There seems to be a slight misconception here about lowering the gear.

You don't normally lower the gear to get the speed down; but you (might) lower the gear to increase the rate of descent in Emerg Descent. I emphasise 'might'.

At low altitude (arriving for landing, say) you might lower the gear earlier than planned if you are a bit high on speed - there was a reference earlier to using gear as airbrakes.

Quite different situations.

One might also consider lowering the gear to get the nose down.

Let's not get into pages of why we put the gear down, eh? We are merely trying to solve CliveL's dilemma about 'lowering the gear if you are to ditch', and I was simply hoping someone could identify from the images whether there were signs of a deliberate extension from jack positions etc. It really is not that important. I think it is fairly evident that ditching might not have been planned from the apparent state of the pax/cabin preparation, and no, CliveL, one would not normally lower the gear in a ditching scenario unless, perhaps a greater over-riding need arose.

To quote PJ2
"Again, when the MLG actually free-fell is immaterial - it did, and it, and its dressings have remained attached to the rear spar and support structure. I think it is more important to rule-in/rule-out the crew extending the gear. It is a debate until the recorders tell us."

Unless someone can tell from the pictures, we will indeed have to wait.

dufc, it may depend on the capabilities of the retrieval ship, on whichever one the government selects. WHOI has several months remaining on its contracted period, so it is not as if they need to rush off to another task.

And WHOI may still be needed. When a Canadian Coast Guard cutter was pulling up a forward cargo door (considered a vital item) from Air India 182, the line snapped as it was about to be hoisted aboard, and the door sank back to the abyss, never to be found again.

I would expect that once retrieval starts, there will be a small flotilla of vessels on the scene, including the French navy, and possibly the Brazilian navy.

Resolution of sonar images
 

The speed of sound in water is approximately 1500 m/s (it varies in important ways with temperature, salinity and pressure, but that is not relevant to this question). The wavelength at 120kHz is thus: 1500m/s / 120kHz = 12.5mm. How many wavelengths across does an object need to be to detect it? That's hard to say, because it depends so much on the reflective and resonant properties of the target. I'm not an expert in this area (same math as radar, so maybe others will contribute), but I would say that 10-100 wavelengths would likely be detectable; so that is roughly 10cm to 1m. That's for detection: having a strong enough echo to detect above the noise and clutter..

Resolution is a different question. Along-track resolution is determined by the beam width of the transducer and the motion of the vehicle between pings. The second is easy: at 600m range, for conventional side-scan, the sound has to travel 1200m to leave the vehicle, reflect from a target and return. With some dead time between pings, that makes about 1 ping/second. In that time the vehicle has moved 2 m, so that will be the best possible along-track resolution (unless the sonar is chirped or uses some other way of getting more sound in the water). I don't know the beam width of the system they are using, but it is likely about 0.5degree; that gives about a 5m wide beam at 600m, so that is another limit. Remember that this is about resolution, not detectability.

The other resolution limit, not usually the controlling limit, is the across-track resolution; that is, in the direction between the target and the vehicle. This is limited by some transducer and wavelength considerations, and also by the number of samples, in time, made of the returning echos. Typically that is between 250 and 2000 (what the eye can see), and so this is easy to make better than the along-track resolution.

The data are commonly displayed as an image built up of scans where each scan is the echo intensity (normalized for range and absorption) as a function of range, or more accurately: time scaled and corrected to represent range. Each scan line is perpendicular to the motion of the vehicle (hence the term "side-scan", the sonar is looking to the port and starboard sides using two separate transducers and receivers).

In the released image, you can see that the vehicle proceeded in an "up" or "down" direction with respect to the image (nearly north or south, note the dark bands under the vehicle where there are no immediate reflections), and that the targets are smeared more in the along-track direction than in the across-track direction. I think that picture is a mosaic of views from both sides of the debris (there is more than one dark "nadir" under the vehicle).

The only thing the side-scan can measure is the time and amplitude (and phase, for some systems) of the returning echos. The colors chosen by the operator to represent the amplitude could be anything. In this case the darker colors represent weaker signals, and the brighter colors represent stronger signals.

Return strength from a target is a very complicated topic. It depends on the material, the internal cavities, the shape, the size the orientation toward the receiver, and many other factors. For this long range phase of the search, they were just looking for targets that did not look like the background everywhere else. While the resolution at 120kHz may not be great, higher frequencies are absorbed by the water and thus the maximum range gets shorter. A 55 gallon oil drum would be a reasonable target to detect using 120kHz at 600m range; it would not be possible to resolve the shape and thus identify this target at that frequency and range, using the side-scan presently installed on these vehicles.

After acquiring the debris field they will have surveyed it with higher ferquency side-scan, at intentionally shorter ranges (better along-track resolution). Of course, by now they will also have about 100,000 photos, most of which will show mud with no A/C parts, but the rest will be interesting.

deSitter:
Hardly a neat separation -- the forged lugs were ripped out from between their forged hoops!

http://i337.photobucket.com/albums/n...dog/Lugs01.jpg

A330 section 19:

http://i337.photobucket.com/albums/n...ction19-01.jpg

Example from A400M:

http://i337.photobucket.com/albums/n...og/Lugs3-1.jpg

The talk regarding composites and AA587 were/are irrelevant to this accident.

auv-ee,

Just to say thanks for that really excellent piece above - I understood all of it (I think)!

takata,

Did I see you and mm43 contributing to that "other place"? Dommage!

Machaca - absolutely superb photos, thank you, - they explain/demonstrate a great deal.

PJ2

Chris,

why do you say I'm wrong when you're emphasising what I said?

While you initially give a rate based on stick displacement, the airplane then holds the commanded attitude (with centered controls!). It hence does NOT behave like an airplane we all learnt to fly on, also the only airplanes we ever had any *real* upset recovery training in.

I rest my case, one should never implement systems which behave differently from what one learnt initially. We had a good example of that in Zurich not too long ago when a Saab 340 stuck it in near vertically shortly after takeoff, the Moldavian pilot had learnt to fly on AH's where the airplane symbol moves rather than the horizon. So he corrected the wrong way for an overbank condition.

Chris Scott,

It was a "shameful" event! But shame on you for looking!

Sometimes a bit of "fact" injected into a nonsense thread will bring it to heel, and I suspect takata will agree.

Machaca... Do you have any photos of the static dissipator tufts on the rudder after the vertical stab was recovered? It appeared in at least one photo during its recovery that several of the tufts were missing. After doing lightning analysis at a major avionics company, I think a possible root cause that should not be ruled out is high altitude lightning. A likely attach point forward could have been near the upper TCAS antenna. If the stroke traveled to the inside of the fuselage, a host of failures could have occurred. I know this is a stretch, but in the NASA F-106 studies that were done decades ago, the energies involved are very large. Recovery of electronic system components will certainly be valuable in the analysis.

Lightning
 

Along that line, Lazerdog, nobody every gave a good explanation for the TCAS Fail in the ACARS message. Everybody just dismissed it as due to the pitot fails.

Again, a pitot fail will not affect the TCAS. A static fail will cause the transponder to revert to essentially Mode A function only, which will cause the TCAS to shut off, not Fail. Three things come to mind for a TCAS Fail:
Processor Fail
Lower TCAS antenna
Upper TCAS antenna

GB

Takata
Perhaps this is stated backwards.
"Why would an upset cause unreliable airspeed indications??", might be a better question.
The answer is in the link below and subsequent discussion.
http://www.pprune.org/6210302-post2647.html

Note: With the discovery of the wreckage virtually under its 2010 position, the case for an immediate loss of control becomes stronger. The key question becomes how can it happen?

I seem to remember that was dealt with by the BEA in Interim Report #2. From memory, the TCAS has an inbuilt function which checks that the static port pressure is valid and that the calculations that result fall within predetermined values. Should the TCAS detect erroneous values, it fails.

I need to check the report for accuracy, but the above is near to it.

Chris, BOAC, let's take a wider view rather than a view immediately local to the MLG.

The belly slaps into the ocean. That provides a sharp dowards jolt to the gear. Perhaps tens of milliseconds later the wing becomes involved near the wing roots. There is a slap on the MLG doors mashing them upwards and likely shattering them. So far nothing has touched the MLG itself except a sharp deceleration. Perhaps it has already broken loose from its uplock and started to descend. At some point the MLG doors, whole or partly shattered touch the MLG. The doors are not nearly strong enough to contain the momentum of the MLG. It simply mashes through the doors or forces them (whole or not) out of the way as momentum pivots it to an extended position. Note that about the time the MLG hits the water the large wing surface is going to slap on the water providing a very sharp deceleration to the wing structure. (I'd not be surprised if the spars folded
up in the middle.) The MLG tries to keep going. The pivot point can't. But the truck and tires end can continue so it all pivots open.

I'd be surprised if the MLG was still neatly stowed. It would indicate a severe (too heavy) over design on the uplocks. I would expect to see a lot of torn and bent materials in this area due to these relative forces.

Mechanical Engineering is not my primary field. But visualizing the sequence simply requires a picture of the plane (Wikipoodle has some) and an ability to think in very small steps. Look at it and try to pretend you're seeing, in your mind's eye, that you are watching an extreme slow motion cutaway picture of the events.

Hi,

When we have the exact location of the wreck .. it will be interesting to compare his position with the position of the vertical tail when discovered
Could there be from those data whether this vertical tail detached on impact or before?
Is the distance between the wreckage and the vertical tail is logic with reference to wind speeds and current in this area?

I thought I had proposed a similar look at the relative forces involved in post #3106, but may be it got overlooked, because I believe that Chris Scott came up with a similar scheme a little later in post #3143.

Oh nuts. That's a line I meant to edit and I posted it too soon. There is no real downward jolt to the wheel. There is a massive upwards jolt to the fuselage which would transfer to the wings as an initial upwards jerk on the hinge assembly and the uplock assembly.

That aside, your comment should not have been glossed over. It is a key to the landing gear down issue. It needs to be looked at step by step with the forces applied to the MLG assembly's various attachment points at least noted if not analyzed.

(Sometimes ya gotta mention things here several times to get them noticed.)

JD-EE

I sometimes prefer to be invisible.:ok:

My vote is that the gear was never lowered, and flaps and slats were also not extended.

And that raises an interesting naif style off topic question.

Presume you have something like an A330 falling like a leaf in some form of level stall with minimal forward velocity. What happens if you could extend flaps on ONE side only. Could that be guided into a new configuration from which escape from the stall would be possible?

I think it would tend to toss the wing with no flap extension downwards. Then the tail would point the nose downwards at a bloody scary angle. But that might allow enough airspeed pickup to allow the plane to get engines started and pull out to level flight.

Altitude and its valid is transmitted on a data bus from the Air Data part of the ADIRU to the transponder. The transponder transmits own altitude on another data bus to the TCAS, and over the air to ATC and other aircraft.

Airspeed is not part of the TCAS calculation. TCAS uses only altitude difference, distance, and rate of closure.

If altitude data is flagged as failed, it does not cause a failure of the transponder or the TCAS. The transponder reverts to Mode A, and the TCAS annunciates OFF.

A TCAS Fail message means the TCAS has failed; it does not mean that it is turned off by an input fail or pilot selection.

It could be possible provided half the assumed current velocity is used. However as pointed out in the past, no one knows or knew at the time what the current was really doing. I am sure that attempts will be made to clarify where and how the V/S and all the other recovered debris made it to where they were found.

The position of the V/S in relation to the bodies found at the same time was reasonable, i.e. the leeway made by the V/S was greater than that of the bodies.

A standardized oceanic search and rescue protocol needs to be established to ensure in future that an initial aerial search doesn't make the same mistakes made with the AF447 accident.

Not disputing any of that, other than in the case of this TCAS, it had a self checking routine that performed a "credibility" test.

From BEA Report #2:
We don't know if normal operation ever resumed. I doubt it.

In post 3120 ( http://www.pprune.org/6355188-post3120.html )there was a detail of some weather overlaid the LKP and a question was asked to Tim Vasques about his interpretation of these colours.

Tim is too busy to follow the thread but his statement about the colours is as follows:

I haven't had time to research the incident since 2009, so I don't have anything to add. I saw your link and the question about colors. The colors shown indicate overall atmospheric radiance in the 10.7 micron infrared window. This would be a measure of cloud top temperature, with the reddest colors the coldest. This has a closer relation to updraft location than it does precipitation intensity, so I would be more prone to estimate turbulence from it than rain, though they will likely be closely associated in the tropics where the atmosphere is weakly sheared.

Tim

Tim produced a magnificent report about the weather conditions which were in place at the time of the accident

TCAS FAULT message
 

BEA Interim Report No.2, 1.6.11.6 Consequences of a drop in the measured total pressure, explains that a sudden drop in measured total pressure entails a sudden drop (300 ft) in indicated altitude, due to the correction of the static pressure.

It would be of interest to know the tolerance of the “credibility” test of the monitoring process internal to the TCAS which applies to the standard altitude parameter. It shouldn't be too difficult for the BEA to get that from the TCAS manufacturer.

Regards,
HN39

Colours on meteosat images
 

For the interested reader there is more information in BEA Report No.1 Appendix 1 and Report No.2 Appendix 3. The first reference has this Note:

Hello ZeeDoktor (re posts #3174 and #3144),

Am wondering if you read my post as carefully as I read yours. I am pleased you have now acknowledged that sideways displacement of the sidestick gives a rate of roll, not an attitude (angle of bank). You seem also to have accepted that the white cross (that you call "caret") is not present in flight. (By the way, it is used - on the ground only - to give both pilots an indication of the position of the duty sidestick, and the resultant stick-to-surface deflections.)

We don't normally deal with the absolute basics of Airbus FBW philosophy on this thread, but to avoid misinformation this paragraph of yours had to be challenged:
"The A3XX sidestick (control) philosophy is not rate but attitude based, i.e. you move the sidestick to the side (and with it a caret on the PFD), and the bus will keep the attitude you demand by pointing that caret. So, for example, you move the caret in the right hand side of the PFD and the bus will maintain an attitude to follow that caret."

That was completely misleading, as I think you now realise. So, in your new post, you now write:
"While you initially give a rate based on stick displacement, the airplane then holds the commanded attitude (with centered controls!)."

That statement is correct. Good. But you continue:
"It hence does NOT behave like an airplane we all learnt to fly on, also the only airplanes we ever had any *real* upset recovery training in."

Also true, and I never said otherwise. Returning to your original post, your next paragraph reads:
"When in direct law [...], it'll start behaving like an airplane you learnt to fly on... and you're in effect flying a rate based control system..."

It is true to say that Direct Law is rather "like an airplane you learnt to fly on" (stick-to-control surface). But that is not "a rate-based control system", as I pointed out in my PS. So actually, the problem for Airbus FBW pilots is the transition from the rate-based Normal (or Alternate) Law, with which they have become accustomed in routine situations, to the (roughly speaking) stick-to-surface Direct Law. I don't think we yet know if the pilots ever had to handle that transition on this flight.

You now say: "...one should never implement systems which behave differently from what one learnt initially." While I have some sympathy with that point of view, I think in the real world it is a tall order when manufacturers are constantly striving to improve performance and efficiency.

Possible behaviour of a MLG leg if still retracted at impact
 

Quote from mm43:
I thought I had proposed a similar look at the relative forces involved in post #3106, but may be it got overlooked, because I believe that Chris Scott came up with a similar scheme a little later in post #3143.

It was also post #3134, actually, but you evidently got their first. You were just too subtle and succinct, I guess!

JD-EE, I think we agree about the initial sequence. CliveL has written an excellent post, as did PJ2, and they both seem to be on similar lines. It's what happens once the bogie/truck has fully emerged from the bay that is less clear.

Yesterday evening, exchanging PMs with HN39, he included the following : "I doubt that the difference in breaking force exerted at the two ends, integrated over the milliseconds time interval that it operates, against the moment of inertia of the gear in pivoting, would be sufficient to pivot the gear over 90 degrees to its 'down' position."

Taking account of what he had said, I offered him this: "I think the bogie/truck would barely decelerate initially, crashing through the flimsy door. But, as you say, it would soon be pivoting outwards (we have seen its pivot has survived). Also, by this time it would encounter the drag of the water. So I share your doubt that it would swing all the way into the fully extended position it looks to be in now. I should be very surprised if it had been in the extended position at the end of the flight, so further extension by gravity seems the most likely explanation."

Chris

BEA Announces Ship for Phase 5
 

Just posted to:

Sea Search Operations, phase 4

Ile de Sein is currently off the west coast of Africa heading north, probably to pick up equipment from Phoenix.

ILE DE SEIN - 9247039 - Vessel's Details and Current Position

Of perhaps more interest is this from the BEA:

This suggests either:
a.) WHOI is pausing its mapping and photography, and will resume after photos are interpreted, or when the Ile de Sein is enroute to the location;

b.) WHOI has photographed the recorders, or where they are likely to be, and thus there is no need for further photography at this time.

Thanks
 

What a thorough description of the sonar imaging process and the creation of the images themselves. Thanks auv-ee.

When I first saw the sidescan image, I thought, "where are the remaining tail surfaces?" But, based on what you said, and my experience with radar, I'm not convinced that one should expect to see any tailplane segments in that image. It's tough enough to make out the wings.

I guess we'll have to wait for the Ile de Sein to learn any more, although I'd feel a little more comfortable if BEA would release some more images from the Woods Hole team.

Machaca - Pursuant to your excellent photos, I think it important to explain why some here are curious about inflight loss of VS. The two lug pairs and supports are from the front (1,2) of the attach, and show fracture due to rollover of the VS itself (side to side). The front lug has pulled with it the hoop structure attendant to the Aft Pressure bulkhead. The bulkhead is CFRP, and responsible for the integrity of the pressure vessel. If the VS separated at the outset of the loss of control, cabin pressure would be lost, and since the disc is not designed for rupture, it is reasonable to assume that some contents of the cabin may have spilled at altitude. This would describe some of the reports of flail and rupture to soft tissue evident in the victims. Of note also are the failure signatures of the rivets holding the lug bracket to the hoops. There is no longitudinal deflection of the hoop forward, which would be evident if the VS had rolled off the fuselage forward. In fact, the fractures suggest more than one episode of stress leading to complete failure. The composite Fin tabs have fractured in sideways aspect, and show no separation one from the other, a condition that would be expected had the single jolt theory of BEA occurred. A similar failure occurred on a 747 in Japan, leading to loss of the a/c due flight w/o Vertical Stabilizer.

Know that this is but a theory, and bears no malice toward aircraft or investigation, simply a recognition of upset leading to structure failure and loss.

bearfoil,

I fear you need to go back to BEA's Report No.2, and to the extensive discussions we have had earlier on this thread. The V/S has three pairs of attachments. The front pair stayed with the pressure bulkhead. What you are looking at in Machaca's first photo is a side view of the middle and rear attachments.

Well, sure, this question maybe stated backwards as, in my opinion, it can't be totaly ruled-out so far. Nonetheless, the A330 operational records should speak by itself as the probability for an "upset" happening some time before 0210, while flying in automatic (protected) mode at cruise level (A/P and A/THR ON) is clearly very very close to zero if related to her systems behavior.

One should remember that the only "system glitch" recorded after more than 15 years of operational duty accross a fleet of several hundred long haul aircraft was QF72. One will also note that this aircraft used a different (faulty?) hardware and would remember that this issue was not an "upset" properly: in fact, even if this situation could have caused some serious harm to the passengers, it did not cause an "upset" as the aircraft did not departed from its safe flight envelope (which doesn't mean that this problem was not dangerous for the aircraft safety).

Now, that the weather alone would put suddendly this aircraft close to an "upset" attitude, while flying in automatic mode at Mach 0.82, would certainly disconnect everything the same way. Then, if this was followed immediately by the freezing of all the probes, this would be quite a serious situation for the crew to manage. In this case, this would mean that they were not aware of the weather situation as they were not flying in "turbulence penetration mode", having their A/THR still ON up to this point. This would also be contrary to the right AF procedure and any cautious weather management at this dangerous spot.

Tim Vasquez' weather analysis was good but it pictured an aircraft position which was wrong as he took the projected "0215" position as reference alongside a wrong 0210 position.

concerning the wreckage position, I still doubt the 5 minutes "flat spin theory" direct from FL350 at a rate of 7,000 ft/mn while she was still powered all along her "free fall" (as no dual flameout occured). But who Knows?
The "deep stall theory", from the same level, will certainly imply a quite different aiframe (with T tail) and much more distance covered from LKP. The crash time (based on ACARS sendings) was estimated by the BEA between 0214:26 and 0215:14.

But, of course, it may have happened later in time, if she was not powered anymore after this point, as nothing, so far, can rule-out also this possibility.

We'll see what is found in the deep sea.

bearfoil:

That curiosity is sadly mistaken.

There is no way to explain the damage seen on the VS/lugs/hoops by any manuoevers and forces while airborne.

This accident really remains a mystery.

I have to say I (along with some others) was strongly in favour of a search close to LKP. The really strange thing about it is now that they found it close to LKP I'm somehow at a loss as to why it is so close to LKP ?!

It would be really interesting to know where it is exactly, but if it is closer than 5nm from LKP, even a 'simple' spin scenario rather wouldn't do it.

From the Pulkovo crash we have a pretty good idea how long it can take from FL400 down to SL in a flat spin.
Looking at the Wing Loading of AF447 being ~580kg/m^2 compared to ~400kg/m^2 for the Pulkovo Tu154 we can assume that the vertical velocity /Rate of Descent in a flat spin should be a bit higher.
So the time for spinning from Fl400 all the way down should be below 200s, maybe rather 180s. (back then I roughly calculated terminal velocity of the A330 @210t as being in the order of magnitude of 140kts which seems reasonable with the ~120kts of the TU154 at Pulkovo))
Now let's assume the overall event took between 4,5 to 5 minutes. that would mean 90s - 120s before entry into the spin. if we decelerate from 480kts to 350kts the plane would travel between 10 and 15 minutes in that time span before entry into the spin. And even then there is still momentum to continue forward travel for some distance.

Looking at these assumptions I tend to assume there was some kind of course reversal, maybe unvoluntarily due to e.g. a massive wing drop ending up in opposite direction after recovery, maybe followed by a second upset this time losing it for good.
Unfortunately it really takes some creativity to get the plane to a point that close to LKP after a 5 minute struggle. Occam's razor seems to be off for vacation.

The other possibility would be that the speed was shed much quicker initially. With a full pull-up manouver it should be possible to decellerate to 350kts in maybe 30s. That would cover ~5nm. But then the remaining time of 4 - 4,5 minutes would require some form of recovery before the final plunge. All this w/o effectively traveling any distance.

None of the scenarios is really convincing. However, somehow it must have happened ????!

http://i.dailymail.co.uk/i/pix/2009/...78_634x346.jpg

@bearfoil, this is a view from the bottom to the VS, it is nearly impossible to generate a nearly left/right symetricle break line like this in the air, every force to the VS in the air will generate a breake to the left or right and must end in a very asymmetric break line

a very nice front view to the gear of F-GZCP is this:
Photos: Airbus A330-203 Aircraft Pictures | !!!!!!!!!!!!!!

"Ile de Sein"
 

In some way, I guess it may give a hint about a stall recovery attempted but the crew, then a possible type of upset causing this crash.

All in all, what will certainly bring to us much more information are the ship from Alcatel-Lucent embarking the ROV from Phoenix International.
Here it is: L'Île de Sein, câblier (460 ft x 77 ft) , displacing 8,000 tons, built in 2002 by Hyundai Mipo Dockyard (South Korea) - her sister ships are: L'Île de Bréhat (at first named by BEA) & L'Île de Ré.
http://www.zdnet.fr/zdnet/i/edit/ne/...in-alcatel.jpg

Mr Optimistic
"But does it matter if the gear was down. Surely the question is about what sequence of events took the a/c from level cruise to initial upset."

Well said my good man. We have had about 3/4 pages dedicated to landing gears. Next we will have posts concerning the toilet ACARS.

Takata, I have to say I read your posts with great enthusiasm, as you are so convincing in your statements, even if you might be wrong sometimes. You could convince me planet Earth was flat. :D

The earth is NOT flat? :ooh: