AF 447 Thread No. 11
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@Machinebird:
Bloggs is right when he says
Some bright spark thought that aeroplanes couldn't fly below 60KIAS so
decided that they'd turn the stall warning off below that. Bad decision. If the
aeroplane's in the air and below stall speed/above stall AoA, keep the stall
warning on!
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.
Bloggs is right when he says
Some bright spark thought that aeroplanes couldn't fly below 60KIAS so
decided that they'd turn the stall warning off below that. Bad decision. If the
aeroplane's in the air and below stall speed/above stall AoA, keep the stall
warning on!
It is a general (others brands are NOT immune!) ADIRU issue:
NCD AoA when air data senses low airspeed.
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Originally Posted by A33Zab
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. 24th Oct 2013 22:23
It is a general (others brands are NOT immune!) ADIRU issue:
NCD AoA when air data senses low airspeed. 24th Oct 2013 22:23
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.
Last edited by Machinbird; 25th Oct 2013 at 06:07. Reason: Punctuation
NCD AoA when air data senses low airspeed.
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.
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.
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.
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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?
Originally Posted by RexBanner
The A330 stall warner is suppressed below 60 knots because the computers believe the aircraft to be on the ground below that speed.
Clandestino's reply
For 15th time at least: go make AoA vane that will work reliable at 500 and 5 kt. You'll make millions out of it, I guarantee you. Well, at least you'll have a hobby that will last you a lifetime.
The A330 stall warner is suppressed below 60 knots because the computers believe the aircraft to be on the ground below that speed.
Clandestino's reply
For 15th time at least: go make AoA vane that will work reliable at 500 and 5 kt. You'll make millions out of it, I guarantee you. Well, at least you'll have a hobby that will last you a lifetime.
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?
Last edited by rudderrudderrat; 25th Oct 2013 at 10:00.
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Originally Posted by tdracer
on the Boeing aircraft I'm familiar with (basically everything save the 737), airspeed doesn't go NCD until 30 knots.
Last edited by HazelNuts39; 25th Oct 2013 at 11:34.
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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.
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Inside AF
The most damning report by the ISR on AF.
Get the .pdf :
http://theairlinewebsite.com/topic/4...a-b/?p=1612830
Get the .pdf :
http://theairlinewebsite.com/topic/4...a-b/?p=1612830
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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:
It is very clear that the pilots in the cockpit simply had no idea of stall phenominon and unreliable speed technique.
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.
Last edited by DozyWannabe; 25th Oct 2013 at 18:01.
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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).
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).
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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.
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 ?
Last edited by jcjeant; 25th Oct 2013 at 19:08.
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Dubois
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!?"
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!?"
Last edited by Winnerhofer; 25th Oct 2013 at 19:31.
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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.
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.
Last edited by HazelNuts39; 25th Oct 2013 at 21:16.
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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.
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.
Last edited by Jetdriver; 26th Oct 2013 at 10:32.
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4th Voice
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.
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.
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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.
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 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.
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Victims
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.
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.
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In the Judicial Experts' Report (not BEA) ordered by the Investigating Judge there's a 4th unidentified voice on the DCVR.
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".
Last edited by HazelNuts39; 25th Oct 2013 at 23:27.
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No - the first panel was convened by the SNPL using the families' group as a cover (and the report contains several glaring errors)
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