takata #1216

Jackscrew, APU, FDR, CVR. etc. very tight zone, and an unmarked piece that looks like the THS right in there, a bit longer than an engine in length, (it should be almost thrice as long if intact), and one cannot disregard what looks like a substantial amount of smaller debris in the area of the identified contents of the tail. As large as the piece appears, it looks like it deserves some ID, as the cockpit parts are likewise bunched, and labelled ?? The main spar(s) of the THS would be almost as stout as the main spar of the wings, so I'm not sure the THS would completely disappear. Like the wings, the strongest parts (to include the box) would remain.

Engine Photos
 

Chris,

The original photos (two) taken on the sea bed are of the same engine, slightly different angle of the photos, one to the other, IMO.

The photo of the engine being hoisted aboard ship is the other engine, not the one on the sea bed, IMO. The notable difference appears in the area of the LPT case. The one on the sea bed appears to have the rear part of the case missing exposing the last stage or stages of turbine blades. The one on board ship has a rather intact LPT case with major damage only to the turbine rear frame from the photographed area.

If she was rotating (either direction), and had not enough D/S to keep from occasionally "falling" tail first, the tail would have dug in with its APU first, shed the VS, and then lost engines as the forward fuselage "flipped" over the top, the cockpit describing a large arc over the Wing center box to plant behind the engines. This means a heading at impact of ENE, and accounts for the position of all the parts, odd though it may sound....To be correct, this would need BEA's aspect at impact. it also requires more than a little horizontal and less vertical.

Strange location of some pieces on debris field
 

Bear,

Another model:

Sea currents dragging to W the light pieces, the bigger (not denser) and the ones with "water braking shape"

This can explain strange location of some parts.

But there are some other exceptions: APU, boxes, THS jackscrew. For this i could imagine rear section of a/c passing over the fuselage. 1)"bouncing" 2) breaking frames due APU mass and THS fuel and "falling" ahead.

For LH MLG/wing parts i have another hypothesis when this wing broke wit a/c tail yaw to port.

Conjectures...


Edit#1:

Both MLG traveled farther due it´s inertia and some aerodynamic due parts of wing still attached. This could explain location of both MLG. The LH aligned with fuselage and RH farther to south with "distorted trajectory" due a/c yaw and perhaps RH wing "ground effect" air disturbance.

Obs. The debris shape IMO is mostly due sea currents. With the coincidence of a/c with near the same trajectory (with also about the same heading when impacted water) tail yawing to port side.

This explaination occured me. If she was rotating, heading at impact becomes purely coincidental. Also, for the cockpit to describe the arc you are suggesting we would be talking pretty significant torque from the rotation.

auv-ee, gee, thanks for the numbers. They strongly suggest the 1700 meters range quote would be extraordinarily conservative. We start with 160.5 dBpa* at 1 meter and end at 30 dBps (18dBpa + some serious margin). That's 130dB of attenuation needed. Apparently we can expect 10dB from the properties of water. So that's a million to 1 range distance ratio before it's not detectable. Somehow I do not think the surface falls outside a thousand km from the emitter since the depth is single digit km.

3900 meters to 300 meters is 3600 meters. Call it 4000 meters and allow some modestly generous slant range. (That's nearly 2000 meters wide swath at the surface. 888*2 actually.) That would be 72dB loss or a level of about 88dBps looking at a 30dBpa threshold. Somehow a nearly 60 dB above threshold signal should blow the sonar operator out of his seat if he could hear it.

So unless somebody introduces new loss sources I withdraw my comments about the submarine not having a chance of hearing the pingers. And I start wondering what in heck happened to them that they BOTH failed to work.

At the risk of becoming very unpopular here this cyberunit wonders if there even IS thinking present at all. There must be as the postings are at least grammatical.

Lemurian - consider also currents encountered during sinking and random walk spreading as the lighter debris settles. You MIGHT be able to draw some rough conclusions if you assume heavy items sank near straight down. But that's not even accurate. If the plane was making headway, even something modest like 60 mph (statute) then a one second difference in time the engines broke loose would lead to an 88' difference in starting point. And indications are that one wing was lower than the other in addition to the indications of at least a small amount of horizontal velocity component.

If one wing was lower that wing's engine would strike early, toss the plane around a bit, alter the horizontal velocity component of the second engine which then breaks away when it strikes the water.

<shrug> It's all not quite random. But there are too many variables to say much of anything other than that the plane seems to have broken up semi-symmetrically. That maybe supports the presumed attitude upon striking the surface.

The field is so concentrated that the currents weren't very strong, were they ?
On another thread, someone posited that two items, one sinking to the bottom in 15 minutes, the other taking 30 mins, in a ONE KNOT CURRENT, they will be separated by 1500 ft at their resting places.
That figure is strikingly close to the dimensions of the debris field, don't you agree ?
Of course I would think that quite a few pieces would have *drifted*,falling leaves-style to tha bottom, hence the *random* pattern we could observe.

Of course I might be all wrong.

Pour on s'amuser avant le déluge imminent...
 

Lemurian,

Notwithstanding JD-EE's and PJ2's slightly gloomy, if realistic, comment above, I think we should continue our speculative discussions right up to the eagerly-anticipated dénouement. "Too many variables" and "too many unknowns" have not discouraged the PPRuNe population (PJ2 included) from two years of almost uninterrupted proposals and counter-proposals.

Don't suppose I'm the only one to have learned an enormous amount from the fascinating and informative contributions of the many knowledgeable, intelligent forum-ites here (bearfoil not excepted), and the cut and thrust of argument has always concentrated the mind.

At this stage, we have suddenly received a bigger averse of data than anything since July 2009. It would be against the spirit of this forum for us to be overawed by the imminent prospect of a déluge of data from the recorders. This promises to trash most of our cherished theories, but that does not necessarily discredit their validity as hypotheses. The post-result learning process will have more relevance and immediacy for us if we shall have kept pushing on to the very last.

Happy holiday, PJ2! :cool:

From some pages ago:The outer fan frame is a part of the engine, and yes, the fadecs are mounted on those sections.

Pinger detection range
 

JD-EE:

I don't see where you accounted for either the spreading loss of the signal or the noise summed over the whole detection filter band (at least 100Hz). Remember that the noise figures I quoted are 1/sqrt(Hz). I refer you back to my original post on this topic (in fact, my first post on this forum):

http://www.pprune.org/5683946-post951.html

Given that Urick lists the noise at 37kHz, deep, as being between 18 and 42db re 1uPa/sqrt(Hz) for sea-states 0-6, I may have picked a little too much noise for my example, at 37db, but no less than 33db would be the right number. I don't think the 18db conditions are common; even sea-state 1 brings the noise to 25db.

Note also, in the case of the submarine (assuming, as I do, that it did not tow a deep array), that it is in shallower water, where its local noise may be a somewhat higher. Urick, first ed., shows little change in amplitude unless within a few hundred meters of the surface, but the only data are for 3kHz and below, so I don't know about 37kHz.

JD-EE

Poser for you. The BEA description of the a/c's aspect at impact also describes a common aeronautical manouver. Do you know which one?? In deference to those who have not ruled out controlled flight, It is an attitude that allows an a/c to dump altitude rapidly and very safely. Perhaps if the pilots had reached desperation, and the weather could not be escaped either up and over, or around, they chose to descend below the monster ?? Without an altitude or airspeed to rely on, they may have gambled that they were higher than they were, and were still in aerodynamic flight, and ran out of airspace in the darkness and madness of the moment ??

This is consistent (strictly so) with BEA's theory. Left wing low, Nose right, rapid altitude loss.

Give it a go ??

It's not : Too much sideways velocity, deceleration of which doesn't match the BEA theory of fin detachment..
Another go ?

Crabbing her in an extreme side slip?

van Horck

Not a crab

Lemurian

Captain, this is for non pilots, no cheating. It actually helps the BEA's theory, as it gives the VS a more forward view at impact, solidifying the "pulled out" postulate. It also gives the fuselage a chance to rupture longitudinally, giving up the less damaged "components" to deposit past the Debris field.

also in range are sinking times between ca. 10 an 60 min (600s-3600s) for falling a vertical distanc of 4000m in water, and a deap water currend with only 0,20 m/s (0.4 kn)......

the deapwater currend with this low speed then flow very laminar! and even the heavy debris need his time to reach this deapness.... as we tried to calculatet here before 4 weeks

Bearfoil, it is a maneuver one might do in a no flap aircraft, and it is not an element of ladies apparel (hint). At the same time, the maneuver is not one used in jet aircraft for any practical purpose except perhaps a U-2. Good game.;)

Looking at the debris field it seems to me possibly the aircraft impacted the ocean inverted....?

gentlemen, if you go back a year yesterday to afriqiyah airways in tripoli the debris field was a pretty well jumbled up mess on hard sand iirc so its possible that this a/c could have been as that one for a second or two on the surface so that would explain the extra jumbled up mess on the seabed.

Presumably the injuries to the unfortunate victims would be rather obviously different if that were so.... and to date I have seen nothing that suggests an inverted impact at least initially - though that doesn't necessarily rule out some secondary tumbling I suppose.

About "From a french forum ......."
 

Re. the drawings copied by jcjeant from a thread on WWW.CRASH-AERIEN.AERO: some people on crash-aerien seem to elaborate on these pictures, so before someone does the same on PPRuNe, it is probably worth precising that as far as I understand, they have been realized by the poster (dreamy) using an Autocad station, and do not originate from BEA. Only the background image showing the debris field is BEA's work.

So we probably can't infer anything from the eastern position of the plane on these images or from the big red arrow suggesting an east-west trajectory at impact time. :=

Looking at the damage we can safely exclude that.
It is one of the few things we can definitely say did not happen.
=> Damage to lower half of engines, damage to lower half of Nose, flattened Crew Rest Module, etc. pp.

I have no idea where this fixation on an orientation E -> W comes from.
Looking at the typical drift speeds, and the time it takes for the debris to sink 4000m to the bottom it is absoultely logical to expect a debris spread like we see here simply due to water currents.
If the aircraft impacted in a way similar to that described by BEA it is very unlikely parts continued for much more than 50 or maybe 100m after impact.
I tend to assume that orientation during impact was not N-S due to this but even that can not be completely ruled out.

If I would have to put my 5$ on an orientation it would probably be something W -> E i.e. between NW -> SE and SW -> NE.

The significant separation of the MLG + Wing parts I attribute to 'helicoptering' and underwater 'flying' down of those parts due to the attached Wing elements. Wings work well underwater too, admirably for that matter.

Don't forget the bouyancy of the tyres too. East to West ? Probably because the a/c at some stage earlier was east of its found position and the general cockpit stuff at the west end and the early-leavers stuff (engines, wings) at the east end. Does it mean anything ? Dunno, but I would put my £1 on it with some thought I may have lost it !

Does it make any difference; probably not. Sheds no light on the factors which initiated the event nor the factors which prevented recovery. The FDR and CVR will be needed for each of those. However what is the alternative, to wait for the final report in silence ? Not many people are good at that, and none here I would suggest !

Engines stall during "the manoeuver"
 

Hi,

In direct law, right?

What happens if engines, one or both, stall before alt to reduce "climb" rate?

The hypothesis of this desperate manoeuver (for a heavy airliner) matches pretty well many discussed scenarios and some facts.

MLG´s far
 

Henra,

Good model! Ok for the one at South (the one we suppose to be RH MLG)

For this one i imagined the right wing disintegrating, bouncing and being affected by air disturbance just after the impact.

But is a coherent model with the other (the one we suppose to be LH MLG) in presence of the (very light) sea currents?

I suggest people give up trying to work out how it hit the water based only on the wreckage pattern.

Take a look at the vids for the Ethiopian Airlines Flight 961 water "landing". Bits ended up scattered every which way. Now imagine they don't all sink at once and they have thousands of feet to descend. Unless you knew what happened I very much doubt you could work out how it impacted the water from just the wreckage pattern on the sea bed.

Likewise the Titanic. The main part of the ship ended up facing north but not many people think it was steaming due north when it sank.

RR_NDB
 

I think this is an good observation. We may find this to be very close to what actually happened, when the recorders start talking...

Seabed debris pattern
 

cwatters,

When trying to model without solid and redundant evidences you are in a risky area.

Time to concentrate in other aspects. It was an exercise and i finished yet.

Only one conclusion: The existence of light sea currents (combination at many sea levels)

For me it will be a surprise if a/c trajectory (heading) was the one we modeled.

I am not killing the model. Just saying it´s chances are low because the global picture is much more complex and we don´t have enough info. But there are chances.

This crash is unique and can not be compared with others like 961 or Titanic in respect to seabed debris. We supposed in modeling almost instantaneous "stop" as per BEA info.

Braced for impact
 

Didn't the Brazilian coroner report (some?, all?) victims were found in the brace position. Any independent confirmation of this from BEA?

CogSim, as I recall the description by the coroner in the New York Times article, the fractures were consistent with an individual's upper torso bending forward to something similar to the brace position, and then being flung backward with arms upraised.

Hi,

I think those researches and speculations about the trajectory at impact can be like the game "wheel of fortune" :rolleyes:

injuries
 

Indeed. Thanks for the correction.

From The Times' article:
It is phrased weirdly. I took the "they were like this" to mean the bodies. Obviously, he is reconstructing the position at impact from the injuries.

Flying wing down top rudder to lose altitude in delebirately out of balanced flight while on an instrument scan due to ... what reason, bear? I am working from "pilots trying to fly the bloody iron" and forwards in my thinking here, not "working backwards from the iron hitting the sea" perspective.

You can descend in balanced flight using power and pitch, yes?

bear, I appreciate the allusion you make, but it doesn't strike me as that good of an idea in IMC/Tstorm conditions at night. Absent airspeed indication, and with the info I've gleaned from this thread and that other one, the attitude reference system would still indicate wing and pitch information. Set an attitude, power, and then determine if you like how fast your altitude is changing. Adjust as needed to retain a comfortable descent rate, adjusted for the odd up draft and down draft you are subject to whilst in the Tstorm ...

Salute!

Thanks for the nice words, PJ.

All should know that the Viper was the first military jet I know of that had data recorders. Some were cosmic, like those in the commercial jets - about one outta 6 for our first few dozen jets. So we didn't have our video "gun cameras" in those. Bad, as we could not show our "home movies" at the debriefs with the folks we had just embarrassed, heh heh. OTOH, our video gun camera/radar display tapes provided valuable data for the accident boards and many jets and pilots were saved down the road. Amazing how the tapes came thru some brutal crashes, and one shows the end-of-flight right up until ground impact.

When I had the leading edge flap fold up on takeoff, I turned on the tape once I had reasonable control of the thing. My intent was to have good stuff for the accident board and other pilots whether I had to punch or not:

http://i120.photobucket.com/albums/o.../rightwing.jpg

Our ejection seat had a solid state recorder of a few parameters, and we quickly learned we could not talk our way out of a screw up. Then there were all the boxes with their embedded recorders for maintenance and trouble-shooting.

With all the talk obout the debris field, I must remind folks that the plane was not built for more than 5 gees or so. Seems I have seen various reports estimate the impact gees over 100!!! So no mystery why the big pieces are so "small". I am amazed that the motors are almost side by side and a few other pieces resemble their "normal" positons.

My biggest fear is that the crew will be blamed for something they could not control. But that's the way it is, huh?

Debris distribution
 

Some ideas based on MIT and US Navy studies on understanding the dynamics of three-dimensional objects freely falling through water.

As a crude rule of thumb, objects with a centre of mass offset from the centre of volume will tend to behave as follows:

Small offset: flutter, see-saw oscillations, tend to horizontally aligned during descent.

Medium offset: plane away from the vertical dependant on degree of offset.

Large offset: near vertical descent in direction of heavy end of object - will usually flip once on first entry if CM is above CV at entry.

Aspect ratio will influence drag and stability, eg an elongated shape will have a different cd falling on the long dimension than end on. Tumbling motion is also observed for objects with small aspect ratios.

Heavy compact objects, for example rocks, when falling freely in water show a variety of characteristic motion patterns determined by their shape. An object might rotate around a single axis, which continuously shifts its spatial position, or develop a single-axis rotation where it rotates around the longest axis, which usually remains perpendicular to the direction of flow.

For a rotating object, the trajectory will be influenced by the direction of rotation and the angular momentum.

Given the above, is there anything we can say about the heavy bits.

Engines: Heavy and compact, and likely to fall near to the vertical.
Unknowns: Nature of attitude at impact - was there any momentum in the shaft which could possibly result in the whole structure rotating once free in the event that the shaft seized and as a consequence influencing the trajectory - possibility of tumble if initial condition CM>CV.

APU: Heavy and compact, so likely to fall near to the vertical.
Unknowns: At what point did it become detached from associated structure and enter free fall.

What else?

FDR: Not heavy, but compact cylindrical shape (missing ULB) and likely to have CV close to CM, so good candidate for vertical descent.

Unknowns: At what point did the FDR cylinder separate from the empennage before free fall.


Conclusion: Too many unknowns....

Coherent or random?
 

Indeed! The debris shows two clear characteristics:

1) LH MLG and eng #1 at one side and it´s counterparts in the other side(*)

2) Debris trail concentrated indicating a light sea current

But positions of APU, THS j/s, distance of MLG´s requires big "effort" to be understood.

* If eng #1 (in the BEA chart) is the a/c eng #1

Anyway we tried and now there is no longer reasons to continue thinking about this pattern.

And no small chances to be a random pattern.

'Bus Drivers
 

Quote from gums:
P.S. I have gained more knowledge from the "bus" drivers here than I ever expected. A very impressive group of folks here.

On behalf of them: thank you, kind Sir. Just like yourself and all flyers, we love the aircraft we're on (or were on!).

Just to continue on a point of academic interest: The original French text (BEA's 1st report) is:
I believe it has been correctly translated. It refers to the S-shaped deformation observed in frames 84 - 87, illustrated again in the 2nd report.

In my post #1143 (p.58) I wrote:
That is correct if the indicated airspeed is correct. If the pitots freeze and IAS drops to a low value, it's quite another story. But that is too many if's, I suppose, just like Machinbird's famous 'pressure cooker', that still intrigues me.