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AF 447 Search to resume

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AF 447 Search to resume

Old 18th Apr 2011, 13:45
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Did anyone see this article? BabelFish translates the heading "Zu hohe psychische Belastung" to "Too high psychological load"

Absturz von AF 447: Kieler Forscher steigen bei Wrack-Bergung aus - SPIEGEL ONLINE - Nachrichten - Wissenschaft
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Old 18th Apr 2011, 14:02
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The engines would probably not tolerate a flat impact without stalling and spooling down ala the A300 at Nagoya
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Old 18th Apr 2011, 14:29
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Originally Posted by henra
While we are at speculating:
...
Any comments ?
Please feel free to challenge/dissect it part by part.
I'm sure you are right that it is significant what happened just before 02:10z - did the auto controls take action on 'bad-data' before disconnecting, was a turn or step-climb in progress etc.

I think you need to revise your timings a bit though to fit in with the detailed ACARS timings - presented in colour here

AF447 ACARS MESSAGES - Color Coded & Interactive Version

Couldn't all the 02:10 messages have been generated early in 02:10, just output in priority order over the next 2 minutes - interrupted only by high priority position report?

The aircraft was clearly in stable enough orientation to stream the messages in with only the occasional missed 6 or 7 second slot until 2:12:16. The BEA identified one missing ACARS that should have been transmitted before 2:15:15, but impact could have been at 2:14:30. A shorter time of fall seems to fit in better with a single stall/ fall rate. Much discussion earlier that true 'flat spins' a feature of T-tail, and 'falling-leaf' delta-wing, still lots of unknowns.
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Old 18th Apr 2011, 14:42
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From the peanut gallery...

Wouldn't the simplest explanation (keeping Mr Occam and his razor in mind) for both engines having lost their entire forward fan sections, including all traces of fan, be that they were singing pretty fast when they hit the water? Also, from the looks of them, near half of both of their remaining fan case sections have been crushed on impact, so I don't think there was much "spooling down" going on... More like sudden stoppage, no?

I've examined the photos and would like to offer my observations...

The wing with the text decals still visible is undoubtedly the left wing.
The wing with gear still attached is definitely the right wing. The pointed bit of structure just inboard of the visible flap track shows some of the plumbing that would indicate where the pylon would have been.
On the left gear, there is a hunk of 'stuff' between the #3 and 4 wheels... It looks like it might be some of the I/B flap track and carriage assembly... which it sort of lives near when the gear is up and locked... Perhaps impact forces allowed for the gear to have ripped this from it's roots on it's way down? Anyway, whatever it is, I'm sure it also has a story to tell...

I too enjoy reading and learning from all of this. Thanks to all of you for the opportunity!
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Old 18th Apr 2011, 14:54
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Originally Posted by sensor_validation
I think you need to revise your timings a bit though to fit in with the detailed ACARS timings - presented in colour here
Yes, the exact timings of the real events related to the ACARS messages that's where I was a bit unsure indeed.
The only thing which seemed reasonable to me was the sequence
Icing -> A/THR /AP lost -> Alt2.
The exact timing may well have been closer together.
so that close to 2:10:05 they were already in Alt2.

Couldn't all the 02:10 messages have been generated early in 02:10, just output in priority order over the next 2 minutes - interrupted only by high priority position report?
Yes, agreed, see above.

The BEA identified one missing ACARS that should have been transmitted before 2:15:15, but impact could have been at 2:14:30. A shorter time of fall seems to fit in better with a single stall/ fall rate.
Agreed that is the second area of uncertainty: It could reasonably have crashed between 2:14:30 and 2:15:15.
I was just on the conservative side, admitting that an earlier impact fits better with the RoD's that can be expected in such a scenario.

I will include the updated timings based on your remarks in my original post.
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Old 18th Apr 2011, 15:46
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henra:
Here comes my scenario which I have in mind based on what we know atm :
2:09:30 Cb with supercooled droplets. Pitots starting to freeze over. 2:10:00 - 2:10:15 Pitot fail, unreliable airspeed. 2:10:15 - 2:10:30 AP A/THR disconnect. (Ovspd induces thrust redux, decel) 2:10:30 - 2:10:45 ADR disagree, Alternate Law 2 2:10:45 - 2:11:30 (significant control inputs not covered by protections => overcontrol => accel stall => wingdrop=> loss of spatial orientation and forced to Unusual Attitude Recovery on instrument scan after stall/upset
2:11:30 - 2:15:00 Aircraft progressively stalled.
henra, my only comment is your supposition of the nose low attitude (20-30 deg nose low) ... which I think you intend to be attitude at impact? (If not, then I misread your post).

I see the crew confronted with three different challenges all at once
1. The stall/upset (agree with your posited wing drop)
2. Stall recovery (3-D) using an IFR scan
3. Unusual attitude recovery on an IFR scan directly related to the stall recovery

I'll add to numbers 2 and 3 (caveat, it may be a load of rubbish if the gyros in the A330 are not prone to tumbling ...)

"these recoveries to be accomplished on instruments with an attitude gyro that has tumbled." (As I was speculating about some posts back.) In other words, a spin (or at least a rotating sort of stall) followed by an unusual attitude recovery, all with a partial panel scan.

There would be an unknown interval of time before the crew recognized that their primary attitude reference is buggered (possibly shown by the PFD reset attempts?) and they are called upon to recover from a 3-D upset using a partial panel scan. Is this trained for? (From my own experience, that particular taks is hard, even when you are ready for it, and in a training environment).

Added to this degree of difficulty is a reasoned belief that for a good portion of the descent, airspeed indications, (primary ref on partial panel scans) are unreliable.

If all I had to rely on to recover from an under the bag spin recovery was turn needle, balance ball, and Vertical speed, I might or might not manage it on the first go. I was trained to use airspeed as a primary reference for partial panel scan.

The aircraft gets to a high RoD ... then airspeed indication finally come back (at lower alt) and the pilots begin to catch up ... maybe unstall again, and then get stuck in a problem of accelerated stall at the end of it all as they 'pull up' (altitude keeps getting smaller in large chunks, one has to break the descent ...). Given "in the goo" scan and possibly disoriented pilots, the plane is in the process of a major pull up (nose at or above horizon) when it restalls yet again, accelerated, and falls ... this time, with no altitude left. (Hence not quite hitting in the nose low attitude you suggest ... )

I base this amplified version of your scenario on a mishap that killed a colleague of mine. He was in a spin or a spiral, went into clouds, and as he came out (finally not in the clouds anymore) was making a major correction to his high rate of descent when he got into an accelerated stall "close to the ground." The eye-witness saw the vapor trails coming off the wings (similar to what you see the Thunderbirds or Blue Angels create in their high G turns at airshows) and reported that he saw the aircraft abruptly controlled flight with little to no altitude left for one last recovery ...

That was a lot of text to suggest why the BEA nose attitude assessment might be spot on, within the general scenario you presented.
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Old 18th Apr 2011, 15:48
  #3627 (permalink)  
 
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Originally Posted by Lonewolf_50
henra:

henra, my only comment is your supposition of the nose low attitude (20-30 deg nose low) ... which I think you intend to be attitude at impact? (If not, then I misread your post).
Hmm, probably my fault.
My assumption was 20-30° Nose up during impact (damage to the lower TE of the fin)
Should have made it more clear, will amend my original post.
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Old 18th Apr 2011, 15:55
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Aha, thanks, then your proposed scenario (high AoA in the end game) seems to match what was in my minds eye pretty closely. (If I read your post incorrectly, apologies).

(By 3-D stall, I meant "a 3-axis upset:" Pitch, roll, yaw)
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Old 18th Apr 2011, 15:57
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Engine damage

@Turbine D

Given only the photos of the engine remains, it is impossible to tell if the engines were operating at high N1, there is nothing to go by at the moment.
Attached is an interesting comparison showing turbine damage on two identical engines, one where most of the blades are broken off about half way between root and tip, operating with some power applied, and another on the same aircraft which, at the time of impact, was stationary or windmilling with little or no power on. Compare this with the two photos of the same engine from AF447, where the rotating blades are missing, apparently torn away at the roots. Another example of a stationary or mild windmilling fan section, is that shown in my previous post where we see just the bottom section of one of TWA800 engines with fan blades bent in both directions away from the point of impact.


PICTURES: BA Boeing 777 Heathrow crash evidence

TWA800 example:

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Old 18th Apr 2011, 16:12
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@ shadoko, aurafleyer

the wing picture just shows a unexpected smal part of the wing, the holder are not between the spoilers they are just between the smaler flaps in front of the spoilers

if I scale the outline of the wing-picture with the holders onto this cutaway, than your red lines follow direkt along the inner part of the middle stringer !!!

the cutaway is on flightglobal.com
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Old 18th Apr 2011, 18:09
  #3631 (permalink)  

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Lone Wolf

Given "in the goo" scan and possibly disoriented pilots, the plane is in the process of a major pull up (nose at or above horizon) when it restalls yet again, accelerated, and falls ... this time, with no altitude left. (Hence not quite hitting in the nose low attitude you suggest ... )
There's another possibility and probably the only one that fits with all the BEA text about vertical acceleration and an attitude comparable to a level flight :
At low altitudes, they recovered all the instruments, checked the descent and were starting to pull out of the descent (dive ? )... they hit the sea surface at the bottom of that recovery curve.
Then you have it all ; centrifugal G forces plus still a downward vertical acceleration, interrupted by the collision with the water, with a lesser longitudinal deceleration which still left important traces.
All the scenarios that involve a stall fail short of the observed attitude published by the BEA.
What I don't know is what law they were in hence whether they could have had a dynamic stall or they just ran out of skyspace.
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Old 18th Apr 2011, 18:18
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Since people are talking quite a bit about a high altitude stall here is a video from the ASB (Australian Safety Board) of a 777 stalling at high altitude due to the computers and AP wrongly using erroneous data from the faulty accelerometers.

.
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Old 18th Apr 2011, 19:52
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Machinbird back at post #3601 made reference to the DFDR flight control inputs trace from an A319 wake turbulence incident investigated by the TSB of Canada.

A enlarged image of the DFDR trace is here
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Old 18th Apr 2011, 19:53
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777 pitch-up incident video

To alph2z :

Now that is chillingly close to the kind of problem I have in mind regarding our thread subject matter, keeping in mind vast differences in design philosophy between the 777 and the 330. Could you please provide a link or reference to the official report ?
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Old 18th Apr 2011, 23:04
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3holelover

I think the problem with the simple solution (Occam's razor) has to do with what lomapaseo pointed out. When there isn't much forward speed, but significant vertical drop speed, inlet distortion comes into play on commercial high by-pass fan engines. The engines become starved of air, stall and flameout during the rapid descent resulting in the spool down situation. Whatever rotational speed is left, it ends at impact. Quite honestly, the vertical speed in this incident, resulted in one of the most significant destruction of a high by-pass engine I have ever seen. Even the TWA 800 engine appeared to suffer less destruction.
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Old 18th Apr 2011, 23:41
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sensor validation, If I am reading Wikipoodle correctly the speed of sound at commercial aircraft altitudes is around 660 MPH or 573 kn. That gives a speed of 7.8 nm/s for .82 Mach. If the plane flew on the entire time the radius would be 31 nm.

Just from ACARS it is pretty clear the plane was not at altitude by the last minute when the cabin pressure indication appeared. Unless the plane was intentionally driven into the ocean at the fastest speed possible without breakup it could not be outside the 31 nm radius. If it was falling, that would indicate, to me at least, that it had stalled. Perhaps some stall recovery could have taken place. However, in a stall my understanding is that the plane is making very little headway with a serious amount of altitude loss.

Admittedly this is in retrospect, basically because I am not a pilot, it seems fairly obvious the plane is not going to be immediately at LKP. And it's probably not going to be much past 4 minutes of flight minus the time it takes for it to fall the full 35000'. You might define an annulus about 5 nm to 15nm. Then erase the part "behind" the LKP. That's a more limited area to search and has the advantage of being the most likely region for the plane to crash. Instead they ass-u-me-d that the plane continued on for a good minute after the last message before deciding to plant itself forcefully into the ocean with small headway compared to vertical speed.

I repeat, what in heck were they doing out there so far from where the plane could possibly get to? (And how-in-'ell could it get 40 nm BEHIND LKP, which they were supposedly ready to search?)

I can buy it that this was ineptitude caused by the intense political pressure, just barely. I am suppressing comments from accident investigators about the reliability of reports. If the accident happens in a third world area, the report quality is poor because of the untrained and inexperienced investigators. If the accident is not politically charged and is in a "first world" nation the reports tend to be pretty good. If politics enters the picture the reports are what the politicians wanted them to say. That's from their experience. I suspect that is what this investigation started out to be. This latest search probably fell out of the unrelenting public oversight and demands. It would not go away. So the plane had to be found. At least that's what I get if I let my cynicism and "too many decades of real world experience" get out of hand. I still expect a political report. But I expect it's going to be as honest as the politicians permit. (And Wikileaks exists as a means of forcing honesty on politicians.)

(As a pair of side notes it has been reported here that the Russians, with (heh) more experience than others with crashes, have found that you start at or near the LKP when searching for crash locations. And I further note that mm43's current backtraces also placed the accident location fairly close to LKP but, if I recall, a bit South of where BEA hinted it actually fell.)
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Old 18th Apr 2011, 23:49
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deSitter, hard desert pan is not ocean water. Reexamine mm43's drawings of how he imagined the plane hit. Note the tail. Think of the tail surfaces. Where is the tail assembly going to go when the tail surfaces hit the water with the rest if the plane trying to force it deeper?

The tail assembly is going to be pushed upwards, distorting it heavily and pretty much pivoting it around a point a little rear of the nose of the tail fin. That fits the damage seen to the leading edge. Pushing it up that way places tremendous strain on the attachment clevises. They break. Tail fin pops off, probably to one side or the other. Back where it lives the only stuff to hit amounts to the elevators and tail cone. Being thrown free of that debris by the combination of the popped clevises releasing hold down pressure on the fin and wind is not nearly a stretch of my imagination.

If it did come off before the plane hit, where is the ACARS message about a massive hydraulics failure? It could NOT have been the precipitating cause of the accident.
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Old 19th Apr 2011, 00:19
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Turbine D

I think the problem with the simple solution (Occam's razor) has to do with what lomapaseo pointed out. When there isn't much forward speed, but significant vertical drop speed, inlet distortion comes into play on commercial high by-pass fan engines. The engines become starved of air, stall and flameout during the rapid descent resulting in the spool down situation. Whatever rotational speed is left, it ends at impact. Quite honestly, the vertical speed in this incident, resulted in one of the most significant destruction of a high by-pass engine I have ever seen. Even the TWA 800 engine appeared to suffer less destruction.
The TWA800 engines and PA103, and etc. etc. all hit the ground/water in free fall terminal velocity relatively flat, shearing the LPT turbine case and last stage turbines away from the rest of the engine. However, that while their fan cases were also sheared away the fan rotosr stayed with the engines and thus the blades were easily visible for examination.

The only thing that seems to be different here is the completely missing (to us) fan disk and blades. No doubt there are lots of other photos that the investigators have to work with so I'm not going to try guessing at their hand
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Old 19th Apr 2011, 00:56
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Might it possible that this was a high speed upset? I think it doubtful that a fully stalled A330 would descend at a much greater rate than 6,000 ft per minute. There is, after all, still some lift being generated even at quite low IAS. The speculated rates of descent in the order of 20,000 fpm are only achievable in steep descent attitudes at high subsonic Mach numbers. The photographs of the left wing section show that a large section of the outboard upper wing surface is missing and broken wing spars can be clearly seen. This kind of damage is often seen when a wing is overstressed in a high speed dive recovery. Of course, such damage might have occured at impact, but it would be interesting to know if those missing outboard wing sections are found with the main wreckage, elsewhere, or not at all.
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Old 19th Apr 2011, 01:09
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svarin

Could you please provide a link or reference to the official report ?
http://www.atsb.gov.au/media/24550/a...503722_001.pdf
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