AF 447 Search to resume (part2)

[GarageYears]

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

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.

[JPI33600]

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.

[henra]

Originally Posted by Octane

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

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.

[Mr Optimistic]

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 !

[RR_NDB]

Engines stall during "the manoeuver"

Hi,

Left wing low, Nose right, rapid altitude loss

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.

[RR_NDB]

MLG´s far

Henra,

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.

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?

[cwatters]

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.

[CogSim]

RR_NDB

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.

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

[RR_NDB]

Seabed debris pattern

cwatters,

I very much doubt you could work out how it impacted the water from just the wreckage pattern on the sea bed

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

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

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.

[CogSim]

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?

[SaturnV]

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.

[jcjeant]

Hi,

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

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

[CogSim]

injuries

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.

Indeed. Thanks for the correction.

From The Times' article:

He leaned forward in his seat and wrapped his arms around his knees. “They were like this,” he said, holding the crash position and looking into my eyes. Then he sat up quickly and held his hand flat above the table. “When they hit,” he said, slamming it down, “fractures.

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.

[Lonewolf_50]

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 ...

[gums]

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:



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?

[BJ-ENG]

Debris distribution

Too many variables. Too many unknowns

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....

[RR_NDB]

Coherent or random?

I am amazed that the motors are almost side by side and a few other pieces resemble their "normal" posiitons.

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.

[Chris Scott]

'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!).

[HazelNuts39]

Just to continue on a point of academic interest:

Originally Posted by Machinbird #1269 (p.64)

Question, does anyone know for sure what type of twisting component they were talking about? (...) And then of course, this was the translated version from the original French.

The original French text (BEA's 1st report) is:

Les déformations des cadres montrent qu’ils se sont rompus dans un mouvement vers l’avant avec une légère composante en torsion vers la gauche.

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.

[HazelNuts39]

In my post #1143 (p.58) I wrote:

If alpha-prot had been activated prior to reversion to ALT law, and continued to be active after that point, it would maintain AoA at alpha-prot, i.e. it would not lead to deep stall. On the other hand, it may have handed the pilots an aircraft at relatively high AoA, low speed and possibly unusual pitch attitude.

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.