AF 447 Search to resume
Join Date: May 2010
Location: MA, USA
Posts: 126
Likes: 0
Received 0 Likes
on
0 Posts
CS, mm43, and perhaps swordfish41,
With all due respect, I think you may be trying to read too much into a few low resolution blips in a sonar image. The dark spot does look like a shadow, but if it is, we should do the math for it.
Using the provided scale:
The eastern target is 360m from the (eastern) vehicle track.
The length of the shadow is 11-13m long.
The vehicle is typically flown at 10% of the maximum range setting of the sonar (10% gives a good compromise between pronounced shadows and not letting the grazing angle on the seabed get too shallow for receiving good back scatter). For the 600m range used here, the altitude of the vehicle is about 60m.
That puts the target 6 times as far from the vehicle as its altitude. Thus the shadow is 6 times longer than the height of the object casting it. So the object is standing about 2m above the sea floor. Does that match your other assumptions? (I see from our intersecting posts that mm43 is wondering, too.)
With all due respect, I think you may be trying to read too much into a few low resolution blips in a sonar image. The dark spot does look like a shadow, but if it is, we should do the math for it.
Using the provided scale:
The eastern target is 360m from the (eastern) vehicle track.
The length of the shadow is 11-13m long.
The vehicle is typically flown at 10% of the maximum range setting of the sonar (10% gives a good compromise between pronounced shadows and not letting the grazing angle on the seabed get too shallow for receiving good back scatter). For the 600m range used here, the altitude of the vehicle is about 60m.
That puts the target 6 times as far from the vehicle as its altitude. Thus the shadow is 6 times longer than the height of the object casting it. So the object is standing about 2m above the sea floor. Does that match your other assumptions? (I see from our intersecting posts that mm43 is wondering, too.)
Last edited by auv-ee; 15th Apr 2011 at 00:47.
Join Date: Jun 2009
Location: NNW of Antipodes
Age: 81
Posts: 1,330
Received 0 Likes
on
0 Posts
Originally posted by auv-ee ...
With all due respect, I think you may be trying to read too much into a few low resolution blips in a sonar image.
With all due respect, I think you may be trying to read too much into a few low resolution blips in a sonar image.
The only thing that the target in question has is a bit of height that has been amplified by the grazing angle of the sonar.
Join Date: Jun 2009
Location: I am where I am and that's all where I am.
Posts: 660
Likes: 0
Received 0 Likes
on
0 Posts
Re the magnified scan, mm43, the wings seem to be awol. I'd expect SOME indication in the distribution that the wings were down there with the plane, somewhere. I'd expect them to be at least a slightly denser collection of debris in a roughly straight line perpendicular to the rest of the debris.
That outlier might simply be the outer portion of a wing if it broke off on impact. That would suggest the other wing might be that slightly thicker bit of debris across the roughly fuselage shaped debris field.
If that is the case we might even be able to infer something modest about the current distribution as the plane sank.
That outlier might simply be the outer portion of a wing if it broke off on impact. That would suggest the other wing might be that slightly thicker bit of debris across the roughly fuselage shaped debris field.
If that is the case we might even be able to infer something modest about the current distribution as the plane sank.
Join Date: May 2010
Location: MA, USA
Posts: 126
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by JD-EE
If that is the case we might even be able to infer something modest about the current distribution as the plane sank.
I meant to look at that a few nights ago but could not find the data. By coincidence, following a link to swordfish41's comments about the Ark Royal lead me right to that discussion of currents.
Last edited by auv-ee; 15th Apr 2011 at 01:54.
Join Date: Jul 2002
Location: 40N, 80W
Posts: 233
Likes: 0
Received 0 Likes
on
0 Posts
Scale
These two images show the approximate relative sizes of the debris field and the aircraft.
--------
--------
--------
The red "pixel" near the aircraft in the second image represents what I imagine to be the effective sonar resolution, based on my understanding (or mis-understanding, as the case may be) of auv-ee's post #3169, "Resolution of sonar images", describing how sonar side-scan images are constructed. The red "pixel" is about 6 m from top to bottom, and the width arbitrally narrower. From the auv-ee's description I understand that the left-to-right resolution can be made as narrow as the constructor wants, but from the image I am guessing not very narrow, to conserve memory requirements. (auv-ee please correct this as necessary.)
---
---
--------
--------
--------
The red "pixel" near the aircraft in the second image represents what I imagine to be the effective sonar resolution, based on my understanding (or mis-understanding, as the case may be) of auv-ee's post #3169, "Resolution of sonar images", describing how sonar side-scan images are constructed. The red "pixel" is about 6 m from top to bottom, and the width arbitrally narrower. From the auv-ee's description I understand that the left-to-right resolution can be made as narrow as the constructor wants, but from the image I am guessing not very narrow, to conserve memory requirements. (auv-ee please correct this as necessary.)
---
---
Last edited by PickyPerkins; 16th Apr 2011 at 04:48.
Chris Scott wrote:
I think auv-ee addressed this recently - he suggests it's probably more indicative of the underwater currents. I think it also depends on the degree of fragmentation. We also don't know if this is the entire field (though it looks to be).
My understanding[*] is that if parts are relatively intact, you get a sort of ballistic trajectory that depends on the resistance offered by the falling parts. You can see an indication of this in the HMAS Sydney report -- see the final page of:
http://www.defence.gov.au/sydneyii/f...apter%2016.pdf
and again on p 218 of
http://www.defence.gov.au/sydneyii/f...apter%2012.pdf
The relative distribution of the parts in turn will be affected by underwater currents pushing on them during the time of descent, but unless they further fragment (eg implosion) what you see in the sonar tends to reflect their original shape.
The question of the relation between resting orientation and orientation at impact is something you'd need expert comment on. My lay impression is that a relatively intact airframe would tend to fall through water nose first, as I presume that would offer least resistance.
However, if the wreckage is heavily fragmented, my understanding is that the final debris field is often spread much further, because each individual fragment behaves differently. The pieces which are both densest and offer least resistance, descend fastest and move least with current. Pieces that are lightest and with the most resistance take the longest to fall and are pushed furthest by the current. Other things fall in between.
The sidescan suggests large parts could be contiguous, but the few photos do show a lot of fragmentation of parts - see at Oprations de recherche en mer : images du site , especially the one titled "Partie de fuselage".
It's hard to tell without seeing more of the cabin, but I assume it hasn't been shown because human remains were visible. From mm43's post, it does however look like the main part of the debris field is about 400m long out of the 600m shown, whereas the intact A332 aircraft is about 59m long? Given the amount of internal parts (eg galley parts) found on the surface, from both galleys, I assume there were either multiple breaks in the fuselage, and/or rupturing, to allow them to escape.
nb[*] Several people here have already shown that they have much more knowledge than I on this and I would defer to them if the above is wrong.
Also, compare the tidiness of the HMAS Sydney image with the AF 447 one. I don't know enough to know if this means anything.
Is there a possibility that Turbine D is right, and that it is the tail section (by which I think he is referring to the aft fuselage)?
Would the debris field alignment (approximately 070/250) necessarily be roughly indicative of the heading at sea-level impact, despite currents on the way down? If the curved piece in the north-east was the aft fuselage, would that suggest the Hdg 250 rather than the 070?
Would the debris field alignment (approximately 070/250) necessarily be roughly indicative of the heading at sea-level impact, despite currents on the way down? If the curved piece in the north-east was the aft fuselage, would that suggest the Hdg 250 rather than the 070?
My understanding[*] is that if parts are relatively intact, you get a sort of ballistic trajectory that depends on the resistance offered by the falling parts. You can see an indication of this in the HMAS Sydney report -- see the final page of:
http://www.defence.gov.au/sydneyii/f...apter%2016.pdf
and again on p 218 of
http://www.defence.gov.au/sydneyii/f...apter%2012.pdf
"As she continued her plunge she would have tended to level off, and she probably adopted a trim by the stern because the shape of the forward part of the ship offered more resistance to the passing water."
The question of the relation between resting orientation and orientation at impact is something you'd need expert comment on. My lay impression is that a relatively intact airframe would tend to fall through water nose first, as I presume that would offer least resistance.
However, if the wreckage is heavily fragmented, my understanding is that the final debris field is often spread much further, because each individual fragment behaves differently. The pieces which are both densest and offer least resistance, descend fastest and move least with current. Pieces that are lightest and with the most resistance take the longest to fall and are pushed furthest by the current. Other things fall in between.
The sidescan suggests large parts could be contiguous, but the few photos do show a lot of fragmentation of parts - see at Oprations de recherche en mer : images du site , especially the one titled "Partie de fuselage".
It's hard to tell without seeing more of the cabin, but I assume it hasn't been shown because human remains were visible. From mm43's post, it does however look like the main part of the debris field is about 400m long out of the 600m shown, whereas the intact A332 aircraft is about 59m long? Given the amount of internal parts (eg galley parts) found on the surface, from both galleys, I assume there were either multiple breaks in the fuselage, and/or rupturing, to allow them to escape.
nb[*] Several people here have already shown that they have much more knowledge than I on this and I would defer to them if the above is wrong.
Also, compare the tidiness of the HMAS Sydney image with the AF 447 one. I don't know enough to know if this means anything.
Join Date: Oct 2007
Location: France
Posts: 136
Likes: 0
Received 0 Likes
on
0 Posts
@auv-ee: thank you for your documented answer #3504.
About bodies injuries vs a/c attitude: it seems (imho) that there is kind of circular arguments (tautology) about them:
So, it is fully compatible with the a/c attitude supposed by BEA.
BUT. Bodies recovered are probably those from passengers who were not attached. And they could have been in every position and place in the cabin at impact, depending of what happened before.
In fact, I can't imagine this aircraft falling from 35000' to 0 keeping a "normal" attitude all along (and not attached passengers remaining in their seats*). Adding a storm, is this "flat" fall truly possible ?
*If that was which happened, thanks for it: passengers kept sleeping all the way. It had to be more rude for the crew.
About bodies injuries vs a/c attitude: it seems (imho) that there is kind of circular arguments (tautology) about them:
Originally Posted by BEA 2nd report p.32
The compression fractures of the spinal column associated with the fractures of the pelvis(2), observed on passengers seated throughout the cabin, are compatible with the effect, on a seated person, of high acceleration whose component in the axis of the spinal column is oriented upwards through the pelvis.
BUT. Bodies recovered are probably those from passengers who were not attached. And they could have been in every position and place in the cabin at impact, depending of what happened before.
In fact, I can't imagine this aircraft falling from 35000' to 0 keeping a "normal" attitude all along (and not attached passengers remaining in their seats*). Adding a storm, is this "flat" fall truly possible ?
*If that was which happened, thanks for it: passengers kept sleeping all the way. It had to be more rude for the crew.
Forgive the noob question on sonar, but is the image produced on a single pass, eg from the rov above the eastern edge of the lane, or is it the addition of two half pictures, one from the east and one from the western pass ? Also what would the effective lateral beam width be, ie the length of image producted by a point object (are the N/S 'smearings' a reflection of pulse width and not debris dimension ?). Noting its a jpeg, any need to be careful about compression artefacts ?
Grity: never heard of Lilienthal: impressively ahead of his time !
The image of fuselage section looks like it supports a limited front/aft impact load, and if people/seats and attachments are intact, that would also indicate realtively limited impact loadings.
Is the linear debris trace trending roughly north from the centre taken to be the remains of a late breaking stb wing ?
Grity: never heard of Lilienthal: impressively ahead of his time !
The image of fuselage section looks like it supports a limited front/aft impact load, and if people/seats and attachments are intact, that would also indicate realtively limited impact loadings.
Is the linear debris trace trending roughly north from the centre taken to be the remains of a late breaking stb wing ?
Last edited by Mr Optimistic; 15th Apr 2011 at 07:31.
Per Ardua ad Astraeus
Join Date: Mar 2000
Location: UK
Posts: 18,579
Likes: 0
Received 0 Likes
on
0 Posts
It would appear to me to be completely fruitless to attempt ANY 'analysis' of heading at impact from the lie of any wreckage. The remains of the aircraft will 'fly' just as well in water as in air, and since most seem to be postulating some sort of rotating motion at impact there is no reason why this should not continue during the 4000m drop resulting in ANY sort of orientation. Until FDR data is recovered, all the wreckage tells us at the moment is roughly where it hit the surface.
Fair comment, stb was perhaps pushing it. First thought was it was a debris trail as if both engines have been pictured, where is the other wing.
With respect to other recent musings, re-reading the BEA report reminded me that a concurrent flight had to carefully adjust the weather radar to get the full picture and that no big issue is made of the difference between ACARS 'WRN' and 'WRG' : it doesn't reference interconnection failure for the latter, just a mistrust.
With respect to other recent musings, re-reading the BEA report reminded me that a concurrent flight had to carefully adjust the weather radar to get the full picture and that no big issue is made of the difference between ACARS 'WRN' and 'WRG' : it doesn't reference interconnection failure for the latter, just a mistrust.
'Morning BOAC,
Quote:
"It would appear to me to be completely fruitless to attempt ANY 'analysis' of heading at impact from the lie of any wreckage."
I'm not sure you or I know enough to make that assumption. Let's keep on interrogating the experts, just in case. As auraflyer (while admitting to be a layperson) says: "The pieces which are both densest and offer least resistance, descend fastest and move least with current. Pieces that are lightest and with the most resistance take the longest to fall and are pushed furthest by the current. Other things fall in between."
Comparing the pattern of returns in the east and west, I have a hunch that swordfish41 and others may resolve the 250/070 dilemma at a glance. However, as I asked earlier, is the orientation of this debris field necessarily indicative of the heading ar sea-level impact?
Quote:
"The remains of the aircraft will 'fly' just as well in water as in air, and since most seem to be postulating some sort of rotating motion at impact there is no reason why this should not continue during the 4000m drop resulting in ANY sort of orientation."
Cannot agree with any of that.
Quote:
"...all the wreckage tells us at the moment is roughly where it hit the surface."
It depends what you mean by roughly. For a start, the engines - presumably both detached at sea-level - would have gone pretty-much straight to the bottom. As mm43 commented some time ago, their position relative to this debris field is of the essence.
Maybe the BEA will divulge the Lat/Long of this debris field eventually. But I, for one, am not holding my breath. Pity: I can't see any third party being able and inclined to interfere.
Quote:
"It would appear to me to be completely fruitless to attempt ANY 'analysis' of heading at impact from the lie of any wreckage."
I'm not sure you or I know enough to make that assumption. Let's keep on interrogating the experts, just in case. As auraflyer (while admitting to be a layperson) says: "The pieces which are both densest and offer least resistance, descend fastest and move least with current. Pieces that are lightest and with the most resistance take the longest to fall and are pushed furthest by the current. Other things fall in between."
Comparing the pattern of returns in the east and west, I have a hunch that swordfish41 and others may resolve the 250/070 dilemma at a glance. However, as I asked earlier, is the orientation of this debris field necessarily indicative of the heading ar sea-level impact?
Quote:
"The remains of the aircraft will 'fly' just as well in water as in air, and since most seem to be postulating some sort of rotating motion at impact there is no reason why this should not continue during the 4000m drop resulting in ANY sort of orientation."
Cannot agree with any of that.
Quote:
"...all the wreckage tells us at the moment is roughly where it hit the surface."
It depends what you mean by roughly. For a start, the engines - presumably both detached at sea-level - would have gone pretty-much straight to the bottom. As mm43 commented some time ago, their position relative to this debris field is of the essence.
Maybe the BEA will divulge the Lat/Long of this debris field eventually. But I, for one, am not holding my breath. Pity: I can't see any third party being able and inclined to interfere.
Last edited by Jetdriver; 15th Apr 2011 at 23:15.
Join Date: Feb 2008
Location: London
Posts: 48
Likes: 0
Received 0 Likes
on
0 Posts
Sonar interpretation
Sorry to get back a bit late into this. I did say "hazard a guess," and it could be the object is the tail section, although I assumed that the swathe width was 700m, and that the altitude of the AUV was therefore much higher than 60m, suggesting that the object was also higher above the seafloor than auv-ee suggests. If it is the tail I expected to see an equaly large object at the western end of the debris trail, and I was influenced in this by mm43's graphic of the likely break up of the fuselage at impact.I disagreed with mm43's view that the the debris would be fairly well confined, and I was wrong about that too. However the two Remus vehicles will have completed the photo mosaic now and BEA will know just where everything is. I've followed all the threads from this incident from day one, and incredibly fascinating its been. Throughout I have had at the back of my mind a story told me by the Chief Lab Technician on Odin Finder. He was engaged to search for an RAF Jaguar that crashed in the Adriatic. The pilot had ejected quite late, and confidence was high that the position of the aircraft on the sea floor was known. After no trace was found he fielded the usual questions, "Is your equipment working properly?" "Have your technicians missed anything?" with his own, "where do you want the ship to go now, north, south, east or west?" My granny told me when I lost something that it would be in the last place that I looked.
With respect to orientation, on reflection agree with BOAC's chastisement. However, the assymetry N/S, with apparent distribution linearly to the north not reflected to the south may reflect something. But perhaps if you stare long enough into the darkness you will eventually see a ghost. Hoped for a clear debris trail.
swordfish41,
Further to previous posts by me and others, is it possible to say if the 070/250 orientation of the debris field has been created purely by the prevailing currents during the descent, or is it in any way indicative of the aircraft's heading at sea-level impact?
Further to previous posts by me and others, is it possible to say if the 070/250 orientation of the debris field has been created purely by the prevailing currents during the descent, or is it in any way indicative of the aircraft's heading at sea-level impact?
Per Ardua ad Astraeus
Join Date: Mar 2000
Location: UK
Posts: 18,579
Likes: 0
Received 0 Likes
on
0 Posts
Not 'heading' in my book. By the way, I'm puzzled why do you not view water as a liquid? "Cannot agree with any of that."
Debris orientation/position at 4000m will be governed only by the currents and the 'flying'/break off motion of individual separate parts and there will be a ZERO effect of any motion vector at impact. All bits will come to a pretty abrupt halt at immersion. Water is hard at that speed. As said, separated engines will go pretty much straight down. The fin/seat cushions etc float. Plot all points between?
Debris orientation/position at 4000m will be governed only by the currents and the 'flying'/break off motion of individual separate parts and there will be a ZERO effect of any motion vector at impact. All bits will come to a pretty abrupt halt at immersion. Water is hard at that speed. As said, separated engines will go pretty much straight down. The fin/seat cushions etc float. Plot all points between?
BOAC,
I cannot DISagree with any of that! But it is completely at odds with the sentence I criticised in your previous post:
"The remains of the aircraft will 'fly' just as well in water as in air, and since most seem to be postulating some sort of rotating motion at impact there is no reason why this should not continue during the 4000m drop resulting in ANY sort of orientation."
Re your latest: would you prefer "track"? Not sure the difference is significant in this case.
I cannot DISagree with any of that! But it is completely at odds with the sentence I criticised in your previous post:
"The remains of the aircraft will 'fly' just as well in water as in air, and since most seem to be postulating some sort of rotating motion at impact there is no reason why this should not continue during the 4000m drop resulting in ANY sort of orientation."
Re your latest: would you prefer "track"? Not sure the difference is significant in this case.
Per Ardua ad Astraeus
Join Date: Mar 2000
Location: UK
Posts: 18,579
Likes: 0
Received 0 Likes
on
0 Posts
Heading/track no matter. Neither apply. 'Track' becomes meaningless with no overall forward speed. Break off part of a wing and see what happens to 'heading' as the wreckage sinks. You can, in my opinion, deduce nothing.
My post is actually COMPLETELY in agreement with my previous. Hydrodynamics work pretty much as aerodynamics at low speeds. A wing will produce a force of some sort. An attached tailplane will produce a pitching motion as the wreckage sinks.
Next time you fill a deep bath, generate a gentle 'current' by moving your hand around in the water. Then throw in a small strip of metal and see if you can deduce from where and how it sits on the bottom which way it was travelling when it hit the water - or how fast, for that matter. Now imagine that bath thousands of times deeper.
My post is actually COMPLETELY in agreement with my previous. Hydrodynamics work pretty much as aerodynamics at low speeds. A wing will produce a force of some sort. An attached tailplane will produce a pitching motion as the wreckage sinks.
Next time you fill a deep bath, generate a gentle 'current' by moving your hand around in the water. Then throw in a small strip of metal and see if you can deduce from where and how it sits on the bottom which way it was travelling when it hit the water - or how fast, for that matter. Now imagine that bath thousands of times deeper.
Join Date: Jun 2009
Location: I am where I am and that's all where I am.
Posts: 660
Likes: 0
Received 0 Likes
on
0 Posts
Shadoko, you may be right that the bodies recovered were those not seated. However, on the old thread a fellow involved in recoveries from water suggest that dead bodies seem to work their way out even from tight seat belts when you have water to work with. They even work their way out of their clothes much of the time.
Given how small the pattern is I suspect those recovered may have been in seats such as those recovered. But they did not float to the surface from a seat still attached to a large piece of fuselage.
I find it interesting so many were not sitting and not strapped in. Were they holding a dance in the aisles for entertainment? It's another of the surprises associated with this accident.
Given how small the pattern is I suspect those recovered may have been in seats such as those recovered. But they did not float to the surface from a seat still attached to a large piece of fuselage.
I find it interesting so many were not sitting and not strapped in. Were they holding a dance in the aisles for entertainment? It's another of the surprises associated with this accident.