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AF447

Old 6th Sep 2009, 04:50
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Dutch Bru,
Your point about no date on the grid I posted is of course valid. It was obviously before 6 June on account of where the FAB seemed to be concentrating its search. The difference is that on 6 June the FAB were finding debris in the area SW of TASIL, whereas on 2 June I believe the visibility was variable in rain/showers, and even though they may have flown near to, or over the 3
°18'N 30°48'W position the v/s is assumed to have been at 1500z on that day, they obviously sighted nothing.

One and a half days after the impact the floating debris pattern would still have been relatively compact - say a radius of 0.5NM, as I construe the BEA's description of the impact as having little or no horizontal momentum - more a tail heavy "flat spin".

In the cruise, I assume the trim tank was in use - not helpful later on.

Still, it puzzles me as to why the FAB had no radar contacts, e.g. a number of metalic objects were in the debris. The spoiler unfortunately would have been a rather poor target - floating flush with the surface and effectively sea clutter.

mm43
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Old 6th Sep 2009, 13:17
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In the cruise, I assume the trim tank was in use - not helpful later on.
Indeed, I also highlighted this point a couple of times back in the thread... unfortunately there doesn't seem to be much acceptance that it could have played a significant role as the systems degraded and heavy turb might have had to be flown manually - something I would have thought would be extremely significant when speed stability was paramount.
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Old 6th Sep 2009, 14:28
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mm43, WOW!

On the chart with the search grids, the boxes lined in red near TASIL were the grids flown on June 2nd, if I recall correctly.

The most extensive article in French that I found on Arslanian's conversation with aviation reporters on August 31 was in France Soir,

Ce sera la troisième phase de recherches. Lundi, Paul-Louis Arslanian, le directeur du Bureau d’enquêtes et d’analyses (BEA), a déclaré que les investigations pour retrouver les boîtes noires de l’Airbus A330 devaient « reprendre à l’automne ». Peut-être la dernière chance de comprendre les circonstances du crash du vol AF447 qui devait relier Rio à Paris dans la nuit du 31 mai au 1er juin 2009. Car « pour l’instant, nous n’avons toujours pas compris la cause de l’accident » a concédé, lundi, le responsable des investigations techniques. Pour cette troisième phase, l’enquête « va être élargie à d’autres pays, de façon à mettre le maximum de vision internationale » a-t-il précisé. Le coût ? « Plus de dix millions d’euros et peut-être plus » selon cette même source. Fin juillet, l’avionneur européen Airbus s’était dit prêt à débloquer entre 12 et 20 millions d’euros, sur une durée de trois mois, au moins, pour les recherches du BEA.

Nouveau rapport d’étape

Le 20 août, les opérations sous-marines engagées pour retrouver les boîtes noires de l’Airbus A330 d’Air France, au large de l’Atlantique, entre 3.000 et 3.500 mètres de profondeur, se sont terminées sans succès. Cette seconde phase succédait à une première étape de recherches acoustiques, achevées le 10 juillet au terme de quarante jours d’investigations. Ce jour-là, les balises, auxquelles sont reliées les boîtes noires, avaient a priori cessé d’émettre. Le 2 juillet dernier, le BEA avait estimé qu’une défaillance des sondes Pitot qui mesurent la vitesse de l’appareil, était « un élément, mais pas la cause » de l’accident. L’hypothèse de la dislocation de l’avion en plein vol avait également été écartée.

Paul-Louis Arslanian a annoncé la présentation d’un nouveau rapport d’étape « dans quelques semaines ». Le responsable de l’enquête espère pouvoir être en mesure de fournir les explications du crash, dans un an, un an et demi.
Perhaps, Arslanian was describing the general area of the search (see Switzerland quote below), or the reporter simply added that. I agree that Arslanian did not say they had found any subsurface wreckage

Reuters has this quote from Arslanian (I assume translated from the French):
"The work is a bit like crossing Switzerland by foot, trying firstly to listen out for the noise of a cricket and now looking for debris with a pocket torch in the dark," Arslanian said.
Bloomberg
The accident occurred in the middle of the Atlantic, near where the earth’s tectonic plates meet one another, Arslanian said. No one knows exactly where the plane went down, he added.
And AFP reported that Arslanian said the BEA had still not received the final autopsy reports from Brazilian authorities. He sounds a bit frustrated

"Our Brazilian counterparts have provided us with a large quantity of information. I am still waiting for the detailed results of the autopsies. I still don't have them," he said.
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Old 6th Sep 2009, 18:35
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HarryMann;

If I may offer some thoughts on why there wasn't much acceptance of a "tail-heavy due to the trim tank" theory and why, in comparison with other theories, it is far less plausible to theorize loss-of-control due to a trim-tank/CofG issue.

The trim tank will carry approximately 4800kg when full. Aft fuel transfer begins at FL255 (if the trim tank wasn't full at takeoff), and forward transfer occurs during flight as fuel is burnt. The fuel load for AF447 was 70.4k kg. I can't recall directly from my own experience with similar fuel loads but am almost certain that the trim tank would have been full at takeoff - I don't have the distribution tables for an A330 with center tanks.

First, the CofG for takeoff was well within limits and the calculated CofG 3:41 into the flight was approximately 37%. My numbers show the aft limit is 39%. The QRH Trim Tank Fuel Unusable Abnormal Procedure states that if the Trim Tank fuel is unusable the maximum flight time, depending upon fuel distribution, is 4hours at which time the aft CofG would be reached.

Since the flight was only 3:41hrs long (BEA Report), the trim tank would have had about 4500kg of fuel which begins transferring forward at cruise altitude. The crew would have to have known about any trim tank problem resulting in unusable fuel at least upon reaching cruise altitude if not slightly after. The flight would require this fuel for the arrival at Paris. Unusable fuel, especially given the weather enroute (diversions), would present a significant operational decision to turn back or continue which would have had to have been made in these first 3hrs.

There is no evidence either by communication or in any ACARS messages received that there were trim tank issues.

Second, the QRH drill then states that "For Landing", *if CG > 39% - Approach Speed Vls+10kt with the landing distance procedure to be applied, (landing distance increase by 1.25).

So a CG > 39% is catered for by a 10kt increase in Vls, meaning that the aircraft can be flown without issue. There are no cautions, no imbalance limits stated between trim tank and wing tanks and no warnings associated with this condition to which the attention of an A330 pilot is drawn in the AOM.

That doesn't mean that handling characteristics in abnormal flight such as approach to, or full stall would not be affected. What it means, as I interpret this as an experienced A330 pilot is, (and what I would expect from my aircraft is), a fully controllable airplane with no squirrely habits or handling characteristics in all flight regimes with a CG > 39%. That is, I expect as a pilot of the airplane, what the certification of the aircraft means - it is controllable even with maximum fuel in the trim tank at the expected landing weight, on approach.

That is why I would consider the CG and Trim Tank theory highly implausible at least as an initiating cause when in heavy turbulence etc.

All bets are off in any severe loss of control/jet upset.
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Old 6th Sep 2009, 23:18
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Many Thanks

I take it c.g. > ## implies forward of

All bets are off in any severe loss of control/jet upset.
Yes, that's what I meant - I don't think either of us had conceived the idea that an event was likley initiated by a trim-tank or c.g. problem.

I am surprised (a bit) that no cautions for severe turbulence, maneouvring or flight near Mmo with full aft c.g. are made, but on reflection, this might logically I suppose be a certification requirement.

Regardless, the fact is, aerodynamically, the a/c must be less stable in pitch anywhere near the aft c.g. than further fwd?
Asking for early or temporary fwd fuel transfer when entering turbulence, would of course, be both impractical as well as somewhat 'worrying'
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Old 7th Sep 2009, 00:05
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HarryMann;

My pleasure as always.

"> ##" is to me a higher CG, so aft is what I meant...BUT, I see what you mean wrt the QRH and therefore it is open to interpretation and it shouldnt' be - may take it up. To me, ">39%" means further aft. If it means further forward, as a pilot I have to assume still, that there is "no risk, no danger" as there are no cautions/warnings.

I'm unsure of what the meaning of "unstable" is in a fbw design. As we both know, fighters are inherently unstable without fbw to reduce drag and increase maneuverability. The 330 is not nearly in that category of course but still, any instability, or flight control problem, (floating spoiler) or CG issue would be masked by the fbw response until the autoflight gave up due to being beyond it's design certification limits.

So "unstable" isn't something an Airbus pilot would be expected to handle/deal with except again, in jet upset conditions, then all bets...etc.

Re "not initiating", oh, ok - I had mis-understood, believing that some were considering an aft CG could have been an initiating item in heavy turbulence - sorry. In heavy turbulence the only caution is to slow down - Mach 0.78 to 0.80 or 280kts if I recall. Also, it is recommended to disconnect the autothrust to keep it from hunting the airspeed.

best,
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Old 7th Sep 2009, 02:23
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That's interesting, my first response to >39% was the correct one, then by context misjudged it to mean fwd of . Mr Semantic-Pragmatic here, maybe it should be looked at - aft/fwd of are not big words, and then it's totally clear!

At the risk of extending a somewhat off-topic discussion, the fbw, however smart, is still working with a less stable machine, so presumably working harder, letting go sooner...

A secondary effect, of such a mass at such a distance, regardless of c.g. position, is an increased pitch and slightly increased yaw inertia. This likely has some +ve and some -ve aspects. One -ve would be higher rear fuse bending moments, which may well be small or insignificant in the whole scheme of things.
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Old 7th Sep 2009, 02:53
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Re bending moments, I know the DC8-61 & 63 series would bend - suspect same with all types, save perhaps the 747 simply due mass and oblong cross-section.

If I may be permitted to wander a bit with some off-the-cuff thoughts...

Agree on the fbw notion - once it "gets there" it springs loose, so to speak? In assessing all this and as a pilot of these things I place a huge amount of faith/trust in the design/certification/manufacture process in the sense that I ask no questions of the airframe or systems. I take "what is" from where I sit and if it disappoints, that is the designer's/regulator's problem. Essentially, none of us are trained test pilots, having no business outside the normal flight regime, (save circumstance, obviously), and so that is the only approach open to professional airline pilots today. We used to do nuts-and-bolts courses, drawing systems, sometimes playing "what-if" across the Atlantic; no longer. Second-guessing the airplane and it's designers is not possible from our cockpits and we have to accept that both the manufacturer and the regulator have done their work correctly. In my experience, I have yet to be surprised, have yet to find an ECAM drill poorly thought out, so I guess they've done okay.

That's why this accident is truly an enigma. I suspect there are many A330 pilots here, silent or otherwise, who have been in the very same circumstances as this crew and are really, really wondering what unfolded so swiftly as to bring the aircraft down. We can all imagine different scenarios, (and have posited them here) but in the end all we know is it took off and it crashed just about 4hrs later.
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Old 7th Sep 2009, 09:23
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You may be aware of claims (on the French forum) that the particular configuration (weight + flight level + assumed full aft CG) was allegedly very hard or impossible to fly with A/P off in the simulator.
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Old 7th Sep 2009, 11:54
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You may be aware of claims (on the French forum) that the particular configuration (weight + flight level + assumed full aft CG) was allegedly very hard or impossible to fly with A/P off in the simulator.
No, not aware, thanks.

Which (degraded) control law were they assuming?

Was this in still air or simulated turbulence?

PJ2 and others estimate c.of g. @ 37% ~ 2% fwd of aft limit at the time of the accident

Last edited by HarryMann; 7th Sep 2009 at 13:22.
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Old 7th Sep 2009, 16:25
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Sorry for the lack of precision. I had in mind a message posted on August 9th on that forum. I try to translate a small part of that message:

"We are currently trying to estimate the CoG after 3h25 flight time. Roughly the aft limit is 38% MAC and the a/c would have been at 37.7%, yet to be confirmed.

In ALT2 or worse in direct law (we don't know yet) nobody managed to fly this at FL350. Try it in the simulator, it feels very odd, dont forget you don't have airspeed information, you are in night IMC, and with turbulence".

So indeed this scenario is more degraded than what one would understand from my previous message.
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Old 7th Sep 2009, 17:21
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Saturn V

Distilling the content from this, we get Arslanian saying the third phase "should start in autumn" and "right now, we haven't understood what caused the accident." The third phase "will be expanded to include other countries for optimal international vision" and will cost "Over € 10 million, maybe more." In August, Airbus said it would allocate €12 to 20 million for at least three months of searching. The second phase sideswept from 3,000 to 3,500 metres and ended Aug 20 in failure.

Finally, Arslanian promised a new status report "in a few weeks" and said he hoped to explain the crash in a year or year and a half from now.


Your original pickup, SaturnV:

Ce sera la troisième phase de recherches. Lundi, Paul-Louis Arslanian, le directeur du Bureau d’enquêtes et d’analyses (BEA), a déclaré que les investigations pour retrouver les boîtes noires de l’Airbus A330 devaient « reprendre à l’automne ». Peut-être la dernière chance de comprendre les circonstances du crash du vol AF447 qui devait relier Rio à Paris dans la nuit du 31 mai au 1er juin 2009. Car « pour l’instant, nous n’avons toujours pas compris la cause de l’accident » a concédé, lundi, le responsable des investigations techniques. Pour cette troisième phase, l’enquête « va être élargie à d’autres pays, de façon à mettre le maximum de vision internationale » a-t-il précisé. Le coût ? « Plus de dix millions d’euros et peut-être plus » selon cette même source. Fin juillet, l’avionneur européen Airbus s’était dit prêt à débloquer entre 12 et 20 millions d’euros, sur une durée de trois mois, au moins, pour les recherches du BEA.

Nouveau rapport d’étape

Le 20 août, les opérations sous-marines engagées pour retrouver les boîtes noires de l’Airbus A330 d’Air France, au large de l’Atlantique, entre 3.000 et 3.500 mètres de profondeur, se sont terminées sans succès. Cette seconde phase succédait à une première étape de recherches acoustiques, achevées le 10 juillet au terme de quarante jours d’investigations. Ce jour-là, les balises, auxquelles sont reliées les boîtes noires, avaient a priori cessé d’émettre. Le 2 juillet dernier, le BEA avait estimé qu’une défaillance des sondes Pitot qui mesurent la vitesse de l’appareil, était « un élément, mais pas la cause » de l’accident. L’hypothèse de la dislocation de l’avion en plein vol avait également été écartée.

Paul-Louis Arslanian a annoncé la présentation d’un nouveau rapport d’étape « dans quelques semaines ». Le responsable de l’enquête espère pouvoir être en mesure de fournir les explications du crash, dans un an, un an et demi.
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Old 7th Sep 2009, 19:22
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Arthur Borges, as I read the French, and quite possibly incorrectly, the depth of the area where the side-scan search was focused was around 3,000 to 3,500 meters, not that the sonar was being trawled (towed) at that depth.

If a second side-scan search is unproductive -- assuming there will be one -- I would think they would need both that and other survey tools to first map the contours of the bottom to high detail. With a contour profile in hand, they could deploy the proverbial torch or flashlight (a submersible with video and lights). And even then I would say -- to continue the BEA metaphor -- they would not intend searching the whole of Switzerland, but only part of one canton.
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Old 8th Sep 2009, 16:00
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Question I call bull****

You may be aware of claims (on the French forum) that the particular configuration (weight + flight level + assumed full aft CG) was allegedly very hard or impossible to fly with A/P off in the simulator.
They must have forgotten how to fly. I find it unthinkable that a legal configuration (and one eminently expected) can be in any way be 'unflyable' in any law state. How could the airplane be certified if that was the case?
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Old 8th Sep 2009, 16:19
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ADR´s did no fail....pitot tubes were blocked by ice !!!

Happened to my and several other A330 drivers in my company...not a "close to zero" probability at all !!! ALL speed indicators went to ZERO...no AP / AT / Rudder travel limiter / Alt Law no protections.....turb was light, we came out of the clouds, ice was melted by probe heat....airspeed was recovered, as well as AP / AT.....alternate law remained, as expected (reset possible only on the ground, no hyd press). Beleive me....airplane is VERY tricky / sensitive to fly !!!
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Old 8th Sep 2009, 20:33
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How could the airplane be certified if that was the case?
That's a good question.
If you allow me to make a comparison:
Some drugs tested and approved and certified by all the official health agencies .. are after some years back down from the market due to unexpected effects.
That can happend for many things.
Just a tough.
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Old 8th Sep 2009, 22:38
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drug comparison

With respect, determining flight capabilities along the entire flight envelope in direct law is a straightforward mathematical and observational endeavor - as opposed to putting drugs or biologics in a human body that is immensely variable. Why, even the patient's mental state (happy/sad etc) may affect the outcome, whereas a happy airbus performs just as well as an unhappy one*

I think PJ2 may say however, that a 'happy airbus' will "go around again after a bounce' but the 'unhappy airbus' will just roll over and have a cigarette - not sure what that means, you may want to try it in a sim!
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Old 12th Sep 2009, 00:29
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Bathymetry - centered on 3°N 31°W

Moving away from what an "unhappy airbus" might do, the following graphic shows possible impact positions from pages 210/217 plus an alternative position (#3) back-tracking the current at 1.5 times the velocity provided by the OSCAR/NOAA data from near 3°30'N 30°30'W.



For those wanting to make a profile, multiple cross sections using slices at all vectors should be possible. However the area of interest seems to lie in a broad valley between -3000m and -3500m. Beware, the isobath lines shown are smoothed and there are ridges and ravines cutting across much of the area.

Note:: The isobath levels, e.g. -3K0 etc. have been added by me following inspection of a color spectrum relief graphic of the same area. The absolute levels could be wrong by +/-100m (or more) - subject to my interpretation of the color data associated with a high spot.

mm43

Last edited by mm43; 14th Sep 2009 at 02:52.
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Old 12th Sep 2009, 01:18
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caiozink -
Happened to my and several other A330 drivers in my company...not a "close to zero" probability at all !!! ALL speed indicators went to ZERO...no AP / AT / Rudder travel limiter / Alt Law no protections.....turb was light, we came out of the clouds, ice was melted by probe heat....airspeed was recovered, as well as AP / AT.....alternate law remained, as expected (reset possible only on the ground, no hyd press). Beleive me....airplane is VERY tricky / sensitive to fly !!!
If this is indeed the case, I submit some serious modifications need to be made...NOW.
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Old 12th Sep 2009, 02:15
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Arthur Borges, as I read the French, and quite possibly incorrectly, the depth of the area where the side-scan search was focused was around 3,000 to 3,500 meters, not that the sonar was being trawled (towed) at that depth.
You read the French perfectly.

Your sentence:
Le 20 août, les opérations sous-marines engagées pour retrouver les boîtes noires de l’Airbus A330 d’Air France, au large de l’Atlantique, entre 3.000 et 3.500 mètres de profondeur, se sont terminées sans succès.
Obtains:
On August 20, underwater operations undertaken at 3,000m to 3,500m off the Atlantic coast to recover the blackboxes from the Air France Airbus 330 ended without success.

The sentence doesn't specify sidescan or trawling with sonar; I inserted "sideswept" from memory of other postings here and, perhaps erroneously, took it as a perfect synonym for "sidescanned".

Happy Skies!
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