AF 447 Search to resume (part2)

[Chris Scott]

Where is the THS?

Tubby,

Since you first commented on absence of a THS label on the BEA image, I've mowed my lawns and had dinner. And still no response... The THS, one of the key players in this matter, is conspicuous by its absence.

This is my first "take" on the labelled debris. If one makes the tentative assumption that the engines, APU and (perhaps) THS screw-jack are the closest to where they were at the sea-level impact point, that the aeroplane did not bounce, that the large parts became detached from each other within a second, and that the under-surface currents had more time to displace the low-density parts than the dense; there seem to be a number of surprises, plus some confirmations.

(1) Position of the L/H MLG with wing section: about 130m to the ENE, whereas nearly all other debris are between SW and west. If the attached wing included the L/H inner fuel tank, could the assembly have floated for a while, drifting and/or sailing away? In the case of the R/H MLG, the photo published by the BEA on 4th April (Phase 4) may indicate rupture of the inner fuel tank: possibly leading to its sinking sooner, if not immediately.
(2) The close proximity of FDR memory-module (and complete CVR unit) to the APU and THS screw-jack seems to reflect their high density, unlike the FDR chassis.
(3) The two items marked as engine fan-casings are not labelled with their engine numbers, and their positions are not easily explained. Looking at the position of the APU in relation to Engine#1, I'm wondering (like OleOle) if the aircraft heading and track might have been very roughly ESE. If the engines had not detached simultaneously, #1 might have dug-in first, while the #2 might have become detached while partly out of the water. The engines may have been at a high N1 at impact, and the fans have a lot of momentum. Could the fan have detached and flown forward, I wonder, taking its fan casing with it?
Turbine_D, would the fan casings have any tendency to float?
(4) Where is the THS? It doesn't look to be with the rear fuselage section in the WSW. The APU is mounted behind it, its screw-jack at its front, and the DFDR just in front of that.
(5) What does "double seat" mean: cabin-crew jump-seat, or pair of passenger seats?
(6) What are the other medium/large items to the WNW and WSW of the engines?

[Mr Optimistic]

Presume the inflated tyres would have led the attached structures to deviate somewhat, at least at shallow depths.

[HazelNuts39]

Originally Posted by mm43

published data leads me to believe the low bank angle was to port

You and other posters may well be right on this. Nevertheless, for the record, I recall that many months ago, when we were discussing the way the V/S separated from the fuselage, taking into account that it departed with a slight twist to port, I argued that this must have been due to the fuselage yawing to starboard, which would mean starboard wing low. Les likely, but possible, is that the impact occurred with wings level and some sideslip to starboard. Let's just wait for the data. Of academic interest anyway.

[Mr Optimistic]

The numbers associated with the engines: are these confirmed as identifying port and stbd. ?

[tubby linton]

Chris Scott some interesting questions are raised in your latest post and unfortunately I do not have any information to answer them. I would be looking for the THS trying to see what angle it was set at to give me a clue to the aircraft's pitch and depending on how much fuel it contained the aircraft cg.
When I looked at the Ethiopian 767 crash I wad struck by how easily the aircraft disintigrated and how the pieces were scattered,many in a random direction in comparison to the original direction of flight This crash happened in daylight in a conventional aircaft that was servicable apart from both engines being flamed out due to fuel starvation. The crew would have mentally prepared themselves for flying a glider with an associated ditching having spent some time trying to convince the hijackers that they did not have sufficient fuel to reach the hijackers intended destination. I believe there was a last minute loss of control was due to a struggle between the hijackers and the pilots.

Contrast this with the AF crew who seem to have been rapidly confronted
with their situation and their demise within minutes of whatever happened at night over a very dark sea

[RR_NDB]

Similar bending of both recorder chassis

Hi,

Question: Are they installed adjacent and with the same orientation? CSMUīs to the front and chassis box to the rear of a/c

If so, the similar bending may explain one "strange" fact at debris field.

[RR_NDB]

Where is the THS?

Chris,

that the aeroplane did not bounce

The bending of both recorder chassis may indicate a bounce of the a/c rear section.

THS (with tanks) could be resting far from main debris field. Light but submersible. Capable to travel farther.

[Machinbird]

HN39

You and other posters may well be right on this. Nevertheless, for the record, I recall that many months ago, when we were discussing the way the V/S separated from the fuselage, taking into account that it departed with a slight twist to port

BEA stated in their preliminary accident report:

The distortions of the frames showed that they broke during a forward motion with a slight twisting component towards the left.

Question, does anyone know for sure what type of twisting component they were talking about? Was the top of the tail twisted toward the port side of the aircraft, or was the leading edge slightly more displaced to the port side than the trailing edge as the VS separated?
And then of course, this was the translated version from the original French.

[mm43]

RR_NDB;

Are they installed adjacent and with the same orientation? CSMUīs to the front and chassis box to the rear of a/c

The SSFDR is installed 2 frames aft of the rear pressure bulkhead and the SSCVR is installed 2 frames forward of the aft L/H door. Both are installed with the interface box facing forward and the CSMU aft. The BEA has published details of their placement, and a search of their website will provide you with the documentation.

[Chris Scott]

Mr Optimistic,

Think we have to assume that, in the conventional notation: #1 = L/H and #2 = R/H. It would be very unkind of the BEA to label them otherwise. (Even if, in Phase 4, the R/H eng had been found first!)

RR_NDB,

Re the THS, I think you make a very strong point about the tank and its possible buoyancy. Maybe it has even washed ashore somewhere...
However, I seem to remember posting that, just as tubby linton says, its tank would have been full of fuel. But the S.G. of the fuel is only 0.8.

[Turbine D]

Chris Scott,

Your quote : Turbine_D, would the fan casings have any tendency to float?

Potentially, at least for a short time. It would depend on the damage. The reason for saying this is the aluminum honeycomb structure sandwiched between the 360° dry kevlar wrap and layer of 360° graphic epoxy and the aluminum inner case (next to the fan blade tips). If the structure stayed partially together for a portion of the circumference, it should at least drift before descending to the sea floor. One engine may be different from the other in terms of damage to this structure.

The vertical impact of photographed retrieved engine was so great, and the kevlar is so strong, I think the fan rotor stopped rotating immediately upon impact as the fan disc was sheared from the shaft. I am thinking that 2/3rd of the fan blades were crushed upon impact. I say this because if anything, fans when free tend to come out forward and the structure forward of the fan was also probably crushed upon impact..

It will be interesting to see how the kevlar wrap survived, it will tell a lot of what happened on impact.

[Chris Scott]

Turbine_D,

Thanks re possible temporary buoyancy of fan casings.

Forgive me: did we only see the state of one of the engines (absence of fan rotor + most of the guide vanes), and not the other? I really can't remember. My proposal is that, as mm43 also suggested, the #1 "dug in", and the #2 didn't immediately.

[Mr Optimistic]

Thanks, but is it that straightforward to identify which is which ? The idea that a current did the sorting and filtering looks difficult if the fan casing positions are compared with teh engine locations: there is no consistency. Think there must have been more to the impact sequence than a belly flop. Also, an impact capable of chewing up the fuselage as shown by the debris is capable of breaking the structure into separate parts which then have their own impacts after a short travel of their own. Presumably something like that is necessary to explain how the galley structures etc 'escaped'. For example, it looks like the cockpit stayed in one piece until a rough impact with the sea bed.

[RR_NDB]

From a french forum .......

A340?

Inverted flight?

Beautiful drawings...

We may ask them where are engines #1 an 4 in their model

[AlphaZuluRomeo]

@ jcjeant (post #1268)

Don't you think the red arrow (that I assume seeks to represent the aircraft orientation/"heading") should be reversed (same issue for the plane silhouette, by the way) ?
The right MLG/wing wreckage is linked to the left one on te plane silhouette, and vice versa.
Same issue with the engines, assuming that the BEA used "#1" for the port engine, and "#2" for the starboard one.

[edit] could you please say / link to the forum from where those images are sourced?

[Chris Scott]

jcjeant,

Thanks for the debris-field pictures from a French forum, which seem to be much sharper than I can get from the BEA website.

Like RR_NDB, I could only follow their interpretation it if the aircraft was flying inverted, which they may not have intended to suggest. They also seem to be treating the debris-spread as if the aeroplane had crashed on soft earth: allowing all the lighter parts to continue forwards, but the heavy/dense parts to dig-in. Do you see what I mean?

[jcjeant]

Hi,

[edit] could you please say / link to the forum from where those images are sourced?

WWW.CRASH-AERIEN.AERO • Afficher le sujet - Air France AF447 : La recherche des boites noires (Partie 4)

[Turbine D]

Engine Casing Locations

Mr Optimistic,

If my theory is correct that the potential buoyancy of the fan casing is because of the sandwiched honeycomb structure, the odd location of each may be due to the amount of damage to one verses the other. The one with the most damage would sink to the sea floor more rapidly than one with lesser damage. Just my thoughts at this point in time.

[CogSim]

debris distribution

Thanks to takata for posting the labeled picture of the debris field. I think the significance of distribution of debris is in trying to speculate the energy state of the a/c. More specifically, how the a/c chose to shed the energy. I realize trying to figure this out is like reading tea leaves, but I wanted to share my views.

Lets look at the debris by clustering like parts. Given a wings level impact, with high vertical and relatively low horizontal velocities, one would expect roughly similar parts of the debris to exhibit a rough symmetry in their distribution.

Let me explain. I think it is a reasonable assumption that the debris sunk relatively quickly. So, given roughly symmetrical forces acting on a/c at impact (given BEA impact profile), and assuming no major shifts in currents from impact on the surface to impact on the sea bed, I found the distribution a bit odd.

Lets pair up some parts:

a. Engine#1, Engine#2
b. Left MLG/WNG section, Right MLG/WNG section
c. Rear fuselage section, Forward fuselage section

Here are the things that look out of place:

1. Left MLG seems to have moved "forward" from Engine#1 whereas Right MLG seems to have moved "backward" from Engine#2

2. If you draw a line connecting both the fuselage sections and another line connecting the MLG/WNG sections, they are roughly parallel. I'd have expected them to be roughly perpendicular.

Just a lowly SP thinking out loud...

[RR_NDB]

THS

PJ2,

There would be nothing left to float given the nature of the impact

Right!

2T+2T inside light and flat structures impacting nearly parallel to surface, very probably make it break in pieces and itīs remains IMO, floats. Thus explaining why not found.

Approximately thirty pieces are external parts of the plane (vertical stabiliser,
pieces of the radome, the engine cowl, the under belly fairing, the flap
actuator fairing, the trimmable horizontal stabiliser and the secondary control
surfaces).

BEA f-cp090601e1.en page 39