AF 447 Search to resume

[MucMuc]

JD EE,

sadly there are no water column measurements available for that area to determine if not exact, at least general deep currents for the time being. There is some stuff on mesoscale eddies, but it's mostly surface or down to 10m. The ITCZ over the area at the time would have some effect on micro-eddies down to 200m.
Also, debris could have trapped air or be neutrally buoyant at various depths, depending on how it sunk and what parts they were (i.e. galley would probably sink faster than outer shell) so that would effect its sink rate significantly.

There is software available for oceanographers and NOAA but i'm afraid that they simply don't have enough data for that area to make the result viable (can anyone confirm this?!??)

[henra]

First iteration is fifteen inches tall, made of layers of heavy paper in a shape quite close to actual, visually it looks roughly similar in weight, weight distribution, and weighted to estimate structure retained by VS. No "Rudder" but the overall dimensions mimic the two panels. Dropped from twelve feet then fifteen, both times drops like a lawn dart, with a very slow spiral. Bottom down, still as a stone, no flutter of any kind

Hi Bearfoil,
may I ask where the Cg of that model is ?
I suspect it's rather low, i.e. below 1/3rd or even rather 1/4th of the span of that model.
What's the taper on your model?
Could you make a small drawing with dimensions and Cg ?
Maybe I'm just gone take me some Depron and try it myself.

Unfortunately that is where we would need to know the real mass distribution.
Edit:
Found something usefull on mass distribution of the real fin, albeit more anecdotal, pls. see link in post below
/Edit

[henra]

One scenario I've not been mentioning lately that I can envision is quite literally a tail strike scenario as the pilots lose control, lose a lot of altitude, regain at least partial control in a dive, and are still trying to pull up when they meet the reality that they didn't have enough altitude to even lay the plane down on the water properly.

JD-EE,
from the damage pattern visible in the images shown by BEA this might even be one of the most plausible explanations because it would cover the vertical as well as the longitudinal decelleration.

Problem is maybe more with the overall scenario:
How do you get the plane so quickly from 35kFt high speed to maybe 1kFt at a a relatively slow speed without breaking up the aircraft during the dive/recovery briefly regain control, drop it again and crash it belly first, nose up during the attempted second recovery? (OK, one way this could happen would be if you lost the engines somewhere in the process).

Henra, in support of bearfoil's concept let's consider the weight distribution a little bit more. The whole bottom of the VS is heavier than the top

If you look at the following image and extrapolate the two belts and pull a vertical line from where the two belts join, you get a quite good idea about the Cg of the actual fin:
http://www.airdisaster.com/photos/aa587/4.jpg

That would be between 40 and 45% of the span, i.e. quite comparable to the areal center. So a homogenous model should fit. Probably the best model would be an unweighted foam model.

[JD-EE]

Henra, I admit I am out on a limb here with saw in hand. My understanding is that the recovery technique for a stall is to get the nose down, gain airspeed, and then do something about that solid object towards which you are not headed at an absurd speed. What I'm proposing is that they were at that last stage with too little height to finish the pull-up or even finish a ditch scenario.

I admit this is a reach. It's one way to come close to reconciling a set of data that seems to be utter nonsense. That it requires an "interesting" coincidence of events indicates it's not one of the more likely candidates.

(Another thing the data and discussions have raised in my head is the absurd image if a tail mounted rocket pointed straight down with the intent of getting a plane out of a flat "spin" or sink into which it "supposedly" cannot get into. Sometimes my mind goes "out there". That usually happens when I get tired and start feeling whimsical. I try not to discard even the absurd ideas. That's how I got the one patent in my name, I'd noticed a phenomenon that was irritating in one set of data I was taking. As it happened it applied well to creating an ultra-low powered SatCom transmitter for somebody who shall remain nameless. I am unreasonably proud of that patent, though.)

[JD-EE]

Henra, in support of your assertion that the VS will not fall straight down I note that bearfoil's analysis is spot on if you consider perfect surfaces. As soon as turbulance appears, as in the instant it leaves the plane, the instability will increase probably with the rudder flapping madly until the whole assembly settles into a leading edge down fluttering spinning spiral into the ocean. I can't kick the simple image of dropping a playing card or the spinning maple leaf. Since the weight at the one end of the maple leaf is much larger than the equivalent on the VS and at the opposite end I expect the angle to the vertical at which it goes down to be much more extreme than the angle of that pesky maple leaf. Horizontal would surprise me considerably. 20 degrees of 30 degrees off horizontal would not. A lot also depends on how extreme the extra weight in the rudder's leading edge is compared to that in the mechanisms and hinges on the trailing edge.

[bearfoil]

JD-EE

I think you may have it. Your exuberant description of the final radian missing from a "too low" Loop, is spectacular. Also chilling. I don't know if you know, but I believe that is what people think happened at Perpignan. In there also was the thought that the a/c may have been "protecting" her feathers at great risk of striking the water's surface (careful boys, too much alpha). Not her fault, the pilots lost the plot and did her in.

henra

A gracious good morning to you. My first model was the one I described from 12 to 15 feet. I am enlarging it, (roughly doubling it). The scale and shape is typical of me, wasting time making it perfect, when the proposal is not deserving of the time. If I painted it in her colors, and you squinted from ten feet...... Well, I am basically laminating more heavy paper on top of the smaller version, waste not want not.

If it gets to hot wire and foam blank, and the shape, 'feel' is correct, I may get some sprayable EPON and Carbon and make a knee board for the son. I'll need my Patissier (apron) version, if I end up cooking the sucker. (Why?).

Seriously, so far the model is too perfect, I don't see how it could represent what I propose may have happened to the VS. The weight may be too heavy at the bottom, I think cg is probably 25% off the bottom, and too far back from the LE. That makes it lean back at the top, and behave even more perfectly. There must be something wrong. If I move the cg forward and up, the bottom front corner would strike the surface, (at this stage gravel) and replicate the bent upward ribs, and the failed Resin LE.

Bear

[HazelNuts39]

rockets for deep-stall recovery

Originally Posted by JD-EE

(...)What I'm proposing is that they were at that last stage with too little height to finish the pull-up or even finish a ditch scenario.

(...)Another thing the data and discussions have raised in my head is the absurd image if a tail mounted rocket pointed straight down with the intent of getting a plane out of a flat "spin" or sink

Regarding your first remark, consider also that according to Tim Vasquez' analysis, freezing level was at 16350 ft, and cloud base 2370 ft, so at some point they would have had airspeed back and become visual, even though it was dark night but moon-lit.

Regarding the second idea, it may be of interest that the prototypes of at least one airplane (the Fokker F28) were equipped with four solid-fuel rocket engines mounted vertically in the tail to permit recovery if the airplane would encounter a super-stall condition during intentional stalls conducted to explore or demonstrate stall characteristics for certification. They were never used in earnest, and were removed after initial tests had shown satisfactory stall characteristics. The F28 has rear-mounted engines and a T-tail, so the risk of super-stall was naturally considered early during its development. An airplane of conventional lay-out like the A330 should be recoverable by normal use of the elevator up to angles of attack well beyond maximum lift, but maybe not at angles as extreme as some posters on this thread have suggested, at which the horizontal tail surface would be fully stalled too. To get to those large AoA, I believe you have to persist in pulling the stick fully back, ignoring stall warning and increasingly heavy buffet.

regards,
HN39

[HazelNuts39]

Originally Posted by Machinbird

First upset was close to worst possible
scenario: 4 degrees alpha prot, 6 degrees anti pitch-up

Sorry for late reply, I was 'in transit'. Yes, that's the statement I was referring to. About 2.5 minutes later there was a second upset, in which the uncommanded nose-down elevator movement was 5 degrees. The report doesn't explain why it was less.

AOA processing algorithm using just two sensors only on A330 and A340

My understanding is that the PRIM's compare the output of the three ADIRU's for all parameters, not the sensors directly. For all parameters except AoA, the PRIM's use only one value, the middle (median) one, and monitor the differences to and between the other two values. In contrast with other parameters - "To calculate a value of AOA to use for calculating flight control commands, the PRIMs would use the average value of AOA 1 and AOA 2. In other words, (AOA 1 + AOA 2)/2."

regards,
HN39

[HazelNuts39]

Originally Posted by bearfoil

The consideration in the rulebook is for 36g's (demonstrated) in the plane of the hinges. This obviously begs the question, why is the arm at a 38 degree bias to the "plane of the Hinges". And that is the question of the day!

And that's not difficult to answer! One end of 'arm 36g' picks up the load at the hinge line, the other end transfers it to the rear spar of the V/S at a point where the spar is supported by a V/S rib. A longer arm at a smaller angle to the next spar/rib intersection would presumably be heavier.

For anyone interested in the rulebook text, I have copied the two relevant sections below. Perhaps it is of interest to note that similar criteria apply to elevator and ailerons.

regards,
HN39


Part 25 AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES
Subpart C--Structure

Sec. 25.303 Factor of safety.

[Unless otherwise specified, a factor of safety of 1.5 must be applied to the prescribed limit load which are considered external loads on the structure. When a loading condition is prescribed in terms of ultimate loads, a factor of safety need not be applied unless otherwise specified.]

Sec. 25.393 Control Surface and System Loads

Loads parallel to hinge line.

(a) Control surfaces and supporting hinge brackets must be designed for inertia loads acting parallel to the hinge line.
(b) In the absence of more rational data, the inertia loads may be assumed to be equal to KW, where--
(1) K = 24 for vertical surfaces;
(2) K = 12 for horizontal surfaces; and
(3) W = weight of the movable surfaces.

[mm43]

HN39 wrote:-

.... consider also that according to Tim Vasquez' analysis, freezing level was at 16350 ft, and cloud base 2370 ft, so at some point they would have had airspeed back and become visual, even though it was dark night but moon-lit.

The moon at 2009-06-01 0212z was bearing 268.7°T with a true altitude of 8.7° and the phase was 60.5% of full. Considering the ITCZ activity was spread along an East/West axis, the chances (imo) of the moon placing any light on the situation would be extremely remote.

Weather wise, the BBC2 scenario of "supercooled rain" may well have been the prime cause of extremely rapid freezing of the pitots, and other surfaces may have accumulated significant amounts of wet ice that then stuck to the -45°C surfaces. The possibility of a warm [wet] cell punching through, condensing and falling back through undercutting cooler air can not be ruled out.

Regards
mm43

[mm43]

Vertical Stabilizer & Rudder dimensions

Bearfoil; henra

This may be of interest to you in your quest to establish the "gliding" capabilities of the Tail Fin.

The following dimensions are approximate, and a Center of Gravity for when recovered has been calculated from images and video viewed when it was floating. The trim along with the rudder angle was used to find an approximate center of buoyancy, and then compared with what trim a homogeneous mass of similar dimensions and volume would float at. An estimate was used to adjust for the additional weight of the clevis joints. This change in trim then provided a reasonable approximation of the Center of Gravity.



Airfoil area (excluding the clevis joints) at the base is close to 4.6m^2, tapering to about 0.5m^2 at the top. Total mass of the recovered Vertical Stabilizer & Rudder including attachments is estimated to be 1850kg.

This image from FlightGlobal.com should give you an idea of where the strength is built in to the Airbus Vertical Stabilizers.



mm43

[grity]

trim tank

@mm43 Total mass of the recovered Vertical Stabilizer & Rudder including attachments is estimated to be 1850kg.

but with sume whight into the trim-tank the CG can change his place a lot..... grity

[mm43]

grity wrote:-

..... but with sume whight into the trim-tank the CG can change his place a lot.

The Trim Tank is in the Horizontal Stabilizer - nothing to do with the V/S.

mm43

[HazelNuts39]

mm43;

I'm pleased to see your estimates of mass and c.g. of V/S & rudder close to those used a little while ago to estimate the V/S attachment loads.

Regarding the BBC2 scenario of "supercooled rain", can you enlighten me in which respect the conditions you envisage could have been more severe than the Appendix C conditions that the airplane is designed for and in which it has demonstrated safe operation during certification?

regards,
HN39

[mm43]

HN39

Looks like we are "singing from the same song sheet!"

Regards
mm43

[bearfoil]

mm43

grity's post has a nugget in it, however. The fuel from the trim tank might have been the source of the "bi" in the "furcated" slick, no? Also, look at the cutaway of the area you posted and notice the "bracket clevis tab" assemblies (six of them), and the size of the tail. Then see if anything comes to mind from a stress perspective. Are you certain the fuel is in the HS (s)?

HazelNuts39

Thank you for the rules data. I've yet to work any numbers on stress or design considerations, but at the outset, it's hard to avoid thinking that given the stated purpose of the "Arm", and its photographed deficits, the design is......strange.

bear

[pgroell]

Fuel in HS

I confirm fuel is in horizontal stabilizer, no fuel in VS.

[bearfoil]

pgroell

Yes, Thank You, 10,593 pounds when full. Google iasa the fuel cg graph is splendid, merci

[Machaca]

Plenty of relevant data contained in NTSB report on AA 587 In-Flight Separation of Vertical Stabilizer:

[bearfoil]

Machaca

Dating from BA038, you do come up with the best and most helpful diagrams.
Wish you'd talk more, but.....

The failed Lug you bring up is what would be 3A if the Lugs were indexed Fore/Aft and Port/Starboard. As I see it in any case. Basically, at the point of peak energy, acting to pull the Lug free (up) out of 3A bracket, The Rudder has just reversed from a Starboard correction (reversal) and the Fuselage has swung right (Tail Left). The Rudder then is commanded full Left, the VS is exposed to peak shear, peak Tension, Maximum Torsion, and just as the Fuselage is at it's most right YAW, the VS is loaded beyond Limit (Ultimate). All three forces reach Limit concurrently, and the Lug Shears/Bracket Releases. The Noise must have been LOUD. The way to simplify the image is to imagine the tip of the VS straining over to the Right, the axis twisting counterclockwise, and Tension is a Triangle, the strongest structure in Engineering. The Triangle consists of the forward and (partially) middle lugs, the tip of the VS and the Left Rear Lug, the Peak of the triangle. There is a fulcrum at 3B.
The failing Lug pulls out, and the VS is essentially at failure. Even at this point, if the Rudder had been centered (by any means, including leaving the a/c), the 300 may have been saved. The first failure was not the Fatal one,imo. The VS still was attached, and more reversals finished the separation as evidenced by the sequence of Thumps on the CVR.

I think if we keep in mind the energy it took to uproot this Vertical Stabilizer, we get to the place of contemplating a solution for the next iterative wide-body, the 330.
Limit load for gust is half that of demonstrated catastrophic failure. At the point that the problem began, Wake Turbulence was behind and the jet should have been climbing out. Is twice the limit load a necessity? No, not at all. The limits are sound, and workable under all conditions. Why did the aircraft crash? WT? No, not in any direct way. It is a cause only in that it started something that should never have happened. Over Control, maximum Ruddering, at maximum rate. Why? The pilot was alternately stomping on each pedal? Out of phase 180 degrees? I do not think so. The pilot and the machine had no idea what the other was doing? Possibly. If the conclusion of the NTSB is that the pilot cycled the Rudder like a novice, also, no.
The Airplane can fly without a Rudder, It cannot stay airborne without a Vertical stabilizer. A small Pitts or Extra can flop its surfaces helter skelter, a 180 ton beast can not. (Not as currently manufactured iac)

Bear