HazelNuts39:
The more I think about the proportion of energy dissipation provided by altitude vs. air speed, with a relationsship of 4:1 for altitude, the more a high altitude stall seems probable to me.
If we stall it first, we would have to have only ~ 0,8m/s^2 to decelerate horizontally to 50kts.
The remaining energy would be dissipated by the vertical drag while falling belly first.
Vertical drag should be massive. Assuming a Cw ~1 in the Vertical plane (which should roughly fit), an A330 would arrive at a terminal velocity of ~150kts.
That combined with a forward 50 - 100 kts wouldn't be too far off the attitude which BEA concluded for the impact.

henra;

I can't quite follow your numbers. To get kinetic energy, you need to add horizontal and vertical components of speed vectorially. If the airplane attained a speed of 50 kt at any time, it would need accelerate to a much higher speed (of the order of 180 - 200 kt) to be able to impact in nearly level attitude, whether stalled or not.

Drag is vertical only if there is no horizontal speed. The terminal velocity for cw=1 is 189 kCAS at sealevel.

regards,
HN39

HazelNuts:
Hmmm, what area did you take for that calculation ?
I took Wing area 362m^2
Fuselage 55m x 5,64m.
Weight 210t
=> I get 140 kts
Or do you have real data ?

Regarding the other numbers:
I was just referring to the forward speed vector. I assumed the forward component was just 50 kts upon impact, just a wild guess based on BEA's description of the liekly impact attitude.
For the pure horizontal deceleration that would be OK, but not for the overall energy state.
Regarding overall energy loss, you are absolutely right: I should have considered the vertical component as well. So the overall energy loss was rather equivalent to 43000 ft than to 45000 ft. Equivalent speed would be 980 kts then.
Thanks for that correction !

Doesn't change the overall picture, though.
This wasn't meant as a scientific analysis, rather a rough calculation, to get an idea about the general proportions

henra;

I was just considering the wing. The cw of a circular cylinder moving perpendicular to its axis at high Re is of the order of 0.4. But as you say,fair enough for a rough calculation. Shall we split the difference?

The BEA speaks about attitude and vertical speed. The latter is based on examination of elements recovered from the cabin, and on 'arm 36g'. Regarding horizontal speed, bear in mind BEA's description of the separation of the fin under longitudinal (horizontal) inertia loads.
regards,
HN39

Thoughts
 

The longer I look at the AF447 loss, the more it looks like the aircraft promptly entered a stall and then descended to the water. The question I asked earlier regarding how protection "collisions" are handled applies. When one protection commands an action and it conflicts with the limits of another protection, how is that handled?? Is it always in fact the logical prioritization?
The latest thought relates to the Vmo/Mmo protection in normal law. If the protection commands an additional amount of g to get the nose moving up and it "thinks" the aircraft is at Vmo, how hard does it pull g. If 1.65 g is commanded and only 1.6 g is actually available, what happens then? It would seem that the protection should apply g as mitigated by the envelope protection software, however if this software had an erroneous CAS input, it might be possible to pull so much g that a departure would result. Ok, you ask, what about Alpha Protect limits.
Well first we have a limits collision in a little explored part of the software (erroneous airspeed input). Does it behave the way we think it should?
Second, I am not entirely sure that Airbus is using actual angle of attack data in all of their angle of attack calculations. They may possibly be substituting inferred angle of attack based upon aircraft configuration data and airspeed.
And finally, it appears that if bogus airspeed data tripped the Vmo/Mmo protections, ACARS messages infer that the aircraft then shifted in a few seconds into Alt2 flight laws where it is possible to stall the aircraft. Has anyone run that kind of scenario in a SIM to see if there are additional implications?
When you see indications of anomalous behavior, it is time to look for a path to how the anomaly could be created. Maybe it is time for BEA to do some forensic software analysis. It might cost less than the actual search for the boxes and be more productive.

Bogus Vmo/Mmo exceedance
 

Machinbird,

If the pitot intake and drains are blocked, the pressure rise due to heating depends on the volume of trapped air, which includes that in the tubing up to the pressure transducer in the ADM, and for the STBY pitot that in the pneumatic line up to the STBY ASI on the instrument panel. Wouldn't that difference result in less pressure rise in the STBY system?

If the airplane really reached the buffet boundary at FL384 with a deck angle of 27.8 degrees (see discussion 29th june), I wonder if the alpha protection authority (4 deg of elevator in QF72 report) would suffice to prevent stalling in normal law?

regards,
HN39

HN39
The same question bothered me, and you are completely correct when the air trapped in the pitot tubes piping is dry air.
When you are at ~FL350 and you have air and moisture trapped in the pitot tubes in contact with heated metal, the moisture will flash to steam and the steam will try to hold a pressure dependent on the temperature of the trapped water. Now this isn't hot steam that you are acquainted with from your tea kettle. It is really just cool water vapor. The situation is very analogous to the newer steam catapults with the boiling water type steam receivers. As the launch valves open and begins driving the catapult pistons, water flashes to steam and tends to hold the pressure constant.
With 3 identical pitot tubes that have just experienced common mode plugging due to weather, you are going to have 3 identical steam generators that will attempt to keep the pitot tube interior at a pressure characteristic of the trapped water temperature. As long as there is water to flash to steam, the pressure in all 3 pitot systems should be relatively constant. The transition from open to plugged pitot tubes should look like a step function on a pressure graph with the system with the greatest volume lagging behind the other two systems by a second or two and all stabilizing at the same (higher) absolute pressure value.

I see the calculation in the QF72 report. I'd like to do some homework before I comment on the second part.

The problem is that it would require the average water temperature throughout the whole tubing to be identical.
Also the steam generators may be identical, but if the volume of the systems is signifcantly different the time to achieve equilibrium will be different between them.
With a long tubing in the stdby system it should take considerablý longer to achieve the same average temperature and thus steam pressure as in the systems with less volume.
Regarding flash boilers:
The constant pressure is achieved by the moving of the catapult in combination with a constant evaporation rate. If the piston wouldn't move, the pressure should rise.

I wouldn't rule out this theory though we may have to think further on how this could potentially happen.

Hi Henra,
The key temperature would be the peak water temperature in the systems. That would control the vapor pressure. See the chart below.In the case of a pitot tube, I would expect the water trap area of the tube to be the warmest spot on a frozen up pitot tube.
The flash boiler doesn't build pressure indefinitely because it is sealed in. There is a characteristic equilibrium pressure for each temperature. In the case of the catapult steam receiver, the water temperature generates about 550 psi steam pressure at equilibrium. (I haven't personally operated any of the newer catapults so I don't know the exact number).
The below chart gives pressure in Torr versus water temperature. 1 Torr= 1 mmHG.
50 Torr=1.96850366457 inches of mercury
100 Torr=3.93700732914 inches of mercury
200 Torr=7.87401465828 inches of mercury

http://upload.wikimedia.org/wikipedi...sure_graph.jpg

Terminal Velocity
 

HazelNuts, henra, Machinbird...

In your terminal velocity calcs, can you include a time variable -- how much time required to fall, say, 35,000 ft.?

With the leaning tower and the feather and stone experiment in mind, seems that a stalled A/C would descend more rapidly at higher altitudes, slowing gradually (smooth asymptotic curve) as air density (drag) increases until sea level. Perhaps 200t of mass overwhelms the influence of fluid density, but theoretically, I should think Terminal Velocity (where drag=weight) would vary by altitude...

Without simulations, hard to tell how much residual aerodynamic lift might also be at play in (what kind of) a stall. Not enough lift to keep the A/C flying, of course, but possibly not zero, either, thus a factor to include when computing Terminal Velocity and estimating duration of fall.

GB

Hi Machinbird,
The peak temperature would indeed define the local max pressure. But if the evaporated volume of water is small compared to the overall volume, the overall presssure throughout the system would be much lower, more a function of the average temperature in the system.

Regarding the Flash Boiler:
Yes indeed, it won't generate indefinite pressure, but in order to ensure the rapid expansion I would expect the temperature (and thus the local /instantaneous pressure) to be much higher than the average required for expansion and moving of the catapult. So if the catapult won't move the pressure should rise to some extent until the temperature of the whole steam in the system is identical to the boiler temperature. Then there would be equilibrium.
I don't think these catapults work at equilibrium of the whole system as in that case the force exerted on the catapult would decrease wgeb expanding/moving

Hi GreatBear,
The Terminal velocity should be roughtly constant, if yuu consider it being IAS/CAS and not the absolute value.

At 35000 ft this would be roughly 1.8 times higher.
So let's assume for a very crude first guess a factor of 1.4 - 1.5 for the average speed.
That would give you (again very roughly) somewhere between 200 - 250 kts.
Which would mean ~20000 ft/min.
So it would take close to two minutes for that vertical free fall.
But this is indeed an extremely crude calculation, not considering any aerodynamic or even local Mach effects.
To achieve terminal velocity at altitude (~280 - 300kts) would only take about 15sec. amd a drop of ~3000ft.
Edit:
This is pure theoretical as it would only apply for a pure vertical drop.
In reality this will be a transition and the plane will not immediately start to fall like a rock at the point of stall.
If you look at a wing polar you will notice that at the stall point the lift drops quite a bit but directly at the point of stall there is still quite some Cl, then decreasing with increasing AoA
/Edit

It has to be considered though that the initial altitude may have been higher, as this is one of the more likely sceanrios to get quickly into a stall in the given circumstances.
The initiating altitude may have been as much as 38000ft considering the initial Energy potential of ~45000ft (see posts above) and a stall speed of 220 kts IAS (equivalent altitude of 220kts ~7000ft. Alternatively: Speed loss 270kts to 220kts gives an altitude difference of ~3000ft).

Again, all numbers very crude, just to give an idea about the orders of magnitude we are talking

Thanks, henra,

Your numbers are valuable.

What is "known" or can be reasonably inferred is

AF447 was in serious upset at 0210.

Af447 was in the water by 0214 or 0215.

Henra, your calculation estimates ~15 secs for decel to stall in the high AOA scenario (ALT Law, no alpha prot) with a gain of altitude, staying under 3g (per JD-EE), and puts the A/C in the water soonest in ~2 minutes from stall.

Once stalled, no control surfaces work. Kick the rudder; nothing happens. Push forward on the stick; nothing happens; aerilons useless. Try thrust to the stalled wing's engine? Flameout? Try this; try that? A/C in a horizontal plane. High g rotational forces in cockpit. A/C pretty much descending vertically. Time running short. All the while, automatic ACARS messages are being sent as the situation evolves...

For the "where," I do hope they mount a Phase 4 effort and look near the LKP. For the "why," I hope they successfully recover the recorders.

So far, there are no answers and a great many plausible scenarios

GB

Not necessarily.
From a pure timing perspective, it would be sufficient to change the flight path 3,5° up. That would mean according to my rough calculation that about one minute later they would be at 38000 ft and 220kts if Throttles remained unchanged (admittedly that is not 100% correct as with the speed decrease the drag would reduce quite a bit so the engines would have some SET, so energy conservation is not 100% constant which it was at 270kts with level attitude for the given N1/EPR). OK, let's take 5° up. (Alternatively, cut the throttle back)
Then they would hit the stall.
As I mentioned the drop would not be immediately like a brick, but after some decelleration the plane might be dropping at vertical velocities towards terminal velocity. lets add another 30 secs for this transition phase. Add 30 secs for the initiation of the pull up.
And then 2 minutes down.
And here we go: 4 minutes.
Just pure speculation though, but at least it could fit.

But even if this was the case, the most important question would be:
WHY ?? And that's why we need the black boxes.
Edit:
What also remains a mystery to me in this scenario, even if it was possible from a timing point of view is the question if a Conventional Tail Airliner can really deep stall straight down. So far I always thought this was a 'privilege' of T- Tails.
The only way I thought this would be possible with Conventional Tail was with elevator or at least Trim full up.
If this assumption would be correct the question would be again: Why ?
/Edit

It is also quite possible the a/c was out of control, never to regain it, well ahead of a/p out. Sanchez shows the a/c exiting the cell. Prior to entering the cell, a/p had control. Entering the ring around the column could involve upwards of 7k fpm up. From cruise, the a/p pulls back some throttle and inputs Nose Down, to cage speed and altitude. So far so good. Maintaining altitude, throttled back, the a/c exits the up column, and encounters neutral or even down air. Now shes "losing" 7k fpm, (indicated, read a/p), but the a/c is too out of trim for the automatics in Pitch and Power, the very thing the book says to fly when a/p is lost. The autopilot trips out because the controls require beyond her installed limits, (expressed as total deflection, or "excursion", the pilots might be surprised because they are trained for additive a/p input, not "recover" reset" she rapidly Stalls, and the floor falls out, loss of a/p, u/a/s ensues (unusual attitudes), and the pilots do......what? Is it time to unfocus our steely stare at Thales?

The Vertical Stabilizer did not pop off the fuselage at impact. There is simply not enough damage to the root or to the assembly itself due to tumbling through the concrete of an upset sea at in excess of 100 knots (at the very least). The damage to the base of the Rudder is consistent with being dragged across a tailcone with ram and Rapid inputs at altitude and highspeed.

@ GreatBear:
Just curious: Did Airbus actually stall one of these aricraft during original operational test to see what it would do? The reason I ask is that flat spins are a beast to get out of, if they can be, even for fighter aircraft that can enter them. Did the manufacturer have enough data to decide that going into full stall was not necessary to prove a point, given the operational environment expected of the aircraft? (Air Transport of persons).
Flaps any help at this point (fully developed stall), or is relative wind too vertical for any airfoil?
I may be confusing this from another thread's discussion, but would not added thrust create a pitching moment (down?) Or do I have that arse backward, and thrust would induce a pitch up moment?
I don't have a clear mental picture of the moment arm the force of the engine would be acting upon in re the CG, but I do have an idea that airflow not roughly parallel to fuselage and engine center of thrust could lead to engine stall/flameout ... maybe a pull to idle would somewhat drop the nose ... but up near the coffin corner, oops, that may not be the help you need. :eek: (Ah, I see bearfoil and I have cross posted, he answers a small bit of my question on what to do with throttles ... )
I suppose that in a Hollywood film, they'd try to drop the gear, but I don't see that as much help in a fully developed stall in real life.
G manifested as negative g/eyeballs out, if I understand the scenario you are painting. Do I have that right?
Interesting, that in what looks like a flat spin, the geometry for the message center signal link could be maintainted ...

I presume you paint this scenario regarding a fully developed stall, which would go through first initial stall, then post stall gyration to get into something roughly "steady state" (albeit a rough ride as described).

This takes me to a question about recognizing stall and incipient spin, and
anti-stall inputs being called for before the stall / spin gets fully developed.

Is there training for that for line pilots? I noticed some pages back that a stall/upset of this sort could sneak up on you up near the coffin corner ... catch you by surprise.

About 20 years ago, the Navy lost a trainer (T-34C) to what was eventually figured out as a spiral, not a spin. One won't get out of a spiral with anti-spin inputs. Ten years later, two more were lost near Pensacola from similar cause. Two fatalities each event, six dead in three wrecks.

In the meantime, on the wet wear side, the training philosophy focused on stall and spin prevention, even though a spin was a standard training maneuver. (And a fairly benign one at that, all things considered). What was lacking somewhat was training on recognizing the difference between a spiral and a spin.

One could, with a poorly executed stall to spin entry by the student, end up in a spiral ... it can sneak up on the IP if he misses that roll input at spin entry.

So with the idea of the stall/upset/spin sneaking up on you, you paint a picture of there being a point of no return in a fully developed stall/upset/spin.

Are there anti stall/recovery inputs for this model aircraft? I realize it's built as a tranpsport, not a trainer or fighter aircraft. Some of the other threads here (and on tech discussion forum) indicate that in some heavies, there is a way out of such upset, though one needs quite a bit of altitude.

Yet even with a recovery via flight controls, it seems that a full throw on the vertical stab (rudder opposite spin?) might, if the rudder bites, lead to material failure whilst one is in the middle of getting out of that rotation! At this point one is short at least one flight control surface and still in upset ... :eek:

Taking that thought a step further, and I think this has been raised a few dozen pages ago, I wonder if your described scenario doesn't suggest a plane breaking up some time interval before impact with the ocean, a prospect that considerably challenges the search effort.

Where did what bit land? The front bit would not necessarily be oriented in the direction of flight if things began to fall apart waaaay up there during the flat rotation.

The Bonanza makes a very iffy training platform, what with ADs and all.(Weren't they all lost via broken main spar One for the AD and the next two chasing the correct strength?

The VS was lost in a Rudder reversal, with 7.9 degrees available and 16 total, rapid and non consonant deflection at M.82, I doubt the VS lasted beyond the first out of phase reversal. Antenna considerations place the VS/separation well into the upset, when in a Stall that is fully developed, the controls are not being operated by cool customers. Can we agree that the pilots were at least, out of phase with the upset? Hence no recovery. Cabin Pressure alert likely happened at nearly cruise altitude, but no where near 9,000 Feet. The BEA should open a shop selling two-legged stools. So that's one for ACARS done at ~35k.

Lonewolf50

It was a very long time ago, and a very unpopular position to take, at the time.

Knew you'd arrive. Pax were lost at altitude, there is no way to explain floating (assumed to be belted but unbelted at discovery) unbelted dead people, with the precise but off target injuries inventory proposed by BEA. Like the VS at impact separation pronouncement, the injuries have a glaring blunder.

I would welcome a discussion of maneuveringVS loss at altitude.....

The following quote reporting on the cause of a BA1-11 prototype test flight crash in 1963 caught may attention - more to do with the wording than anything else.
Bearing in mind that that BA1-11 was an aft powered T-Tail, and the circumstances of its crash identified the "deep stall" condition, I couldn't resist being drawn to the "center of gravity" comment and the possible implications of that in the case of AF447 if in fact it entered a stable stall with a +20°nose-up attitude and low IAS. The later part of the quote replicates the BEA's description of the crash.

I believe the original crash report determined that G-ASHG descended from FL180 in 80 seconds - 13,850 fpm. How accurate that figure is or how it was determined, I have no idea.

Some important questions spring to mind in respect of AF447 -mm43

It most likely had six thousand pounds of fuel in the tail (trim) tank adding a bit of impetus to any noseup control. No need for Warning from FADEC, the engines soldiered on. The auto pilot trip limits are rather impressive, I doubt any control was had after a/p left the loop. RTLU was set at 16 degrees sweep, per BEA. Without a/s or statics, the game is up. The ACARS was a snitch after the fact. I think no one was alive to feel the impact. The litany of ACARS are all we have. Wanting to "fly" is the design consideration for all commercial a/c, and she did what she could, alone, and witless.

It seems intuitive, with all respect.

1. A "Born Free" autopilot

2. Auto flight in trash Wx

3. No positive control (by definition) at A/P OFF

If the a/c was nosedown and behind on power leaving the unstable (VS read), Mach Limit, Yes? (ACARS). Recovering with full power and nose up, that's the ranch, Hank. Especially if the pilots started a "recovery" before the a/p quit, and inputs were ADDITIVE. With an emphatic Pitch Up, the a/p quits, that is unlikely but possible. It's very quiet, must be post last call.

bearfoil

Just semantics, Henra. Bearfoil uses "out of control." My thoughts are that the aircraft was, indeed, in trouble and upset before 0210. It was at 0210, FOLLOWING a set of unfortunate events already underway (the upset), that the AP gave up, which was at the same time the aircraft reported in with an automatic position update and began its cascade of ACARS messages. Could have already decelerated. Could have been by then higher or lower than FL350.

I spent a few frustrating minutes unsucessfully looking for mm43's link to his ACARS message list. Whew! This and the old thread show about 6,500 mostly relevant posts. Would be neat if someone had the time to properly index this rich material with hypertext links based on content... Hint, hint for volunteers. :O

Lonewolf 50, you ask many good questions. My understanding is that spin testing, while required for certifying light aircraft, is not part of the certification process for transport aircraft/heavies. If Airbus knows how an A330 might fall in a deep stall, they haven't shared that simulation with us, as far as I know. Probably not an animation a manufacturer would want to submit to YouTube, in any case. There have been many conjectures on this thread. My own conjectures are based on a single experience many years ago in a light aircraft (my CFI got us out before 360 degrees with a gutteral comment "ooh, that was close!"), some study, and my imagination -- so my scenario should be discounted appropriately.

Bearfoil, how does your breakup scenario account for 4 minutes of ACARS messages successfully sent? Following "Rudder reversal, with 7.9 degrees available and 16 total, rapid and non consonant deflection at M.82" and loss of the V/S, does the rest of the aircraft continue to function? Continue to broadcast ACARS maintenance messages, none warning "Hey, I can't find my vertical stabilizer?" When/where is the Crew Rest spit out? The bodies? The tray trolleys?

GB

So at 02:14:28 following the likely confirmation receipt of the Cabin Vertical Speed Advisory back at the aircraft, the aircraft commenced to break-up! Why do I say that? Well, it couldn't have been doing the things you have described without primary source power, i.e. engine or APU alternators. The ACARS may well have been a "snitch after the fact", but the fact that we have them indicates that the a/c was intact until at least the time given above.

mm43

It is not a scenario, it is not that developed, but I do mention that the VS left the a/c well into ACARS (and perhaps after it went quiet and at cruise altitude), or thereabouts. It left with critical antennage, so it left late. ACARS, to have been well enough developed but preclude a descent of a final nature, meant the a/c carried on at some a/s and alt. Those numbers are wet, but not forgotten. The arc of discovery of the remains is somewhere between LRP and M.82 rate plus, in a widening curve North and South of the area not investigated.

LRP, not LKP, like ACARS everything of value has only a percent value of what is real.

It is possible 447 set up in some kind of stubborn Phugoid, on "course", but altitude unpredictable. This would explain ACARS being received until TOD (Upset, leading to total and permanent LOC).

edit mm43: as above, you assume Engine problems. At the beginning of the first thread, that was dismissed, now it is a given? PJ2 was first to answer my supposition of asym. thrust and engine Stall. Since that time, I think too much has been made of engine failure, especially in the absence of evidence to support it.

You assume too much. "After the Fact" is after "Upset" (see Phugoid). I do not specify "Break Up" of any kind prior to last reception of ACARS. You are putting words into my keyboard.

02:14:28 is the time I accept as well, where have I disagreed with ACARS? I disagree only with your explanation of what you think I wrote.

"Upset" is different from "Loss of Control" is different from "Phugoid" is different from "Break-Up".It seems a fair bet to assume loss of bits after "Cabin Vertical...." which was the LAST of ACARS. I'm trying to locate where I have posted that 447 did anything without power, or supernatural, as far as that goes. I stipulate that the airframe was intact until 02:14:28. What it was doing during is within what I have described is the capability of an intact 330.

cheers bear

GreatBear;

The ACARS messages link you are looking for can be found in Post#1611

mm43

GreatBear

A question. In your review of ACARS furnished generously by mm43, (reference final position report)

Why is the LRP considered "Fortuitous"? It is reminiscent I think of Msr. Gourgeon, in dismissing the "off course " 447 as the result of bad luck on the part of the pilots, and their obvious "difficulties" in "reading the radar return."

If I wanted real time Mx from my pilots, I most certainly would NOT leave them out of my very expensive ACARS system. The Computer is not the only "Brain" aboard. I am amazed no one has offered the PR as the final com from a doomed crew, who knew their com was crap, and ACARS presented a way to shepherd rescue.

Of course, the crew may be blocked from ACARS utility, but, my goodness, that seems just dumb.

Although this may present the crew as professional, engaged, and alert, instead of detached, poorly attentive, (They missed the Radar, remember), or casually reading Le Monde, while 447 danced, betrayed by her "unlucky escorts", I give them at least the benefit of the doubt.

bear

Bearfoil, If AF447 lost the VS anytime except within seconds of impact, wouldn't we have ACARS messages regarding loss of hydraulic systems? Is it really necessary to have lost the VS to explain how the aircraft was lost? Isn't a deep stall sufficient?
OCCAM'S Razor says don't make things more complicated than they need to be.

Henra, wouldn't all water trapped in the pitot system that was above its temperature flash point flash to steam, and the last bit of water to flash to steam as the pressure increased would be the hottest water that remained in the system after the pressure rise shut off the flashing of the slightly cooler water. Unless you assume blockages behind the main blockage or high flow velocities in the tubing, all the trapped volume of "air" in a particular pitot system will be at the same pressure.

bearfoil:
"Knew you'd arrive. Pax were lost at altitude, there is no way to explain floating (assumed to be belted but unbelted at discovery) unbelted dead people, with the precise but off target injuries inventory proposed by BEA. Like the VS at impact separation pronouncement, the injuries have a glaring blunder."

I thought you were around in the old group when it was explained that water action can ease bodies out of their seats even when fully belted in. Somebody with experience in this regard explained it well.

Thanks, mm43,

That page of posts (page 81) was good to revisit. With the WRN (AP kicking out) at 02:10:10 and the FLR (pitot disagree) 1 minute 39 seconds later (fault msgs batched in minute intervals), any chance the pitot disagree was NOT a precursor (by blockage, bad airspeed indications) to the loss of AP and entry to ALT law, but rather triggered by attitude, airflow, and speed events occuring during the upset itself? Thinking out of the box and possibly against the grain, how certain is it that the pitot's did "freeze." A considerable amount of money has been well spent changing pitots in the whole Airbus fleet to cover that possibility, but wasn't freezing/blocking just a possibility, not a certainty in this case?

Wish I had the gear deployed in the North Atlantic around the Titanic this week (and a known place to use it in the South Atlantic). As many have said, we need the FDR and CVR to reduce the possibilities to certainties.

GB

GreatBear, you might also ask bearfoil about the apparent period of communications loss. A flat spin does not account for it with an ACARS antenna's beamwidth. A full roll could accomplish it.

In this regard I have thought of something to try on for size and see if it fits. There is the comunications outage. Presume messages are mostly kept in a queue by order of arrival. Just how many such messages that were really important were left queued at the time of impact?

And I'm still not sure I see in bearfoil's scenario the applied forces required to stop the plane apparently very suddenly then having it drop. Could a violent pitch up cause this? If so what would tend to rotate the plane to roughly horizontal for the fall and not continue rotating it to a nose down attitude from which recovery is possible?

bearfoil, what is critical about the antennas in the VS with respect to ACARS messages? The ACARS antenna is a "flat" panel phased array antenna mounted to the top of the fuselage.

Machinbird the quick answer is the VS loss would deluge the ACARS, but not if it left after loss of ACARS.
As with any discussion of 447, there are few absolutes. There is evidence, evidence I use in saying the VS parted the airframe at the pinnacle of g, complicated physics included, but also Three separate VS disarticulations. Here I include 447, along with 587 and Perpignan. As with 737 frozen Jacks, the failure is similar. I simply put the percent of confidence in a midair separation well above dislodging due to water impact. The need to explain impact separation only follows BEA's report that it is a finding, a fact. What preceded the type of aspect needed for entry according to BEA is not less chaotic, but more so. Unwind their logic, and see if you don't start to entertain a high altitude VS failure, and one promised by BEA's logic, although inadvertent. What commands a high altitude separation? UPSET. Gentle? partially managed? Crew at the controls fighting to ennable a ditching? I say no. A flat spin is what BEA claims.
Let their claim embrace a loss of controlled flight, a loss of directional control, and parts in their inventory of reclaimed wreckage that speak to high speed and high altitude partition, with extremely dynamic and jumbled accelerations in all directions.
Forget the handy simultaneous betrayal of all three pitots and statics. I say it is far more likely the uas, TCAS, g loading and control deflections from a maxed out Autopilot are likelier to have been caused, not effected. Cause not Effect. I'll throw in my confidence in the crew, having trained for uas, been in and out of ap hundreds of times (even in WEATHER); It was not they who allowed ap use in Weather, it was AF's training syllabus. Given their confidence in ap (proven), it strikes me the ap was bolloxed not the crew. Everything on ACARS seems to me to be not cause, but effect, stemming from an initial upset whose iterative effect was to cause the accident.

Here I rely on the aircraft's reputation. Initially, AF claimed Lightning, then "Turbulences Forte", then poor crew utility re Radar. Why did they do so? They believed the evidence was unlikely to be found. It isn't more evidence that is solidifying the "Cause", it's the lack of any need to explain what everyone fears happened, as time passes.

ACARS was a leak, not a Press Release. Initially I believe there was Corporate damage control, followed by new explanations, anticipating a controlled or controllable investigative authority.

editJD-EE confused with HF, sorry. Also #1974 presents a possibility where ap gets the a/c nose down and Throttled back, followed by a radical departure in sensed v/s and/or a/p "thinking the a/c needed more "up" and power than its limits allowed, followed by trip, and pilots trying to correct Mach Limit, by reducing throttle and full nose up (they were "protected", no worries, not, followed by an immediate Stall.

Coffin Corner: Can't climb, Stall. Can't dive, overspeed. Can't turn, Stall. Can't increase decrease power, Stall, overspeed. The only thing that can rationally happen is UPSET. At FL35, close to max alpha, heavy with aft cg, Dark as a Lawyer's heart, wet, noisy, bumpy, I think it was not long before bits started to depart.

Where was the aft most "array"? was it underneath the Dorsal?

GreatBear We must have cross posted or we are thinking in kind, which is worse?

Bearfoil
Apologies! I have enough trouble with my own keyboard, let alone playing tunes on yours.:ok:

Cheers
mm43

bearfoil, "Where was the aft most "array"? was it underneath the Dorsal?""

My understanding from pictures in the old thread the array is about aligned with the wing roots on the top of the aircraft. There's only one array. It's electronically steered.

"arm 36g"

Altho it has been a couple or three pages since this term was mentioned, I just wanted to inject a note of caution about assuming that this means the tail of the aircraft impacted the water with a resultant deceleration of 36 g's. The cited strength of 120,000 newtons is about 27,000 pounds.

For example, it has got to be highly unlikely that this part, which resists the vertical component of forces on the rudder, would be designed for 36 times the force resulting from the static weight of the rudder.

We are just not furnished any info (English version) as to how this 36 g's is derived (I intend to see what the French version says). It may be that the 120 kilonewtons is the strength at a midsection of the arm which is oversized to allow for the making of adequate connections at the ends.

One visible end has a single hex bolt as the connector. It is difficult to easily see how large this bolt is, or how in the assembly the +/- 30 degrees of rudder deflection is accomodated by the lower joint. (Is this deflection correct?)

The thing to know in this is that a single bolt hole will induce a surprisingly high amount of stress concentration, and that the smaller the bolthole, the worse the problem can be-- depending in part how fatigue from accumulated service enters the situation.

This in turn depends on whether and which parts of the joint and arm are made of plastic. We are not told, nor is it clear which part broke-- there is just a lot of fuzz in the picture. Where plastic is involved, the impression I am getting is that there is a lot of ad hoc design even now, 50 years after the early research. (I was such a researcher, doing original research, with glass-reinforced parallel-filament plastics, that long ago.)

I would assume the design loading here for vertical component of rudder loading is to prevent rudder disablement following a tailstrike on takeoff.
For information, an AB representative testified that the design basis of the VS attachment was the gust loading (testimony at the AA Brooklyn 2001 hearing). Presumably this was the crosswind gust allowance on takeoff and landing, altho that was not said, IIRC.

There also appears, somewhere in [possibly other] testimony or furnished data, that in the history of these AB fins, a change was made in the percentage to be used for ultimate load. It was an increased percentage over what may have been the working load (as I would call it for clarity in my view), and was a substantial increase.

However, any discussion of the terms limit load and ultimate load in regard to stresses gets a bid complicated. These terms occur in the CFR (USA) and are complete with percentages dating to 1965 without change, IIRC. This situation was sufficiently murky to many (my characterization, true) that NTSB inquired of the AB rep exactly what "limit load" meant, in the case of the fin.

The reply (hearing cited above) was that it was the load not exceeded, without elaboration IIRC. Further clarification was not sought by NTSB, again IIRC. My conclusion was that it was the load at which, if exceeded, the fin would in theory be replaced.

One example of a replaced fin is of course the Canadian AB that overflew Miami and turned back to its origin in the Caribbean. There you would have the say it was the ultimate strength that had been exceeded at some of the attachment points. The reinforcing fibers leading to the attachment points in these fins (not the rudders) are carbon, and that is true of all at least through the 340 as far as I know.

I also believe that the statements that AB did not approve reversing the rudder from lock to lock in flight might have been backed up by reasoning that this would cause the limit load on the VS attachments to be exceeded, altho I have never heard a specific reason given by AB. The margin between limit load and ultimate load in plastic fins does appear to narrow with age of A/C, based on the sparse data from AB.

This is hardly a full discussion of the structural aspects, and is already far more verbose than I had intended. Just hitting the high points for now.

OE

Machinbird,
Yes all wtaer above that temperature (which depends on the ambient pressure) would also evaporate. My point is that the temperature of water and air in more 'remote' locations in the system, e.g. in the tubing would simply be colder and in order to heat it up, that would take some time and would also cool down the steam in the system accordingly.
Yes after a certain time there would be equilinrium, but it's the heat transfer not the pressure transfer that would take time.
It could happen rather quickly however, if the only water in the system was around the heater itself, nothing in the tubing. In that case the steam would have indeed a pressure close to equilibrium pressure for the temperature of the heater.

This article appeared today in IEEE spectrum:

IEEE Spectrum: Beyond the Black Box

There was discussion about this in this thread, so...

OldEngineer

There is a pages long discussion of the salient design characteristics of the VS and the "36" g arm much earlier than only two pages ago. I'll find it. For now, it was not determined whether the term 36g was used to identify focal stress on the arm at "impact", or as an architectural identifier, nomenclature indexing this part for plans purposes.

As a very general impression, this restraining arm, along with the "Lateral rods" speak to the bandaid approach that may have been applied to mitigating the knocks on the fin from conclusions made about the A300 "weak points" in its VS. As you say, the design is old, my impression is this arm had nothing whatever to do with "planned for" stress of a tail landing in water, but had more to do with retaining the Rudder to the fin in reversal/airspeed events. Not an integral part, but perhaps more like a "leash" in case of hinge failure, or partial failure. As I have said more than once, this is counterintuitive from an aeronautical standpoint; if the Rudder is in danger of pulling the VS completely off its mounts, it would be critical to lose the Rudder rather than both the Rudder and the fin.

An aircraft can be flown with no Rudder (essentially a "trimming device" after all), but without its Vertical Stabilizer, the smoking hole is inside the horizon at best.

If I look closely at the Bolt that fixes the arm tip to the Pinion, I do not see any evidence of failure in tension. Rather, it looks as though whatever bit was lost may well have departed due to vibration (plus tension) or even corrosion, and perhaps not even on this flight. The Bolt is bedded in sealant or resin, and looks absolutely pristine. There is no sign that the bolt was deflected in the direction of the tip.

Beyond this, there is simply no evidence in the photograph of vertical deflection of the Hinges themselves. The Energy needed to pull the VS Rudder assembly vertically and forward completely out of the more robust Fuselage attachments would have deflected each of the seven hinges radically downward, each hinge shows no evidence of this, a vector not designed for, except parenthetically as a follow on to radial strength. The flattened lower 1m of leading edge (VS) could be explained as contact with the top of the Dorsal fin, but that would involve a hesitancy at the forward join in letting go the VS. This leading edge damage is telling. If the fin had parted at altitude, its assumed aspect after "stabilizing" would be LE down, trailing the Rudder. I doubt it fluttered. the weight distribution would suggest the LE impacting the water at speed, and the Resin collapsed in folding fashion, its aft edges held beyond the failure of the Frontal vertical seam.

The forward/bottom corner would enter the water first, explaining the lack of further LE damage upward as the fin tapers in chord and width. This brings us to the relative merits of Two Phase materials v. Metallic.

JD-EE

Howdy. I think the "wave action" was used to explain away the loss of clothing from some of the bodies. I don't recall it being used as support for wave action removing people from seats. At depth, the seat/body would compress, and thus resist reflotation. BEA has not answered the question re: "Seated people" being discovered at all, since seats were not recovered, with the exception of the utility stools attached to the bulkhead cover. I would propose that all who were seated went with their still attached chairs to the place we wish to find.

I think a "full roll" is not required to interrupt signal of the Sat. You would know this. I would say that with the possible exception of the Philippines, a roll past 90 degrees is not at all surely lethal. The a/p can roll the a/c to 50 degrees limit, so the signal break would not need a roll past vertical?

What is your thought re: the transmission of the last reported position? ACARS generated? Pilot/crew input?

mm43

For purposes of discussion, It helps me to picture this accident as one of the most difficult around which to establish a chain of events, least of all a chain of failure. When I suggest the airframe has lost pieces, I am not necessarily attacking the "Intact at impact" postulate. I don't find a fatal fault with "En Ligne de Vol" for that matter, but here is the dilemma: BEA reports a slight rotation at impact. For obvious reasons, this precludes absolutely a "Line" of flight, or "heading". The second problem is this a/c is not anywhere close to what anyone would presume even loosely to be "Flight". It is a ballistic structure falling at an assumed peak rate after calculating drag. The expression is misleading in the extreme, I believe it is not picking at straws to characterize it as such. Again, I am willing to accept a mere "language" misunderstanding. Do you have a thought in re: LRP? Automatic and "Fortuitous" or the calculating mind of a pilot trying to potentiate a rescue after his hopeful Ditch?

Thanks gents,
bear

Old Engineer
I believe somebody some time ago pointed out the part's part number was 36g? Or did I miss that getting refuted.

{o.o}

bearfoil to me: "What is your thought re: the transmission of the last reported position? ACARS generated? Pilot/crew input?"

The transmission interruption is either from no messages, loss of power later restored (with no message mentioning this), or a roll probably more than 70 degrees. If I recall the plane was not quite "under" the satellite. So maybe a 60 degree roll would do it. A flat panel can have usable response out to perhaps 70 degrees off the normal to its surface. Since it's electronically steerable with a beamwidth of around 60 degrees if the plane REALLY suddenly (seconds?) rolled as little as 25 degrees from its normal flight position the antenna might lose lock. The antenna probably aims in 10 degree steps so that figure accounts for the antenna already being slightly off boresight to the satellite.

I believe the antenna gets some input from the IMU system for both position and plane attitude. If that's the case the roll would have to be really fast. If it's freely tracking then the roll could be slower. I'd hope it was designed to accommodate normal aircraft dynamics. Ship board units definitely are designed to track the satellites despite ship dynamics. I worked at qual testing such an antenna during my time at Magnavox in Torrance.

The ACARS generated basically tell me one thing within my expertise - something apparently caused the aircraft to be in an attitude or experiencing dynamics such that the antennas could not lock to the satellite so that data could pass back and forth.

Regarding the pilot and crew I cannot say anything meaningful beyond noting it's a wee tad hard to hold a joystick steady in the presence of externally generated high dynamic buffeting. (Fighter G forces don't hit with a rate of acceleration nearly as high as what wind buffeting could do. In the fighter the pilot is the driver of the car, if you will. He KNOWS when the plane is going to move one way or another. In the wind buffeting case the pilots would experience the G forces first and then have to react, much like the person in the passenger's seat of a car swerving in traffic. The driver sits steady knowing what's going to happen. The passenger sways with the sudden movement. I remember guys doing this on dates when I was younger to get me leaning on them. I learned to anticipate this when bucket seats became popular.

{^_-}