A33Zab

@Machinebird:

NOT, the stall warning is NEVER turned off, not even by WOW.
It is a general (others brands are NOT immune!) ADIRU issue:

NCD AoA when air data senses low airspeed.

Machinbird

A33Zab,
Of course, you are literally correct. It is the NCD issue that turns off the stall warning. Essentially, it is an engineering problem that was too hard to solve at the time and they waved the magic wand and decided that an aircraft in flight would never get in that situation. AF447 proved that that reasoning was a bit flawed.

It is not an insoluble problem however. I've flown older aircraft that had a stall warning that did not have the NCD problem. Were they properly corrected for Mach Number in the absence of A/S? No they weren't, but they still gave warning before you completely lost control because they were not digital.

The engineers need to scratch their heads a bit more so that the system handles things like A/S failures gracefully. NCD for such a critical system is not acceptable.

tdracer

The link doesn't work, but at least on the Boeing aircraft I'm familiar with (basically everything save the 737), airspeed doesn't go NCD until 30 knots.

Chris Scott

Clandestino,

In your eagerness to respond in a single post to several pages and many contributors, you have a tendency to select snippets of text out of context, and comment rather dismissively on them. In doing so, you misrepresent the contributor's argument. (I'm wondering if you suffer from a short attention-span - not unusual in hot-headed youth...)

Quote from me (replying to PJ2), as quoted by you about 18 hours ago:
As I've said before, I also wonder if the APPARENT sudden loss of about 300 ft of altitude (due to the removal of correction for airspeed when the IAS went AWOL) might have provoked a knee-jerk (of the wrist) response.

Your response:
I only wish it were so - there would be general mushing around new indicated FL350 but not a few thousand feet climb.

You have ignored the rest of my paragraph.

This is what I went on to say:
But the realisation that this was just another of those UAS events should quickly have dawned, followed by a return to the familiar pitch-attitude for cruise flight. As you say, simply maintain the status-quo...
Inappropriate initial reaction is one thing, but what happened after AF447 had completely vacated FL350 climbing was irrational and inexplicable in a competent pilot who had spent many hours monitoring the flight instruments in the cruise and step-climbs on dark nights - much like the one in question.

rudderrudderrat

Hi Clandestino,
Please explain why you dismiss, for the 15th time at least, a vertical descent rate of 10,000 ft per minute (about 100 kts) does not qualify as a valid speed for angle of attack vanes.

The continued stall warning, whilst they were stalled, might just have improved the Captains' SA.
Edit. Is it really that difficult to have stall warning Valid >60kts AND on ground, Or valid when airborne?

HazelNuts39

When the AoA exceeded about 30 degrees the IAS dropped rapidly. There was about 1 second between 60 and 30 kts IAS, and another second to negative IAS.

vilas

It was sad but it was slaughter of the innocent. It is very clear that the pilots in the cockpit simply had no idea of stall phenominon and unreliable speed technique. They did not seem to know the normal pitch in level flight. Instead of TOGA had they just switched off ATHR, AP went off anyway and done nothing else they may have been safe till the captain got back. Alternate law except protections is like normal law. But they do not seem to have been trained properly for the situation. Even continuos stall warning although desirable would have made no difference in this case.

Winnerhofer

DozyWannabe

When you have AoA vanes that are only certified to operate at >=60kts IAS, and the unavoidable fact that Stall Warning is a function of AoA - absolutely!

Regarding your point about the airflow from the VS in the stall - I don't know. You'd need a proper aero engineer to be certain, but I'd say there would be too many variables involved to allow for considering readings in that scenario as accurate. Certainly the DFDR output from the AoA vanes once the stall is established seems to degenerate very quickly into flipping between extremes - and to my mind would only cause more confusion.

@tdracer - we're not talking about IAS going NCD, we're talking about AoA vanes that are only certified to operate reliably above 60kts IAS.

Machinbird's F4 would have had the wind over the deck plus the airspeed generated by the motion of the ship - a very different (and somewhat simpler) design problem to solve. An F4 is a fighter, and the AoA systems specification would by the very nature of difference in application be a very different kettle of fish. Machinbird - your AoA vanes may have been "live", but with all due respect I doubt you paid a significant amount of attention to how reliable the readings were in that scenario - and I think you'd have been far too sensible to try and test the theory by stalling your F4 to the extent that your pitot tubes were being fouled and registering IAS below 60kts!

@vilas:

I have a very tough time believing that a highly-qualified sailplane/glider pilot* (such as PF FO Bonin) would have been completely clueless about stall - which is why I've long maintained that he had some kind of psychological shock response which threw him sufficiently to get muddled. PNF FO Robert tries to correct him verbally several times regarding his pitch attitude ("you're going up, so go down") during the initial zoom climb, but as the aircraft moves into the stall regime and more of the instrument readings stop "making sense" he seems to lose his earlier confidence - which was undoubtedly a tragic shame.

We've been through this countless times before and no consensus was reached - in part because many posters are wedded to their own notions of what the real problems were here, but one thing that needs to be remembered above all was that the Stall Warning functioned correctly for at least around a minute before the aircraft went too far out of the flight envelope, and it was apparently completely disregarded**. For those that want to compare brand A with brand B, one only has to look at the Birgenair 301 B757 crash, where the Captain disregarded the stick shaker in favour of the first (erroneous) warning he got, which was overspeed.

* - EDIT - I'm not saying 'no pilot would...' here, I'm saying that in order to fly a sailplane/glider to a high degree of competency one has to have a very thorough appreciation of the mechanics of flight, because in a glider there is no TOGA detent or switch - approaching stall one has no option but to trade altitude for airspeed!

** - EDIT 2 - The point I'm trying to reinforce here is that while the Stall Warning was silenced at approximately the same time the Captain returned, it sounded correctly and continuously for long enough that the two FOs should have at least acknowledged it. And there were enough secondary indications (unstable pitch, dubious airspeed, rapidly unwinding altimeter) that a Captain should have been able to use to diagnose a stall.

DonH

Chris Scott - in your response to Clandestino, I concur with your remarks. I think quoting and responding has its merits and offers succinct thinking and keeps posts to reasonable lengths!, but it is very important to retain the context of the original remarks being critiqued. Sometimes there is a historical dialogue going on and brief quotes which appear out of context to others are really in context in "the long line" but I thought yours and perhaps one other's were a taken a bit out of context. I think reference-links to actual Post # being quoted so others could refer back would resolve the matter, and others can make up their own minds regarding the critique offered.

As regards the matter at hand and as I know you know, whether an actual pitch-change and altitude loss or purely an indication issue, (which this was), one never responds swiftly in a transport aircraft, particularly at cruise altitudes where aerodynamic damping is much lower. The argument that the roll was PIO and that the pitch up was a response to the indicated loss of 300ft are both defeated by subsequent occurrences - the first because the more-sensitive roll was brought under relatively quick control, and second because, once the 300' "altitude loss" had been "regained", the PF kept pulling.

The majority of stick positions is, by the data, "stick back". As said many times, I think there is probably something to the stall warning NCD matter but, as you have observed, it isn't a C-150 where the little piece of metal is permitted to flip forward due to reduced airflow at it's point of installation setting off the approach-to-the-stall buzzer! The designers had to resolve the matter within purely digital systems to avoid the greater problem of false warnings at critical times, and, rightly in my view as an experienced A330 captain, concluded that no crew was going to stall the airplane and keep it there such that the AoA was so great, (45° +), as to actually render the pitot's unserviceable, (entry angle too great - no speed indication, ergo speed < 60 = NCD).

jcjeant

More again about Dubois :
The first words he pronounce when entering the flight deck are (Ref CVR)
What are you doing ?
So .. as the rest space is only equipped with a buzzer ( employed by Robert) and no phone communication ... before entering in the flight deck Dubois know that's something is wrong .. and he don't ask "what happend ?" but instead the famous
What are you doing ?
Is this question is related with the feeling of not full confidence he can have in his crew ?

Winnerhofer

Exactly.
Dubois wasn't in the Crew Rest Area but seated and relaxing next to his ladyfriend.
This is why the buzzer was useless because he wasn't lying on his bunk.
Remember that F-GZCP wasn't equipped with an intercom in the CRA as it is an option but standard chez DL so the buzzer was the only means of communicating.
Why did he come charging back onto the F/D?
Because he felt the plane was rocking and rolling.
What was his first reaction?
Not what's up, what's wrong or what's happening but an emphatic "WTF are you guys doing!?"

DozyWannabe

And your evidence for that "theory"* is?

* - In lieu of a suitable sobriquet for "unsubstantiated rubbish that you just made up".

HazelNuts39

Just a question I've always wanted to ask: Is there a handset in the cockpit to contact the cabin crew?

What intrigued me is the sound as from a microphone striking a wall, and sometime later a female voice asking repeatedly "hello?", as if answering a call but not getting a response.

DonH

HazelNuts39;

Re, "Is there a handset in the cockpit to contact the cabin crew?"

Yes, the control panel for the handset is on the overhead panel and the handset is mounted on the aft pedestal, captain's side. The "Cabin Rest" is a call to the Cabin Crew Rest Area/Module. In some aircraft it is a permanent installation, usually in the aft end of the aircraft below the passenger deck whereas the portable crew module, as on AF447, is located just aft of door L3 below the passenger deck.

As shown on the panel, there are also communications to the Flight Crew Rest area wherever that may be - the asterisk inside the triangle means, "as installed". On the B777 it is upstairs; I don't know what the arrangement is on AF's A330's. The one with which I'm familiar was seat in Business that would fully recline and was curtained off. In this arrangement, there are no communications at the seat, so any urgent need for the crew member, (normally the captain) would have to be first communicated to one of the F/As who would then go to the seat and alert the crew member.

Winnerhofer

In the Judicial Experts' Report (not BEA) ordered by the Investigating Judge there's a 4th unidentified voice on the DCVR.
There'll be now a 2nd Judicial Experts' Report as demanded by Airbus with a new panel who happen to fly Airbus rather than the theoretical 1st panel.
Airbus were 90% happy with the 1st panel's report but this time they really want to come out fireproof pre-trial to get a "non-lieu" i.e. insufficient grounds to proceed.
Airbus' attorneys are invisibly off radar but beware of those who don't bark for their bite is most brutal.
Airbus doesn't depend on AF to survive.

DozyWannabe

Yes - the cabin crew member.

After the PNF asks "(!) where is he er?" at 2:10:49.8 there is a "high-low" chime consistent with a CC call at 2:10:53.5. The "feminine voice" saying "hello?" is recorded at 2:10:55.9. This would likely be consistent with the PNF buzzing the CC to find out where the Captain is as a failsafe measure.

No - the first panel was convened by the SNPL using the families' group as a cover (and the report contains several glaring errors). Airbus probably don't have an opinion either way. Even if the legal process finds Airbus liable for some aspects of the accident it will have very little or no tangible effect on the company.

Winnerhofer

There's been a split in French Victims' Association.
Some 10 members including ex-Head left to go solo.
A new Head took over as of 01 June 2013.
NB: The Dubois and Robert families have never been part of any Victims' Association only the Bonin family.
What's odd is that not a trace of Robert's corpse was ever found.

HazelNuts39

It's also in BEA's report: female voice on track 1 "allo?" ... "oui" ... "allo?"
then: "bruits similaires à un combiné de l’interphone cabine qu’on essaye de raccrocher" (the english translation omits the "trying to").

Keep in mind that the airplane is in "deterrent buffet".

jcjeant

Well .. sorry but I must ask you what you are smoking ....
The panel of experts (the judicial experts) was ordered by the "juge d'instruction" and was required to answer a lot of precises questions
Those experts are from a group of experts who are stand by for such judicial requests
Families and unions have nothing to do with their investigations and reports