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AF 447 Search to resume

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AF 447 Search to resume

Old 15th Aug 2010, 02:21
  #1901 (permalink)  
 
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PJ2;

I agree with your comments, and had previously said that a fuel dump wouldn't have left evidence on the surface to be detected by the SAR satellite radar. It has been suggested to me in a PM that an attempt could have been made to dump the Trim Tank (if it was even thought about!), though a transfer to the center tank would possibly have yielded a better CG result.

mm43
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Old 15th Aug 2010, 02:40
  #1902 (permalink)  
 
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PJ2 (and others) have verified my contention that there is no scenario in which one would contemplate dumping fuel (if so equipped) in a mid-Atlantic ditching event. And even if fuel had been dumped at altitude (or otherwise released in a pre-impact break-up scenario) there is no way it would arrive at the surface, nor remain on the surface, in such a detectable form.

So let's agree to ignore the Drift Group's use of the phrase "voluntary or not" and simply deal with the "slick" or "pollution" or whatever it was that existed on the sea surface when the satellite took that shot. The "stain" (as I would prefer to call it because we don't know what it actually is) is approximately 1km in length at its longest point and perhaps half that in total width (widest point of separation of the two arms). Did it show in any other shots taken in the hours or days before or afterwards? Seems not, or that would have been reported, so all we know is that an anomaly existed that could have been kerosene at a time and in a location that generally corresponds with the disappearance of AF447.

So my point is simply this: If that exact location was not surveyed thoroughly by the undersea location resources when they were available, it could turn out to be a major blunder.

Discussion?
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Old 15th Aug 2010, 03:09
  #1903 (permalink)  
PJ2
 
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mm43;
It has been suggested to me in a PM that an attempt could have been made to dump the Trim Tank (if it was even thought about!), though a transfer to the center tank would possibly have yielded a better CG result.
Yes - it's possible to dump the trim tank but indirectly: The jettison system removes fuel from the inner and center tanks which would in turn be "replenished" by the trim tank (valve opens on jettison) and outer tanks when the inners reach a certain level until a number of conditions are met which stop the dumping including crew control, the Jettison Gross Weight FMGEC entry.

The CG would move forward as you say. However, moving fuel forward from the trim tank to alter the CG, (the CG is thoroughly monitored by this and other systems and as such there shouldn't be a CG problem in any flight regime), can be accomplished without dumping if such is not required, (and given the dump rate, it is likely to be unhelpful in an emergency). The T.Tank selector switch can be used to OPEN the Trim Tank Transfer valve and all fuel will transfer forward to the center tank. The process of transfer seems to take a while but I've never directly observed/timed it.

In any case, I think we've kind of beat this one up...

PJ2
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Old 15th Aug 2010, 03:58
  #1904 (permalink)  
 
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PJ2 wrote:-

In any case, I think we've kind of beat this one up...
... and a transfer let alone a dump wouldn't have been on anyone's mind.

Thanks
grizzled wrote:-

So my point is simply this: If that exact location was not surveyed thoroughly by the undersea location resources when they were available, it could turn out to be a major blunder.
In the cold light of day, the Drift Group were working with the positions of recovered debris, positions of drifter buoys that had passed by the area, and attempting to analyze satellite data on surface levels and winds to determine how those objects came to be where they were found. They have looked at the Pollution Spot (stain) and have determined that its position in relation to the other debris didn't make sense, and have legitimately dismissed it - though acknowledging its existence.

It may well prove to be a bad call, but we with 20/20 hindsight are left to argue and wonder about the spots relevance. In my original post on the subject, I indicated that further work may bring this Pollution Spot into sharper focus. On the other-hand it may turnout that the Drift Group were right. Either way, we are in the "know" and will be able to say, "We told you so!", or quietly merge into the background noise.

mm43

Last edited by mm43; 15th Aug 2010 at 05:20.
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Old 15th Aug 2010, 12:09
  #1905 (permalink)  
 
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Regarding the pollution spot it would be important to know how frequent the satellite crossed/pictured that area, i.e. if it took images the days before and after.
Having that information one could conclude from the preceding or succeeding images the relevance of this pollution for AF447.

As a standalone information it is not sufficient to derive or rule out the relevance.

Any one here knowing/having an idea in which intervals this satellite would take pictures of the same area ?

But to be honest I'm a bit surprised BEA ruled out the relevance of this image/information so quickly and decidedly !?
Ruling out information that does not match one's preconceived idea of how thimgs happened is not a good idea in investigations of any kind.

And for sure not in the investigation of a still largely unexplained aircraft accident....

Maybe they have further information which allowed them to rule it out for good reason ?! But why not pass that information to the public then ???
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Old 15th Aug 2010, 12:20
  #1906 (permalink)  
 
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mm43;

thanks for pointing out the wider range of possibilities. I was just addressing the 'bottom line' of mr. Squair's analysis. So, based on the ACARS messages alone, the ROD in the final seconds could have been anywhere between 2463 and 16320 fpm, while the average ROD in the preceding descent was of the order of 7850 fpm: 35000 (2:10:10) - 2176 (2:14:21).

I also believe that the airplane probably stalled one or more times in those final minutes. Is it certain that it was stalled in the final seconds?

some juggling of a flight termination time could give a v/s that fits with the BEA reports (high vertical speed, 'en ligne de vol', and 'arm 36 g' etc..).
The 320 ditched in the Hudson at 780 fpm, 125 kt, 9.5 deg pitch. Its fuselage received substantial damage but stayed in one piece.

The Turkish 737 in Amsterdam impacted stalled at 3000 fpm, 100 kt, 22 deg. pitch, its fuselage broke into three sections.

AF447's stall speed (Vs1g; V_alphamax) was 158 kCAS; 162 kTAS; 274 fps. The corresponding alphamax can be estimated as 14.5 degrees. Interpreting "avec une assiette positive, une faible inclinaison et avec une vitesse verticale importante" as 2.5 degrees nose-up, leaves an FPA of 12 deg. down, or 3418 fpm.

So was it stalled?

regards,
HN39

Last edited by HazelNuts39; 16th Aug 2010 at 08:20. Reason: error corrected: Hudson ROD is 780 ft/min
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Old 15th Aug 2010, 16:23
  #1907 (permalink)  
 
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HN39
Just a gut feeling at the moment, but I suspect there is another still higher angle of attack where drag+ lift will balance the aircraft weight in a nearly level attitude. Problem is, no one has published the data for A330 Cd & Cl at ridiculously high angles of attack. You may be able to find data for other type jet transport accidents and get meaningful data since at very high angle of attack the actual shape of the airfoil becomes less important than wing area, aspect ratio, and wing sweep angle. In a 40 degree AOA for example, wing twist factors will likely have minimal impact. If sufficient data from older accidents is not available, I suppose you could use NASA panel codes to come up with meaningful data. Unfortunately I am not sufficiently versed in Aerodynamics to produce a useful result in a useful time frame.
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Old 15th Aug 2010, 16:37
  #1908 (permalink)  
 
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Fuel dumping

Just to stop the fuel dumping speculation, Air France A330s are not fitted with a fuel dumping system.

Last edited by pgroell; 15th Aug 2010 at 16:38. Reason: Typo
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Old 15th Aug 2010, 19:25
  #1909 (permalink)  
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With great respect for all who post here, allow me to briefly summarize an area that has gotten little credence, perhaps understandably so.

The Industry, like others, is not without elements of other highly competitive and cutthroat endeavours at times. Betrayal is a part of modern commerce as it was in the days of the Silk Road and the Rum, molasses, and slave triangle.

Financial? Tech? Airframe? Regulatory Agencies, and investigative Boards?

Farming out highly critical aspects of a large and highly visible Investigation is par for the course, but comes with the possibility of failure (s), and inaccuracies. As the "Slick" was dismissed out of hand by BEA without evidence, followed by garbled and nonsensical language("Whether voluntary or not,") The fumbling of the Medical data, conclusions about structural evidence without "substantiating data", and the limitless hypothesizing about a flight path that is without evidence of any kind, What should have been a straightforward discussion of "Smoke on the Water" was ignored, actively, might I say, by the Trustees of Aviation safety, while 20 million was spent trying not to find the aircraft.

oily film? bunker fuel dumped by an anonymous ship,

Fuel? voluntary or not, which makes no Flight sense.

En Ligne de Vol? Useless phrase, impossible to know, and misleading, of course.
 
Old 15th Aug 2010, 19:41
  #1910 (permalink)  
 
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henra wrote:-

Any one here knowing/having an idea in which intervals this satellite would take pictures of the same area ?
The following COSMO satellite data may be of assistance. It is published by the Italian Space Agency, and even though some browsers may reject the site certificate, it appears to be "safe".

The SAR feature also has a SPOT mode which utilizes doppler/chirp technologies to provide a 1m by 1m resolution. Unfortunately, timely prior requests are required to enable scheduling of this feature over a particular area. As a matter of interest, the French representative organization for the COSMO project were represented on the Drift Group.

In 2009 there were 3 COSMO SAR capable satellites in polar sun synchronous orbit. I believe they were in the same orbital plane, equi-phased at 120° apart.

mm43

Last edited by mm43; 15th Aug 2010 at 19:52.
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Old 15th Aug 2010, 21:41
  #1911 (permalink)  
 
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Originally Posted by Machinbird
I suspect there is another still higher angle of attack where drag+ lift will balance the aircraft weight in a nearly level attitude.
Yes, your quite right, but it requires a higher airspeed. The lift-coefficient at alpha-max is 1.45 at sealevel. The proverbial barn door held perpendicular to the airstream has a drag-coefficient of the order of 1.1. I would think that your condition is somewhere in between, but suspect that it is closer to the barn door than to a high-tech wing with attached flow.

regards,
HN39

PS:: For example, taking the coefficient 1.1 for the resultant force of lift and drag (ignoring thrust); your AoA of 40 deg, and mm43's pitch of 5 deg. NU, would give a rate of descent of 10840 ft/min at 181 kCAS.

Last edited by HazelNuts39; 16th Aug 2010 at 17:01. Reason: PS
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Old 15th Aug 2010, 22:54
  #1912 (permalink)  
 
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The thing I find interesting about the Cosmo image was it was taken 30 hours after the event before any wreckage had been sighted by the search teams.
Now, understandably that satellite probably downloads thousands of images which there is little point in analysing, but it’s curious this one may have languished on a server until someone had a brainwave and checked it.

Wonder when that was.
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Old 15th Aug 2010, 22:57
  #1913 (permalink)  
 
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HN39 wrote:-

I also believe that the airplane probably stalled one or more times in those final minutes. Is it certain that it was stalled in the final seconds?
That is relevant, and is the question that somehow doesn't seem to generate a positive answer, especially when we are faced with -
"avec une assiette positive, une faible inclinaison et avec une vitesse verticale importante"
or - "with a positive attitude, a low [bank] angle and with a significant vertical velocity"

BEA Reports provide some indicators that support the stall theory, but whether the descent was marked by a series of stalls and partial recoveries, is like everything we are dealing with, just conjecture. The tail yawing to port on impact provides (imo) a small clue as to how the "positive attitude", "low bank angle" and "vertical speed" were attained, i.e. in a "deep stall" where a clockwise rotation had a stabilizing outcome in the "lost lift" vortex.

The ROD from your calculations with 5 degrees nose-up may be interesting.

Damage to the Radome showed a significant upward moment, but the horizontal moment at impact failed to shatter the top section. So the GS at impact "en ligne de vol" would appear to be quite low - 60 knots?

mm43
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Old 15th Aug 2010, 23:03
  #1914 (permalink)  
 
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BackOffice;

At a guess, not until the Drift Group was set up, and those with the appropriate expertise knew where to go "fishing".

mm43
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Old 16th Aug 2010, 00:22
  #1915 (permalink)  
 
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The 320 ditched in the Hudson at 1500 fpm. Its fuselage received substantial damage but stayed in one piece.
25 ft/s at touchdown, during and after the flare... ?

Last edited by HarryMann; 16th Aug 2010 at 11:00.
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Old 16th Aug 2010, 01:29
  #1916 (permalink)  
 
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Drift re-analysed using a simple approach

The Drift Group did their analysis by calibrating their models to things like the drift buoys etc which were drogued relatively shallow compared to a deep ocean but relatively deep when compared to floating debris. If we just take the first 22 bodies (due to their improved consistency relative to other items and not too much time from the impact), calibrate the model to the pollution spot (or slick) and using a method of least squares (Excel) force the curves to go through this point then the potential point of impact extrapolates to 30.51W 2.62N.
(This is achieved by changing time to slick time and using a grid centred on the slick to force the curve through this origin, then converting back from slick time and slick co-ordinates ie using a slick method). The items in the analysis that appear furthest from the ‘true body line’ (when all items are considered) are the first sightings by the merchant vessel then by the navy. Also the VS recovery position and then (to a lesser extent) its sighting position. The first 2 bodies are also slightly north of the ‘expectation’.
These bodies show a spreading out in an ever increasing wide ‘triangle’ (over this180 hours) from the extrapolated impact focal point as they head north which would be expected due to ‘randomness’. There is also a very slight ‘general’ easterly drift. The bodies are found with very little northerly spread (at one time period) but both this northerly and the easterly trends may not be statistically relevant and may simply be the way the retrieval was done considering only 10% of the bodies were recovered.
So IMO the slick is statistically relevant and its position is useful.
regards. Ian
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Old 16th Aug 2010, 02:59
  #1917 (permalink)  
 
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FluidFlow:

Wow. Thanks for that work and contribution.

mm43: In light of all your incredible and insightful work I'd like very much to hear your comments on Ian's post.

grizz

Last edited by grizzled; 16th Aug 2010 at 03:18.
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Old 16th Aug 2010, 11:09
  #1918 (permalink)  
 
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Mea culpa

HarryMann;

Sorry, I shouldn't have trusted my memory, and my thanks to NeoFit for correcting me by PM. The Hudson event rate of descent at touchdown was 13 ft/s (780 ft/min).

regards,
HN39
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Old 16th Aug 2010, 14:31
  #1919 (permalink)  
 
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Fourth search phase

For those interested, here is a link to a BEA summary of the Drift Group report; nothing really new though, but it gives an idea how BEA sees the report:

http://www.bea.aero/fr/enquetes/vol....de.travail.pdf

What is perhaps no longer news either, but I had missed that so far during the holiday period, is that AFP quoted the French State Secretary for transport, Dominique Bussereau who talked on 12 July last talked about a possible fourth search phase:

"I shall have beginning of September the elements from the Bureau des enquêtes-analyses (BEA) that will allow me to propose a possible resumption of the search".

It may sound over-obvious, but this is what he apparently said in addition to that: "The analysis of the three search phases has demonstrated places where one does not need to go back to, places where one perhaps should return to because one of the [search] phases has perhaps missed something and places where we have not been".

AFP also notes that "the decision [about a next search phase] may be deferred if the analysis of the previous phases takes more time than foreseen."

BEA-director, Jean-Paul Troadec, is said to be favourable to launch a fourth phase: "The balance sheet [of the searches] has not been finished but we think we have used powerful means that should permit us to detect the wreckage".

In that context he also is to have said that the searchers so far have found on the ocean floor objects that are a good size smaller than the wreckage.

"We will try to make the point that a new [search] phase has chances. If we look at the right place, we'll have to find the wreckage, except when it is in a very deep crevice and consequently no technical means will be able to find it", according to Troadec.

regards,

Dutch
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Old 16th Aug 2010, 18:12
  #1920 (permalink)  
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Certainly the slick was analyzed as to origin. Must be some mistake that it wasn't covered in the report. Sunk on December 7th, 1941, the USSArizona still leaks .It is eerie, the way bubbles come up and turn into rainboes 69 years after the fact. Maybe it's not too late, for 447.

Last edited by bearfoil; 16th Aug 2010 at 18:49.
 

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