s-mode data do not show zoom climb: vertical velocity is always negative after initial event

No trim tabs here. It's FBW.

Just big elevators controlled by the ELACs and SECs, two actuators per elevator, one each side is from blue hydraulics and the remaining two are from green and yellow respectively.
ELAC 2 is normally in control, if it fails then ELAC 1 takes over, if it fails then one of the SECs does.

Any GPS readings after the initial event are likely to be unreliable, as I explained in an earlier post http://www.pprune.org/rumours-news/5...ml#post9168602
Both GPS antennae are normally on the top of the fuselage, one over the cockpit and the other a little further back and most usable satellites are above the height of the aircraft. The antenae require direct line-of-sight with no obstruction. With the aircraft tumbling its very likely that that will not be the case for much of the time. This will cause a lot of random spikes as my earlier post explained.

100% "Intriguing. I have put the broken part back in position, but they still make little sense."

Could they be scrape marks from sections of the HS flailing around as the whole assembly tumbles, prior to departure of the two main HS components ?

In previous pics of the HS on the ground, there are numerous strips of composite about the width of the scrapes.

andrasz It was one guy from Smolensk, not me.

@Filler Dent

"No trim tabs here. It's FBW."

The jackscrew is the trim mechanism.

On the idea of the huge variations in vertical speed without corresponding altitude changes: This is fairly easy to explain. (At least possibly)

After the tail separated the plane almost certainly tumbled numerous times. (This also explains the disintegration of the weakened rear fuselage up to the wing box- where it was strong enough to resist the continued failure of the fuselage skin...) As it tumbled roughly around the middle of the now altered CG the nose would have gone through a series of oscillations in quick form. Down at an extreme rate until the nose passed through the vertical facing downward, then up at a fantastic rate while the nose rotated up to the vertical again, before once again beginning the down cycle as it passed through the vertical.

Because the pitot static system is located in the front of the airplane (almost as far forward as it can) the readings would have been way out of whack, and would correspond at least generally to what was seen on the traces.

Finally: A flat spin: This almost certainly did not happen as there was nothing left to induce the adverse yaw necessary to initiate the autorotation required for such a spin. Further the impact shows pretty clearly that the wings were not rotating about the yaw axis in any meaningful way. If one engine failed and the other continued generating thrust it is at least theoretically possible that the airplane could have been forced into a spin, but given the weight and balance of the failed fuselage to that point it is incredibly unlikely that this happened.

Just my .02 as always,
dce

While this would be true in general but the gps data in s-mode also include gps accuracy and the first high g spike (~50g) is recorded while accuracy is still high, the issue here is that we do not have a timestamp at the transmitter but only at the receiver so it is hard to claim accuracy when computing accelerations

Are you sure? A large part of the leading edge of this one appears to missing entirely.

http://www.pprune.org/rumours-news/5...ml#post9174846
(trying to link to picture of the broken HS in FDMII's post #1862)

The VS isn't exactly in good condition either... ?

While the last reported instrumentation readings may not be reliable for directly showing the flight path of the plane, they may still be indirect evidence of it. Assuming (yes, big 'if') that the sensors were still functioning properly, can anyone with knowledge of the plane's systems suggest what gyrations could produce those readings?

Juggling the dimensions, I hope I got it right when I estimate the red arrow to be 94 cms long.

Pasteboard ? Uploaded Image

Hope you can see the picture. It is from the tail fin.

in answer to the questions about the engines.
the damage on the fan blades is not consistant with a blade failure. i have lots of pics to compare against, unfortunately cannot share. IP reasons
if you watch the A380 blade off test on utube around 4:50 you will see the damage being done to the tips of the blades, not very detailed but best there is out there. i was hiding when they filmed that.
damage is ground impact damage.

To whom it's fancy to read a lot of Russian letters - another explanation of cause of tail separation, based on forums investigation.

TLDR: fatigue failure of upper APU section mounts

For me it seems unreasonable that gap in the tail part can be unnoticed for a long time.

Oh nice work boys re the VS and putting it the right way up :ok:


RYFQB I think you were right that there is one further line, partly visible on the original image at least. It appears to be the same distance apart again as the other two are from each other.


I cannot find an image of the internal structure of the VS that shows anything at this particular angle though.


If it was an external object which caused what appears to be paint loss along these lines, I can't for the life of me think what it can have been.

scratches on fin
 

Thanks for doing reconstruction image of tail fin. I had something like that in my mind.
these vertical scratches were not present before crash. And they must have happened in flight.
They are located right over HS trailing edge. Could be marks from departing HS. Note how parallel these scratches look! Same event?
It could mean that forces that made HS to fail were from below, relative to fuselage of course.

@triumph61
 

When you try to make sense of these pictures, the questions with these components are:

a. are they in the place they landed on impact ?

b. or were they lifted or dragged to the side after impact to either get them out of the fire, or get better access to put out the fire, or lifted to search for and recover the victims ?

when a., this could suggest an inflight fire,

when b., this would require checking for dragging marks on the ground, and if not, for a vehicle with a crane with sufficient capacity,

I have not checked the ground or debris for dragging marks (again a better top down view picture would help). But have seen the white vehicle/truck with the 0.5-2.0 ton crane at the back. So lifting and being laid to the side is a clear option.

My impression is - low probability that both the L2 and R2 panels broke away from the fuselage at almost exactly the same time and altitude, and at low altitude (because they are so close together) ... So the burn marks could well have come from being exposed to the fire that destroyed the forward fuselage. And the panels then moved to the side, away from the center of the fuselage.

By the way, this is an example of the fact that investigators have better access to this class of input information.

What you really need to examine are all the fractures. Which is precisely what the investigators will do. Those fractures will tell you the direction of the forces that caused the fracture, and from those you can start to build a picture of which bit broke what.

None of which can be extrapolated from a bunch of photos.

In the mean time (!) here's a very approximate superimposition of the original airframe onto the previous photo:

http://i64.tinypic.com/2mmrur.jpg

@HundredPercentPlease
 

Parallel lines ... rudder departure scratch marks ?

Elevator hinges and THS appear less probable.

This requires measurements.

There is redundant set of actuators, and hinges, and ...

++
Options:
- Rudder 7-point attachment to the fin structure.
- Three rudder actuators - unlikely, too close, for a standalone scenario,
- Structural failure exposing CFRP stiffeners or brackets - might explain the close parallel lines.
- Structural failure exposing GFRP stiffeners or brackets - might explain the close parallel lines.

or a mix of these options,

++++
If you extend these lines downward you stay within the 'envelope' of the plane and reach the tailcone behind the aft firewall of the APU space. However, these components have been found and are unlikely to cause these parallel lines.
So the options you get is either a lower piece of structure breaking out of the VS, and rotating up relative to the VS box, such a part is missing. Or the CFRP strip or rudder departure. In each case you have to put the tail section tail down to get these marks. Which would suggest this is not the immediate cause but a follow up fracture.

++++++
The lower line is at about 12 degrees, the upper at about 15 degrees with the vertical ...

PersonFromPorlock wrote: With regard to the altitude errors I'll add this.
The baro altitude is sensed either side of the aircraft and converted to a digital signal within a few inches of the static ports for the Capt and FOs systems. In normal flight, both sides sense the same static pressure, it's converted to a digital signal and sent to the ADIRUs. The ADIRUs sum this received signal to generate the Capt and FOs altitude. (ADIRU 1 for Capt, ADIRU 2 for FO)

Since the signal is summed a large discrepancy in sensed pressures (or a failed ADM) will cause a corresponding altitude error. ie. If one side sensed 20000' and the other side 10000' the ADIRU would compute 15000' and display that.

I would suggest an airplane horrifically tumbling out of control would most probably generate these errors before electrical power was lost completely.

Different view of the parallel lines.

http://i.imgur.com/mrERkyI.png
http://i.imgur.com/dCsqxVT.png

Investigating a line of thought:

Can you operate the A321 with the APU running in the air to supply a generator (in the case of one generator inop?)

The line of thinking is that if the above is possible, what are the odds a catastrophic failure of the APU causing VS and HS damage to the point of them separating or controlling the steep climb?

How far apart are the rudder attachment fixings on the VS? (anyone got a spare A321 hanging about and could grab a ladder?)


ETA: Looking at Sardak's post I think it's clear there are some more funny camera effects going on, and it isn't paint loss at all, and is related to internal structure as suggested earlier.


Sorry for wasting time.

VS image puncture & scratch marks
 

On the VS image near the bottom left of the blue paint looks like an entry hole, with white paint removed and primer or raw metal showing.

Horizontally above the door the left end of the scratch-like mark coincides with the concave turn in the fuselage yet strangely does not pass across it.

A challenge to discern the causes?

@Yankee Whiskey:

Practically every big jet ever made lacks pitch trim tabs. Instead, they trim by changing the angle of the horizontal stabilizers to the fuselage. That's the function of that jackscrew people keep banging on about...

@susier:

Those parallel scrape marks on the vertical stabilizer are intriguing .... indebted to you for noticing and pointing them out. I struggle to imagine how they came to be, in combination with the stabilizer being so grotesquely fractured.

A0283's notion of the departing rudder makes a lot of sense. But what does it mean, that the slipstream was (presumably) at that angle with respect to the stabilizer? Were the marks made while the vertical stabilizer was still in its normal relation to the aft-most fuselage, or after the fracture?

Whatever story the empennage is trying to tell us, its condition surely bears witness to the intense extremity of the circumstances that ensued once the airframe began its breakup. Dreadful to contemplate.
____________________

Edited to add:

The long parallel scrape marks don't resemble any photographic artifact I am familiar with. I am confident that they accurately indicate the surface condition of the vertical stabilizer. Anyway, they are clearly visible in photographs taken from different perspectives -- the camera didn't make them.

I don't know what the inside of the A321 VS looks like, but typically the internal structural elements are nearly parallel to the long axis of the (tilted aft from vertical in the normal orientation of the VS), and more or less at right angles to that (horizontal in the normal orientation). If an aerostructure isn't built in this manner, it is likely to be needlessly heavy (for a given level of stiffness and ultimate strength). I don't see how it would be structurally efficient to have elements at the angles of the scrape marks.

I have tried and tried, but I am unable to visually correlate the photos recently posted by sardak with the photos showing the long parallel scrapes (which are farther aft in normal orientation, than the area shown in the sardak close-ups).

Has anyone considered the following scenarios:

Explosion destroys Fly By Wire signals to elevator and rudder, causing control surface run away to extreme travels, resulting in structural failure of the empennage due to huge aero loads.

or

Hydraulic lines are severed to elevator and rudder servos, loss of pressure allows the control surfaces to flutter, as they are now not held "stiff" relative to the HS and VS. Remember that these surfaces are not mass balanced, relying on hydraulic actuators to prevent flutter.

Or a combination of the above?

Notice that both elevators and the rudder came off, suggesting flutter. Elevator flutter would also be a reason to lose the HS halves as happened.

The lines can be seen here in this link provided earlier by Mitrosft:


? ???? ? ? ????? ?? ???? ????????... - ???????? ???????

re cvr and fdr
 

#1924 (permalink)

One earlier photo of the CVR was such that the label with a little magnifaction clearly spelled out solid state memory cockpit voice recorder

see

http://www.pprune.org/rumours-news/5...ml#post9168948

note the mangled attach points and a split in the lower orange mounting ' tray'

now look at

http://www.pprune.org/rumours-news/5...ml#post9169622

to determine how and where it was mounted compared to the FDR ( which mounted different but above and with a badly bent ' tray " in the hands of ?? as shown in

http://www.pprune.org/rumours-news/5...ml#post9165152

but no obvious ( in this view ) aluminum colored tray or attached framework.

Which is why I think that same section hit the ground with CVR still ' installed" and was taken away before press access

IMO damage to CVR and FDR was most likely from impact with ground while attached to a heavy object such as HS wing box and jackscrew brackets, etc. :hmm:

Initially on seeing the tailplane missing from the tailcone and the skin below the tailplane ripped out, the most likely explanation seemed the jackscrew parting company with the tailplane leading to the tailplane pivoting down and being torn out by aerodynamic forces.

But we now have both exterior halves of the tailplane with so far no joining structure (likely containing jackscrew and hinge mounts).

Given the abrupt cessation of data to the FDR and CVR, perhaps the same event (explosive or structural) severed data buses and/or hydraulics, pneumatics etc for the flight controls, which then overloaded themselves.

re hydraulic-FBW failures
 

#1949 (permalink)
problem with both electrical and or loss of hydraulic.

Your comment would be correcct IF hydraulic clyinders were directly used to position HS. BUT both systems drive motors which turn the jackscrew

Any cutting of wires or hydraulic lines would simply leave the jackscrew non moveable by rotation, and absent other issues HS would stay in place. :ugh:

I was not referring to the screwjack.

The actuating servos that move the rudder and elevators are FBW and are hydraulically actuated.

Yup, with you - my mistake. I expected the FDR to be a box+cylinder & the CVR to be box+drum - I guess it's all in the length. Looks like FDR on top from Kulverstuka's photo at 996. Thus:

http://newsimg.bbc.co.uk/media/image..._blackboxi.jpg

RE HS and Rudder servo?
 

#1954 (permalink)

RIGHT- MY GOOF re rudder servos- but does HS also use servo elevators on Airbus instead of whole HS ? :confused:

The VS scrape marks aren't visible in this photo.








http://www.pprune.org/rumours-news/5...ml#post9174686

CVRs/FDRs can come in different shapes/sizes. The CVRs I worked with were in standard oblong boxes, same external shape and size as many of the other avionic boxes, except they were painted Yellow/orange. The crash-fire-proof container for the tape (it was a long time ago) was inside. Only the pinger was visible, being mounted outside on the back.

@Orestes:

Interesting! The long parallel marks are not visible at all in the photo to which you linked ... but very clearly visible in more than one photo, including this one from susier.

It seems to me that the crucial difference among these images, is that yours (the one showing no marks) is some combination of the perspective angle, and the position of the sun when the photo was taken.

The images showing the marks have brightly highlighted regions, in which the surface is reflecting the sun toward the camera. The image to which you linked is "flat" in terms of illumination: no strong highlights.

On this basis, my interpretation is that the marks are NOT paint scrapes, but rather contours in the VS skin (presumably furrows, but possibly ridges). This would explain why they don't show under different light angles.

If these are skin contour marks, then I suppose they might be the consequence of either:

(a) object(s) indenting the skin (but not removing the paint) as they flew past

or

(b) wrinkling of the skin, perhaps due to extraordinary deformation under the forces of the calamity

Somehow, (b) seems more probable. I've seen a number of examples of skin wrinkling on old non-pressurized planes, which didn't look anything like the patterns on the VS. But the fuselage skin on those old birds was mainly there to keep the wind out, and the construction of an A321 stabilizer is a world apart.

More so than I realised - this is what threw me (I won't embed the pic because it's 1300px wide):

http://www.fineksaviation.com/images...0all%20FDR.jpg

Second from left is a CVR, third from left is FDR - it's all in the length.

@CONSO:

The jackscrew (moving the entire horizontal stabilizer) makes slow / large changes of pitch moment, essentially for trim.

The hydraulically actuated elevator surfaces make fast / smaller changes of pitch moment for control of airspeed and flight path.

Jet transports have very broad CG limits. They can also experience changes of pitch moments with airspeed variation (mach number effects) and flap operation. For these reasons, they need the gigantic pitch authority provided by the movable HS.

Russian (MAK)--because it was their citizens and their flight.
Egyptian (ECAA)--because it landed in their territory
French (BEA)--because it was their plane.

I assume BEA will mostly be doing consulting. I suspect MAK will lead it if for no other reason than the Egyptians have no technical ability to handle the task. Of course, the last time that happened we had the Flight 990 fiasco...

Irish (2 x AAIU 1 x IAA) - because it was leased from Ireland
I heard about German team also - because of engines.

CVR with explosive decompression
 

Someone asked if an explosive decompression would be heard on the CVR. I think CAL611 is relevant to Metrojet 7K9268. This is an image of it's CVR which was explosive decompression from tailstrike repair metal fatigue.

http://i.imgur.com/osIeoUt.png

SRC:
http://www.fss.aero/accident-reports...2-05-25-TW.pdf

Yeah, there's that which is doubtless making the Russians less than pleased, in terms of what they are looking to deal with as the investigation continues ... :(