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AF 447 Search to resume

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AF 447 Search to resume

Old 20th May 2010, 02:50
  #1101 (permalink)  
 
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Update: "Seabed Worker" - position

The following are the latest positions:-

19 May 2010 19:41 Hdg 092.6 Spd 02.3 304'52"N 3051'54"W
18 May 2010 20:14 Hdg 304.0 Spd 01.3 308'23"N 3052'48"W

They have been added to the graphic in post #1093

mm43
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Old 20th May 2010, 12:02
  #1102 (permalink)  
 
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Originally Posted by Chris Scott View Post
Haven't seen the "SHOM slideshow" (?), but has anything been said about the possible depths of the mud in these lower-lying plains and, in particular, the valleys? Sure I'm not the only one wondering...
Hey Chris.

which suggests that most of the SW unexplored regions of the 40 NM circle are rocky.
Or refer directly to http://www.bea.aero/fr/enquetes/vol....hom.050609.pdf page 4/8.
Jeff

Last edited by Hyperveloce; 20th May 2010 at 18:19.
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Old 20th May 2010, 13:34
  #1103 (permalink)  
 
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but my surmise is that there are very large (relatively) pieces of 447 on the bottom
I concur. I believe that the airplane was intact when contact with the water occured, and that break up was minimum. Given that few bodies and limited debris was recovered leads me to believe that the airplane settled to the bottom rather quickly. If true, then the footprint of major components will not be large, however, a miriad of misc items will make the overall area much larger. The deep water would allow items to drift some distant while sinking.
ww
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Old 20th May 2010, 14:58
  #1104 (permalink)  
 
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Mudslide

There is always a chance that the debris triggered a mudslide when impacting on a slope and got buried. Heavy pieces like the engines would be more likely to be buried while lighter parts might "float".
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Old 20th May 2010, 15:14
  #1105 (permalink)  
 
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Uh-oh! Now there's a thought. What if the debris got buried...so do I understand this right? The side-scan sonar being used now, effectively builds a picture of the ocean floor. So a mudslide could conceivably hide enough of the wreckage to make it unrecognizable? Does that sound feasible?

Assuming so, are there other techniques that could be used to search? First thought to pop into my mind - magnetic anomaly detection (MAD). If there enough metallic content to make this a feasible proposition?

- GY
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Old 20th May 2010, 21:44
  #1106 (permalink)  
 
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Hi,

So a mudslide
http://www.pprune.org/5703918-post1096.html
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Old 20th May 2010, 22:56
  #1107 (permalink)  
 
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MAD Effective Range

Assuming so, are there other techniques that could be used to search? First thought to pop into my mind - magnetic anomaly detection (MAD). If there enough metallic content to make this a feasible proposition?
Many decades ago when I had some experience with MAD as installed in anti-submarine patrol planes, the effective range was around 1,000 feet. That may well have improved over the years but I would imagine that given the depth of the water in the vicinity of the AF447 crash, any MAD gear employed would have to be carried by some kind of submersible.
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Old 20th May 2010, 23:17
  #1108 (permalink)  
 
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Mudslide

Originally Posted by RatherBeFlying
There is always a chance that the debris triggered a mudslide when impacting on a slope and got buried. Heavy pieces like the engines would be more likely to be buried while lighter parts might "float".
Possible? Yes. Likely? No. I have not ever visited the bottom of the ocean near the mid ocean ridges, but my understanding is that the rocky parts, seen as a rough texture in the bathymetry, are truly rocky, and the sedimentary parts, seen as smooth texture in the bathymetry, are reasonably level. I am guessing that this is due to the slow currents that exist down there slowly levelling things out. I suppose there are some sediment slopes at the margins, but I don't know. So there probably are few places that a landing object could trigger an slide.

Couple that with likelihood that the a/c sank in pieces, spread over at least a couple hundred meters, and there is even less chance that all of it could be covered.

Originally Posted by GarageYears
The side-scan sonar being used now, effectively builds a picture of the ocean floor. So a mudslide could conceivably hide enough of the wreckage to make it unrecognizable? Does that sound feasible?
If some part of the a/c were completely covered, it would not be visible to the type of side scan that is in use. However, a recently triggered slide might itself be visible as a track like a scour mark or a rough area in a smooth field.

Originally Posted by GarageYears
Assuming so, are there other techniques that could be used to search? First thought to pop into my mind - magnetic anomaly detection (MAD). If there enough metallic content to make this a feasible proposition?
Detection of magnetic anomalies requires the sensor to be relatively close to the object being detected, and that object has to be magnetic (either having a permeability different from free space, to perturb the earth's field, or having a magnetic field of its own, i.e. a permanent magnet). The detection distance for a perturbation of earth's field probably requires approaching within 3-10 times the longest dimension of the object.

How many parts of an a/c are magnetic? Not the aluminum or titanium. Likely the engines have enough iron to to be detectable, but at 5m length, you would have to be within 20-50m to detect one. Flying a sensor within 10-20m of the bottom is difficult in this terrain, and flying lines only 20-30m apart, to increase the likelihood of detection would reduce the search rate far below that achieved in phase 3.

Sub-bottom profilers use low frequency sound (a few kHz) to see below the bottom, but they also have narrow coverage in order to have the resolution required to be useful.
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Old 20th May 2010, 23:24
  #1109 (permalink)  
 
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Would mud 'disturbed' by the impact of an item be detected by the array of equipment deployed, that is would the different textures of the 'disturbed mud' be 'seen' as different to the original, long time settled mud?

Mike
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Old 21st May 2010, 02:41
  #1110 (permalink)  
 
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Update: "Seabed Worker" - position

The following are the latest available positions:-

20 May 2010 17:45 Hdg 224.7 Spd 00.4 307'21"N 3055'15"W
20 May 2010 16:35 Hdg 227.3 Spd 00.8 310'50"N 3051'41"W
20 May 2010 07:20 Hdg 147.3 Spd 00.6 310'46"N 3050'43"W
20 May 2010 05:33 Hdg 001.5 Spd 00.6 310'21"N 3047'28"W

The following graphic shows them in orange -



IMHO, the area in the southeast corner of the above graphic is a highly improbable location, but you never know. I would have expected the remaining area to the southwest to have had priority, and hopefully it will get done.

At this stage there will be less than a days searching left.

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Old 21st May 2010, 04:22
  #1111 (permalink)  
 
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Originally Posted by mm43
IMHO, the area in the southeast corner of the above graphic is a highly improbable location, but you never know. I would have expected the remaining area to the southwest to have had priority, and hopefully it will get done.
I agree, but not because I know anything about the flight path or debris drift, but solely because the SE corner is a rectangle (G-30) that BEA already marked as having searched for the pingers with a "good reliability index" (second interim report, page 82). It seems as if all the area that was covered by the USN TPLs could have been eliminated from the search, because the TPLs were towed deep and would have heard any functioning pingers. It seems reasonable to assume that, with two pingers, at least one would be audible, unless both pingers failed or landed with the pinger substantially obscured. It just seems like the areas of low pinger reception probability should have the highest priority for search.
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Old 21st May 2010, 04:38
  #1112 (permalink)  
 
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originally posted by auv-ee ...
It just seems like the areas of low pinger reception probability should have the highest priority for search.
Totally agree. For that reason, and subsequent to the SNA sonar reassessment, the SW corner and south of 3N for about 12NM between 32 and 40NM from LKP falls into the category of rugged terrain. It is from the ridges, slopes and valleys in this not-so-deep area that the pinger signal could have radiated and was faintly detected by Emeraude.

We don't know when Emeraude visited the area, and consequently if it was late in the battery life, there could have been a marked drop in the pinger output level.

mm43
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Old 21st May 2010, 08:30
  #1113 (permalink)  
 
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Originally Posted by mm43
We don't know when Emeraude visited the area
1st july
HN39
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Old 21st May 2010, 10:50
  #1114 (permalink)  
 
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HN39 wrote:-
1st July
Thanks - so battery life was in its "twilight" and pinger output would have been reduced by at least 3dB.

mm43
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Old 21st May 2010, 11:08
  #1115 (permalink)  
 
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I really do hope BEA or the search team management are keeping a watching eye on this thread - maybe 'blue sky' thinking is inappropriate but that's what comes to mind...
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Old 22nd May 2010, 00:45
  #1116 (permalink)  
 
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Update: "Seabed Worker" - position

Latest positions follow:-

21 May 2010 16:35 Hdg 198.5 Spd 10.5 313'34"N 3111'59"W
21 May 2010 06:02 Hdg 245.2 Spd 01.8 310'04"N 3048'55"W
21 May 2010 04:23 Hdg 258.6 Spd 01.0 310'51"N 3050'10"W
20 May 2010 19:36 Hdg 125.4 Spd 01.3 309'08"N 3048'28"W

Note:: Not all have been plotted, and it seems that the area to the east they have been working on is now complete and the Seabed Worker is now engaged in tending her AUVs in the remaining area to the west.


HarryMann wrote in part ....
... maybe 'blue sky' thinking is inappropriate ...
Sometimes the "blinkers" go on and subsequent knowledge gets tainted by the "already known". In this particular case:-

KNOWN
1.. A position sent at 02:10:30z.
2.. A number of ACARS messages indicative of an upset.
3.. The location and condition of found bodies and debris.
4.. Aircraft impacted the ocean in an intact condition [BEA].
5.. No reported tell-tale signs of overspeed damage to aerofoil surfaces recovered.
6.. Satellite data, e.g. MeteoSat[wx ir images], OSCAR[surface current], QuikSCAT[10m winds].
7.. Limited drifter buoy data.
8.. No pingers were detected in areas searched using USN TPLs
9.. Possible pinger detection on reanalysis of Emeraude sonar tapes.
10.. No bottom debris located during sidescan searches.

UNKNOWN
1.. Why the aircraft got into a LOC situation
2.. How long the aircraft continued flying.
3.. Where it impacted with the ocean.

So, as you can see, the "Known" is actually a lot, whereas the "Unknown" is quite small. Logic tells me that with the correct approach and open minded analysis of the "Known", methodology can be developed to narrow down a likely impact position to no more than a 5NM radius (78.5NM2).

The biggest factor in the backtracking of debris, is knowing how accurate the surface current and wind data is that you are trying to work with. That can be dealt with in this case by careful analysis of the track each individual item found will have traveled over the 12 or so days from the location of the first to that of the last. Comparison of the plotted debris path and that of the OSCAR surface current data along with the QuikSCAT wind data will allow meaningful corrections to be applied to the satellite data which can then be used to adjust the data for the earlier 6 days for which we have no surface plots.

The whole reason behind this approach is to minimise the affect that that one erroneous piece of data will have on the outcome. So rather than having lots of erratic tracks drawn all over a chart, the amalgamated smoothed lines will all lead to a near common point.

Looking at the Vertical Stabilizer which had a reasonable amount of windage affecting it, and the Port Outer Spoiler which effectively had none, it is obvious to me that a retrace of their individual tracks accounting for both current and wind where appropriate will show that at a critical point the V/S became caught in the North Brazil Current and the Spoiler headed NNE toward the Equatorial Counter Current. Every other item's position will relate in one way or another to these tracks, which in the case of the V/S can be adjusted for the windage to reveal the mean current it traveled in.

Anyway, here's hoping that this last area to be searched will reveal the hidden!

mm43

Last edited by mm43; 22nd May 2010 at 05:37. Reason: grammar!
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Old 22nd May 2010, 09:06
  #1117 (permalink)  
 
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Known and Unknown

MM43
Your summary of the "knowns and unknowns" presents a helpful review of the situation to date.

Looking at the Vertical Stabilizer which had a reasonable amount of windage affecting it
I wish it were so straight forward. The VS weighed about 1800 kg and had an area of 53 m^2.



I estimate only 10% of the surface area of the VS was above sea level and subject to windage. In summary, the VS had a lot (90% submerged) of underwater drag that may have attenuated the wind effects. Note the VS was submerged at a slight angle that may have "dug in" with the wind drag.

Your own estimates of the aircraft's location on the sea floor using OSCAR/QuikSCAT data were particularly well done and the AUVs are searching that area now, but so far... no cigar. So big the question now is....

"what have we missed?"

Could the aircraft go beyond 40 nm in the last 4 (or more) minutes? Did the aircraft continue more or less along her original course contrary to the modeled debris backtracked estimates (models do not always reflect the real ocean). Do the mountainous areas from the Emeraude sonar tapes need to be searched with higher resolution.

I do not know the answer, but this effort is proving to be a challenging mystery, and we all want to find the answer.

However the search is still continuing, and "it ain't over til the fat lady sings"
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Old 22nd May 2010, 14:07
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Originally Posted by cc45;#1116
Do the mountainous areas from the Emeraude sonar tapes need to be searched with higher resolution.
Just wondering, does the survey conducted with TPLs also produce audiotapes and, if so, would these lend themselves to re-analysis with the latest Thales software?

HN39
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Old 22nd May 2010, 16:13
  #1119 (permalink)  
 
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So far the search has been heavily concentrated along the planned course from the LKP. There has so far been a small minority of search in the area suggested by mm43. The same search effort along the accident track and possible impact site derived from mm43's work may have been more fruitful, but it's the holders of the megabucks who approve the search plan.

Passing the hat in PPRuNe likely would not pay for so much as a minute of sea time
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Old 22nd May 2010, 20:37
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Vertical Stabilizer - in drift mode!

originally posted by cc45 ...
The VS weighed about 1800 kg and had an area of 53 m^2.
I am mindful of a video showing the recovery of the V/S. The rudder is clearly jammed at around 30 degrees to starboard, which is consistent with the V/S initially being propelled off its clevis joints in a forward and to port motion. It will have "belly-flopped" into the water on its port side and the rudder will possibly have been rammed over to starboard at that point.

The torn off fuselage skin on the starboard forward side will also have had a part to play and I believe the V/S was moving through the water along a line drawn through the fuselage skin piece to the top and aft end of the rudder, i.e. with the rudder leading the way. On top of that the V/S including the rudder is a large and light aerofoil (8.5m [base] 9.3m [high]), which in this case will not take much wind to get it moving and it will "sail" along quite nicely. The effective waterline length was around 13m (LOA 15m), with the top of the V/S pitched up a few degrees, and the hydro-dynamic drag would not have been high as the base was open to ribs #2 & #3 and didn't present a solid bulkhead.

We don't need the "fat lady to sing" - and hopefully never!

mm43

Last edited by mm43; 23rd May 2010 at 02:53. Reason: added LOA
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