim etc etc..."
to keep the poor man calm (if Any bright spark wants to automate the emergency response )

[rudderrudderrat]

Hi mm3,

Thanks for the graphic. I'm confused why the stab trim does not move significantly (up to your yellow band) - whilst the CAS has dropped from 275 to about 225 kts. I would have thought the auto stab trim would have followed the real reduction in airspeed. I realise it appears that PF seems to have pulled 1.4g then reduced to 0.5g during this period.

Does the delta g prevent the movement of the stab trim during those manoeuvres?

[jimjim1]

I get the idea that many real pilots here (I am not one) do not understand the Airbus pitch trim. As far as I can see it's not in any sense Trim as we know it Jim.

As I understand it:-

With autopilot off and hands-off the stick in Normal and Alternate Laws the aircraft maintains constant g (hence absent other inputs - pitch attitude). As I understand it the crew of AF447 (and indeed any AB not in direct law) could have wound the pitch trim wheel as much as they liked and as long as the elevator did not run out of travel no aircraft pitch changes would have occured. The computer would have matched the manual THS movements with elevator movements to exactly compensate so that aircraft g (pitch) was maintained.

The Airbus auto-trim merely seeks to keep an adequate range of elevator authority available (zero degrees of elevator deflection?) - however with a long time constant (delay if you like) so that it does not try to follow every little twitch of the stick/elevator. In Normal and Alternate Laws it has *no* influence on aircraft pitch while there remains elevator movement in the required direction.

So:- the THS and auto trim had NO BEARING AT ALL on this incident. Nil, null, zip, nada.

I will allow that perhaps when in the deep stall at extreme AoA (60 deg was it?), certain THS/elevator combinations may have been advantageous but that is strictly in Chuck Yeager territory and in any case no serious attempt was made to get the nose down so artful trim twiddling was never going to be considered by this or probably any other crew.

Of course all is not sunshine and roses. In direct law the pilot must ensure that the THS is positioned manually so as to allow adequate pitch authority. The exact same issue however occurs on Boeings too and Boeings too have crashed as a result. Airbus knockers can just therefore put their toys back in the pram forthwith:-) The issue of extreme THS "trim" and subsequent lack of needed pitch authority in rare circumstances appears to me to be an industry wide problem. It can occur in Boeings on autopilot disconnection and in AB on reversion to Direct Law. The burden of being in an unusual attitude and needing to use manual trim to get adequate pitch authority to recover is surely pushing at the boundaries of The Average Airline Pilot?

[rudderrudderrat]

Thanks jimjim1 for that lucid explanation.

So even in ALT2 Law, it would have been useless to hold the stab trim stationary by hand - since the computers would simply displace the elevators to a new "null position" and "trim the new attitude". Longitudinal speed stability is still not returned, hence no feed back of feeling slow and hence heavy in pitch

@DozzyWannabe.
Twitchy my foot. Control at altitude is about very small, corrective movements until you get a feel for how the aircraft is responding (even this "know-all", "office-chair" non-pilot knows that much - and no, that is not directed at you... ) - he was mashing the stick halfway to the stops from the get-go, so much so that the PNF repeatedly chastised him for it.

I wish I was as good as you. You make it sound so easy. Please see:
http://www.pprune.org/tech-log/376433-af447-132.html post 2632.
I have flown an A330 in ALT2 due to a twin ADR disagree situation (one blocked pitot + a different failed ADR) and I was quite surprised at how rapidly the aircraft banked versus the normal roll rate. It also exibited a strong natural tendency to return to wings level with the stick neutral. It is very easy to overbank in ALT2 law.

[gonebutnotforgotten]

Posted by jimjim1So:- the THS and auto trim had NO BEARING AT ALL on this incident. Nil, null, zip, nada.

Exactly, at last someone has noticed the absolute irrelevence of much that has been posted about this accident, particularly concerns about autotrim and alleged skittishness of 'manual' control at high altitude. All these would be appropriate to a conventional aircraft controlled in a conventional way, but the Airbuses after the A320 are NOT conventional in their control systems, and as jimjim says the sidestick commands g. And it is a confessed non-pilot who has to point this out. One minor quibble maintains constant g (hence absent other inputs - pitch attitude) is only true if the AT is maintaining speed correctly, if the thrust is insufficient for the drag, the speed will reduce and the controls will maintain g by increasing pitch attitude until... stall, which is what happened here. You can argue whether this is a good way to control the aircraft, but the first duty of anyone flying one is to understand this crucial point. Clearly the AF447 crew, and many others posting here, don't.

[takata]

Hi deSitter,
I don't know why the apologists for automation cannot simply admit that they are wrong, or at least to admit defeat and claim that they are right anyway, as a face-saving maneuver
A very long time ago, this case was closed for any people able to understand how autotrim works and that manual trim is available, at any time, if one doesn't like what autotrim is doing. One, which is able to understand it, obviously doesn't need to save his face either.

AF447 case is all about pilot's imputs which are not coherent with the situation, not about an automatism which stupidly followed orders given; it is like asking that the elevators should not follow nose up orders when stall warnings were sounding. In fact, it is a case calling for more automation as some would have liked that this aircraft could be able to determine all by itself that pilot's orders were stupid and should not be followed by any aircraft stupid control surfaces.

[takata]

Hi rudderrudderrat,
So even in ALT2 Law, it would have been useless to hold the stab trim stationary by hand - since the computers would simply displace the elevators to a new "null position" and "trim the new attitude". Longitudinal speed stability is still not returned, hence no feed back of feeling slow and hence heavy in pitch
Sorry but it doesn't make sense. How would the computer "simply displace the elevators to a new "null position" and "trim the new attitude" without changing the THS setting? When trim is activated manually, autotrim is frozen, can't displace anything anymore. If one is trimming manually, he's overiding autotrimming and computers would resynchronise with manual imputs after this point.

[rudderrudderrat]

Hi takata,
When trim is activated manually, autotrim is frozen, can't displace anything anymore. I can't find any reference to that - it would appear to be in error.

How would the computer "simply displace the elevators to a new "null position" and "trim the new attitude" without changing the THS setting? In the same way the system copes if the stab is "frozen" in a position with the loss of the relevant hydraulic systems.
Similarly I'm saying that if the stab trim is held stationary, it makes little difference to Normal or ALT LAW in pitch, because the elevators will be repositioned to compensate - until they run out of authority.

edit.
In fact, it is a case calling for more automation as some would have liked that this aircraft could be able to determine all by itself that pilot's orders were stupid and should not be followed by any aircraft stupid control surfaces.
The design of Pitch stable Law without Alpha Max protection, on an aircraft which is inherently naturally speed stable (by design concept), during UAS is not logical. Why would you want to do that?

[takata]

Hi jimjim1,
The computer would have matched the manual THS movements with elevator movements to exactly compensate so that aircraft g (pitch) was maintained.
It is not correct. THS do not replace elevators control and elevators are not used to replace THS trim.
(In flight phase) The C* law is activated. It combines the elevator control and the THS controls (AUTOTRIM function). It generates a load factor demand as a function of the position of the side sticks and inertial feedbacks. The gains depend on the speed (Vc) and center of gravity.

Consequently, any large change of pitch is not compensated by THS change and longitudinal stability is maintained. Moreover, in alternate law, C* law gain is reduced, hence 1g is not maintained "at all cost", and certainly not when the sidestick is moved back and forth.

I can't find any reference to that - it would appear to be in error.
See yourself:

THS control
The elevator orders are progressively transferred to the THS through a low-speed integrator to decrease the drag. This is the AUTOTRIM function. The THS movement is inhibited:
- under 50 ft in manual mode (100 ft in AP mode),
- when the high-speed and Mach protection is active,
- in case of manual action on the hand wheel,
- when the load factor is lower than 0.5 g,
- in case of abnormal condition law.
The THS movement is limited in up direction:
- when the alpha protection is active,
- when the load factor is higher than 1.25g,
- when the bank angle is above 33 deg,
- in case of low speed protection (alternate law).

[HazelNuts39]

FCPC using median AOA (or outvoted AOA#1), AoAsw using highest AOA value. According to the ATSB interim accident report on QF72, the FCPC treats AoA differently from the other parameters (which was an important factor in the QF72 occurrence):
Angle of attack data processing algorithms
There was a potential for the AOA sensors on the right side of the aircraft (AOA 2
and AOA 3) to provide different values to the AOA sensor on the left side of the
aircraft (AOA 1) in some situations due to aircraft sideslip.28 In order to minimise
the potential effect of this difference, the PRIMs used different processes for AOA
compared with other parameters when determining the value to use for calculating
flight control commands. More specifically, the processing of AOA data involved
the following:
• As with the other parameters, the PRIMs would continuously monitor the AOA
values from the three ADIRUs. AOA data was sampled about 20 times per
second.
• To confirm the validity of the AOA data, the PRIMs would compare the median
value from all three ADIRUs with the value from each ADIRU. If the difference
was greater than a set value for more than 1 second continuously, then the PRIM

(Note 28 - Sideslip: a condition in which the oncoming airflow is at a sideways angle to the aircraft’s
centreline.)

would flag the ADR part of the associated ADIRU as faulty and ignore its data
for the remainder of the flight.
• To calculate a value of AOA to use for calculating flight control commands, the
PRIMs would use the average value of AOA 1 and AOA 2. In other words,
(AOA 1 + AOA 2)/2. This value was passed through a rate limiter to prevent
rapid changes in the value of the data due to short-duration anomalies (for
example, as a result of turbulence).
• If the difference between AOA 1 (or AOA 2) and the median value from all
three ADIRUs was higher than a set value, the PRIMs memorised the last valid
average value and used that value for a period of 1.2 seconds. After 1.2 seconds,
the current average value would be used.
In summary, in contrast to other parameters, only two values of AOA were used by
the PRIMs when determining flight control commands. However, several risk
controls were in place to minimise the potential for data inaccuracies to affect the
flight control system.

[rudderrudderrat]

Hi takata,

When trim is activated manually, autotrim is frozen, can't displace anything anymore. Did you mean for the rest of the flight?

I interpreted the line "in case of manual action on the hand wheel," meaning only whilst the hand holds the trim wheel.

elevators are not used to replace THS trim
How does the system cope with stab frozen then, either due to relevant double hydraulic loss, or if the stab trim wheel is held stationary by hand?

[GarageYears]

Did you mean for the rest of the flight?

I interpreted the line "in case of manual action on the hand wheel," meaning only whilst the hand holds the trim wheel.

Manual trim overrides autotrim (micro-switches disconnect the auto-drive if I remember correctly) for the duration of manual input... hold the trim wheel or move it and that prevents autotrim - the computers monitor the trim state during manual trim and on manual 'release', the computer reacquires control from where the manual inputs left off.

So let's assume PF realizes he has inadvertently driven the trim to +13NU due to his excessive NU elevator demands - all he has to do is twiddle the trim wheel ND to something he likes (let's say +3NU) and let go. The trim will remain at or about +3NU unless he starts waving the SS in a nose up position for a long enough to cause the lagged THS autotrim to decide that the PF really wants more NU. To be honest it doesn't seem at all evil or that hard to understand, so long as you are half-aware of the systems of your aircraft - you know the one you are qualified to fly.

[Graybeard]

an aircraft which is inherently naturally speed stable (by design concept)Doesn't speed stable also mean pitch stable? When I studied aerodynamics a hundred years ago, the instructor said all conventional airplanes are unstable in pitch. Their sphugoid may be long in period, but still there. Nobody challenged him.

From what I read, the A330 was not designed to be pitch/speed stable, but pitch/speed neutral.

[CONF iture]

To be honest it doesn't seem at all evil or that hard to understand, so long as you are half-aware of the systems of your aircraft - you know the one you are qualified to fly.
It seems nice the way you tell things, but now if you have a look at the Airbus documentation, where is the quote, where is the "BE AWARE" that in some cases you would be better use MANUAL TRIM despite the fact AUTOTRIM is active or at least operative ?

In other words, which simulator exercice has ever encouraged such way of thinking ... ?

[Lyman]

To be simple, this aircraft is not meant to be hands fly. To keep some stabilities, a pilot must be known to fly with gentle move. No offense to this Airbus, hand fly is a definition to Pilot. To know this aitcraft is to know in his Law, the rolling is by direct to controls. This why the aircraft is worming through the air, sometines great, but always for the Pilkot mto be anxiuous, because he is causoing these rolls.

Trim is not an emergency to control for recover stall. It is to reduce drag, and too much small moving the elevators. It is slow for rewasons as above, the elevators are the prefer mechanism.

These Blue Angels fly their plane close to the ground, loudly, and slowly, with the mush,. it is as ballet.

But when these planes go 'depaert' in the altitude, the pilots must let go for the RBW to get flying back normal? Recover by wire. Red face rfor pilots who let go. Wht not some help automatic for these pilots of the 447.

Who wants trim to be silent, large, and possible to kill in this Stall. Automatic trim. This is for nonsense. See if you like, this pilot was not gentle. He was not confident, but he was stubborn. These make a pilot the choice not to be flying, but others. Where is this Captain?

Self confidence is good, but not bravado. For rolling, possible this right wing is trimmed down, for some reason, but pilot can control, but he plays back and forth, instead of holding some gentle trim? This trace for roll is too accurate to be some weather, too. consistent.

For Mr. takata Does this THS not start moving UP during the first Pitching UP by pilot? This because he is accedlerating above 1.2 g and the THS inhibits in this region? Would it have started to move soonerr, if he was more gentle in the pitch? Thank you sir.

[JD-EE]

3holelover re my comment about the plane image control surfaces clue, "Airbus will also display that on the ECAM FLT CTL page. (but you all knew that, right?... Is the suggestion for a separate screen always displaying this?"

Yup. It's there when you need it. Otherwise ignore it. If it also included an arrow to show AoA that would kill two birds on one separate display that is ignored most of the time. "Mousing" through a list of display menus when in the situation the plane fell into is not feasible - even if it is one push button beside the FD display.

[Lyman]

I think a new picture is nice. But, for who? For you? The answer is not in new. Old is the secret for this survival. Old pilot named Captain. Too much lights, too many colors, no one understands, and Captain is gone. More lights and pretty pictures....that is the tickets?

[JD-EE]

rudderrat and takata, when rudderrat said or quoted "The elevator orders are progressively transferred to the THS through a low-speed integrator to decrease the drag." was this necessarily correct? Is that from documentation or a presumption?

If I think about the apparent intent of the THS it aims to keep the elevator's mean position at neutral. So it's really integrating the elevator's position not the stick input commands. It will continue to drive the THS downwards as long as the PF does not push the stick hard enough for the elevator to go nose down, at which time THS would move. One comment I received suggests it would move nose down faster than it had moved to full nose up.

[Lyman]

So I see your position from flying. Nevermind my question.

Pilot 'sees Nose Down, and right drop. First thing he thinks is, not does. "I might need to stop that." Stop only, not reverse. That is next, maybe. He is too much the big picture, not enough, gentle, and patient.

He is trying for UP UP UP, if he sees this bird, and sees the bird UP UP UP, he thinks, 'more is wrong than at first I thought'? He is not the one to be flying, a new picture makes him more confused and more stubborn, some one else please to fly, maybe the one who asks, can we go down, now?

When "everything" wrong, the "right" thing can only make this worse, new pilot please. Time later for apologies and courtesy. And perhaps to be fired? get new job.

[JD-EE]

As a thought experiment I started looking at the data available to the computers that inform the pilot (and autopilot system component) with information about the plane's position, velocity, acceleration, orientation, rate of orientation change, and the rate at which the orientation rate is changing in three dimensional space.

They have GPS.
They have at least one very good ring gyro system and perhaps several more prosaic inertial reference units.
They have pitot tubes.
They have air pressure sensors for altitude.
They have AoA sensors.

And I'm tired enough just now I am probably forgetting something. Modern computational techniques (Kalman filters) can take all these inputs, known data about their goodness for measuring the data about the qualities for various aspects of their data. GPS measures the position (and time) the plane had in three dimensional space at some point in time relatively recent depending on the time scale involved, closer to milliseconds than seconds. It says nothing about velocity without considering the differences of at least two readings and ideally a string of readings for averaging. Accelerometers are good with the rate of change for the plane's three dimensional velocity. And so forth.

Presume some information is lost. That Kalman filter can adjust its parameters to reject or at least partially disregard data that is not present. This degrades the solution; but, you still have a pretty darned good idea of what the plane is doing.

Take the data and work back to extract more data, specifically wind speeds acting on the plane in three dimensions. (An AoA vane on the top of the plane might be handy for deriving a cross-wind data independent of calculated guesswork, by the way.)

Now we step off the cliff. What is the largest wind speed change a plane in normal (non-hurricane) conditions likely to encounter translated to a change in airspeed as measured and corrected? Is it 60kts, 75kts, what? This number gives you a wind velocity change range in which to look for a solution. The plane is without airspeed indication it is willing to accept. But it still knows its orientation and inertial velocity with cross checks from GPS. If flying pitch and power is sufficient to keep the plane flying I suspect AoA and power is even better. The plane knows the AoA. It knows the power. It knows attitude. It knows position. It can work backwards from the pitch/power figures to figure out what airspeed, actually what air velocity set, could have the plane moving the way it is with the pitch and power settings it also knows. It calculates a substitute airspeed of quite remarkable accuracy. (I'd then judiciously feed this back into the Kalman filter for a quality check on pitot readings.)

Presuming no CPU cycle limitations there is no reason for the plane's computers to decouple from most of the automation control of the plane. In fact I am willing to assert that the plane could actually have continued on to Paris and even landed on the mark under computer control with aggressive enough software.

At the very least that suggests even a modest '386 class machine should have been able to guess airspeed well enough to be able to issue a quite adequate stall warning at all times.

I am somewhat bemused by the APPARENT fact that the flight displays only relied on a very small subset of the sensors available. I'm sitting here idly wondering why these computers did not make use of the full suite of adequately accurate instrumentation available on the plane.

(And I suspect I ignited a stink bomb with this observation here among a batch of pilots, mostly good ones at that.)

[3holelover]

One comment I received suggests it would move nose down faster than it had moved to full nose up.
It drives the same speed in both directions, but from it's zero point it's got further to go nose up than it does down.
One of the tests we do on the THS involves testing it's auto function as well as that it'll stop auto-functioning when the wheel up front is held. We position a man in the tail to verify a valve moves to close and the THS actuator stops.

[Smilin_Ed]

JE EE: If flying pitch and power is sufficient to keep the plane flying I suspect AoA and power is even better.

Except AoA isn't very useful at cruise airspeeds. At cruise speeds, AoA varies much less per knot of airspeed than at approach speeds. Trying to fly AoA at cruise speeds is like trying to balance on top of a bowling ball. Not easy.

On the other hand, when trying to prevent, or recover from a stall, AoA is exactly what you need.

[Smilin_Ed]

Tyro: Only one question: In a FBW Airbus how will you as pilot sense which way to trim?

Without any feedback in the stick, it makes it hard doesn't it? The only thing you can do is to try it one way or the other and see what happens, but I sure don't want the system changing what I had set. If I'm trimmed in pitch and have the power set right in cruise, I really don't want to change anything. All I want to do is make very gentle changes to hold altitude but I don't want to change the trim.

[3holelover]

Why not leave the stick alone and fly with trim?

[Smilin_Ed]

Only one question: In a FBW Airbus how will you as pilot sense which way to trim?

Because in turbulence you want to preserve that trim setting which will cause the aricraft's positive longitudinal stability to get you back to a correct AoA. Several pilots here have said that simply letting go is the classic way to get out of a difficult situation, and that is true, but once the trim is changed, letting go is no longer an option. In fact, with the neutral longitudinal stability brought about by the autotrim (when hand flying) if you let go, the airplane will hold the existing pitch at one Gee and if it is nose up, you will either mush along or stall when you run out of kinetic energy. Several posters here have commented that the Bus has wonderful positive longitudinal stability. We should take advantage of it.

[HazelNuts39]

Interesting as personal preferences as to what autotrim should do or not do may be, I fail to understand what relevance to AF447 these have. Between 02:11:40 and 02:12:10 the PF pulled the sidestick fully back. If at any time in the descent he had pushed the SS fully forward 30 seconds and the THS had not moved, then it would have been an issue in AF447.

[CONF iture]

Interesting as personal preferences as to what autotrim should do or not do may be, I fail to understand what relevance to AF447 these have. Between 02:11:40 and 02:12:10 the PF pulled the sidestick fully back. If he had pushed the SS fully forward 30 seconds and the THS had not moved, then it would have been an issue in AF447.
HN39,

At time 02:11:40 was already mainly full NU.
The relevance is that the trim moved to that position under STALL WRN, it is true to state that the inputs were more UP than DN :

http://i45.servimg.com/u/f45/11/75/17/84/wiz_pi12.gif (http://www.servimg.com/image_preview.php?i=109&u=11751784)

... but is it unreasonable to think that the PF would not have manually trimmed or at least to that extent ... ?
And if he had, then I would not show up here to reply to your post.

As I said earlier, leave to the pilot that responsability to trim if that's really what he was looking for.

[Lonewolf_50]

mm43, thanks for that trace. It painted a very sad picture for me. At around 2 and 13, you had two pilots making control inputs, and given the way the SS inputs are summed, PNF's inputs (though this was a very late in the game state, maybe not recoverable by that point, somewhere around 10000 feet) of nose down were nulled out by PF.

Horror of horrors, to me, is that even after the control change to LHS the RHS was still making SS inputs.

:(

[Lyman]

takata has told the THS is inop for trimming up with accelerations above 1.25 g. It will not Auto trim when 'manouerving with this load or more. Elevators only.

Looking at the track of g just after pilot 'Ihave controls.' The Ths has not moving during all g above 1.25, so we should be thankful it has courteously not cause even a faster crash. This THS did as was told. Too bad the pilot isn't counting these chickens.

[Lyman]

The Ths became the factor mafter excess g load was lost in the climb. It is inhibited above 1.25 g for trimming. So up til the time of Ths starting to trim up (plenty of time to Sa and calm down and do as pj2 says.)

At this much g in the first climb, it wants a new display to tell the pilot "nose down, please?"

Human factors? Fancy words for manhandling the Poodle?

[CogSim]

Originally posted by spagolia:
It also struck me how (with the few exceptions just noted), neither PF nor PNF, nor the CDB once he returns, ever speaks of pitching up or pitching down. They constantly speak of going up and going down.

Consider this bit of conversation on page 90 of the report:

Watch your speed
Watch your speed
Okay, okay okay I’m
going back down
Stabilise
Yeah
Go back down

What does "Go back down" refer to? I think it refers to KIAS not altitude. If so, aft stick fits in with the conversation.

Again on page 95:

The speed?

One second later:

You’re climbing
SV : “Stall, stall”
You’re going down
down down
Am I going down now?
Go down
No you climb there
I'm climbing okay so
we're going down

I think "climb" refers to altitude and "going down" again refers to KIAS. Otherwise, the conversation doesn't make sense.

On page 96:

Amazingly this is the first mention of the word altitude.

What do we have in
alti?

And both the Captain and PNF react with total surprise.

(...) it’s impossible
On alti what do we
have?
What do you mean on
altitude?

On page 98:

Nine thousand feet
Climb climb climb climb
No no no don’t climb

Why would the Captain ask not to climb after PF calls out nine one thousand?

[Lyman]

Because it is at this point he sees PF climbing (wrong) as PNF is trying to descend. He sees they are both inputting, and hears it on the SV prompt.

It is this PF overcontrol he demands be stopped.

[Shadoko]

@ CogSim

Climb and Go down are from the French Monte et Descend. There is no ambiguity in French. "Descend" can't be any else. IMHO.
I pasted the French (pages 98 ans 99) beside the English page 95:

http://i44.servimg.com/u/f44/14/14/01/64/95en_f10.jpg

If you want to try some "electronic" translation from French, you can have a "à" with Alt+133 and "ç" with Alt+135 :)

[CogSim]

Because it is at this point he sees PF climbing (wrong) as PNF is trying to descend. He sees they are both inputting, and hears it on the SV prompt.

It is this PF overcontrol he demands be stopped.

But its the PNF who has asked for the climb. I think the Captain is overruling the PNF here.

[DJ77]

If at any time in the descent he had pushed the SS fully forward 30 seconds and the THS had not moved, then it would have been an issue in AF447.
Looking at the BEA plots or better at mm43’s re-arranged plots (#1770) pitch response to the few consistent nose-down sidestick inputs appears very weak. Except the last one, pitch curve minima seem more related to high roll angle than stick down input. During these nose-down sick periods the elevator angle never increases above -15 deg. Why would the THS start moving up?
A possible reason could be that in the stall domain decreasing AoA increases a little Nz in an almost unchanged trajectory. Remembering that the pitch control is still C* it is easy to see that an Nz increase will decrement the actuating signal in the control loop. Moreover, the default gains used when CAS is invalid likely play against a fast response.

[Lyman]

I think I am correct from nine thousand. Both piloits are at cross purposes. I am so sad to say, that Though I may be wrong, or right, it does not matter/ none of the three knew either, and they were There./

[CogSim]

Originally posted by Shadoko
Climb and Go down are from the French Monte et Descend. There is no ambiguity in French. "Descend" can't be any else. IMHO.
I pasted the French (pages 98 ans 99) beside the English page 95:

Thanks for the clarification Shadoko. Why not just use descend in the translation then?

[Shadoko]

@ CogSim
"Why not just use descend in the translation then?"

For an old man like me, the PF speaks a very poor French. I think to make this understandable in English, they use what they think the simplest words. I am not enough fluent in English to tell if they achieve that.

[takata]

rudderrat and takata, when rudderrat said or quoted "The elevator orders are progressively transferred to the THS through a low-speed integrator to decrease the drag." was this necessarily correct? Is that from documentation or a presumption?
Sorry, I'm a little bit lazzy (or too busy), as I didn't quoted the reference. It is from my notes about AMM 27-90-00, but I suppose it was from an A320 document as the g-load limits for an A330 THS is rather 1.3 / 0.5 g (instead of 1.25 / 0.5 g quoted). But both THS are basically the same thing, as far as the operating system is concerned.

[safetypee]

Lyman, (#1804)
I suspect that BEA’s examination of ‘Human Factors’ will consider the many aspects within the scientific discipline. This should avoid the often bigoted dismissal of human factors, human error, etc, as a coverall for many complicated and interacting issues in such accidents.
Such an investigation might only be comprehendible with some speculation; this requires activity beyond the scope of ICAO guidance for accident investigation (factual reporting), but this work could provide a valuable resource for learning about the crew in AF447 or similar humans/situations.

The major threats in accident scenarios are in the extremities of the ‘SHEL’ human factors model. The risks are in the interface with the central ‘L’ – the human interaction with the situational environment.
The contributing causes to an accident can be found in all aspects of the model – threats, risks, situation, and management – human activity; the difficulty is deciding which had the greater contribution, or which might be more effective for improving safety.
A human factors view might only be another view, but in such a complicated accident another view might be valuable.
With hindsight, perhaps the crew of AF 447 would have benefited from another view.

[xcitation]

One thing that stands out is at circa FL350 the Captain should have taken his seat. Why would he not do that?
Why would a Captain decide to be only a back seat observer and commentator?
With my limited experience I have found that all the pro pilots (civy and military) are of the assertive/like to have control personality more than passive observer personality. (sorry I'm not a psychologist so I lack the fancy words).
Equally the PNF should have given his left seat back to his boss and insist he take it. Especially after the insane teenage nagging conversations he had with PF.
What am I missing here - is there an AF policy in an emergency for CAPT to stand back and oversee/bark orders?
I don't think trading seats would take that long given the adreniline.

[jcjeant]

Hi,

What am I missing here - is there an AF policy in an emergency for CAPT to stand back and oversee/bark orders?I think that at that time the rule in AF should be absent .. or if it existed .. it was not considered by some pilots
According to the Colin report .. it seems that a certain indiscipline prevailed (and perhaps still exists) in AF
Colin report (2006) available here (PDF french)
rapport_colin__juin_2006_.pdf (http://www.mediafire.com/?o7t5u31cxso5t7o)

Extract


Conclusion

Au terme de ce rapport et pour revenir à I'essentiel, la commission souhaite rappeler en
quelques points clés les observations et conclusions auxquelles elle est parvenue.
. Air France est particulièrement exposée aux risques aériens du fait des
particularités de son réseau, de l'architecture de sa base principale et enfin de son
histoire récente.
. En analysant les facteurs de causalité principaux dans les événements graves et
dans les Incidents Carburants, elle observe que les facteurs humains (conscience
de la situation, synergie, processus de décision) sont les facteurs que l'on retrouve
dans 8 événements sur 10, très loin devant les facteurs organisationnels,
environnementaux et techniques, même s'il convient de ne pas négliger les
contributions potentielles de ces facteurs.
. Des faiblesses importantes en terme de formation, d'appropriation réelle et
concrète et de capacité d'évaluation, de ces facteurs humains, ont été observées
dans la population PNT comme d'ailleurs dans toutes les populations dont les
actions et les décisions ont des conséquences directes sur la sécurité des vols.
. Ces faiblesses en terme de fonctionnement transverse - de synergie en langage
CRM - n'ont pas permis à I'entreprise d'avoir une vue claire et objective de ses
performances en matière sécurité aérienne et d'y apporter les solutions concrètes
et adaptées, en temps et en heure.
La commission est convaincue qu'il y a lieu d'établir un lien formel de causalité entre les
faits constatés et ses résultats en terme de sécurité.
La commission recommande à l'entreprise de se mobiliser pour mettre en ceuvre ses
recommandations conienues dans le chapiire Vlll en gardani à I'esprit les trois
principes :
Raw google translation

conclusion

At the end of this report and to return to the essential, the Committee wishes to recall
some key observations and conclusions it reached.
. Air France is particularly exposed to risks because of air
peculiarities of its network, the architecture of its main base and then his
recent history.
. By analyzing the causal factors leading to serious events and
Incidents in the fuels, it notes that human factors (awareness
of the situation, synergy, decision making) are the factors found
in eight of 10 events, far ahead of organizational factors,
environmental and technical, although it should not be neglected
potential contributions of these factors.
. Significant weaknesses in terms of training, ownership and real
concrete and evaluation capacity of these human factors were observed
in the crews (pilots) and indeed in all populations with
actions and decisions have a direct impact on flight safety.
. These weakness in terms of cross-functional - synergy language
CRM - did not allow the enterprise to have a clear and objective of its
performance in aviation safety and to make the concrete solutions
and adapted in a timely manner.
The committee believes it is necessary to establish a formal link between the causal
findings and results in terms of safety.

[wallybird7]

It seems to me that what everybody is forgetting, is that the co-pilots have never had the opportunity to hand fly the aircraft at altitude nor in different modes/laws. And therefore all of the inputs were merely trial and error. At altitude and during turbulence and under stress.
How this could have been overlooked is literally unbelievable to me.

[rudderrudderrat]

Hi wallybird7,

How this could have been overlooked is literally unbelievable to me.
I agree. According to: http://www.pprune.org/tech-log/376433-af447-132.html post 2632, the author points out the handling of the aircraft with UAS was different to the simulator.
I think the sims. will need better data to imitate the handling more truthfully.

[CONF iture]

In a FBW Airbus how will you as pilot sense which way to trim?
No different as any conventional aircraft.
You did trim already in the sim when the aircraft was in direct law, didn't you ?
How was is any different ... ?

[RetiredF4]

CON fiture
Quote:
Originally Posted by TP
In a FBW Airbus how will you as pilot sense which way to trim?

No different as any conventional aircraft.
You did trim already in the sim when the aircraft was in direct law, didn't you ?
How was is any different ... ?

O come on, you are kidding?

In a conventional aircraft you set desired attitude with stick input and relief the resulting stick pressure (either natural or artificial one) with trim.

would not work in an aircraft without feedback?

[CONF iture]

In a conventional aircraft you set desired attitude with stick input and relief the resulting stick pressure (either natural or artificial one) with trim.
OK Franz, how is it different from direct law on the bus ?


Have you ever flown the bus ?
Have you ever flown the bus in direct law ?

[RetiredF4]

CONfiture
Quote:
Originally Posted by RF4
In a conventional aircraft you set desired attitude with stick input and relief the resulting stick pressure (either natural or artificial one) with trim.
OK Franz, how is it different from direct law on the bus ?
Have you ever flown the bus ?
Have you ever flown the bus in direct law ?

No, i´ve flown conventional aircraft with natural and artificial feedback,therefore i know that forcefeedback to the stick is an elementary necessity for trimming.

And i know also, that there is no feedback to the SS in airbus.

That is all i need to know, that trimming must be different.

I dont say, that it is not possible or more difficult, but it is not like trimming a conventional aircraft with feedback.

I would be very interested though in a detailled description, how it is done when autotrim is not available. I.e. concerning the pitch, do you steer pitch only with the trim like turning the trim wheel and look what it gives? Then readjust and finetune?

[CONF iture]

I would be very interested though in a detailled description, how it is done when autotrim is not available.
In a conventional aircraft you set desired attitude with stick input and relief the resulting stick pressure (either natural or artificial one) with trim.
Same procedure is used with the FBW in direct law - As long as stick deflection is needed in order to maintain the choosen attitude, it means the aircraft is not properly trimmed.

To trim the Airbus feels as natural as trimming any other type.

[takata]

And i know also, that there is no feedback to the SS in airbus.
Is it another urban legend?

A. Side Stick Controller (Ref: AMM 27-92-00)
Two side stick controllers are used for pitch and roll manual control one on the captain lateral console, another one on the first officer lateral console. The two side sticks are electrically coupled. The arm rest is fixed on the seat.

General concept is a fail safe concept i.e. mainly that a single failure provides:
- Neither total loss of artificial feel
- Nor undetected uncontrolled pilot order.

The hand grip includes 2 switches:
- A/P disconnect pushbutton is used for: A/P disconnection in A/P mode; Priority logic between sticks in manual mode
- Push-to-talk button.

The red light of the ANN-SIDE STICK PRIORITY, CAPT (23CE1) or ANN-SIDE STICK PRIORITY, F/O (23CE2) comes on in front of the pilot who has lost the priority.
The green light of the ANN-SIDE STICK PRIORITY, CAPT (23CE1) or ANN-SIDE STICK PRIORITY, F/O (23CE2) comes on in front of the pilot who has priority as long as the side stick which has not priority is not a zero.
In case of simultaneous action on CAPT and F/O side sticks, the green lights of ANN-SIDE STICK PRIORITY, CAPT (23CE1) and ANN-SIDE STICK PRIORITY, F/O (23CE2) flash at the same time.

Space provision is provided for mounting of a datum-adjust button (used in A/P mode).

The side stick includes:
- a hand grip
- a protection boot
- two axes
- two spring rods for pitch artificial feel
- two springs for roll artificial feel
- two transducer units ; one for roll, the other one for pitch
- one solenoid to introduce, in AP mode, a higher threshold to move the side stick out of the zero position.http://takata1940.free.fr/sidestick0.jpg

To trim the Airbus feels as natural as trimming any other type.
Thank you for mentioning that.

[hetfield]

Artificial feel - with a spring rod.

Aha.....

So it feels the same in a stall as with 340 kts.

[3holelover]

Artificial feel from springs is not the same as feedback. ...but yes, it should be sufficient to tell the pilot what forces he's having to maintain, and therefor, how to trim.

[gums]

Interesting about trim feel, and it could have played a role in Viper stick implementation.

The thing uses stick force per gee or roll rate, so it was real easy to trim off the control pressure to get a gee (gear up) or AoA (gear down). Max force was about 24 pounds in pitch and 16 or 17 pounds in roll. Neat thing about roll was the jet would command up to 180 deg per sec calculated aileron deflection at ZERO stick input to maintain zero deg/sec actual rate. This saved a jet and pl' Gums when one leading edge flap folded up on me after raising the gear one day ( see the pic in my profile bio).

So maybe force per aircraft movement could be emphasized for the 'bus.

[RetiredF4]

@takata and @ CONfiture

Please note again, that i didn´t comment at all on the subject, that the trimming feels like trimming an conventional aircraft or that it is worse or better or not possible.

I said (at least that was and is my intention), that it is not like concerning the process of doing it.

The SS has an artificial feel, i did not deny that. It tells you stick deflected NU, than trim NU to equalize, or vice versa. It´s not comparable to a tactile feedback (be it natural or artificial), where the amount of mistrim and therefore the amount of necessary correction can be felt in the hand on the stick due to stick deflection from neutral and force required to keep it deflected. It is therefore airload related feedback.

That is IMHO one of the main reasons, why there is autotrim present and necessary in normal and alternate law, as in those laws SS deflection in pitch results in a change of loadfactor, which is kept stable when SS is back to neutral (as long as protections do not intervene). If i understand the system, the elevator is positioned by the flight control computer upon ss input, feedback from the response of the aircraft is fed back to the flightcontrol computer (not the SS) and elevator position is again adjusted by the flight control computer. With some delay the THS trim will zero out the elevator deflection. During this process (except the initial SS input) the SS is in neutral position. How should a pilot zero the elevator demand with manual trim without tactile feedback? Look on a gauge with elevator position? On behalf of the aircraft reaction? Therefore the need of autotrim.

That also poses problems to disable the trim in special flight conditions in normal or alternate law, where to start and where to end the input of autotrim? It would solve one problem and cause some others.

In direct Law there is a direct relationship between SS deflection and elevator deflection (some other factors like CG and configuration and ??? play a roll though), but neither tactile feedback to SS nor to the flightcomputers. Only the feedback from the behaviour of the aircraft is present. But this feedback is dependent on how fast the aircraft reacts to the inputs (as in this stall very slow to react to ND inputs), therefore trimming process (trim, check, trim again, check, trim some more, uups that was too much..) would be slower and a process needing more attention.

Unfortunately (in my oppinion) AF447 didn´t go into direct law, otherwise the aircraft behavior and the trim behavior could have changed the outcome of this accident.

Hope that clarifies my statement somewhat, no intention to post urban legends or to dsicredit airbus or to join any anti airbus comunities. I´m a german tax payer and lot of german tax money is working with EADS.

I´m just trying to understand the system in its detail like i was used in the aircraft i´ve flown, but in looking on many posts with different understandings on two threads and reading nearly every available documentation from AB over a period of 2 years still keeps me mainly in the dark concerning lots of subjects.

And i´ve the impression that the crew of AF447 found themselves in a worse situation, because all the time they´ve got where a few minutes.

[Lyman]

Is it possible then that the autopilot was not sufficiently rapid to keep control? (447) What happens when 330 Auto can't be so quick as your Viper?

What happens if roll rate for gums is too slow by half when one slat fouls?

What happens to 447 when auto is too lazy? airplane is an airplane?

F4 For two years, no progress has been made on either side. You and smilin have nailed the problem each time, and each time it is ignored by "The a/c did what was directed."

It also did what was directed, apparently, by NOT trimming whilst the a/c was in an aspect commanding certain g. So if the Autotrim is disabled when the airframe is under maneuvering load, whty does it return "automatucally" (at the top of the gd climb, of all places), to seal the fate of the pilot who probably couldn';t have recovered anyway, even knowing the Auto trim was active?

Don't be sly, messrs. AB. Whether the pilot knew or did not know the Autotrim was active may well have been irrelevant. "Red Herring"? A "helpful" Gremlin in the tail cone, with a prod to mystify the crew? Changing the handling of this airframe in ways not EVER practiced by the humans?

[gums]

My point about force versus deflection is that the stick felt more like what we were used to. We trimmed off pressure not stick deflection. the thing only moved about 1/8 th inch.

Unless the 'bus springs are weird, it should take more "force" to move it further, so manually trimming off "pressure" should not be a big deal.

In my case, the jet commanded a left roll to counter the loss of right wing lifties and roll due to yaw. That sucker had lottsa drag. So I had to add more control surface deflection, and post-flight analysis indicated I had about a pound or two force to play with. In short, I basically held full left stick for about 10 or 15 minutes.

As other pilots point out, the ideal stick would require increased pressure/movement according to dynamic pressure. Just like old days when you could feel the forces on the control surfaces due to those air molecules. Go fast and stiff stick, slow down and stick gets mushy, as does the plane, duh.....

If the force feedback system fails, then you have the basic spring/torsion tube/whatever built into the thing. No big deal.

The problem with the 'bus is that a small continuous input from neutral eventually causes the HS to move ( ours didn't do this - it always wanted to get back to the manually set trim gee or trimmed AoA). The autotrim is neat when maintaining level flight or a climb/descent, as you can gradually relax pressure.movement to get the desired attitude or AoA.

However, in this case it helped the plane to achieve an ever-increasing AoA due to speed decay and the "one gee" default trimmed gee condition. Had the pilot used only roll and a neutral back stick, the THS would not have continued to command nose up.

Once zooming thru all the AoA protections with back stick, the plane entered uncharted territory and only a few folks would have understood the exact aerodynamic condition and need for manual down trim and forward pressure. Despite some folks' thots here, I don't think pure elevator can overcome the pitch moment that the HS can exert when fully deflected one way or the other when flying slow. Mach effects could have been a player initially, but once slow enough, they probably were not a significant factor.

[Lyman]

"I basically held full left stick for about fifteen minutes" That sounds eerily familiar to 447. Drag? Right wing drop (Chronic and/or acute?)

Don't forget though, that PF could not "forget about aft stick", he had a bobbing nose to lift and drop to maintain "level" and avoid a SPIN. He heard the initial Warning, and if he was a pilot, he knew instinctively if he hears the horn, he gaddam better keep the wings level.

He "started" his "climb" WITHOUT AUTOTRIM, for once he exceeded 1.25 g, the slab inhibits (g prot). After his load (g) diminished, the Autotrim started up, at the top of his "climb", did he know? Could he have compensated if he did know?

The entry to manual reversion is not addressed at all well. Someone take a breath and discuss what may have happened if roll rate demand was beyond AutoPilot, and did the "Upset" (at handover) corrupt the Speedata?

Honest question. Was Pf "playing the g prot" his inputs were not held initially, he appears to have been "bumping" the elevators. How does he lockout Auto Trim? His full back and held inputs come later, AFTER the THS has planted on its Stops? Is mayonnaise a technique to lockout the slab by pilot device, and not in the FCOM?

[takata]

The SS has an artificial feel, i did not deny that. It tells you stick deflected NU, than trim NU to equalize, or vice versa. It´s not comparable to a tactile feedback (be it natural or artificial), where the amount of mistrim and therefore the amount of necessary correction can be felt in the hand on the stick due to stick deflection from neutral and force required to keep it deflected. It is therefore airload related feedback.
This is what the transducers are supposed to do. Feedback from every control surface is recorded, digitalized and corresponding pressure is applied back to each sidesticks axis. What should have created the legend of "no sidestick feedback" is due to normal C* law feeling of being always correctly trimmed (which is the case).

[Lyman]

Since the a/c was almost immediately in "test pilot territory", what role could immediate Autotrim NU have played in a potential recovery? The THS, as takata has said, does not trim UP when g thresholds are exceeded. At the least, it would have provided a more immediate climb, and not required the PF to continue his ever increasing NU demands. Can't think of everything, I guess. That "Zoom" thing. We know that 330 can recover from STALL, it is patent.

Seems if this THS had not held back, the a/c would have STALLED with a great deal more energy in its airframe, perhaps emphatically dropping her nose, etc. The tail drag did them in.

then again, the safety record is exemplary.

It is assuredly coincidence, but when the THS was needed for climb, it was not available. Later, when it was not needed, it came back, and ruined the trajectory. Still later, it prevented a recovery by limiting elevator authority all the way down.

The way I see it

[takata]

It is assuredly coincidence, but when the THS was needed for climb, it was not available. Later, when it was not needed, it came back, and ruined the trajectory. Still later, it prevented a recovery by limiting elevator authority all the way down.

The way I see it
Welcome back, "Bearfoil..."
It was, at first, quite hard for me to parse what you were saying exactly, but now, from a couple of your last post, it becomes perfectly clear again that your style and focus could not be so perfectly immited!
Are we going to chase our tails again on every mentioned subject?

[Lyman]

takata

We are a committee. One is a writer, an editor, actually. A retired Pilot, an active PPL, and others, a designer, a mechanic, etc.

If this is illegal, then we say adieu.

If not, when you gather your thoughts, can you respond? You brought it up. The THS is dormant to help in the NU demand. Later, with a climb initiated, it activates and zooms the a/c.

BEA: At PITCH +10, the a/c started to climb, (they mean ascend?)

Are you willing to admit the THS has caused a problem? However unfortunate for the AB Philosophy, (It did as directed), do you have the stuffing to admit that whether the flying pilot knew or did not know, there is a problem when Autotrim interferes in an emergent maneuvering regime?

We have our own moderator, and he cares little for ruffled feathers. You have always seemed fair and passionate. Are you willing?

bon chance

[takata]

takata
We are a committee. One is a writer, an editor, actually. A retired Pilot, an active PPL, and others, a designer, a mechanic, etc.
If this is illegal, then we say adieu.
If not, when you gather your thoughts, can you respond? You brought it up. The THS is dormant to help in the NU demand. Later, with a climb initiated, it activates and zooms the a/c.
BEA: At PITCH +10, the a/c started to climb, (they mean ascend?)
We have our own moderator, and he cares little for ruffled feathers.
bon chance
Well, Bearfoil, I have no idea why you (incl. teamwork!) are doing this!
Moreover, me (alone) absolutely never complained about your (multiple) identities!... and behavior to anyone (here, I meant moderators).

I just think that this is a very serious proof of something very wrong with yourself - your many "minds", objectives, agendas.... (including how many other clones?)
I won't complain either as I'm all for open free speech, and it's not my job to moderate you if you (and whoever) are unable to understand that.
My precious...!

[DJ77]

FCOM 1.27.10 P3:

"The two controllers are springloaded to neutral, and are not mechanically coupled."

[Lyman]

You grant me way too much power. You make more sense when you stick to the topic.

g hobbles? (Preventions) Pilot/Auto "Misunderstanding?" Etc. ?

:ok:

[takata]

Hi DJ77,
"The two controllers are springloaded to neutral, and are not mechanically coupled."Yes. Which meant that when Captain moves his sidestick, there is no mechanical relation with F/O's position.

Hi PJ2,
On landing, the Flare Law introduces a slight ND tendency, against which the pilot must pull, naturally creating the flare manoeuvre.How could this ND tendency be introduced if there was no way to change the pressure applied on the sidestick pitch axis?
My understanding is that sidesticks behave differently in auto mode and manual mode, hence will use different circuits. Documentation about those details is lacking in manuals (like many other details: find, for example, the detailed matrix of Airspeed, Alpha, etc; function monitoring).

[A33Zab]

PJ2 & Takata:

There is NO feedback to SS.
Both roll and pitch channel have identical dampers.

Roll channel two rotary spring elements which ensures artificial feel.
Pitch channel two artificial feel spring rods.

The required artificial force in the pitch channel:

http://i474.photobucket.com/albums/rr101/Zab999/SSForce.jpg

[GarageYears]

Welcome back, "Bearfoil..."

Oh, no, the frigging V/S is going to fall off again.... :{

[Jutta]

even though I am not a "flying" person other than sitting at the rear of a plane I've followed this long discussion with enormous interest.
Many questions turn around my head, but I will continue reading here to find some of them answered.
Nevertheless there is one point I would like to have answered: I love the computer, it's technical side as well and have no problem to understand, not all, but most of the problems which might arise. But I know that not only in my family but also among my friends, there are people who dislike using the PC, even though most of them have to use them at their work, in private they tell me after weeks "oh yeah, i have to go and look at my mail" :}

Now the profession of a pilot is first of all to know how to fly a plane, which in itself is already very demanding. But what about a person who loves to fly but has no interest or notion of a computer? He or she just doesn't understand what's it all about as he doesn't care. But in modern flying this is essential. When reading about the reaction of the PF I could not help wondering if he really understood the planes computer and everything connected with it.

[CONF iture]

The Flare Law doesn't affect the stick, but it instead "rolls in" a bit of ND bias, against which the pilot must then pull.
I know 320 and 330 work things differently in the flare phase, but I believe the "rolls in a bit of ND bias" is produced by an automatic amount of down elevators, which 'detrim' the aircraft.

[sd666]

Lyman/Bearfoil wrote...


We are a committee. One is a writer, an editor, actually. A retired Pilot, an active PPL, and others, a designer, a mechanic, etc.


OMG - Bearfoil has evolved into some kind of HIVE-MIND!

Before you shoot off on another wild goose chase concerning the THS, make sure you understand what an "integral" term does in a time-domain control system. (or just look up "integration" on wikipedia). If you understand that, you will understand that the THS position was entirely correct and by-design during the incident.

[DozyWannabe]

Now the profession of a pilot is first of all to know how to fly a plane, which in itself is already very demanding. But what about a person who loves to fly but has no interest or notion of a computer? He or she just doesn't understand what's it all about as he doesn't care. But in modern flying this is essential. When reading about the reaction of the PF I could not help wondering if he really understood the planes computer and everything connected with it.

Hi Jutta - and welcome.

I dont think it's a case of the PF failing to understand the computer (which in this case, outside of autotrim, wasn't actively doing anything to assist his inputs anyway). He seems to have broken a few basic rules of aeronautics which remain the same whether you're in a Cessna, a 747 or an Airbus - chief among those being that you do not pull up into a stall warning*. Other contributing rules include "Do not make large control inputs at cruise level/at the limits of your aircraft's achievable altitude", and the basic rule of CRM, which is "ignore your co-pilot at your peril, doubly so if he or she has more experience than you".

The fact that the Airbus uses a computer to manage many of its functions is neither here nor there anyway - the fact is that if you are certified to fly an airliner and you have people in the back, it is incumbent upon you to know your aircraft's systems well, whether they consist of modern technology or cables, pulleys and bellcranks.

[* - By which I mean the stall warning that was sounding for nearly a minute before the AoA readings became unreliable, during which time he was still pulling up. ]

[Jutta]

and your explanation.
What I found very disturbing was the fact that the CDB, when he came back into the CP, did not take his seat immediately. Even if I understand that there are certain rules which have to be followed. But the situation was exceptional, he must have felt that!? Both the captain and other co-pilot put their lives into the hands of a person who was visibly in a lot of stress, mildly expressed. For a laywoman :) this is not comprehensible at all.

[infrequentflyer789]

Well, Bearfoil, I have no idea why you (incl. teamwork!) are doing this!


With respect, not sure you are correct there - although maybe you have info I do not. Bear came to (more or less) a conclusion in this post:

http://www.pprune.org/rumours-news/447730-af447-wreckage-found-131.html#post6620025


The ship seemed fine at 2:10:05. What happened next (and is still happening, one fears), has to do with some basics, and that, as a pilot, is embarrassing.

Given the lengths to which he has gone over the past years to find theory after theory to absolve the pilots, that was probably a painful end to the journey. Give the guy some credit for posting that.

I think it unlikely he would be reopening previous arguments after concluding in that way, and even more unlikely that it would be done hiding behind a different name - thin skin was not an attribute of the old bear.

[Lyman]

sd666

Hmmm.... The "performance as designed" is not in dispute. The THS did in fact, perform as designed. Clear? Because you like many others are stuck on "Design", and 'right' or 'wrong'.

It is, out the gate, quite possible, even likely, that the THS and the PF BOTH performed to "spec".

Fundamentally, the question is this.

The THS lay dormant for a time when the PF was attempting to climb the a/c. It is not programmed to TRIM NOSE UP when the airframe is experiencing g accelerations above, let us say, 1.25g.

The a/c, when the THS came back on line, was climbing, even rotatiing further NU. If unexpected, this could certainly create a "Zoom". A radical PITCH UP, and an unwanted extension of time in aspect (Climb).

So the THS started to TRIM NU from -3 to -13+ without stop, as the PF was still "stick back". Energy, both aerodynamic and ballistic, paid off and the a/c STALLED. Now, the THS is fully NOSE UP, and remained that way till impact. Insufficient ND from PF? Possibly. Stall warning when A/C was close to recover at each ND excursion? So we are told.


Finally, what is the a/c specific performance in Pitch with the elevators free and the THS full NU?

Elevators are sheltered from airflow in this configuration when deflected NOSE DOWN.

They are fully exposed to airflow in this configuration when deflected NOSE UP.

The THS in FULL NOSE UP is in and of itself a very powerful fixed full up Angle of INCIDENCE.

I can frame the question any of a number of other ways. It is meant to be clear and straightforward. Your thoughts?

Please do not feign exasperation to escape answering, as others do.

Again, the THS is not being questioned either as to Performance, or DESIGN.

[DozyWannabe]

and your explanation.
What I found very disturbing was the fact that the CDB, when he came back into the CP, did not take his seat immediately. Even if I understand that there are certain rules which have to be followed. But the situation was exceptional, he must have felt that!? Both the captain and other co-pilot put their lives into the hands of a person who was visibly in a lot of stress, mildly expressed. For a laywoman :) this is not comprehensible at all.

Right, so one of the takeaways from this incident so far is that CRM (Crew Resource Management - plenty of material online if you need more background info) at Air France was in need of review when this accident occurred.

The difficulties in the Captain re-taking his seat are as follows however:

- The PNF, who seemed to have a pretty good grasp of the situation, yet sadly did not feel the ability to directly intervene was sitting in the Captain's seat. Technically the Captain could have taken the PF's seat, but in doing so would have been putting himself in a position where he wasn't as familiar with the controls as he was in the left-hand seat.

- The two F/Os had been at the controls as the situation was developing and as such, the Captain was unaware of what had led up to the situation - it would have been reasonable for him to assume that the F/Os had better situational awareness than he did at that point (though it was a sadly misplaced assumption)

- The aircraft was pitching and rolling to a significant degree. Exchanging seats at that point would have been difficult and probably would have taken a significant amount of time, and as such could have put them in more danger than they were in already as far as the Captain knew.

Personally I think that the logic for not re-taking a seat at the controls was understandable. What bothers me is the fact that he felt it OK to leave two F/O's, one of whom was fairly junior and probably still a little demob-happy (having just returned from vacation) in charge as the aircraft was transiting a known problem weather area.

[@if789 - I got a very well-written and heartfelt PM from bearfoil just after the report was published, expressing an understanding that human error was probably the largest contributing factor, and a desire to take some time away from the forum - nevertheless he was back on less than 24 hours later having picked up sonething CONF said about control logic and saying that it couldn't have been the pilots' fault again. ]

[jcjeant]

Hi,

Originally Posted by Jutta http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/buttons/viewpost.gif (http://www.pprune.org/tech-log/456874-af-447-thread-no-5-a-93.html#post6632439)
and your explanation.
What I found very disturbing was the fact that the CDB, when he came back into the CP, did not take his seat immediately. Even if I understand that there are certain rules which have to be followed. But the situation was exceptional, he must have felt that!? Both the captain and other co-pilot put their lives into the hands of a person who was visibly in a lot of stress, mildly expressed. For a laywoman http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/smile.gif this is not comprehensible at all.


More:
http://www.pprune.org/tech-log/456874-af-447-thread-no-5-a-91.html#post6630926

[hetfield]

Artificial pitch feel

Please enlighten me.

Is it a function of elevator load?

Or is it just a spring rod, no matter if the aircraft is in a stall or at 340 knots?

Thx

[sd666]

Bearfoil,

The fundamental issue is that the PF applied mostly nose-up inputs - hence the THS progressively trimmed up (by integrating his input).

If he had applied the correct stick-forward action in response to a stall, we wouldn't be talking about this at all. The design of the auto-trim is not the cause - the THS acted in response to the PF's input. His inputs were not appropriate. Cause and effect.

In fact, if he had flown pitch and power, it wouldn't have stalled at all.

[hetfield]

In fact, if he had flown pitch and power, it wouldn't have stalled at all. Indeed,

but what about tactile (pitch) feedback?

Shouldn't a multi-million dollar airliner have a stalled feeling at 100 knots or less?

[Lyman]

sdf666

It is the initial handoff that killed this plane, imo. I think that, for whatever reason, the PF wanted to climb, and may have not anticipated a lock out of the Autotrim with a robust Pitch UP. So he kept increasing input (NU), and the a/c started to climb, which lessened g forces, and started the THS TRIMMING NU. This caused a very emphatic PITCH UP, one he addressed with insufficient NOSE DOWN ELEVATOR to reverse the climb angle. In short, because (possibly) he had expected some kind of NL assistance with his pull, and getting none, he kept pulling. When it took hold, he lost his surroundings (SA) possibly, and never caught up with, nor understood, the UPSET handling of his a/c.

I am convinced that some variation of this is what started the problem. What cause dit to be ultimately insoluble is left to others.

Sufficient lack of initial SA, a correct, (though perhaps forgotten) behaviour of the THS, and the rest is coffee table.

Thanks for your response. Finally, look again at your initial statement, separate the sequence of both points, and voila! The initial 'disconnect'

IOW. The THS was NOT TRIMMING up with his first NU inputs. K?

[infrequentflyer789]

takata

We are a committee. One is a writer, an editor, actually. A retired Pilot, an active PPL, and others, a designer, a mechanic, etc.

If this is illegal, then we say adieu.

If not, when you gather your thoughts, can you respond? You brought it up. The THS is dormant to help in the NU demand. Later, with a climb initiated, it activates and zooms the a/c.


With that collection of expertise, plus a copy of the report, you ought to have figured it out unaided.

C* control law is no mystery, it is a feedback control loop that moves the control surfaces to achieve the demanded movement (by g-load). Autotrim is no mystery either - THS follows elevator to unload it, slowly and with some hysteresis.

At the start of the incident, at cruise speed and alt, the elevator movement required to achieve the demanded climb was small, and the THS moved little or not at all to compensate because it didn't need to. The THS never zoomed the a/c - it started moving only after the zoom climb.

As airspeed bleeds off the control deflection required to achieve the demanded "climb" increases, and as the plane stalls the controls are trying to achieve the aerodynamically impossible - the elevator hits the stops and the THS follows. In the stall. In the stall, because that is what it is being asked to do. The basic control laws have no concept of "stall", just like previous generations of cables and hydraulics - and nor should they, it is far too complex a concept to attempt to build into such low level critical systems.

[Jutta]

thx for the link. I can agree in some aspects, knowing the other side of the Rhein well ;)

[Lyman]

Hey. Absolutely, and in a perfect world. This a/c did not immediately respond to climb input, in spite of cruise speed and controls effectiveness. So, we are left with a need to explain the sluggish response of a highly vaunted "Twitchy" platform. Evidently not? A sluggishness replaced with a near instantaneous and remarkable need for Altitude? After handoff, Throttles were not touched, and the a/c loitered at 34,700 (Read)?

My point is that no one has sufficiently put together a logical continuum of the initial UPSET. There is perpetual reiteration of everything but.

TAG. You're IT.

And of course, you know the diff twixt UPSET and LOC?

[infrequentflyer789]

the PF wanted to climb, and may have not anticipated a lock out of the Autotrim with a robust Pitch UP. So he kept increasing input (NU), and the a/c started to climb
[...]
I am convinced that some variation of this is what started the problem. What cause dit to be ultimately insoluble is left to others.


Look at the report. The trim does nothing until the a/c is at top of climb and proabbly already stalled. It does nothing because it didn't have to - small elevator movement was enough. Only as it becomes increasingly difficult to maintain the (impossible) climb does the elevator start to move significantly NU and the THS follow. There was no lockout of autotrim. Look at the traces.

[Jutta]

Originally posted by DozyWannabe
Personally I think that the logic for not re-taking a seat at the controls was understandable. What bothers me is the fact that he felt it OK to leave two F/O's, one of whom was fairly junior and probably still a little demob-happy (having just returned from vacation) in charge as the aircraft was transiting a known problem weather area.Yes indeed that was a strange decision.
Another thing which bothers me is the fact, that the captain asked his co-pilot if he had a licence just bevor he went to rest......... means quite well advanced with their flight.

Is it not normal bevor departure that the team gets at least acquainted and the commander clears important questions like that, bevor boarding?

[TyroPicard]

A while ago I posed the question "In a FBW Airbus how would you sense which way to trim?" to smilin-ed and the answers generated show that many posters don't understand the system.

To answer my own question: "The only sense which can solve the problem is sight - look at the ECAM F/CTL page. If the elevator is neutral with sidestick released the a/c is in trim. If the elevator is displaced then trim in the same direction until elevator is neutral. This will only work with 1g demanded i.e. no sidestick deflection in pitch."

The point I wish to make to smilin-ed is that you cannot feel if the a/c in in trim (except in Direct Law). Autotrim was not the reason for this accident.

[DozyWannabe]

Is it not normal bevor departure that the team gets at least acquainted and the commander clears important questions like that, bevor boarding?

We can't tell the tone of voice in which the question was asked, because all we have is the transcription of the CVR. It may turn out that it was just a joke that the Captain was making before he went to get some rest. As is the case in all large airlines, it is possible to get a rostered crew that have never encountered each other before on the flight deck - it's just the way the rostering system assigns personnel.

For example, in the case of one of the best examples of CRM there has ever been (the crash of United Airlines 232 at Sioux City), none of the crew had been personally introduced to Captain Denny Fitch - who was a DC-10 training captain who was "deadheading" on the flight - ever before. But what you hear on that CVR is the trust that all the flight crew, plus their new member, have in each other and the decisions that meant that a lot of people walked away from a crash that was likely to have killed everyone on that aircraft. What I'm trying to say is that in the airline environment, it's a regular occurrence that you'll be working with people that you haven't worked with before - that's not unusual.

Unfortunately, what we're looking at here appears to be at the other end of the scale - a Captain who puts his faith in his two F/Os to manage that leg of the flight, but when things start going wrong it is apparent that at least one of the F/Os (in the right-hand seat) is not handling the situation correctly, and the other F/O (in the left-hand seat) doesn't feel that he has the authority to take over when something goes wrong and waits for the Captain to return, by which time it is effectively too late.

Wuenschen wir doch, als unser Piloten alles klar verstehen koennen. :)

[Lyman]

Perhaps the best of the lot, as it was ad lib.

Wir fliegen mit grosstem vertrauen in unsere piloten

[Smilin_Ed]

Tyro: The point I wish to make to smilin-ed is that you cannot feel if the a/c in in trim (except in Direct Law). Autotrim was not the reason for this accident.

Tyro, I am well aware the truth in both of these statements. My points are:

1.In my opinion, not having any change in the feeling of the side stick as flight conditions change makes it harder to trim properly. Some people seem to think otherwise, but that is their opinion. This, however is not even a contributing cause of this accident.

2. Autotrim did not cause the accident since the person flying did not even try to recover from the stall which he caused by his persistent nose up inputs. However, if he had tried to recover from the stall it would have been more difficult because autotrim caused the THS to move to the full nose up position. It would have taken more time to attain a nose-down pitching moment than if trim had stayed at the cruise setting.

[deSitter]

Smilin_Ed keeps making crushing points from the point of view of a real pilot with his human cargo in tow, well aware of how to ensure their safety to the best of his considerable skill. It makes me happy :) There are still real pilots around, with pride and skill in their craft.

[GarageYears]

Look at the report. The trim does nothing until the a/c is at top of climb and proabbly already stalled. It does nothing because it didn't have to - small elevator movement was enough. Only as it becomes increasingly difficult to maintain the (impossible) climb does the elevator start to move significantly NU and the THS follow. There was no lockout of autotrim. Look at the traces. Please don't ask Bear to look at anything, that is akin to work (not even hard work), but inconvenient. The reality of facts gets significantly in the way of today's (or tomorrow's theories...).

The obsession with the THS and autotrim is becoming tedious - the THS did what it was told to do, according to the design of the aircraft. The millions of miles covered by the A330 platform presumably are a reasonable certification of the designs basic soundness - let alone the other Airbus aircraft types of basically identical design.

[deSitter]

There is no obsession with THS, it stayed at +13 because no one was flying the airplane, and the Airbus itself was unconcerned with where it landed.

[Machinbird]

Looking toward the future, how much nose up trim do you really need at FL350?

Are you ever going to drop the flaps up there?

Maybe the control laws need to be looked at in this regard.

Shouldn't some limiting AOA shut down nose up autotrim in Alt law before it gets really ridiculous?

I hate the thought of limiting control authority in some corners of the envelope, but it seems we are moving in a direction where future pilots will need yet more coddling.

[Lyman]

Bear is in Alaska, visiting his Polar cousins.

Machinbird, that is a strong point to make. Not new, but strong. Airbus has installed a Trimming system for its elevators (strictly, for the a/c Pitch). There is a reason, a good one. The elevators are a part of a balanced system of demand, and managed stress. As you say, why such an exaggerated system? Possibly, with un"limited" authority, the elevators are subject to large air loads. A movable Stabiliser spreads this stress away from the smaller controls, the elevators.

So why the need for such large excursions in control surface? Why indeed.

Certainly not for authority? At cruise, the deflections are necessarily small, and actually create a danger of damage if they are too large. For added control at Approach to Stall? :ugh:

The RTLU? Ever more important than the Rudder are the elevators. Yet there is no protection at high Mach for these critical surfaces (els)? As has been mentioned many times since AA587, a Rudder can be lost and the flight saved. A vertical Stabiliser if lost is the end of times.

Is the THS indeed a separate approach for control surface protection at high Mach? Then why not fly TRIM? Lock the elevators (a la RTLU), and use the slab to control Pitch. With a dampened and restricted stick at Mach, there will be no Mayonnaise. Likewise ROLL. How can it be so that this dream machine can wobble right and left, inviting a spin, due to PILOT? Especially with such rapid moves?

Always look in the corners, and bring a torch. This investigation has no conclusions as yet. Save those of the Armchair jocks here, evidently.

And those based on nothing more than prejudice and Pride.

Machinbird, the trend is toward more tech, and less pilotage. Shouldn't AB be more attentive to the different "requirements" of the cockpit, and its protections? Is that the question? In the interests of safety and pragmatism, yes of course.

To get defensive (and derisive) not to mention dismissive of decent questions is not only amateurish, it is lazy, even sloppy.

[deSitter]

Looking toward the future?? What future? Who needs people? They pay taxes, but you have to feed them. Zero sum game.

I always thought pilots were a cut above, and it still may be so, and what I'm seeing is only the cross-section of the mediocre who bother with forums. I'd hate to think that this is it, in these forums, 3 or 4 real pilots plus a bunch of bull****ters, but it may be so.

[airtren]

Maybe this set of graphs can help a number of points made or questions asked in several posts during this past week or two:

Stall Warning Active and THS Nose UP, from -3 to -13 degrees (max) during the same time interval - see the Gray Area.

http://farm7.static.flickr.com/6090/6030855675_0e5081bb6f_b.jpg

Looking toward the future, how much nose up trim do you really need at FL350?

Are you ever going to drop the flaps up there?

Maybe the control laws need to be looked at in this regard.

Shouldn't some limiting AOA shut down nose up autotrim in Alt law before it gets really ridiculous?

[Lyman]

airtren

Perhaps a narrative? In the gray? Because I'm seeing a dogleg at the ELEVATORS/THS Hinge axis. Maybe it's just late.....

How did the aircraft get to be so out of shape with the elevators and THS at virtually the same deflection as where the A/P had them? It Stalled with max Elevator position +/- 2 degrees? And the THS parked at -3 til 2:10:51? Looking for the Dunce cap.......

[gums]

Well thank you, De Sitter, and hope I am one of the 'real" pilots.

So maybe we take a break and actually discuss philosophy involved with the design considerations and the training and the so-called CRM ( we called it crew coordination). And BTW, Doze brought up the best example of CRM most of us have ever seen. TY.

Unlike Smilin' and 'bird and Retired, I actually flew the grandfather of the FBW systems. Unlike the Airbus folks, we called our "limits" limits, not "protections". But make no mistake, we had one feature that was intended to prevent us from getting into a spin, and another that 100% disconnected us from the stick ( our deep stall). Nevertheless, our limits were intended to enhance our mission capabilities and not make things easier for us.

There is no doubt in this ol' feeble mind that crew error will be the major finding. There is also no doubt that the Airbus control laws and reversion sequence will get some scrutiny. As another contributor points out - why allow the THS to reach full deflection? And the system seems to ignore some valid inputs because other inputs are considered invalid. Sheesh. What do I have to play with?

I would hope that training is improved for the folks flying the electric jets. The basics still apply - both aerodynamics of the jets and proven pilot responses to strange/unusual situations that have served us very well for a century. There is no substitute for being exposed to unusual attitudes and aerodynamic conditions you may never encounter. Just a few training hours, or even minutes, will come back to you when the real thing happens. I never had the responsibility of two hundred folks depending upon me, and I never wanted it. But if forced to do it, I would want to know everything I could about the plane and how to fly the thing in every imaginable situation, wouldn't you?

[Old Carthusian]

desitter
I rather get the impression that you have an agenda and that agenda is the sort that gets in the way of the truth. It is clear from the actual airbus pilots that the accident was perfectly recoverable provided the flight crew identified the correct circumstances. Nothing to do with Smilin Ed's rubbish about autotrim delaying recovery.
I will repeat for all of those who seem to be under the impression that the aircraft was a factor in the accident that this is not the case. This is an accident caused by human factors and at the base a flawed and falacious company culture. Almost non-existent CRM and total failure to follow SOPs doomed the aircraft. No other type of aircraft would have survived the PF's actions on that night. Try to focus on that - pilot actions were the cause of the accident nothing else.

[Jutta]

Dozy: For example, in the case of one of the best examples of CRM there has ever been (the crash of United Airlines 232 at Sioux City), none of the crew had been personally introduced to Captain Denny Fitch - who was a DC-10 training captain who was "deadheading" on the flight - ever before. But what you hear on that CVR is the trust that all the flight crew, plus their new member, have in each other and the decisions that meant that a lot of people walked away from a crash that was likely to have killed everyone on that aircraft. What I'm trying to say is that in the airline environment, it's a regular occurrence that you'll be working with people that you haven't worked with before - that's not unusual.oh I do understand all the logic behind the planning taking place all the time with an airline (my son had worked with LH for some years).
But one should not forget to mention in all this: Whatever decision a captain takes to get out of a difficult situation, it is in the first place to safe his own life a nuance which seems to be a bit left outside in all these discussions ;) (the instinct of self preserving is the strongest, together with preserving the human race *laugh*
That he gets the applaus of the world by having saved the aircraft plus its contents is of course justified!

[CaptainGef]

Hello Guys
Here is an excellent analysis of Operation and Safety editor David Learmount about the Loss of control of AF 447 and the 6 LOC that happened since year 2000.
I share this analysis about the atrophy of the mental skills of pilots with the new automated liners, this lack of training of mental skills being directly responsible for the work overload of the pilot during flights in degraded mode.
AF447 full.mov - YouTube

[BOAC]

Thank you Captain G. An excellent summary by DL and I am completely in tune. Now, how do we get anyone to notice?

[Old Carthusian]

In his own words - seductively credible but also rather flawed. An examination of airline accidents stretching into the past will turn up a long list of LOC accidents. Automation is not the cause of this nor is it a new phenomena (Clipper Skippers anyone?). Pilots have been losing control for various reasons for a long time and will continue to do so. An examination of one of his examples - the Adam Air accident he mentions suggests other causes for the accident, more relating to CRM than mental atrophy. A reading of the Air France audit (somewhere on this thread) will prove more productive than watching this video.

[hetfield]

Thanks Cpt. G :ok:

Here is some more excellent stuff of D. Learmont

Learmount (http://www.flightglobal.com/blogs/learmount/)

[GarageYears]

Looking toward the future, how much nose up trim do you really need at FL350?

Are you ever going to drop the flaps up there?

Maybe the control laws need to be looked at in this regard.

I fear we head for a circular discussion.... previously in this thread we have decried the obnoxious Airbus automation as somehow evil and root of all issues. I feel we have gotten past that, however now we appear to be calling for limits in Alt Law, which as we all know (right?) is invoked ONLY due to some failure of the system - in this case UAS.

The transition to Alt Law is a heads-up to the crew - something is broken (temporarily or otherwise), since the interaction of the automated control system relies on the sensed performance parameters, would that highly trained human sitting up front please take control?

In the case in question, the aircraft was handed to the human in a reasonable condition, it was not stalled, it was not overspeed, it was not balanced on a wingtip... I accept that the hand-off was unexpected (aren't all system failures unexpected?) and this requires a considered and thoughtful reaction on the part of the PF.

The reaction appears to not have been that, and judging by the amplitude of the control inputs (3/4 travel this way or full to the stop that) excessive - perhaps at low speed/altitude appropriate, but not at M0.8/FL350... did the PF forget where he was, never had experienced hand-flying at this speed/alt (likely, given the Air France training info), or simply panic.... but the crux here is the automated systems and protections/limits available in Normal were by design no longer there, since the inputs and control data necessary to compute those limits were no longer considered VALID.

And so, why would you limit elevator/THS travel based in ONLY AoA? I venture you need a SPEED input to make a sensible judgement on limiting elevator/THS travel... but speed was the input in question.

Was the problem the aircraft did too little, or the pilot too much of the wrong thing?

Last thought - what would have happened if the autopilot/autothrottle had NOT dropped offline when the speed inputs went U/S? What if the system simply went into an extrapolation mode for say 3 minutes... using GPS computed ground speed as the delta control? I'd bet we would not be looking at this thread.

[overthewing]

DL makes valid points about the automation / human interface. However, I'm not sure that this accident illustrates his point all that well.

As far as this passenger can tell, airlines prepare for dropout of automation by providing lists of actions to be carried out; in this case, the UAS checklist. These action lists allow the pilots to keep the aircraft safe for a short period while their physiology adapts to the new circumstances.

It deeply shocks me to read the CVR transcript and NOT see the AF447 pilots going automatically into that sequence. Surely there must be something in the displays / warnings that triggers the pilots into recognising why the A/P has dropped out? Concentrating on the UAS actions might have given them time for hands to be steadied, or even for the ice to clear and the speeds to come back to normal. Neither of them said anything along the lines of 'Help, the displays have all gone black' at the start of the trouble, so I assume the information was available to them.

The plane wasn't in immediate danger, apart from the fact that it was ploughing straight through some very bad weather. It was doing this because that's what the human crew had elected to do, not because the automatics had misread the situation. This was not the most low-risk strategy available to the Captain, but he had not only chosen it, he had also reduced the chances of managing the effects of the weather by choosing to absent himself at the critical time. Anxiety about the plane's course seems to permeate the younger F/O's words, and perhaps contributed to his later reactions.

The human /automation interface is undoubtedly a factor in this accident, but I can't see that it's the principle one. The finger has got to point at Air France and their training /management of aircrew, and quite possibly at their culture of performance measurement and rewards. Or is this standard of cockpit discipline the norm in other airlines, and I'm just an innocent to believe otherwise?

[Smilin_Ed]

O.C. Nothing to do with Smilin Ed's rubbish about autotrim delaying recovery.

You need to go back and read my post 1863. :ugh:

[Lyman]

One is not fearful of appearing 'dumb'. Too much in evidence here the posts to state a conclusion, claim others are incompetent, and seek to draw to a close this gfascinating thread. imo

I'll bite, and reiterate. airtren's tracks of specific data challenge me. Here, #1870, is the adress of these data.

The stick stirring, the commands, are quite "over the map". The results of the commands seem to be benign, as expressed in the two trails of elevator position and THS.

With all the stick activity, the controls seem to have responded very little.

They describe very little deviation from the far left, the time when the Autopilot was inputting.

At The STALL warn (the continuous level), the Pitxchups start to go seriously NU.

How did the a/c PITCH up to 10 degrees and "start to climb"?

I am sure am answer will make me look foolish. Bring it.

Anyone?

[BJ-ENG]

@overthewing

Anxiety about the plane's course seems to permeate the younger F/O's words, and perhaps contributed to his later reactions.....

Maybe there is something in that statement....

Article 3 - Inattentional blindness: let's not blame the victim just yet : The Canadian Aviation Maintenance Council / Le Conseil canadien de l'entretien des aéronefs (CAMC - CCEA) (http://www.camc.ca/fr/SMS_40/Articles_270/8.html)

quote:
Inattentional blindness accidents are especially likely when expectation and distraction combine......

http://ntl.bts.gov/lib/33000/33700/33708/33708.pdf

http://www.humanfactors.illinois.edu/Reports&PapersPDFs/TechReport/90-08.pdf

[jcjeant]

Hi,

As we like read PDF's :8
Some article interesting to read .....
Current Issue | Flight Safety Foundation (http://flightsafety.org/aerosafety-world-magazine/current-issue)
Flight Safety June 2011
http://flightsafety.org/download_file.php?filepath=/asw/jun11/asw_june11.pdfRead from page 24 to 27
"Drappier, the Airbus representative, added, “Airbus does not recommend encouraging airline pilots to fly the airplane manually [during line operations] because the airline passengers have
paid to get the maximum level of safety. Most of the time, the autopilot is the best route.”

Ironic ?

[CaptainGef]

That's it: Now, pilots are no longer required to fly the aircraft. they are required to apply procedures. They don't fly anymore with their brains and
their mental skills. So how can we expect to analyse and understand.
Just call the hotline when there is no procedures.....

[ChristiaanJ]

Article 3 - Inattentional blindness: let's not blame the victim just yet : The Canadian Aviation Maintenance Council / Le Conseil canadien de l'entretien des aéronefs (CAMC - CCEA) (http://www.camc.ca/fr/SMS_40/Articles_270/8.html)

quote:
Inattentional blindness accidents are especially likely when expectation and distraction combine......
That particular article should be made obligatory reading for all the posters here and on the other AF447 thread.....

[Lyman]

Scale, please. Good scout, I read this "scolding". It is propaganda. A shiny trinket to hypnotize while the real deal slinks away.

Unintentional, I am sure. A stone, while rolling, gathers moss, and analysis paralysis.

Simple is good, for simple things. Just as distractionm is the topic of this "paper", it is itself a distraction. Unintentional, certainly.

It is a bogeyman, and a slap dash solution. How many people when reading this opiniuon forget the dream machine gives up and surprises the crew? This is the real deal, and has a simple solution. Motorcycles are not airplanes, and pilots deserve more respects than "He just hit the pedestrians".

[ChristiaanJ]

"Lyman",
Is your last post supposed to mean anything?

Go easy on the Jack Daniels.

[Lyman]

"ChristiaanJ"

You have obligated several hundred people to read something.

An uninvited Teacher is merely a Preacher.

Lem Motlow, now trhere was a man.

Power issues? You have called people Ignorant, drunks, and other nasties.

You should be more polite.

[GarageYears]

Bearfoil/Lyman/whatever....

Your disjoint ramblings are simply a waste of screen inches.

No one is "obligated" to read anything posted or linked here - choice is an individual act.

Previously there was a discussion regarding not bounding any problem and looking for free thinking "outside-of-the-box". But once the box is clearly misplaced or simply ignored, those comments become redundant or in the case of the recent crop, disconnected and hence worthless.

If it is being suggested the words appear to be Jack Daniels influenced, it is because that is how they appear... not because of any agenda to "get Vinny".

[Lyman]

GY
What is an abject waste of Space? All things personal. Check me brother, find some personal attack I have made. Response? you gd betcha. For ChristuiaanJ......

Look at airtren's traces, and please explain to me why I am having sincere trouble why I cannot see how PF's stirring appears to have no effect on the Elevators?

I will not moderate this thread, neither should you. Answer my question or find your golf clubs.

sorry, it's post #1870. IMO, this trace is the maijn plot. Neptunus, can you help explain? Because otherwise, your post is just an editorial?

[Neptunus Rex]

Can we please get back to the main plot here?

[ChristiaanJ]

Check me brother, find some personal attack I have made
Well, let me quote just one.....
"ChristiaanJ"
You have obligated several hundred people to read something.
Power issues? You have called people Ignorant, drunks, and other nasties.
You should be more polite.
That's what I call a personal attack.
And please, don't run to the mods this time, to weep on their shoulder again.
Hiding behind yet another 'user ID' is despicable....

[Lyman]

ChristiaanJ. Of all people, I know tyou can help. The elevator record? How is it that the traces of elevators/THS don't show much response to the PF's mortar/pestle? frrom airtren #1870?

[3holelover]

Bear, Lyman, or whoever you are... If you'd ever handled hydraulically actuated controls on an aircraft, you might have noted the same thing... the more demand there is, the more likely will the surfaces be responding a little slowly to your demands... call it a kind of hysteresis. As more fluid flow is asked for (many of those actuators use a fair bit of fluid from stop to stop!), the more the pressure can drop and the slower they'll go.

[Owain Glyndwr]

Bear, Lyman,RWA or whoever.

We know you have difficulty with simple concepts, and I am probably wasting my time, but one more try.

With a FBW airplane operating under C* laws there is no simple relationship between sidestick movement and elevator deflection. The sidestick movement is a delta 'g' command and the FCS adjusts the elevator movement to suit the actual flight conditions. Moreover, the FCS has a pitch damper function, so the elevator movement is further modified by a term that depends on pitch rate. You simply cannot make the sort of comparison you are attempting - it is futile.

Secondly, as has already been stated many times, the THS movement is not linked directly to elevator movement either. The THS is moved in response to the SUMMATED stick demands over a period of some seconds. This quantity varies much more slowly than the actual elevator deflections, so the THS movement is correspondingly sluggish.

No great mysteries, no cover ups and no failures!

[takata]

The elevator record? How is it that the traces of elevators/THS don't show much response to the PF's mortar/pestle?
Trajectory = pitch/power settings + turbulences.
THS is long term, slow rate... do you know what is trim?
Did you even look at thrust change?
Control surface efficiency is never "absolute", being all the time affected by aircraft equlibrum in the air.
As this has been already discussed previously, maybe you should try some reading instead of constantly trolling and hijacking this thread with your (not so funny) clones.

[xcitation]

It's amazing how graceful/forgiving the A330 behaves below its flight envelope (stalled, storm and low airspeed)?

Before this incident if you asked me if a transport can be controlled at ~30kts in a storm then I would guess no, probably tumble and break up. Remarkably the reality is yes albeit requiring aggressive stick inputs to maintain level wings!

Was there a special reasons why AF447 remained controllable at ~30kts? Did the free fall/stall (100+kts vertical) acting on the superstructure provide aerodynamic stability even thought the wings were not flying?
Why did asymetric engine thrust/drag not induce a spin?
Why did the ailerons/rudder generate enough force to keep the a/c in a graceful attitude albeit oscilating in roll?

[Lyman]

Power. CONFiture has framed Power for me. So OK. Dozy has said she is not twitchy, so OK. Trim is familiar, so OK. I understand Hydraulics.

I also see that THS has not killed her, it comes in only after the STALL. It is at -3 from ap loss to STALL. The aggressive action of the Pilot is not relevant, except in the long term, takata, you have said that.

So, from handoff, this aircraft exhibits no bad habits, except perhaps following the orders of PF?

I guess the question I have left is, she is well protected, docile and easy.

Until it is absolutely necessary that she be protected, then she is not?

All those protections, but when they are truly needed, they hide?

If controls are deliberate, then mayonnaise is not important, but the controls will slowly take her to STALL? Three pilots are wanting to know what is going on, but she is....silent. Sweet.

At STALL warning and STALL, the THS trims to the stop NU? Fix that?
With a committee of three on deck and focused, can we see what the other guy has done, is doing? Fix That? Can we off some of the extraneous ECAMS when we are about to die? Fix That?

It is a machine. get up off your knees and stop genuflecting.

[Jutta]

Originally Posted by takata: Bearfoil_Lyman_RWA_Jutta_HowManyOther?peut-être je suis la seule genuine ici :ok:
bisous (quand meme *rire*)

you should have understood by the way I posed my naive questions, that that was quite feminine and until now I've never met a real man being able to copy a woman in whatever role imaginable et bien sure vice-versa:= (sorry for the OT)

[takata]

peut-être je suis la seule genuine ici bisous (quand meme *rire*)
you should have understood by the way I posed my naive questions, that that was quite feminine and until now I've never met a real man being able to copy a woman in whatever role imaginable et bien sure vice-versa (sorry for the OT)
[Edit: Very sorry Jutta, and welcome (ouch!); I was obviously completely wrong about you!]It is not funny Bearfoil, you're completely lost into your stupid stereotypes, please, stop playing with people by wasting their time.[Edit: see what happen now, Bearfoil? I'm sure you liked it: even genuine ladies would be treated like silly Bears!]

[PJ2]

Please ladies and gentlemen, it takes two to tangle. One cannot control another's behaviours, only one's own. If a poster's contributions consistently bother one, go to "User CP > Edit Ignore List > Add User To Your List", then click "Okay", then to exit, place a tick in the "Check" box and click "Save Changes".

The user's name still shows up in the thread but not the post's text. There is a "View post" prompt in the top-right corner of the post so if you wish to view an individual contribution you can do so by clicking on the prompt.

If someone is making your experience here unpleasant, rather than engaging, use the ignore feature and keep contributions to this thread on-topic. If you wish to engage, perhaps the PM feature is a good alternative.

Some enjoy the fight but the thread has deteriorated so badly and there are so many posts to wade through already that it is getting tiresome and unattractive as a technical discussion on AF447.

[takata]

Please ladies and gentlemen, it takes two to tangle. One cannot control another's behaviours, only one's own. If a poster's contributions consistently bother one, go to "User CP > Edit Ignore List > Add User To Your List", then click "Okay", then to exit, place a tick in the "Check" box and click "Save Changes".
Of course, you are right and I fully agree...
Until the guy, being ignored by most posters, come back under many identities, spamming, enlighting, his previous postings that always will re-trigger the same odd discussions, over and over again!!

Now, this game is 2 years old.
At one point, all people reading this thread should be aware that someone is constantly playing with them; that many here are wasting their precious time at building serious argumentation; that they are, nonetheless, constantly fooled by someone which is playing this sickening game.

At one point, this should really end, or this thread (and R&N one) won't be worth continuing anyway.

[PJ2]

As I say, it takes two to tangle. One quickly recognizes someone who is serious about discussing this accident and who has other motives. The second kind of dialogue shouldn't last two years, it should last two or three posts which is all it should take to realize someone is fooling with us. Otherwise, by responding one chooses to become part of the game, sustaining it, which is fine as sometimes it is challenging and fun for some, but it is so at the expense of the continuity and pleasantness of the thread. The truth of things always comes out sooner or later regardless of how one or another wish otherwise and who try to push conclusions upon others by all means available.

The choice too, for some, is not to come here anymore and for many who enjoy dialoguing with serious, like-minded professionals, that would be a shame.

Disagreement, even vehemently so, is different and should be tolerated and encouraged. And it is very easy to tell the difference.

Anyway, I've said my piece. The thread will go where it will go regardless, so we'll see.

[ChristiaanJ]

PJ2,
Thanks

[takata]

As I say, it takes two to tangle.
Wisdom is talking. So lets try it again... and see what happen.
:)

[sensor_validation]

Back to old obsession:- what exactly was happening just before the incident started - were the controls acting on bad data? I think its possible but only for a few seconds before the air data correctly flagged as inconsistent.

One possible failure mode of pitot tubes when encountering ice is that the drain holes block first and cause a small over-read, then under-read as the total port blocks. With the air speed under auto-control this might not be seen on the Mach No - but may be seen to be calculated as change in wind speed.

Is it it just a coincidence that it all seems to be coincident with the selected Mach drop from M0.82 to M0.80? This seems to have been commanded at 2:09:50, unfortunately the plot of "Navigation Parameters" on English P109 is corrupt while the selected Mach is 0.82 - as mentioned before it appears they are plotting 0 when no update.

The engine N1s start to ramp down from 2:10:00, but seem to have little effect on the indicated speed - but presumably is responsible for the co-ordinated drop in pitch angle? The longitudinal acceleration suggests the plane is slowing (although I don't understand the negative bias on the plot).

It appears the ISIS calibrated airspeed when recovered after the dip is "stuck false high" in period 2:10:10 to 2:10:13 - during which the engine N1s are locked low - but groundspeed doesn't drop off much (perhaps due to plot scale).

It's not all consistent to my eyes, and I hope the BEA can recover more detail data the control hardware around this time (especially the right hand display indications) - BUT - I think you need significant shifts in wind speed/temperature to make it all add up - what if they "nearly missed" a Cumulonimbus?

[Mimpe]

Im in general agreement with Smiling Ed and machinbirds posts, however the trim issue was a small hurdle to further overcome at the end of a long list of errors. I certainly respect the lifelong experience represented by so many of the forum posts- the kind of experience that safes lives when things go really wrong.

I think in this kind of accident there is a very large list of factors, and they all seemed to concoct for the worst on the day, at the edge of the flight envelope, and the PF's ability.

A few quick matters....I can see a very good argument for visibly linked controls. Its such an aid to situational awareness, and I feel non linked controls are a bit of a by product of low accident rate complacency.

Also,I dont see why an intelligent explicit emergency use of extrapolated speed data with sensible caveats may have at least alleviated the anxiety that seems to have paralysed the situational and perceptual awareness of the crew

The mental fog appears to have descended on the aircrew very early. There must be some professional habbits and training that can overcome what appears to have happened here. How effectivley do AF and the major carriers/ training organisations train to deal with false perceptual expectations/distraction/poor self awareness/anxiety/lax flight discipline/life
threatening CRM issues.

Im not sure how "worlds best practice" pilots do this. I know how I was taught by my most respected instructors and try to practice at my own aviation level.
I try to constantly practice "what ifs" as a trainig tool, as well as reviewing my first emergency responses so they are fluid, at times when they are not needed.
It was that kind of lifelong learning, self discipline,professionalism and deeply embedded training I saw in Sullenberger, that I dealy wish to emulate, and which set such a great example to all.
My day job is medical, but in my years working in emergency medicine, we used to have a saying..." In a crisis, take your own pulse first".

[Lyman]

There is in accidents what is called the "procuring cause". It is the beginning; what follows is related, and interesting, but subtract this one first "hole", and 'groundhog day', it is as if nothing has happened. Shall we leave it at that?

Of course not. To leave what follows this first slice as irrelevant is foolish, and a disservice to those who paid.

One does not treat the booboo without focusing on the hemorrhage first?

This hemorrhage, this first slice, was one of 32 previous slices. Shall we wander into confusion? Strikes me that Pride and Prejudice, if allowed at all, should wait, until other more pressing matters are dealt with. One could almost get away with saying: This was NO 'accident'.

Generally, to qualify as an accident, it must meet this: 'UNFORESEEN'.

[jcjeant]

Hi,

How effectivley do AF and the major carriers/ training organisations train to deal with false perceptual expectations/distraction/poor self awareness/anxiety/lax flight discipline/life
threatening CRM issues.
That's not difficult to understand
This was the AF (by the directeur général adjoint des opérations aériènnes Mr Schramm) reaction after the disclosure of the BEA report N°3
This man tell already the contrary of the report .. and some plain lies ... :eek:
Unfortunately in french :) but some here will well understand
It's pretty embarrassing
Vol Rio-Paris: réactions au rapport du BEA sur la catastrophe - YouTube
http://www.youtube.com/watch?v=aAL8kTTKpUw&feature=relmfu

[takata]

Is it it just a coincidence that it all seems to be coincident with the selected Mach drop from M0.82 to M0.80? This seems to have been commanded at 2:09:50, unfortunately the plot of "Navigation Parameters" on English P109 is corrupt while the selected Mach is 0.82 - as mentioned before it appears they are plotting 0 when no update.

Nothing looks corrupted here. Change of Mach mode "Selected", set at Mach 0.80, occured at 0209:58 (not 0209:50), only 7 seconds before UAS. Previously, it was Mach 0.82 and the blue line drop is readable behind the "Mach Number" green line. Before this change, the flight guidance mode was different ("Managed"), hence it is painted (in blue) differently with down lines, but the top of blue block is showing Mach 0.82 until this point.

I think that it is not a coincidence as the turbulence level slightly increased, hence aircraft speed was reduced... while the phenomenon occured at this point. The conditions were changing: feeling of warming, smelling, noise, etc. The very same elements were also described during other flights encountering UAS conditions.


The engine N1s start to ramp down from 2:10:00, but seem to have little effect on the indicated speed - but presumably is responsible for the co-ordinated drop in pitch angle? The longitudinal acceleration suggests the plane is slowing (although I don't understand the negative bias on the plot).

Maintained airspeed is primary due to momentum rather than immediate thrust change at 0209:58. In fact, it seems that the first result of this thrust reduction was a slight drop in pitch, down to zero or slightly below, which was followed by a small acceleration, small loss of altitude, slightly negative vertical/speed and also an increase of ground speed (turbulence can play its role also). This looks consistent with airspeed slightly increasing up to 0210:07, when ADR1 became invalid. Hence longitudinal g should have followed the same trend. Once this inertia moment was consummed, pitch increasing, low thrust and climb started altogether to bleed airspeed. But this was not effective before five or six seconds following A/P disconnection (about 0210:11, when gentle descent stopped and climb was resumed).


It appears the ISIS calibrated airspeed when recovered after the dip is "stuck false high" in period 2:10:10 to 2:10:13 - during which the engine N1s are locked low - but groundspeed doesn't drop off much (perhaps due to plot scale).
I don't think that ISIS is either "stuck" nor reading "false high" at this point. Last valid ADR1 was 274 kt at 0210:07 and climb was still not to be resumed until 4 seconds later, hence, 270 kt on ISIS between 0210:10 and 0210:13 doesn't seems false reading but actual airspeed.

[Shadoko]

2nd video (may 27 2011, before BEA 3rd report, but after BEA "Note":
... [0:53] Personne n'a le droit, pour l'instant, d'émettre une quelconque hypothèse sur ce qu'il s'est passé [0:58] ...
... [0:53] Nobody has the right, for now, to make any assumption about what happened [0:58] ...


1st video, may 29 2011 (just after 3rd BEA report press conference):
... [0:51] bien évidemment le pilotage, en manuel, en haute altitude, dans une (régio...) zone turbulente, en mode alternate, c'est probablement très particulier [0:59] ...
... [0:51] Of course flying in manual, high altitude, in a turbulent (regio...) zone, in alternate mode, it is probably very special [0:59] ...

Knowing the CV of this man ( Air France - Corporate : Eric Schramm, Executive Vice President Flight Operations (http://corporate.airfrance.com/en/the-airline/corporate-governance/executive-committee/eric-schramm-executive-vice-president-flight-operations/) ), it seems (IMHO) this wording is quite as astonishing than the one of the AF447 crew. Have we to think this "Qualified as Boeing 777 flight captain" doesn't know how flying is like in altitude when external and internal conditions are not smooth???

Is it the same in other compagnies?

[jcjeant]

Hi,

Have we to think this "Qualified as Boeing 777 flight captain" doesn't know how flying is like in altitude when external and internal conditions are not smooth???

Maybe it's the reason why they keep this man in the offices instead let him flying ........

[vbp.net]

@Sensor_Validation (post #1765)

Quote:

Has it been confirmed what AoA sensors were fitted?
Pretty likely the Thales C16291AA given the choice of Pitot tube, if so one could have been suffering an extreme variation of the known fault at low temperature:-

According to La Tribune newspaper, the EASA is about to require the change of about 1,600 Thalès AoA sensors known to have a flaw. It seems the fabrication process might be responsible for some oil to be left unnoticed in the mechanism. With decreasing temp, the oil can slow or even block the sensor movement. This problem happens at random during manufactoring according to the article. Also, it restricts the affected Thalès AoA sensors to A320. But we would need to cross-check that, wouldn'd we ?

Source:
Airbus : des sondes thales de mauvaise qualité (http://www.latribune.fr/entreprises-finance/services/transport-logistique/20110811trib000642142/d-autres-sondes-thales-doivent-etre-changees-sur-des-airbus.html)

[3holelover]

Hey, I've got an idea!.... It just came to me in a flash.... Maybe all airlines should remove anything that Thales built and replace it with something from a reputable manufacturer? :cool::ok:

[Diagnostic]

@vbp.net:
According to La Tribune newspaper, the EASA is about to require the change of about 1,600 Thalès AoA sensors known to have a flaw. It seems the fabrication process might be responsible for some oil to be left unnoticed in the mechanism. With decreasing temp, the oil can slow or even block the sensor movement. This problem happens at random during manufactoring according to the article. Also, it restricts the affected Thalès AoA sensors to A320.
The EASA AD kindly found & linked by sensor_validation in his post #1765 specifically mentions A330 & A340 and not A320?! IMHO the answer we don't yet know, is whether that model of AoA sensor was installed on AF447...

Reading the comments from other contributors here, it seems unlikely that whatever was wrong with AoA sensor #1 had a material impact on the events on this flight, although yet another fault added being into the mix is obviously a worry. Or do you believe the issue with this AoA sensor #1 was significant in the events that occurred?

@3holelover: I was going to apply for a job at Thales. I'm now re-thinking that plan :(

[sensor_validation]

Hey, I've got an idea!.... It just came to me in a flash.... Maybe all airlines should remove anything that Thales built and replace it with something from a reputable manufacturer? :cool::ok:

It's not as simple as that - what AoA inst were involved in the Perpignan crash?

Ans:

D-AXLA was equipped with three Goodrich angle of attack sensors with type number 0861ED

Thales make a lot of great kit and and its used extensively throughout many aircraft flight control systems - NB all with appropriate Airbus/EASA approval.

[CaptainGef]

I think that David Learmount is right when he talk about the flying skills of old pilots. New pilots apply procedures instead of "flying", that's the way Airbus told us to use his aircrafts to lower the number of accidents.
This new technology has saved many lifes, but new accidents appears and I think that, by applying procedures only, we just transfer human errors from the pilots to human errors from enginers that create those fully automated aircrafts.
If we want to progress in flight safety, we must mix old flying skills with new flying procedures. CPT Shullenberger proved us it works.

[CONF iture]

Reading the comments from other contributors here, it seems unlikely that whatever was wrong with AoA sensor #1 had a material impact on the events on this flight, although yet another fault added being into the mix is obviously a worry. Or do you believe the issue with this AoA sensor #1 was significant in the events that occurred?
Diagnostic,

The first worry above all is how the BEA didn't talk a single word about it ...

Second worry is that such oversight is not isolated.

[Diagnostic]

@sensor_validation:
what AoA inst were involved in the Perpignan crash?
I thought those (Goodrich) AoA probes had been effectively mistreated (due to the incorrect pressure wash forcing water past the seals), so they were not to blame. At least that's how I remember it, from when I read the report years ago... My memory is not perfect, of course.

Diagnostic,

The first worry above all is how the BEA didn't talk a single word about it ...

Second worry is that such oversight is not isolated.
I take your points, thank you. I try to see the best in people, and so the apparent oversight at this stage, might just be caused by them not having yet added this detail into the latest interim report, and perhaps it may be mentioned (as inconsequential?) in the final report. But, it may not be mentioned even then - and them totally missing something like that even in the final report, would indeed be a worry!

[A33Zab]

The first worry above all is how the BEA didn't talk a single word about it ...

Second worry is that such oversight is not isolated.


-The AOA replacement program was already in progress before publication of the 3rd BEA report.

-They did found the cause: 'machine oil residu left after the fabrication process' and so they know the solution too.

-There was no relationship whatsoever with this case.

[Diagnostic]

@A33Zab:
-The AOA replacement program was already in progress before publication of the 3rd BEA report.
Understood - but in that case there seems no reason for them not to say "FYI, we saw AoA #1 misreading - but this issue is already known, see EASA AD ...". If they wrote something like that, it would show that they recognised, evaluated, and dismissed that this needed further investigation. By not mentioning it at all, that leaves open (at least in my mind) the possibility that they didn't recognise it, although as I just mentioned a few mins ago, it might become a footnote in the final report - we'll have to wait until then to see if it is mentioned.

[HeavyMetallist]

Since the BEA went to the trouble of including that parameter in the (very small) subset of FDR parameters that they included in the interim report, it seems very unlikely that they didn't notice such an obvious apparent discrepancy. Why they didn't mention or explain it, however, I don't know.

[vbp.net]

@ Diagnostic & Sensor_Validation

Quote : Reading the comments from other contributors here, it seems unlikely that whatever was wrong with AoA sensor #1 had a material impact on the events on this flight, although yet another fault added being into the mix is obviously a worry. Or do you believe the issue with this AoA sensor #1 was significant in the events that occurred?

Very hard to tell, but I would say probably not since we know the STALL warning went OFF as soon as the speed was deemed to be less than the prescribed 60 kts. What we are really seeing when looking at the AoA traces of the data is another story, IMHO. Keep in mind, though, that the "speed" (of the falling aircraft-object?) was certainly well above that : only the derived horizontal vector of it was calculated to be less than the trigger. Calculated from the pitot, at an angle out of the normal range... What I mean to say is the following: the AoA sensor was probably giving meaningful output since the flow of air around its actuator was certainly capable of moving it adequately. So, it remains very strange that the STALL warning would be muted in these circumstances when the "system" knows pretty well: 1. the aircraft's altitude and 2. there is no weight on wheels. I have little doubt that, recommendations from BEA or not, Airbus will implement some changes there in the future.

I wouldn't like to seem cynical, but can you imagine the benefits to be derived from the data retrieved from the bottom of the sea? A fully stalled 200+ tons aircraft data during the whole descent. No wonder Airbus did finance some of the recovery costs. To them, this is a goldmine. And they pretty well know how to interpret the data! Future aircraft generations (and even the current ones) will benefit from this disaster, whatever the BEA conclusions and recommendations will be. I'm confident.

This leaves the industry with the problem so adequately pointed to by the excellent video brought to our attention by CaptainGef (post #1867). Captain Sullivan also tried to wake up an almost empty audience in the Congress about the same problem. Trouble is: nobody seems much interested...

[Diagnostic]

@HeavyMetallist:
[...]it seems very unlikely that they didn't notice such an obvious apparent discrepancy. Why they didn't mention or explain it, however, I don't know.
Agreed. I know from my writing of RCA reports when things go wrong (but thankfully not accident reports), that it is important to mention what data has been considered & dismissed (and why), exactly in order to avoid people spotting things that I did see in the data but were not causal and hence not addressed by a "fix", but they would otherwise think I didn't see them...

I'm sure the BEA have people with much more skill & practice in this area than me, which is why their omission is odd, and leaves open multiple interpretations - from "there wasn't enough time in this interim report to mention it, but of course we saw it, and it wasn't important here", through to "oops, we didn't notice that", and everything in between.

[Diagnostic]

@vbp.net:

Many thanks for your comments. That helps to crystalise some of my own thoughts about what is important. Although discussions about the stall warning logic were removed from this 3rd interim report, like you said, I'll bet that there will be changes implemented in that area!

[CONF iture]

-The AOA replacement program was already in progress before publication of the 3rd BEA report.
-They did found the cause: 'machine oil residu left after the fabrication process' and so they know the solution too.
-There was no relationship whatsoever with this case.
That an AoA replacement program was already in progress is one thing, that AoA 1 on AF447 was stuck at 2.1 deg is another.

It may be your call to state that there was 'no relationship whatsoever', I may think differently, but it is BEA duty to touch the subject in a third Interim Report.


1- HN39 had already pondered (http://www.pprune.org/6629160-post1779.html) one of your previous post (http://www.pprune.org/6628363-post1767.html) :
so AOA#1 could be effected, however didn't had any influence.
FCPC using median AOA (or outvoted AOA#1), AoAsw using highest AOA value.
2- There is no such thing as a "FCPC outvote an AoA"
If one AoA sensor is stuck, there is a possibility that its own ADR anemometric value will be rejected.
Now, remember that in the meantime, was taking place an ADR anemometric values rejection process based on pitot unreliable informations.

So, we end up with a very complex situation, maybe unknown territories ...


I can see too much insistance from BEA, media, people here around to put everything on the pilots back, when in the meantime, FDR data analysis is kept to a strict minimum.

Those FDR data are too serious to be left in the BEA and Airbus hands only.
Victim's families must obtain them too. Alternatives ressources for Analysis are available on this planet Earth.

[jcjeant]

Hi,

Those FDR data are too serious to be left in the BEA and Airbus hands only.
Victim's families must obtain them too. Alternatives ressources for Analysis are available on this planet Earth.

This is a judiciary investigation under progress ..
They will have the FDR data .. so it's not left in BEA and Airbus hands only.

[syseng68k]

takata, #1826


This is what the transducers are supposed to do. Feedback from every
control surface is recorded, digitalized and corresponding pressure is
applied back to each sidesticks axis.
I don't know where this myth came from, but if you look at the side
stick drawing, you can see that the only feedback is from self centering
springs. There is no force feedback from the control surfaces as there
are no motors etc in the side stick to provide this. Genuine "artificial
feel" provides stick feedback from control surface load, whereas the ab
stick is more akin to a video game controller, though I understand that
even some of these have real force feedback now.

A serous dropoff imho and may be compared to the difference between a
good sports car, where you can feel the road through the steering and
something like the old Jags, where over servoed power steering removed
all sense of tyre and chassis loading.

The sidestick transducers are there to sense position, they are not motors...

[Diversification]

CONF iture (http://www.pprune.org/members/104576-conf-iture)
The following excerpt from the Australian interrim report has already been posted in this thread. However, I will bring your attention to the statement which I have printed in bold.
"From AO2008070_interim, page 40-41
Angle of attack data processing algorithms
There was a potential for the AOA sensors on the right side of the aircraft (AOA 2 and AOA 3) to provide different values to the AOA sensor on the left side of the aircraft (AOA 1) in some situations due to aircraft sideslip. In order to minimise the potential effect of this difference, the PRIMs used different processes for AOA compared with other parameters when determining the value to use for calculating flight control commands. More specifically, the processing of AOA data involved the following:
• As with the other parameters, the PRIMs would continuously monitor the AOA values from the three ADIRUs. AOA data was sampled about 20 times per second.
• To confirm the validity of the AOA data, the PRIMs would compare the median value from all three ADIRUs with the value from each ADIRU. If the difference was greater than a set value for more than 1 second continuously, then the PRIM would flag the ADR part of the associated ADIRU as faulty and ignore its data for the remainder of the flight.
• To calculate a value of AOA to use for calculating flight control commands, the PRIMs would use the average value of AOA 1 and AOA 2. In other words, (AOA 1 + AOA 2)/2. This value was passed through a rate limiter to prevent rapid changes in the value of the data due to short-duration anomalies (for example, as a result of turbulence).
• If the difference between AOA 1 (or AOA 2) and the median value from all three ADIRUs was higher than a set value, the PRIMs memorised the last valid average value and used that value for a period of 1.2 seconds. After 1.2 seconds, the current average value would be used.
In summary, in contrast to other parameters, only two values of AOA were used by the PRIMs when determining flight control commands. However, several risk controls were in place to minimise the potential for data inaccuracies to affect the flight control system."

I have two points that may need clarification.
1. How big should the difference from the median AoA be in order to reject ADR1?
2. Could this be the cause of a) autopilot disconnect, (b) false interpretation as due to pitot problem if ADR1 was permanently rejected due to AoA error.

regards

[Shadoko]

If there was some kind of AoA discrepancy due to one sensor stuck, and calculators "saw" that, didn't have to be some ACARS about that? Otherway, except the study of this flight FDR, nobody would know this problem (if any) happened during this flight?

[A33Zab]

Hi CONF iture,


1- HN39 had already pondered (http://www.pprune.org/6629160-post1779.html) one of your previous post (http://www.pprune.org/6628363-post1767.html) :

Quote:
Originally Posted by A33Zab
so AOA#1 could be effected, however didn't had any influence.
FCPC using median AOA (or outvoted AOA#1), AoAsw using highest AOA value.

2- There is no such thing as a "FCPC outvote an AoA"
If one AoA sensor is stuck, there is a possibility that its own ADR anemometric value will be rejected.
Now, remember that in the meantime, was taking place an ADR anemometric values rejection process based on pitot unreliable informations.



Thx for recalling this post, I did reply on that one but at the same time
the forum was 'under maintenance' and I forgot later on.

Each Aoa vane drives 3 identical resolvers, 1 remain unused.
(may drive AoA indicator in future?)
Due to pin programming the other 2 can be used as averaging value or
- as pin programmed in the A330 - 1 is active and the other used as
backup in case of failure of the active resolver.
Resolvers sin and cos are AoAi input for the ADIRU.

ADIRU calculates the AoAc from the AoAi to compensate for position
errors (identical AoA sensors used for all 3 positions) and S/F config.

(BTW: the vanes are dampened by eddy current, no oil based damper is used)

Each ADIRU sends his AoAi (LBL 221) and AoAc (LBL 241) values in ARINC 429 format to all FCPCs.

In normal operation the FCPC uses the median value of the 3 AoA values
BUT if an AoA signal deviates a predetermined value(?) from the median
the FCPC will reject this AoA signal (for remainder of the flight) and will
use the average value of the #1 & #2 sensor.

If the difference between AoA#1 or AoA#2 and the median value from all
three ADIRUs is higher than a set value(?), the FCPCs use a memorized
last valid average value for a period of 1.2s.
After 1.2s the current value is then used.

http://i474.photobucket.com/albums/rr101/Zab999/MedianAoA.jpg



The FCPC uses the AoA value for the protections(limits) in NORMAL LAW.
In ALTERNATE LAW those AoA protections are not available anymore and
FCPC can do without any AoA signal.

They salvaged 800VU rack(FCPC2/3), separate mounted FCPC#1 and AoA sensors.
After investgation of those components they will surely respond to that,
but you are right! they could have made a comment already in the
footnote about this AoA#1 sensor.

[Old Carthusian]

I haven't really had much chance to post my thoughts on this accident which is why I may have seemed short - apologies to all. This accident is not a machine driven thing but a human issue. The S and L of SHEL apply. But first some history - I have referred to Clipper skippers and this has a bearing on the accident under discussion. Pan Am during the sixties were one of the dominant airlines and their captains and co-pilots very highly regarded. However, this induced a culture of arrogance and complacency - pilots who were not suited to command were passed and protected by their friends. Checking methods were ignored and training especially with obscure and difficult airports was poor and perfunctory. This led to a series of accidents in the late 60s and early 70s with many fatalities. It also led to a culture change but Pan Am never really recovered from the problems caused. The parallels which struck me were a casual culture and a failure to train properly and address training issues. Air France seem to have developed a similar culture. I am sure that there are many responsible and professional pilots in that airline but reading their safety audit one could see issues that needed to be urgently addressed. Training has been neglected and too much faith placed in automation. To be honest I have no problem with automation - I have never flown an automated plane but would prefer to travel on one. Some of the stuff I have flown has very strange quirks and I am glad when I don't have to deal with it. Learmount totally misses the point when he blames automation - in itself it is not an issue with proper training. If the proper training is lacking then problems arise but as in the Pan Am illustration they are not restricted to automated airliners. Thus we can safely disregard automation or the machine as having any bearing on the accident apart from an initial causal incident.

What impressed me about the CVR transcript (and I do read and understand French well) was the failure to follow procedures and the total lack of CRM. Learmount characterises it as bewliderment but to my mind this is going too far. We have no evidence that the pilots were bewildered - rather that they were inadequately trained and had developed a culture which neglected SOPs. PJ2 in a reply to another correspondent mentioned that SOPs were vital. I fully concur - in the stuff I fly if you miss something you are very soon in trouble. You as a pilot are responsible for your aircraft and for being aware of your aircraft and its features. If you are an airline pilot you have an extra responsibility for your passengers but any pilot carrying extra people has an extra responsibility. This to my mind means you have to be extra careful and be aware that your actions will affect others lives. This means knowing your aircraft and knowing what to do if the aircraft gets into unusual situations. It means training and anticipation - avoidance is better than reaction. None of this happened in the case of AF447. We unfortunately must assign responsibility for this accident to the aircrew and the airline not the aircraft or its automation or its manufacturer. No other conclusion is valid and despite the agendas of some of the other posters this is the reality.

[overthewing]

Old Carthusian, thank you for your post, which eloquently confirms from a pilot's point of view what I, as humble SLF, tried to express in an earlier post.

This bit especially jumps out:

This means knowing your aircraft and knowing what to do if the aircraft gets into unusual situations. It means training and anticipation - avoidance is better than reaction.

Surely pilots must think beyond the parameters of training courses? Especially in a working environment where unexpected problems can kill you, don't pilots ask themselves a ton of 'what if' questions? 'What if the autopilot drops out at night, in cruise, and we happen to be in bad turbulence?' would seem the kind of question I would hope the chaps up front had asked themselves as I strap myself into 12F.

Or are pilots today encouraged NOT to think that kind of thought?

[AVLNative]

I also thank you, Old Carthusian, for an insightful post.

For other SLFs like myself, the SHEL acronym refers to Software, Hardware, Environment, Liveware, as explained at the following link:

http://www.skybrary.aero/index.php/ICAO_SHELL_Model (http://www.slideshare.net/guest4f592b/shel-model)

[spagiola]

Two new articles in Flight today:

AF447's initial altitude drift went virtually unchallenged (http://www.flightglobal.com/articles/2011/08/12/360432/af447s-initial-altitude-drift-went-virtually-unchallenged.html)

and

Airbus clashes with pilots over AF447 alarm
(http://www.flightglobal.com/articles/2011/08/12/360681/airbus-clashes-with-pilots-over-af447-alarm.html)

[bubbers44]

Overthewing, any pilot that doesn't consider every possible failure and how to handle it shouldn't be flying. There is not enough time to train him for every possibility. He needs to think about it himself while he is droning along or driving to work. One of the best ways is to look at accident reports and put yourself in their shoes and decide what you will do if it happens to you. It has saved me numerous times. 23,000 hrs and never making the papers or an accident report was because of that.....and a bit of luck.

[A33Zab]

For the guys wondering about the absence of (force) feedback to the stick.

Which F/B signal should be applied, A/C RESPONSE or surface deflection signal. (FEEDBACK SIGNALS)?

http://i474.photobucket.com/albums/rr101/Zab999/FeedBacks.jpg

[A33Zab]

I have two points that may need clarification.
1. How big should the difference from the median AoA be in order to reject ADR1?
2. Could this be the cause of a) autopilot disconnect, (b) false interpretation as due to pitot problem if ADR1 was permanently rejected due to AoA error.



1/ Don't know, actual values are not given in the documentation.

2/ a) No, all AoAs are within 1 degree of one other @02:10:05
2/ b) No, an AoA error wouldn't reject all ADR signals, its the CAS <60Kts which will invalidate the AoA signal (0 degree and SSM to NCD).

Regards.

[hetfield]

As the stall worsened, the aircraft's airspeed bled away and it began to descend, the angle of attack increasing to 41.5° before the airspeed fell below 60kt and the angle of attack became "non-computed data" - an invalidation which shut off the stall alarm.
In the 75s following the shut-off, however, the stall warning sounded another eight times as the angle of attack data briefly became valid again, each time at values from 38-43°, as the airspeed fluctuated with the aircraft's attitude.
Airbus clashes with pilots over AF447 alarm (http://www.flightglobal.com/articles/2011/08/12/360681/airbus-clashes-with-pilots-over-af447-alarm.html)

Sidestick fwd - stall warning
Sidestick aft - no stall warning........


Great design:ugh:

[ChristiaanJ]

For the guys wondering about the absence of (force) feedback to the stick.
Which F/B signal should be applied, A/C RESPONSE or surface deflection signal. (FEEDBACK SIGNALS)?
Nicely 'loaded' question , A33Zab....

Don't ask me, I'm an ancient "AFCS", not "AFS" (artificial feel) engineer.....
You have me wondering......but then I've never flown anything 'big' or 'fast' so I doubt I can contribute anything.

In something totally basic as a Piper Cub, your 'stick' cues are stick deflection = surface deflection (minus trim), and stick force = surface hinge moment. I very much doubt that would be what you want for an A330 sidestick?

Whoever did the artificial feel on Concorde obviously got it right.... there are enough comments from pilots on how well she handled. And that was a supersonic airliner, not a subsonic Coke can.

Maybe... not enough was 'fed back' from the early sidestick trials on 'SB, or maybe the issue of 'force feedback' was not yet addressed during those trials. I suppose I'll have to find again the few items of doc on the subject.

[sensor_validation]

If there was some kind of AoA discrepancy due to one sensor stuck, and calculators "saw" that, didn't have to be some ACARS about that? Otherway, except the study of this flight FDR, nobody would know this problem (if any) happened during this flight?

Lots of info on AoA sensors and processing for the Perpignan A320 in the BEA report, assume similar for the A330

for example

In straight and level flight, when the Mach greater than 0.75, a comparison between the attitude and the aeroplane angle of attack is made by each ADIRU. A class 3 maintenance message (not presented to crew during flight) is generated if the difference between these two parameters exceeds 0.6 of a degree.

[syseng68k]

A33Zab, #1939


Which F/B signal should be applied, A/C RESPONSE or surface deflection signal. (FEEDBACK SIGNALS)?
Ok, i'll bite: Let's analyse what you have drawn:

Is it a loaded question ?. We have two functional units: The execution
end looks like a standalone feedback servo. Linear demand input
translates to linear control surface deflection, though there are other
considerations, such as rate and travel limits and there may be
non-linear laws involved in the translation. From the way that the loops
are drawn, the execution end just follows demand from the compute end..

The compute end is the clever bit. This translates stick input to an
output, but has the current 3d state of the a/c, other inputs such as ir, baro
and control laws taken into consideration to decide just how much ss
is appropriate. The compute end is only a little box, but it's where
all the complexity lies

Perhaps revise the question to: a/c response, or control surface loading ?..

Hack the above to bits if you like.

Have noticed from your posts that you do seem to have rather eclectic
information sources. For example, the logic diagram in thread #5, Post
#620, with "mod 1139 11/08/06" in the top right corner. Nuff said I guess :-)...

[Welsh Wingman]

Helpful and thought provoking post.

The only word of caution that I would add is that we must be very careful before separating "automation" and "training" - the former implies new skills in addition to existing airmanship skills (for when the computer trips out, David's GIGO), not just new skills, and somebody has previously commented that it was a battle for AB's training personnel to maintain even the same level of training in the face of their salesmen arguing cost savings through buying AB and automation costs savings. I fear that the two issues are, or have become, inextricably linked as automation automatically feeds through to training issues.

The CVR so far disclosed is not pleasant reading, from a CRM perspective, and cockpit discipline left something to be desired. I am shocked at how PF got to a stall at FLT380, due to a temporary UAS. The flight should have been immediately stabilised at FLT350, and SOPs should have taken care of the rest, if the pilots had been properly trained. I have previously drawn attention to AF's 3 hull losses (the first for each aircraft type - Concorde/A330/A340), and I see where you are coming from re: an airline culture (your Pan Am example). But I don't think this is a particularly AF issue, and is a much wider problem. AF have many excellent "flyers", particularly those with an ex-military or private aircraft "hobby" background (alas none aboard AF447, to recognise and fly out of the stall once created). So I am broadly, save for this linkage, of the same view as you. Maybe trying to bridge the gap between you and David?

I am always wary of becoming dragged into the Boeing v Airbus debate, not least because I have never flown the latter, but I do believe that AB should never have been marketed as more automation implicitly equals less crew training costs (which their salesmen, at least, did). It should have been that the training costs would go up, as the systems operator skills were added to underlying basic airmanship skills (which would need more simulator honing, as flight crews became increasingly reluctant to - or have been banned from - "hand fly"), and the "saving" should have been marketed as the additional flight envelope protection and reduced risk of a "pilot error" in itself triggering a crash and all the reputational damage caused by an aircrash. Plus the weight/fuel efficiency savings from FBW operation.

It contributed to an "aircraft fly themselves" perception in some quarters (particularly amongst "line" finance directors) , and the number of LOC incidents in recent years is far higher than automation should have permitted if there was not an underlying mischief still to be remedied. So it takes us back to the man/machine interface, and that is heavily training......

Perhaps you, David and I are not so far apart after all (even if we all have a slightly different slant, mine being that training is a sub-branch of automation rather than a separate but linked issue)...?

[xcitation]

Pardon my ignorant red neck question :}, I am not a native french speaker.
Obviously I understand the international aviation convention is english.
However is the A330 stall warning obvious to a native french pilot?
Isn't the word "Stall!" in french meaningless?
Is "Caler!" the translation? Would "Stall" always be used in french aviation training or the french word.

After reading the transcript again and again I realize that my assumption the pilots (under duress) knew the english word "Stall" could be wrong !!!


02 h 10 min 10, 4 : SV : “Stall, stall” (without cricket)

02 h 10 min 11: What is that?



02 h 10 min 10, 4 :VS : « Stall, stall » (sans cricket)

02 h 10 min 11: Qu’est ce que c’est que ça ?


It is not clear if the PNF cannot translate it (what is that), or cannot make sense (why is that). I suppose he could be ignoring it completely and looking/pointing at an ECAM and exclaiming "Qu’est ce que c’est que ça?". No native english speaking pilot would hear the word stall and say "What is that?". However if I heard the french word "Caler!" I would say "What is that?".

[takata]

It is not clear if the PNF cannot translate it (what is that), or cannot make sense (why is that). I suppose he could be ignoring it completely and looking/pointing at an ECAM and exclaiming "Qu’est ce que c’est que ça?". No native english speaking pilot would hear the word stall and say "What is that?". However if I heard the french word "Caler!" I would say "What is that?".
French word for "Stall" is "Décrochage".
And no, there is absolutely no need to translate Alarms/Ecam/Interface in French for the pilots to understand what it means.
Hence, this is due to the French exclamative expression "Qu'est-ce que c'est [que ce bordel]!"which cover a larger range of signification than its litteral translation of its words in English.
That's only an expression of surprise that the stall/décrochage alarm was sounding at this point. Nothing more.

[xcitation]

@Takata

Thanks for debunking that.
Isn't that phrase a little nonchalent for the warning of death?
More appropriate for a knock on their door or an accidental release of digestive gas.
I suppose we would need to hear the emphasis of the actual CVR audio.

[DozyWannabe]

...but I do believe that AB should never have been marketed as more automation implicitly equals less crew training costs (which their salesmen, at least, did).

Actually I'm pretty sure that's an oversimplification. In the early days, Airbus's sales crew did emphasise how simple the automation made flying the aircraft. But I don't think that "lower training costs" sales angle referred to the automation. As I said before, Airbus's ace-up-the-sleeve with training costs is and has always been that the similarity of the flight-deck layout on the A320 up to the A340 (and the A380, despite having more advanced systems in some respects, the general layout is still nigh-on identical) means that conversion training between types is considerably easier and more straightforward than most of their competitors.

I'm not saying they weren't overconfident in the ability of the automatics to handle everything, as well as the ease with which pilots would take to the new systems in the very early days (1988-1994 in particular) - but I've long suspected that reports of "more automation = less training" was two distinct aspects of the new design lost in translation via the press.

[Lyman]

Seven seconds after the First STALL WARNING. "What was that?"

Not sufficient exposure of the sensor to the signal, the CRICKET was not triggered.

So, a 'transient' event.

"What was that?"

1. "Was that STALL?"

2. "Was that a Stall Warning?"

3. "IF STALL warning, WHY?"

OTHER:

"What was That?" "WAS IT.........?"

What it was, almost certainly, was a rhetorical interrogatory.

What it likely meant,

"Did you hear, see, feel, sense, understand, smell, or otherwise become aware, of anything you might be able to help me with?"

A guess could be, Buffet, Vibration, or an otherwise unexpected event, of some importance, that could or should be addressed "by the both of us?"

It is likely on the CVR, this...... ".......that" imo.

Since this comment may annoy or upset some, I will acknowledge that a possibilty may be that something broke, snapped, twisted, banged, fractured, cracked, or become unserviceable and created a noticeable sound, or unusual event that had naught to do with Pilot Error.

Otherwise known as something that had to do with the a/c that is impossible, either in fact, or in professional intuition.



add. IMO I don't think it had to do with the WARNING. They both knew what that meant. Because of the timing, I think it may point to a noise, or event, that may be associated with rapid change in aspect of the a/c. A chair rail creaking? A food trolley falling over behind the CD? Perhaps a FA falling? Maybe to do with Turbulence.

xcitation. This STALLSTA... happened at 2:10:04? How can Autopilot produce a STALLWARNING?

[takata]

Isn't that phrase a little nonchalent for the warning of death?
0210:11: PNF: - Qu'est-ce que c'est que ça?
Look, it is 6 seconds after A/P disconnected... It is a very common reaction in French in such case. Don't you really think that they could not be quite surprised to hear this alarm sounding, considering that, before this point, they might never have heard a single stall warning during a real flight?

Your "warning of death" will certainly add a lot of drama into it... with 100% hindsight. What most other crew did, in the very same circumstances, was to disregard the alarm as spurious. It did not last long enough, only few 10th of second, as it was due to very short flight spikes exceeding alpha treshold.

Additional note for any conspiracy theorist still unable to read what is reported:
- AP disconnected at 2:10:05
- 1st Stall Warning is recorded exactly (CVR) at : 2:10:10.4
- PNF comment is recorded at : 2:10:11
Comment was made with a 0.6 second interval (not 3 hours later) and was obviously due to this alarm, not because he heard aircraft structures falling appart.
And, of course,... everything (SW+comment) happened 5-6 seconds AFTER autopilot disconnected. It's perfectly clear from the report for anyone sober enough, or one not reading it up side down on purpose.

[TJHarwood]

I have come late to this crash thread, and apologies if I repeat what has been said before, but when Airbus were trying to induce my airline away from Boeing and McDonnell Douglas use in the late-1980s, their sales pitch was very much that automation would also save flight crew training costs (this was long before the entire AB family became a reality, and easy conversion training thereafter became important). Whether this was intended at the corporate boardroom level is another matter altogether but, to be fair, the previous post did say "implicit". It wasn't the main thrust of their sales pitch, but it definitely was in the mix. Overconfidence in automation (can easily) = underconfidence in crew training needs. Two sides of the same coin, which is how I interpreted the previous post........

[Welsh Wingman]

I accept your good point re: conversion across a range of aircraft, but I recall that my airline (when it spoke with AB before retiring its BAC1-11s) clearly was left with the impression that less training costs would be incurred separate to the conversion costs issue.

It shouldn't have, but more automation equals less crew training costs did enter the mix and it can't be blamed purely on the press. AB's (then) salesmen had to compete with the Boeing and MD duopoly.

The issue is whether the PF and PNF were properly trained to deal with the problem they encountered, UAS leading to A/P disconnect under the flight conditions encountered by AF447, because nobody would argue that it was the time for their manual flight training (in alternate law)? I have my doubts, on what I have so far seen......

If not, it is not conveniently "pilot error" but rather a deeper / wider systemic problem for the industry.

If the A/P cuts out, which admittedly is very rare, manual flight must still be second nature (or at least not an absolute novelty) to have a better than even chance of a happy outcome.

[DozyWannabe]

I accept your good point re: conversion across a range of aircraft, but I recall that my airline (when it spoke with AB before retiring its BAC1-11s) clearly was left with the impression that less training costs would be incurred separate to the conversion costs issue.

Firstly, was that BCal? If so then my first ever flight would have been on one of those 1-11s.

It shouldn't have, but more automation equals less crew training costs did enter the mix and it can't be blamed purely on the press. AB's (then) salesmen had to compete with the Boeing and MD duopoly.

Maybe so, but the fact is that neither of us actually *know* what exactly was said.

Case in point - I've spent the last few weeks struggling with a project and got a fairly good demonstration together - it fixed all the issues brought up at the previous demonstration, and showed that we'd made some headway with new features that had been mentioned, but not specified at the beginning. The feedback from the group was good, but halfway through the meeting the supervisor came in, looked at it for five minutes, said it wasn't enough and that he was told the product does something out of the box that we know it in fact does not. The salesperson involved left the company a short time ago, so we'll never know if he was willing to bend the truth to get sale or whether this supervisor simply misunderstood.

The issue is whether the PF and PNF were properly trained to deal with the problem they encountered, UAS leading to A/P disconnect under the flight conditions encountered by AF447, because nobody would argue that it was the time for their manual flight training in alternate law? I have my doubts, on what I have so far seen......

If not, it is not conveniently "pilot error" but rather a deeper / wider systemic problem for the industry.

Which is in fact what the BEA is implying if you read the report, as opposed to press articles that are all saying "pilot error".

[Welsh Wingman]

Thank you.

(1) No, not BCal - you can work out my former airline from my profile.....
(2) I spoke with two BAC1-11 captains who went to Toulouse (shortly after their return to the UK), and I know exactly what was said to them. And their unease at the "sales patter", even if they had no doubt that AB's flight training experts would have also been uncomfortable. Let's not forget that the duopoly in those days was an all-American affair, and AB was facing a huge challenge to break in.
(3) Most contributors to this thread well know what the BEA has said, and many are also concerned by what it will become in a 50 second BBC/CNN/Sky/Fox soundbite report. Pilot error, or pilot error with a long caveat to the effect that this really means training shortcomings rather than an inexplicable error by a perfectly trained flight crew? In this forum, of all places, "pilot error" should be very carefully used....

It was not the easiest of environments, in the absence of thorough high altitude manual flight training (CMB in ITCZ, no moonlight, early hours of the morning (PNF had just come off rest), no CDB on the flight deck, UAS leading to A/P and A/T cut out and the loss of flight envelope protection). The many comments on the SS inputs (NU), THS and trim, absence of stall recognition and cockpit discipline (particularly the non-reporting to the CDB upon his entering the flight deck) should all be read in this context.

[Welsh Wingman]

Yes, good way of putting it - flip sides of a coin (implied automation savings, separate/additional to conversion costs across the later range of Airbus aircraft).

[jcjeant]

Hi,

Maybe so, but the fact is that neither of us actually *know* what exactly was said. This is what is exactly said now ...
OPERATIONAL BENEFITS


Operators benefit greatly from this key innovation, which allows for simplified crew training and conversion. In addition, pilots are able to stay current on more than one aircraft type simultaneously without supplementary takeoff/landing requirements, recurrent training and annual checks.


INCREASED PRODUCTIVITY


http://www.airbus.com/typo3temp/pics/b48294febe.jpgAirbus’ unique commonality results from pioneering use of fly-by-wire technology, along with application of standardised cockpit layouts and operational procedures.
With Airbus’ Cross Crew Qualification concept, fly-by-wire qualified pilots are positioned for an easy transition among the single-aisle A320 Family, the twin-aisle A330 and A340 aircraft, as well as the A380 through straightforward and rapid differential training – rather than full type rating training. For instance, transition training from A320 Family to the A330/A340 is 27 days, compared to a full course A330/A340 training duration of 49 days.
Such streamlining results in lower training costs for airlines and considerably increased crew productivity, with annual savings in training and payroll costs of up to $300,000 for each new Airbus aircraft added to the fleet. It is also more economical for an airline to recruit new pilots who are already Airbus-qualified; for pilots, this benefit provides greater mobility and better prospects for employment.





More to read:
A CORNERSTONE OF AIRBUS (http://www.airbus.com/innovation/proven-concepts/in-operations/fly-by-wire/)

[Lyman]

IMO, what marketing does cannot be used as concrete evidence there is a lack of line competence, period.

Manufacturers build a tool that is sold to a second concern, one that is directly responsible for folding the machine into its useful life.

It is naive and misleading to think that salespeople have degraded hand flying skills. A trustier airframe does allow for changes in procedures and focus.


I keep in mind that airmanship and flying skills are acquired as we train, not after conversion to heavy and fast.

There is some inexplicable evidence to be explicated here, but to think that Typing on a widebody shoud include a refresher in Gliders, aero, or other for goodness' sake basics is a reach.

[TJHarwood]

Simplified crew training and conversion, not just simplified crew conversion - and from the horse's mouth! Not operational design, almost certainly, but no doubt the unintended consequences of cut-throat commerce.

[jcjeant]

Hi,

0210:11: PNF: - Qu'est-ce que c'est que ça?
Look, it is 6 seconds after A/P disconnected... It is a very common reaction in French in such case. Don't you really think that they could not be quite surprised to hear this alarm sounding, considering that, before this point, they might never have heard a single stall warning during a real flight?

Your "warning of death" will certainly add a lot of drama into it... with 100% hindsight. What most other crew did, in the very same circumstances, was to disregard the alarm as spurious. It did not last long enough, only few 10th of second, as it was due to very short flight spikes exceeding alpha treshold.

Additional note for any conspiracy theorist still unable to read what is reported:
- AP disconnected at 2:10:05
- 1st Stall Warning is recorded exactly (CVR) at : 2:10:10.4
- PNF comment is recorded at : 2:10:11
Comment was made with a 0.6 second interval (not 3 hours later) and was obviously due to this alarm, not because he heard aircraft structures falling appart.
And, of course,... everything (SW+comment) happened 5-6 seconds AFTER autopilot disconnected. It's perfectly clear from the report for anyone sober enough, or one not reading it up side down on purpose.

Just for vent ....
Indeed .. all the CVR reported conversations are typical (syntax and words used) of a common animated conversation between some friends in a bar (ou au zinc) and easy to understand by any french speaking people but seem's not common for professional pilots in a event who require all their technical knowledge and analysis power ...
It's another language for that (at least .. other words .. even in french)
That's was about the conversation...
Now .. about the acts performed ... they were in a language not understand by many professionals pilots ....
They still struggle for understand why they acted like .. that night.

[xcitation]

@takata,

I don't understand your comment "conspiracy theory" etc. Let's stick to the data and refrain from presumptions and personal accusations.

I am trying to understand why they ignored the stall warnings. I leave the blame game to others.



Here are the data points:
On first stall warning they say "What is that?". You state a better translation of the meaning is "What a surprise, probably just a blip".
The pilots talk like school boys arguing over a bicycle, hardly consistant with the grave situation of master warning and stalls.
Not once does any pilot say the word "Stall" or "Décrochage" in 4 minutes of blaring stall alarms and master warning.
Not once do any of them call for any procedures.
Not once do they consistently respond to the stall with a strong nose down or even change what they are doing.
No regular call outs.
Can you forgive me for joining the 6 points that are all consistant with the pilots not understanding "Stall". Do you have any data points that convince you that they did understand "Stall"?
The pilots are with the flag carrier, i.e. "gold standard" pilots. Here is the big question: if they thought stall was false then why would they not articulate that?
I am the first to admit that I am a fool, but hopefully a fool can learn.

These kind of mistakes happen all the time. Contracts get made in Europe with mil. meaning 1000's in french but in english that means millions - fail. The hubble telescope was designed in euro cm's but was built in USA inches - fail. Sorry but sometimes the obvious mistakes happen to those most qualified. I subscribe to the mess up theory, not the conspiracy.

[Welsh Wingman]

Salespeople can't do anything by themselves, from whichever manufacturer, but you had line management directors (particularly in finance) looking at deregulation and casualty after casualty (Eastern/Pan Am/TWA/Sabena/Swissair).

You can't blame them for selling planes as "planes that fly themselves" and (implicitly or explicitly) save on (expensive) piloting costs, because they knew they were sowing on fertile ground. The real problem was within line management, and also the aviation regulation authorities.

To a pilot who never flies his plane at high altitude by hand, was the scenario facing AF447 ideal non-simulator practice? The position was not quickly brought under control in the first minute after A/P disconnect, and it got a whole lot harder thereafter......

Over to PJ2 on this subject....

[takata]

I don't understand your comment "conspiracy theory" etc. Let's stick to the data and refrain from presumptions and personal accusations.Someone posted in between my answer to your post, this was not aimed at anything you said. Read it (post above mine).
Here are the data points:
Beside, I only corrected your interpretation for other readers; crudely said, that meant WTF!
That's all. You can try to paint the dark side of the moon bright yellow with it, this is not my concern anymore, whatever conversion from metric to imperial caused whatever disaster...

[Lyman]

WW

The best sales people don't sell, they teach their client to sell himself. I make my point that the responsibility lies with the Line to incorporate all new equipment into the culture that exists. As you say, the ultimate responsibility is with the Line; not even pilots need to step up any longer, should they memorize the SOPS well enough.

Can there have been a blunder at AF large enough to potentiate these outcomes? If as you say the monopoly was Binary, and strictly American, Airbus had to supply something competitive, Another Banana is just another Banana.

It is not for want of a reason "new" is attractive. Was it oversold? Or was it merely undersupported, and then neglected, left to achieve its marketing claims, or not, In the vacuum of false confidence?

Sometimes in "Anticipating", and selling (FBW), what turns out to be an evolutionary trend in the long haul, means rushing technology? And if not a rush to technology, then a rush to new crew capabilities? Some disciplines are not well served by "hurry". Fast, yes, not Hurry.....

xcitation

I cannot attest to the accuracy of the CVR timetable. A STALLSTA.... takes longer than .6 seconds, and recognizing it, processing one's awareness of it, forming a question, and speaking must mean the PF started his "What was that" perhaps before, the Warning.

In any case, is it not possible that the PF was vocal in re: something that happened before the STALL Warn chirp, and that they "coincided"? Perhaps the focus of his remark something that may have preceded the WARNING? That is a pretty well packed 1/2 second, NO?

[Welsh Wingman]

Lyman

I think the history is the key - AB was developing in the context of 1985, a truly horrid year for the aviation history e.g. Boeing had lost several 747s, part of the US 101 Airborne Div had been decimated on a MD DC8 at Gander and Lockheed lost a L1011 at DFW. The design philosophy was safety through automation, including "protection" against pilot mistakes. The marketing took a different twist, as competitive industry pressures shortly afterwards came to the fore and training/conversion/fuel cost savings became critical. The question of what airmanship skills were still needed in the (rare) circumstances (such as AF447) where the flight envelope degraded slipped through the net. The industry has not proceeded on the basis that automation training is a bolt-on to underlying airmanship, which is my gripe (as you may have worked out!).

[TJHarwood]

Yep! I bet you never expected to see me on a network like this, so many years after my retirement?! I will e-mail you privately, to spare the readers of this thread.

[Lyman]

WW

Automation most definitely should be seen as an adjunct to airmanship.

I am not persuaded this fellow was not a competent sort. What shouts to me through all the noise here, is simply an airman who is not familiar with his a/c. That is first call (Along with flying Catch up). Second is what you elegantly describe as the "environment". Thank you for that; I doubt but a few here have experienced the type of sky these gents encountered.

[Mimpe]

The pilot and CRM aspects are quite clear to me.

Deeper questions relating to how the automation mileau (visually, culturally, psychological) has interacted with the pilot to produce the accident MUST be explicitly addressed , item by item, in the final accident report.I still feel there is insufficient respect for the power of sensory disorientation, for example. There is no mention of the likelihood of it in BEA report, even though the PF made clearly disoriented command inputs that are classic for a somatogravic illusion.

What is it about the alarm system that leads top of the line pilots to ignore or not belive it?
Is the altitude indicator tape, VSI and Artificial Horizon hard to INSTANTLY comprehend when one most needs to ? Did the dangerous autotrim full aft despite high nose attitude contribute?How much did the reversed/paradoxical stall actives and inactives further confuse at the last possible moment for saving the flight?Is this a an engineering concept unsuited to LOC management, or is it a human intereface problem?Why is it so important in the design concept that control inputs NOT be visibly dual/ linked?

The accident is a fascinating case of everything that could go wrong did go wrong.....many layered aspects.

[Welsh Wingman]

When the computer computes "I do not compute", as it did on AF447 (due to UAS data), you should always have the underlying airmanship upon which to fall back on...

There are one or two clues early on that PNF was on the right track, despite the CRM issues, but this did not happen over Western Australia at midday with clear visibility and no CMB as with the A333 in QF72. PF troubles me, particularly as he was the "alert" pilot.

I will wait the final report, and more detailed CVR, before taking a final view on whether this crew could have recovered the situation once the death plunge began at FLT380. Intimacy with hand flying their aircraft was missing.

My experience of the ITCZ and CMBs was more en route to Southern Africa than to South America, but invariably overnight (particularly after the 747-200s were re-engined for non-stop).

[JD-EE]

CaptainGef, I agree with David Learmount on everything within his field of excellence and experience. It's perhaps coincidental I came to most of the same conclusions.

The chief item I'd take issue with is his lament that there will be a drive to push pilots out of the cockpit completely. That is an ongoing phenomenon. Military pilots may last a lot longer than transport pilots. They fly under completely different "rules of engagement"; and, military pilots face far greater problems with things like landing an aircraft under real or potential enemy fire.

Strangely enough the requirements for safe flight in the AF447 situation were well known. And the computer had full access to data, some of which was not but should be available to the pilot. I believe it was politics and limitations of the rather antiquated (in computer terms) computers and software on the AF447. No, this is not a "bit rot" thing, not a software bug. It's more a slow computer, political limitations issue, and knowledge about what to do sort of issue.

I get the feeling that it is known that pitch and power is how you fly when airspeed is lost but it is not trusted that this is enough. Therefore pilots are thrust into the loop. For the time being they are in the cockpit anyway because humans are still somewhat better than machines at picking their way between bad weather conditions if they actually use the radar properly.

The progress I see is along the lines of UAS being handled by the computer since it is becoming more and more obvious that computers don't face "instinctual drives". They face biases that are not built into the software and can be very complex. More and more the pilot will become a cockpit executive. "Plane, go there. Make it happen."

This will be followed by computers able to thread the needle based on radar and other instrumentation to the point that any condition the computer cannot literally learn to handle would be way beyond any human's capabilities - someday.

I note the Google has a self driving car that uses video cameras for situational awareness. The Chinese have stepped in with their version. Neither is ready for prime time. One of Google's cars suffered a collision lately. It was under manual control with the driver trying to get into a very tight parking place. Apparently something as mundanely complex parking may be "the final frontier" for computerized cars. I wonder what will be the final problem with fully automated flight. I suspect much of the increased automation I mentioned will come with the next generation of aircraft based on A380 and Dreamliner experience.

I've been watching the computer industry because I am in it. A time will come when pilots are as obsolete as people who know how to drive a car or make a buggy whip.

I cannot say I am emotionally pleased at this. And I see this as part of a completely destabilizing trend for society. But, it's going to happen regardless of my emotional reactions.

[TJHarwood]

The problem with a cockpit executive, and many of the old timers on this thread no doubt believe that AF447 proves that we are already there (at least with some flight crews), is that there is no Plan B when Plan A goes wrong. We are a long way from safe automated pitch and power flight (groundspeed GPS?), without reliable airspeed.

[HarryMann]

GarageYears

Once IN THE STALL many of the systems necessary to understand the situation are compromised.

Solution = avoid STALLING Mmmm. :=
Seems a naive viewpoint to me... it's this kind of thinking that has actually caused such an alarmingly poor crew response in this situation! (i.e. no need for the native skills to fly the plane in these conditions because 'you' won't allow it to ever get there)

I personally believe the instumentation is extremely poorly conceived... position error should be minimised 'by physical design' not using PE corrections (e.g. probes far fwd away from pressure field around wing or fuse, as in test fl;ight a/c). AoA instruments to be much more robust and reliable, balanced to work down to a few knots.
Thus IAS not dependent on a/c AoA and AoA not so dependent upon speed (after all, does it not occur to EASA engineers that AoA (primarily for stall avoidance and warning) is most likely needed to be reliable at some (fluctuating) but arguably very low airspeeds :confused:

================

And as before, pretty well every post of mine will point to the sidestick culture.. so many downsides and the more we look at this (admittedly strange& hopefully rare) accident the more one can't imagine it ever happening with a fully visible and centred control device... whatever that may be.

[JD-EE]

jcjeant - actually pilots should be encouraged to fly. The computer should monitor flight parameters and if the PF does something stupid the computer takes it back for five minutes before the PF can reacquire control. Too many of those incidents and he is flunked for his "training exercises."

These days there is enough computing power to make this feasible as a way to keep the pilots on the ball, well experienced, and well trained.

[HarryMann]

I will wait the final report, and more detailed CVR, before taking a final view on whether this crew could have recovered the situation once the death plunge began at FLT380. Intimacy with hand flying their aircraft was missing.Of course it was recoverable...

And let's call it a final descent, or similar, not a 'death plunge' - no one was consciously diving off a hotel roof !

[JD-EE]

ChristianJ - let's not feed the troll. Simply ignore him using the control panel.

[Welsh Wingman]

HarryMann

The key issue was to avoid the stall, after the A/P and A/T disconnection.

But there was still plenty of height to play with in which to recover from this aerodynamic stall, if properly diagnosed and addressed. You can't rely on one pilot up front always having come into civil aviation from a military fast jet background.

JD-EE

Yes, regulations should require some manual flying within the AB flight envelope - as opposed to line pilots having to explain to flight ops why manual flight has taken place. Emergencies such as this are not the time to try out any neglected basic airmanship skills.

[Welsh Wingman]

(1) The key words were "this crew", in the context of the CRM issues that have arisen. It is much easier to avoid an aerodynamic stall, than to recover from a FLT100 per minute plunge.

(2) "Death plunge" - provocative language, but to remind some posters what an (uncorrected) aerodynamic stall involves. There is only ever one ending.

The stall alarm repeatedly sounded, when within parameters.

[Linktrained]

JD-EE

One limitation of automated cars at present is that they may see and avoid a ball coming from in front of a parked car - but not anticipate that the ball may be followed by a child, as yet unseen.

Traffic on the taxyways gets held up by dense fog, as happened at Heathrow a year or two ago. Decca Navigator was almost accurate enough to use as a landing approach aid at Manston. We used to ink the charts. (The runway was very wide and we used the centre part anyway. FIDO had been removed.)

Reverse taxying would need practice. Do remember to take your feet off the brakes when going backwards. You MUST use forward thrust to stop going backwards or...!

[Lyman]

A theoretical.

The Pilot accomplished the climb with the a/c following his commands.

WW, Harry Mann

Had the Pilot recovered the STALL, found himself in a high velocity descent, would the a/c have responded with similar control movements, and 'g'? Could he have commanded sufficient Nose Up to exit the dive successfully? Does the a/c limit the g available at the stick to prevent a recovery before hitting the Ocean? What are the limits to a successful recovery (pullout), imposed by the a/c's control system?

Again, a hypothetical.

Thanks

[DozyWannabe]

@Lyman

If you are indeed another alias for bearfoil - which is in itself a breach of the rules on most forums, then you'll know full well that the question you've just asked was answered - several times - on previous threads. If you're having a good cackle forcing people to repeat themselves over and over, it's not big and it's not clever.

For the benefit of new posters/followers of this thread I'll repeat once and once only - The aircraft was in Alternate Law 2 (aka NO PROT) - in this control law there are *no* hard limits on the attitude that the aircraft can be put into. There are soft limits, but the pilot can override them simply by manipulating the flight controls (as demonstrated by the THS response). The pilot has *full authority*.

[Lyman]

I have not read the answer before, that is fact, and you have not answered it still.

The Pilot did not have "Full Authority" in the climb, his stick wanted it, but the a/c responded with less than the absurd amount he was commanding. Until the loss of energy, when the a/c allowed/deflected the controls to the limit, and kept them (THS) parked at max through the STALL, and down the other side. The climb was allowed by the a/c in "bumps" of elevator only, the THS stayed rigid at -3 degrees. That is NOT full authority, and good on it.

My question involves the descent. Why did the THS stay hard against the curb, independent of elevator command, and why was the elevator deflection ineffective in curing the STALL? Did it have to do with 'g'? airspeed? What, then. The last part of my question I repeat. If the pilot had gotten her flying, Would the pullout be hindered by the same limits I see in evidence in the CLIMB?

This is getting old. As you know, we have communicated PM, as I have with the others who prefer getting upset to being forthcoming.

There are enough high horses here to have saved Napoleon. One or two might consider dismounting.

What is abjectly lacking here most of the time, is deference to the dead; Instead we get childish fan clubbing, and wounded egos.

Website PROTOCOL? Are you serious?

[hetfield]

The stall alarm repeatedly sounded, when within parameters.

Indeed

Sidestick ND - stall warning on
Sidestick NU - stall warning 0ff

:confused:

[CONF iture]

This is a judiciary investigation under progress ..
They will have the FDR data .. so it's not left in BEA and Airbus hands only.
As Airbus have them, why not the victim's families ... ?


And as before, pretty well every post of mine will point to the sidestick culture.. so many downsides and the more we look at this (admittedly strange& hopefully rare) accident the more one can't imagine it ever happening with a fully visible and centred control device... whatever that may be.
Amen.
Now, would you expect any FINDING in such line of thought in the Final Report ?


Diversification and A33Zab,
Thanks for your documented replies.
Nevertheless, let me quote the D-AXLA report on P92 :
When the real angle of attack increased, the blockage of AOA sensors 1 and 2 at similar values caused the rejection of the ADR 3 anemometric values
In the AF447 case, there is an open door for ADR 1 anemometric values rejection.


Other BEA omission :
As initially reported (http://www.pprune.org/6618515-post1496.html) by A33Zab.
And as further questioned later on (http://www.pprune.org/6619963-post1552.html).

Anyone ?

[HarryMann]

It did not last long enough, only few 10th of second, as it was due to very short flight spikes exceeding alpha treshold.

IMHO, if that is the modus operandi then it needs looking at too..

Any 'spike' triggering the Stall Warning, should ensure that it sounds for a minimum time. (say 1 or 2 seconds) OR continue until AoA is below a preset delta below trigger point (say, 1/2 degree above 20,000 ft and 1 degree below)

[Welsh Wingman]

I am not the right person to comment, having not been in a real high altitude aerodynamic stall since 1967 (not a passenger airliner, I hasten to add!), but stall recovery should never be considered an absolute given with a VSI of minus FLT100 per minute. The pilots had to both get the ND (the THS?) and not lose all control of the aircraft in the process. Never a certainty, even if the stall had been diagnosed in time. The critical period was shortly after A/P disconnect, to maintain stable flight and avoid the stall in the first place.

[CONF iture]

Military pilots may last a lot longer than transport pilots.
Isn't it the opposite happening already ... ?

[TJHarwood]

An issue limited to reconnaissance flights, particularly unmanned drones these days. That is an issue going back beyond Francis Gary Powers. There will be fighter jet pilots for a long time......

[Ian W]

An issue limited to reconnaissance flights, particularly unmanned drones these days. That is an issue going back beyond Francis Gary Powers. There will be fighter jet pilots for a long time......

Google Combat UAV and you will find that the long time may be a shorter time than one would think. The costs involved with keeping a pilot on the aircraft in terms of maneuverability (g limits) and environmental support cooling/heating/pressurization/protection of the cockpit are very large. There are already trials of air refueling combat UAVs, carrier landings with combat UAVs. But remember, these are rarely 'pilot-less' robot aircraft they are remotely piloted FBW aircraft with the pilot sometimes in a different continent so these fighter pilots will be around just not in the same place as the aircraft. A comfortable position to be in that allows the pilot to take more risks and walk away from every hull loss.

Simulation vs Reality

This raises a human factors issue on AF447 and training that I have not seen raised.

Simulations are used for training of all sorts of exigences there is no-one I know that has got into a simulator check ride where it is a boring flight and everything goes smoothly. It is expected that emergencies and failures will be exercised purely because they are not exercised 'in real life' - the raison d'etre of the simulator industry. This mentally sets up the trainee to expect problems in sim rides - and not to expect any emergency in the thousands of hours of mundane real world flight. There is a huge mental difference between being in a nice safe simulator exercise trying to please the training team behind you and being in a real world aircraft that has suddenly started an unscripted series of alarms and instrument failures knowing that your life is on the line -- or perhaps not fully understanding that your life is on the line.

I like many military pilots was fortunate (?) to be trained in an era when simulators were unreal and extremely expensive and actual flying was considered cheap. So all real emergency handling practice was carried out in real aircraft with imaginative instructors causing the emergencies. Instrument recovery from unusual positions was carried out from under a 'hood' with a 'you have control' midway through a high g aerobatic sequence - multiple times an hour. The trainee was in a REAL aircraft and having to do REAL recoveries.

The mental shock of a 'simulator exercise' suddenly happening in real life can lead to all sorts of human factors issues - some people who are good in simulated practices go to pieces in real life. Its a little late to learn that when the AP drops out with the wrong PF.

There could be a need for some kind of psychological assessment for FBW pilots. Or, more likely, even if the bean counters wouldn't like them, the old methods of using small aerobatic training aircraft to assess pilots were the right ones.

[HeavyMetallist]

HarryMann:

Seems a naive viewpoint to me...
It's not naive at all. Plenty of aircraft have very unpleasant stall/departure/spin characteristics, which no-one in their right mind would want to explore outside a very carefully managed flight test environment. That isn't to say they can't be operated safely, just that their pilots need enough warning to be able to stay away from the stall in the first place.

I personally believe the instumentation is extremely poorly conceived... position error should be minimised 'by physical design' not using PE corrections (e.g. probes far fwd away from pressure field around wing or fuse, as in test fl;ight a/c).
Actually the engineers designing these aircraft aren't stupid, and go out of their way to position static sources where the inherent pressure error is at a minimum over the normal flight envelope of the aircraft - those probes and static plates aren't where they are for convenience. Sure you can do better with a massive probe on the nose or trailing a static cone from the fin (or presumably several for redundancy :eek:), but why got to all that trouble and expense when you can get acceptable accuracy by applying corrections for AoA etc?

[CONF iture]

An issue limited to reconnaissance flights
Almost ...
Pakistan: 4 morts dans un bombardement de drone américain (http://www.lepoint.fr/monde/pakistan-4-morts-dans-un-bombardement-de-drone-americain-01-08-2011-1358455_24.php)

[john_tullamarine]

Thread #6 continues here (http://www.pprune.org/tech-log/460625-af-447-thread-no-6-a.html#post6638041)