AF 447 Search to resume

[Machinbird]

Mr. Optimistic
Is everyone so sure that the orientation of the debris doesn't give more information ? If the fwd and aft ends of the a/c are subsequently found at either end of the debris trail, it would be a clincher wouldn't it ie (ie that the debris reflects heading at impact)?

I suspect you are being a bit 'optimistic' sir. The bits on the bottom probably do reflect the orientation of the aircraft at impact, but not in the way you suggest.
For example, if the aircraft impacted in a N-S attitude and the wing tip navigation lights broke off neatly from the structure in comparable size lumps, you would find the green light fixture approximately one wing span to the east of the red light fixture and located roughly along the centerline of the wreckage pattern.
If the aircraft impacted in a E-W direction, you would find the two light fixtures north and south of the wreckage centerline, separated by approximately one wing span, and the line between the two fixtures would be approximately N-S. The displacement from the right edge of the wreckage field would be dependent on fall rate through the water column and initial position on the aircraft in both of the above examples
There is a dispersion factor as aluded to by JD-EE. The dispersion factor is essentially a bell shaped curve around the calculated bottom impact position (based on the integral of local current velocity over fall time) and the span of the dispersion is proportional to radius of curvature that an object describes in its hydrodynamic trip to the bottom. You also have to consider possibility of collisions between particle elements deflecting them away from their original trajectories through the water.
All and all, it is a bit daunting problem in locating components of interest, but not impossible. If you find an element of comparable mass and hydrodynamic drag to a component you wish to find, and if you have an idea of initial aircraft orientation, you can significantly reduce the area to search for a target item, but you need to have an idea if the item immediately began to sink or might have traveled before sinking.

[Mr Optimistic]

Machinbird, thank you for the considered answer. One point though, the bell curve (by which I guess you mean 2-D gaussian distribution) clearly had very different dispersions in x and y to give the narrow CEP.

[mm43]

Originally posted by chrisN ...

... just clarifying - you mean the impact trauma at the sea surface

My references to "impact" are of the aircraft with terra-oceania, and contact of debris with the seabed can more readily be called a "landing".

[mike-wsm]

Perplexed

Dunno why you all bother. The whole lot has been photographed in great detail. When we see the pics all will be revealed. I rather suspect all this argument about dropping thimbles into buckets of water is being wasted because some vital fact has been misunderstood. For example, how do we know the sonar scan has the same horizontal and vertical scales? It's not a map, is it?

[PJ2]

mike-wsm, understand what you're saying, but for some here, it's just what we do... ;-)

[Mr Optimistic]

The Bea slide had the scales. The 'why bother' observation could be applied across the piece. Perhaps it's just in the nature of people to want to know. Is there any harm in it ? It could be a long 2 year wait for an inconclusive answer and an unsatisfactory response.

[Machaca]

No harm in a bit of component identification and moderately informed speculation while we wait for better official information. None here expects to discern a full explanation from the keyhole view afforded us so far.

The contributions by those who are expert in various related fields have greatly expanded our understanding on a multitude of fascinating topics.

We all eagerly await greater understanding of the actual contributors and causes of this tragic event.


Here's some wing images for the sea floor tin-kickers:

[Machinbird]

Mike-WSM
Why bother? It relates to the factors involved in trying to find particular objects on the bottom. A photomosaic map of the bottom is but a starting point. Until an item in question is recovered, it is still in Neptune's grasp.
Even after they find the recorders, prudence would say to continue recovering items that tell about critical events on the aircraft as it fell.
Suppose the recorders are destroyed by corrosion. Wouldn't you think it prudent to learn the position of the slats and THS trim actuator? Wouldn't you want to look for witness marks on a whole range of components? Wouldn't you want to see how the cockpit switches were set up? Wouldn't you like a look at the engines to determine power setting at impact?
Mr Optimisitic

One point though, the bell curve (by which I guess you mean 2-D gaussian distribution) clearly had very different dispersions in x and y to give the narrow CEP.

Actually I weasel worded my earlier statement to indicate two wingtip lights with equal geometry and mass. The ballistic CEP has equivalent scale in all directions, but there is another probability at work as well. Supposing one wing tip light retained a tab of metal that influenced its sink rate compared to the other. The uncertainty in configuration causes a second dispersion (or uncertainty) in the underwater current direction only.

[henra]

Originally Posted by Machinbird

I suspect you are being a bit 'optimistic' sir. The bits on the bottom probably do reflect the orientation of the aircraft at impact, but not in the way you suggest.

When looking at the N-S extension of the main Debris Trail, I have to admit I'm somewhat in the boat of Mr. Optimistic here.

The N-S extension of the trail is mostly below 100m.
Considering a length of the 'bus of almost 60m this is really not much. It would suggest that nothing broke lose on impact and stopped immediately or no parts continued in forward direction after impact at leat for a couple of dozen meters.

IMHO if any significant forward speed (>50kts) was present I would consider a N-S heading rather unlikely. In that case I would not expect only single pieces outside the main trail basically forming something like
-+- but rather a more rectangular wider area with random debris.
So if I had to put money on the general heading I would put it on something more West to East.
But as always: Happy to stand corrected after FDR Data has been examined and published.

However, I agree the length of the trail and the distribution of the bits and pieces along the trail would be basically purely drift due to currents.

[Machinbird]

Hi Henra,

The N-S extension of the trail is mostly below 100m.

Please check your scale. I see large components of the wreckage spanning 180-200 meters in the N-S direction. They are located both south and north of the centerline, part of the 'outliers.'
I've added arrows to some apparent large chunks of wreckage using PickyPerkins' original graphic. You can see that they appear to relate to the original size of the aircraft fuselage, but sonar returns can be tricky to interpret.

[henra]

Originally Posted by Machinbird

Hi Henra,
Please check your scale. I see large components of the wreckage spanning 180-200 meters in the N-S direction. They are located both south and north of the centerline, part of the 'outliers.'

Hi Machinbird,

The 100m was referring to the main trail w/o the outliers.

That's what I meant with the -+-. The width of the outliers is wider but they are on a single axis vertical to the main trail. with very little drift spread along this orthogonal axis.

In case of N-S impact with some remaining forward velocity I would expect the 200m not only in one line but more or less over the full length of the trail.
I.e. something like IIIIII or maybe IIII+-- instead of ---I--

Why would only the mid- part drift differently due to currents ?
And even more mysterious : Why would the bits lost at the beginning of the sequence drift equally far to the bits at the end of the impact sequence, i.e. have similar flotation /drag characteristics and everything in between have a very wide spread of drift / flotation characteristics.

[Mr Optimistic]

Machinbird, thanks once again. My experience in this subject is limited and I hope I don't sound presumptious.

[grity]

@PJ2 in this picture of F-GZCP I see the text"do not walke..." only two times written on each wing

http://images3.jetphotos.net/img/1/7...1238106997.jpg

Currents must have been really slow compared to the rate of fall through them.

@JD-EE, if a light peace will fall with mayby 0,6 m/s and if the currend moves with the 0,1 m/s, than it will move horizontaly around 600m after the falling time over 4000 m.....

and compared to a heavy part, falling mayby between 4-10 m/s the same currend will be very slow, it moves <50m horizontal

a slow deapwater currend with 0,1 m/s will flow very laminar, and after a longer time there is no reason that the speed will be much different in different levels, the deapwater currend is part of a big stream with amount the same water volume like the golf stream, until it is the backroute of the same water... grity

[Turbine D]

PJ2 & mm43

PJ2, thanks for the enlarged enhanced photos, prior to these, I was cautious about saying much about the engine that was photographed. So now, here is my observations about the engine:

1. The first photo depicts the central conical hub just aft of what would have been the fan blade rotor, in fact, the fan disk drive arm to attaches to this hub, but is gone. Also, the "A" roller thrust bearing is at this same location but is also gone.

2. With the exception of two visible by-pass guide vanes (one at 6 o'clock - the other at 1 o'clock), everything is generally missing forward of the one piece titanium fan frame. That includes fan booster blades and vanes (3 stages) forward of the fan frame.

3. It is possible that a portion of the fan frame (7 o'clock to 12 o'clock) is missing.

4. In the second engine photo, I think the white (shiny) tube that curves around the top, just aft of the conical hub is the "A" oil feed line to the "A" bearing.

5. In the second engine photo, all of the active clearance control tubing is stripped from the LPT module casing, at least on the visible side.

6. The engine orientation sitting on the sea bed appears to be resting on its side as I think that part accessory gear box is visible behind the fan frame.

7. I fully agree with mm43's assessment that the engine hit the sea bed LPT module end first. With all of the fan, fan casing, kevlar fan containment, booster vanes & blades missing, the rear of the engine would be much heavier than the remaining front end.

According to the BEA interim report, the aircraft hit the water with a high vertical rate of speed, a lesser forward motion in a slight bank orientation with a pitch upward. Depending on what is meant by "slight bank," the engine on the low wing would be first to hit the water. My thoughts for discussion would be that the engine was torn from the left wing pylon (engine sits ahead of the wing). Could the structure being seen in front of the wing be the most forward part of the pylon bent around to the left and twisted rather than the internals of the slats?

Machaca & Shadoko, thanks for all the great photos and diagrams

[deSitter]

Pretty clear that the airplane shattered on impact. Like the one in Libya a while back, that belly flopped on final. So why was the fin spared? Could be the part some distance away is the empennage?

[PJ2]

grity;

@PJ2 in this picture of F-GZCP I see the text"do not walke..." only two times written on each wing grity

One thing consistent about airplanes is a "variations on a theme" of entities which are under constant modification and updating.

We have 3 such variations here, (and this is only one small item), ...the diagram, the wreckage and now the photo of the subject aircraft.

For those driven by knowing and positing, ...how the airplane ended up like this, how the wreckage rests and the what the relations are between the location of parts are important because sense can be made of seeming chaos and seemingly unimportant small details. But the tiny flashlight we are forced in total darkness to use means the details can be argued until someone inevitably sees a different pattern and changes our view or knowledge becomes unimportant and superceded in the light of later developments. The best description about all this is, it's "tea leaves" even as some remain driven in the face of it.

[lomapaseo]

For those driven by knowing and positing, ...how the airplane ended up like this, how the wreckage rests and the what the relations are between the location of parts are important because sense can be made of seeming chaos and seemingly unimportant small details. But the tiny flashlight we are forced in total darkness to use means the details can be argued until someone inevitably sees a different pattern and changes our view or knowledge becomes unimportant and superceded in the light of later developments. The best description about all this is, it's "tea leaves" even as some remain driven in the face of it.

PJ2

I'm not sure that I see what detail of the latest pics is necessary to understand vs what is fun to explore on a discussion board.

So far what I see is confirmation of what the BEA said initially about how the aircraft hit. Of course even before they released that info some of us had deduced that from the recovered wrechage photos

The clock positions of the damage to the major case behind the fan (with the struts) viewing both engines would both confirm if the engines were both attached (same wreckage area) and what roll angle the wings were in. Views of the inlet cowls on the bottom would also both confirm this as well as the pitch.

So far an awful lot of what we see fits nicely into Occams razor of a flat impact per the BEA. If there is some other theory I haven't seen anything in the latest pics that points to this.

[Machinbird]

Machinbird, thanks once again. My experience in this subject is limited and I hope I don't sound presumptious.

At the moment, I have a mental vision of how the aircraft reached the bottom scattered as it is. All I can do is explain the concept as best I can until someone with a better understanding comes along and blows my mental construct out of the water. Like some of the others on this forum, I've kicked the tin remaining from an accident and tried to interpret the meaning of the damage patterns. There are always surprises to be found. But one consistent fact is that the impact energy is passed through the structure in interesting ways and almost nothing escapes some form of damage.
So if I have presumed too much myself, please be kind as you explain the error of my ways.

[mm43]

Current v Object terminal velocity

For what it is worth (IMHO), I wouldn't go getting too "excited" by the bottom spread. There are four important factors that have helped each independent part of the debris to arrive where it has. They are:-

• Current profile, i.e. vector and velocity at different depths.
• Object profile and terminal velocity.
• Distance, i.e. depth of water.
• Time.

Generally, those items with low density and poor hydrodynamic profiles will have taken the longest time to reach the bottom, and those with the highest density and best hydrodynamic profiles will be the fastest. The observed debris pattern would suggest that the overall current vector was about 270°T, and as the aircraft has impacted with a high AoA and high rate of descent, its residual horizontal momentum was arrested in less than 10 meters. It could further be deduced from the sidescan sonar image that those objects located to the east (right) of center arrived on the bottom first, probably with the exception of the eastern most outlier. The remaining objects heading west now fit into a low density/poor profile category and are the stragglers.

As for the outliers, their positions will ultimately come down to what happened as the aircraft broke up, and whether their profiles gave them the opportunity to "kite" off rather than "spiraling/spinning" to the bottom.

We all think we know what air is, and likewise water. As simple as water may seem, its structure has properties that are anomalous when compared with other liquids.

London South Bank University - Structure of Water

[PJ2]

lomapaseo;

Of course, you're right...I just didn't want to use the term 'fun' but for those who take to puzzle-solving and examining "the trace", even ones with serious and tragic origins, it is, (as I observed), "what we do", so to speak. The other aspect of this is the discussion itself, in public, which is often helpful for those who may be affected or who are seriously curious about the how and why, even if the general facts within Occam's famous notion are known but who may not ordinarily see or even take part in such a discussion. The thread is among the best in a number of excellent threads on PPrUne and for me, is the singular, fundamental value of such a place. And then there are those who live in JB-land...aiyaiyai...