I'm sure the logic was well looked at, and proposing that it need be scrutinized now, is misleading the herd. Perhaps another look, then?

Once STALLED, allowing the cessation of the WARNING is inexcusable, by any stretch. Perhaps disabling all but the few critical prompts (and certainly the ECAM) might be a start.

Me too (along with most rational people, one would hope!). What I'm saying is that until we know the reasoning behind the logic tree, we need to be careful about making snap decisions over the changes we'd like to see applied. Right now we're talking about a single accident among tens if not hundreds of thousands of safe flights made by the A330 over its service life and the risk is that making a change based on a single incident without properly identifying the potential consquences of that change could make the type less safe rather than more.

20/20 hindsight is a wonderful thing, but the problem here is that the aircraft was so far outside of the flight envelope by the time the stall warning stopped that the very devices used to calculate the data used for stall warning were considered to be unable to generate reliable data.

Look at the response on here when the initial flight recorder data was released - most pilots were in a state of stunned disbelief that a professional crew could have put the aircraft in that state - it's not a major leap of imagination to suggest that the engineers and designers were equally incredulous both before and after the incident.

But that's the very reason the systems are designed the way they are - i.e. to logically separate out any spurious warnings. The ECAM tells the pilots what is wrong with the aircraft - what good would disabling that do?

We're in danger of losing sight of the fact that the stall warning operated correctly for some time after the aircraft had departed from it's certified envelope. No amount of fiddling with the logic at the extreme level of the envelope excursion concerned can alter the fact that the warning was not heeded, and right now there's no evidence that any of the crew were distracted by any other noises or displays.

A (very) large red Herring. The critical data involves the total of UAS incidents (accident) and the HSP altitude excursions, plus other identified anomalous unsafe conditions. If we start to add in the degradation of flying skills at altitude and other locales, we have a distressing snapshot of the status quo, to include other manufacturers, to be sure.

Beware the statistical distraction. Its purpose is not to emphasize safety, but to disguise the lack thereof, imho.

I'll just comment that there's no easy way to flag data as reliable enough for some purposes, while unreliable for others.

A FBW system using alpha as part of the control laws is rather more sensitive to AOA accuracy than a conventional type 9which frankly hardly cares until you get to low speeds where the AOA should be doing stuff). i *suspect* - and I confess its nothing more than a semi-educated guess - that one of the reasons for declaring AOA invalid at low airspeed was that the AOA vane could not be stated to provide the required accuracy at such low speeds, and that this accuracy was specified in the context of normal law operations. Gross AOA, good enough to fire the shaker, wouldn';t be good enough to drive the FBW laws.

Now, you could say "ah, but you can't be in normal law at such low speeds" - and normally that'd be correct. But the design was probably trying to cover all bases, but with the assumption that defending the normal law scenario against erroneous and dangerous AOA data was the more important thing to do.

Now, with hindsight, we might try to provide for discarding the AOA data for the control loop closure, while retaining it for the warning. But that's also complexity - and the golden rule in designing complex systems is to not make them any more complex than they need be. Judging the point of "need be" is the trick, of course.

Dozy is correct, in that the discussion is at the tail end of a long sequence of remarkably disintegrating cruise flight.

At STALL, there is no reason to suspect the a/c format of anything untoward; save the fact that two, and eventually three pilots disregarded what should have been a butt puckering cacophony rather than a demure SyntheticVoice in concert with a child's click toy.

Harsh? What is it to be, then, for a lack of recognition of the death rattle of a two hundred million dollar a/c with 228 sob? No comment? Nuttin?

Incredulity remains. There is more to this than meets the eyes. Perhaps the clamor for better pilots is a response to what may be something that is utterly unbelievable on its face.

None of what is offered as explanation or redress is acceptable. None.

Will this come clear? Will the record be complete, and be made public?

Dozy, you are overthinking this.

Dozy, we are not flying with the first design of Airbus 330 control laws nor even the second.

The software design is a work in process.

Airbus has an extensive protocol and infrastructure for maintaining flight control software. At this point, it is an engineering problem and capable of being handled without more than the usual superhuman effort.:}

Mad Scientist.
Doesn't C* use 'g' for control loop closure at high speeds and body angle at low speed?

http://i45.servimg.com/u/f45/11/75/17/84/af447_11.png

Airbus documentation is simply false.

What a ridiculous pseudo reason really !

Those AoA vanes move at nothing. I took the opportunity to manipulate them the other day and 15kt of relative wind is probably already in excess to place them in the wind on. No wind on them, they also stay in the position you place them, like absolutely not affected by gravity.

Some documentations ....

AirbusPapers.pdf

- Whoa! Isn't that going to deny any AoA 'protection' unless you inhibit it only in normal law?

@ jcjeant
 

Good read that.

Remembering the title is Operational Philosophy, the devil will be in the detail, or more precisely, lack of knowledge/practice off, which is becoming more and more obvious in the case of AF447.

I agree. I couldn't find crew's operating history on days prior to accident. If capt and senior F/O had 24 hours layover in Rio, their clock would be still on CET and that would put the time of the accident at just past the middle of the circadian low, at 4AM. What effect on the junior F/Os body clock had the alleged R&R in Rio, remains to be seen.

Stall warnings gave unwarranted warnings on older types too, like L1011 at KJFK in '92. Fortunately, outcome was less messy. Try hard as we might, we'll never make perfect and infallible stall warning system. Best we can hope for is good enough system combined with good enough crew and hope that system's and crew's low don't overlap. EK Gann understood it very well and to say that much has changed from his times would be displaying very shallow understanding of the aviation.

Hmmm.... inhibiting autotrim when stall warning is present, like it's inhibited in high speed protection? Interesting idea which might have some merit. While I currently can't think of any reason why it shouldn't be so, so far AF447 investigation has not uncovered a single reason why autotrim wouldn't work with pilots input. If pilots pushed forward, which is universally accepted as good idea when faced with upright stall, THS would follow.

Parbleu, monsieur! You have managed to invalidate calculations of Airbus engineurs which were accepted by certifying authorities on your own by conducting a simple manual experiment. I assume you've done it single-handedly. Congratulations... not! Do you have any idea what's the difference between dynamic pressure at 60 KEAS and 330 KEAS, everything else being identical? Only when you calculate it, we can discuss about precision and reliability of AoA vanes under all conceivable operational circumstances and whether would be too much of designers to come with those working under inconceivable ones.

Minor point re: STALL WARNING. There was nothing whatever wrong with it, it functioned correctly. What failed happened later, and focusing on the lack of a Horn when one minute into LOC is like nibbling on the plastic garnish in your sushi.

Without comment, BEA does not address BUFFET. The entry into STALL was not 'conventional', and lacked a true break. That left the crew to rely on a System (SW) that was at best 50 percent dependable in the identified problem, (UAS)). That it was correct meant nothing to the crew, how were they to know?

PF was obsessed with Overspeed, and the ROD was not completely non-indicative of HS? The climb was similar in nature to an HSP ascent, and NOSE DOWN 'not responsive'?

Each time the guff gets to this point, someone needs to remind us of the conditions, the failures, and the not well understood UAS problems.

Not even BEA has condemned the crew as yet. Have they cynically relied on the public to convict?

This topic was already discussed a few pages back. From the FCOM:
When angle of attack protection is active, THS is limited between setting at entry in protection and 2° nose down (i.e. further nose up trim cannot be applied).
Basically, the idea was: why not do the same in Alt Law? (with the AoA protection remplaced by the Stall Warning, of course).

Lyman:Each time the guff gets to this point, someone needs to remind us of the conditions, the failures, and the not well understood UAS problems.
Exactly!
Let us try to be fair:
Simulators (Airbus test pilots have sais so) do not simulate in a useful way for training crews, piloting sensations at high altitude: that means the fact that a small stick input will give much more important nose up or down effect than at a lower altitude. How do you train then as airlines do not encourage hand flying in high altitude cruise?
Protections (although here, as we do not know exactly when the alternate law came in, this may be out of the subject) kick in with the same enthusiasm at 2000 ft and at 35000 ft in a heavy, rear centered airplane, with no regard at all for the flight envelope: see the Caracas A340 incident.Unbeliavable to me: you may have a 1,75 positive g "protection" at 39000 ft!
Speed indications coming back but not trusted. Understandable.
No AOA indicator. (I flew with one in the A300 for years, and, believe me, it is useful).
Nose up from 0 to max 10 degrees, variable, with an angle of attack (unknown to the pilots) of 40 degrees! Difficult to guess for them that their AOA is so high.
Trim wheel: never looked at, never used manually in thousands of hours..
Variometer unreadable in those planes, when leaving "normal values" and probably not read in the chaos.
Only the altimeters unwinding at full speed were an indication of what was really happening to them. I do not say they did very well. I say, without doubt, that they were not test pilots and that the situation was totally out of reach of the training they were provided.
Their experience was onlyA320 A340 A320...Where would they have learnt unuasual positions ?
I have a lot of hours, and have learnt to be really modest. Let us all give a thought to the very many, distressing missing informations in the BEA report. I hope the next one will be a little more complete.

As I understand it the underlying reason isn't to inhibit the stall warning below 60 it's to prevent spurious data when the airflow is outside the vanes spec. Stalled or not stalled, a warning that airspeed is less than 60 knots when there is no weight on the wheels would be equivalent. If that situation can only arise when stalled, then fair enough allow a warning. Seems quixotic to cancel an existing warning when the speed goes out of range and it is likely that that very same stall caused the speed to go out of range.

Hope it's allowed to quote myself when I subsequently disagree. After a bit more thought I would give the designers some slack on this. Reasonable (and correct in this instance) to think that the stall warner would have done its job as best it could, well before speed decayed to 60knots. Can't blame the messenger if no-one gives it credence. My supposition is that it was discounted when it was real the first time round but believed when it reactivated on ND.

The approved flight data package that is used by the simulator manufacturers comes from Airbus. It includes automated tests utilized to periodically check & assure that the simulator is performing consistent with the actual data accumulated from flight testing within the aircraft operating envelope, at any altitude.

Why would company test pilots make a statement like this?

Hitting the wall
 

Does anyone have a comment on the fact the PF (right seat) was found with lap belt undone and his audio channel sounding like he hit his mic on a wall? This correlates with the maxima of the acceleration graph on page 43 (+ 1.15g up).
Anyone know if AF pilots always fly with restraints attached or treat them in a casual manner? I could not find the AF policy for pilot seat belts.

Because the simulator "matches where it touches" - it reproduces the manoeuvres specified by the data provided, and not necessarily any other manoeuvre. In practice, sims do better than that minimum, because the manoeuvres matched do cover reasonable variety of manoeuvres and across a fair bit of the envelope.

But go far outside the envelope of the specific manoeuvres and you are on your own. I suspect that is what the test pilot statement likely alludes to.

No, just too simple. Possibly lost something in translation also. It should be perfectly obvious, with only a small amount of thought, that the warning cannot possibly be permanent if AOA is not recovered.

Possibly (guessing a bit) because in Alt Law you're there because things are broken, and therefore airdata (for one) may not be assumed to be as reliable.

There is a difference between giving pilots a warning (which may be ignored...) and taking affirmative action to limit or override the pilot. The latter should requrie a higher degree of confidence in the data you are acting on - and that may not be available in Alt-Law.

xcitation. Without too much comment, there is a possibility nomenclature is not being understood. "On the right, 'side seat' (#4)", there was no belt attached. This may mean there was no remnant of belt attached to the seat frame. It would not mean there was no belt attached to a body, since without restraint, there would be no body remaining attached to the seat frame. BEA would ordinarily identify each seat by number, and RHS would be #2.

You say they identify "his mic". Not necessarily. They say "the mic". This could mean the ambient mic (one of, eg).

Either way, having found no belt attached to the seat, strictly speaking, it means that the belts were lost from their attachments (at impact?).

The original post clarified (cut from the quotes):

that means the fact that a small stick input will give much more important nose up or down effect than at a lower altitude.

i.e. claiming the real thing is a lot twitchier than the sim.

It shouldn't be - ample data should be available for that, and if that statement is true, I would say the sims need fixing.

False positive alarms
 

Having read most posts since the recovery of the recorders, and coming from a medical-statistical background, DozyWannabe in #833 raises an important issue:

When checking for errors/illnesses, the false negative type is typically the one that gets most attention, while false positive alarms may be more harmful in the long run.

False negative in this case would mean not to report a stall, that is indeed happening, while false positive would be to report one that isn't there. A false positive alarm is a cry wolf, insensitizing pilots to a particular warning. The "shut up gringo" incident, the tripped circuit braker on NW255 and (maybe) AF447 reactions are indications of this happening.

Actual stalls are very rare, so even though a system may have a low propabilty of reporting false positive, that scenario is still more likely than a real stall (true positive). In general, minimizing both types of errors may not be so simple, and lowering one type can lead to a rise of the other one.

@Lyman...
And nor will they. From their homepage...

The sole objective of the technical investigation is to collect and analyze useful information, to determine the circumstances and the certain or possible causes of the accident or incident and, if necessary, to make safety recommendations in order to prevent future accidents and incidents.

TyroPicard, re: "objective"

Except when it becomes necessary to support a manufacturer with a Press Release, and in doing so, laying Blame on crew by default. That Press release was a complete embarrassment, and an abdication of the very charge you quote.

A Mission Statement can be a promise made in Haste, prior to the challenge of the Real World.

The responsibility of those who are served is to challenge the Mission.

Them's the 'Rules'.

Why not ???

To the contrary, it is paramount the warning does not quit before the stall exit is complete. More than a question of regulation, it is a question of common sense.

But I’m curious here : When would you stop it otherwise ?

AFAIK 'dynamic pressure' applies on both side of the vane ... but please tell me more.

Hi CONfiture,

I think IF789 was joking at the language translation.

If you are stalled, then the warning can not possibly be permanent, because if AOA is not recovered, then the crash would stop it.

Yes, but perhaps it should be a good idea to have a stall warning, even if the IAS is NCD / < 60kt.
If you have a NCD / invalid AoA... well... I don't know. But that's not the point.

I totally agree with you, here.
But I was not proposing to limit or override the pilot, but to limit nose up autotrim.
I cannot imagine a situation where it would be dangerous not to autotrim nose up, when stall warning is ON:
- if the stall warning is correct (i.e. most of the cases), one would not trim up, but lower the nose
- if the stall warning is incorrect (e.g. wrong AoA sensed...) => false positive:
---> would it be a problem/dangerous to inhibit autotrim NU? (note: manual trim always possible)
---> is this scenario likely versus the above one?

Lyman, you may be in need of a "chill pill" again. Not only was there nothing in the "note" released prior to the 3rd interim report (which is presumably what you are referring to) that was in support of the manufacturer, either explicitly or implicitly. All it said was that there appeared to be no technical or mechanical failure of the aircraft before the departure from controlled flight over and above the pitot blockage/UAS issue we already knew about.

Firstly, it's a logical fallacy to say that making a statement of that nature "lay[s] blame on crew by default" - that is simply not true, and an example of what many on here will recognise as a "false dichotomy" - a neophyte debating tactic.

Secondly, the press release did not directly lay any responsibility on the crew (nor was it a "cynical ploy" to get the public to do so). All it did was state the facts of the matter, among which was the indisputable fact that the crew appeared to mishandle the aircraft following a UAS incident, leading to a stall and loss of control. It was but one factor in the holes in the cheese/chain/graph of events that led to the accident. That the press may have oversimplified what was actually said in order to provide a more sensational story (and thus sell more papers) cannot be laid at the door of the BEA. Remember that the press have skin in the "face-saving" game here, having popularised the "baby pilot crashes aircraft" meme a couple of years back when the facts were very thin on the ground - to go back on that would make them look very foolish.

In part, it was this constant attempt to re-tread things that you have already brought up several times under several aliases that got the R&N thread closed down and transferred to Tech Log. Do you want the mods to shut down this discussion too?

rudderrudderrat has it right.

The impact (ground/water/whatever) will stop it. Until stall exit is complete you are falling, not flying. Falling is not a permanent state (unless you are in orbit).

It is common sense that the manual cannot mean the warning is permanent without qualification.

Someone is taking a disagreement a bit too far. BEA's Press Release allowed Airbus to claim no "new" issues with the a/c. That they did, and since no one was available to prompt no "New" issues with the crews, there you go. It was cynical, callous and sly, imo.

You disagree? Awesome....... A difference of opinion is healthy, up to the point where personal slander and hyperbole get slung. Not one time have I attacked you or your "chill" quotient. You seem intent on expanding ad nauseum on things not being discussed.......

A disagreement is not an insult, so there we are. You continue to have my respect and my admiration for such a complete grasp of the topic.

I tire of being "warned" that I am somehow compromising the thread.

Are you saying the thread disappeared due my posts? That would be odd, since ordinarily it is the poster who garners the ban, not the discussion, and you may have an issue not with me, but with the mods.

Back up a second - the BEA "note" was the first time *anyone outside of the investigation* had any idea what the crew did, so if there was no further technical failure highlighted by the flight recorders then there could be *nothing but* "'New' issues with the crew" presented. That the pitot tubes had failed and caused a UAS incident was something that the investigation and the public already knew, so this was not "cynical", "callous" or "sly", this was simply a release of the information gathered from the new evidence available. I'm sure that if an obvious technical or mechanical failure presented itself then they would have mentioned that.

Not at all, but let's be honest here, you've consistently popped up every few pages to reiterate your pet opinions or theories, thus leading to the "hamster wheel" effect that the mods described. I'm not entirely innocent of that either, but I'm pretty sure I've only ever repeated myself in response to questions or suppositions put forward that had already been asked and answered multiple times.

I'm in disagreement with the release of this note
The BEA mission is not to make some "dummy interim report" in a note to the public (and press)
It's not the rule ...
They have not to answer to press articles (they answer the press in meetings)
If they are in disagreement with the press (lies .. defamation .. etc ..) the court of justice is available and is the place for such dispute
The release date of this note .. is at least suspicious .. and it's easy to link the dots
This note was a error of the BEA .. and this added nothing to their credit of transparency or independence

Clandestino. This is all very irrelevant to the accuracy of the AOA vane as far as being useful. The AOA transmitters only send out an angular measurement. Nothing that is rocket science.

If the aerodynamic forces on the vane are enough to override the inherent friction in the mechanism, the vane will swing to very closely align with the relative wind. At very small AOA relative to the local air velocity vector, the inherent friction may be sufficient to create a small error provided the velocity is just above the 'come alive' speed. But in reality, once a vane comes alive, it is pretty accurate.. As I mentioned earlier, 'come alive' speed is typically in the 15-20 mph range. By the time you get to 60 knots, dynamic pressure is about 12 times higher than 'come alive' speed. More than sufficient to point the vane with extremely high accuracy. (much more than you need for basic stall warning)

The primary mode of failure that I've seen has been sticky transmitters due to contamination of the bearings and physical damage. They are really interesting gadgets. If you haven't already done so, find an opportunity to handle one.

BUT for this non electric tool you need a compensation orifice..... might also icing like pitot tube

Not every pressure sensing kit needs be an orifice. I still rather like the flexible membrane, or Tympanum. For that matter, a nicely calibrated skin would suffice, were it connected to a sensing rod, and pot.

Total Energy
 

Grity,

Thank you for your comment.

In sixty years there have been improvements in battery performance in terms of capacity and weight.

A battery powered Pitot/ Static system might have been invented by now, to go with the more modern GPS fitted gliders which already in THIS century have flown higher than FL50.0. Ask elsewhere about wing deicing ! ( I am out of touch.)

For the 'Bus drivers
 

This may be a silly question... but the captain returned to the flight deck and apparently from the BEA transcript did not receive any briefing from the PNF or PF on what had happened and what they had tried, just questions.

So - would it be immediately apparent that the aircraft was in Alternate Law or would the captain assume that it was still in Normal Law and had a plethora of unexplained 'errors'.?

It would explain his calls to the PF to 'pull up' despite obvious indications of a stall.

The non-acknowledgement of Alt Law seems to me to be a major issue. Either the pilot did not understand Alt Law, or more likely in my opinion, he did not understand that it was activated. Maybe he sort of filtered away that information as "not important enough" when the PNF called it out.