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AF 447 Search to resume

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AF 447 Search to resume

Old 27th Aug 2010, 20:18
  #2021 (permalink)  
 
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GreatBear

In Post #1673 I included a screen shot taken in the Recife RCC showing that the FAB were searching from the LKP.

SaturnV

I have overlaid the FAB's Position of Corpos graphic information on the equivalent data published by the BEA. The reference points were the background Google Earth bathymetry. This leads me to reiterate that the data published by the FAB's media arm bore little or no relationship to the truth.



The FIR boundary (red), the Último Reporte position (red) and TASIL position (black) from the FAB's graphic have also been included.


mm43
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Old 27th Aug 2010, 20:41
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Bearfoil:
The "Airfoil" shape hasn't anything to do with The VS' purpose.

Without an airfoil shape the VS wouldn't create lift and therefore couldn't provide vectored force (work) upon the airframe, no?
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Old 27th Aug 2010, 20:53
  #2023 (permalink)  
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The VS exists to prevent the a/c from getting out of shape, period. A Rudder isn't a necessity, as you know, which means the VS needn't be so equipped, and the shape in cross section does not create an airfoil. Technically, and I insist on it, an airfoil has an asymmetric cross section, not a symmetrical one. An a/c can fly with large razor blades for wings, airfoil isn't at all necessary. Examples abound, but I've started a discussion in Tech Log, rather than here, hope to see you,

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Old 27th Aug 2010, 21:15
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Originally Posted by bearfoil
Technically, and I insist on it, an airfoil has an asymmetric cross section, not a symmetrical one.
As an aeronautical engineer, I totally diagree ; I consider your definition of an "airfoil" to be quite simply wrong.
A plank can be an airfoil, a lousy one admittedly.
The F-104 has wings that are little more than razorblades, and with a symmetrical profile (with the flaps up). They're still airfoils.
There is a whole library of symmetrical NACA airfoils, and there are aircraft flying with them.
I saw you mentioned a separate subject in TechLog on the subject, so I'll go and look there before any further comment.

As to all these discussions about a detached V/S behaving even vaguely like a wing.... anybody here made up a model with about the same shape and roughly the same mass distribution and tossed it off a 10-story building? If not, why not? It would give you some real ideas about the weird and wonderful things a shape like that can do when falling through the air.

CJ
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Old 27th Aug 2010, 21:31
  #2025 (permalink)  
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ChristiaanJ

bonjour! I used to walk by Yeager's F-104 (at the time on a pylon outside the lounge) on the way to "work", and the hard points at the tips were quite visible. The wing in cross section was thin alright, the LE had a cover on it, it was 1mm radius I believe. The wing also had a definite asymmetry, not so much in chord but it had a double curve, looking straight down the tip, it looked like a noodle. It had massive Flaps, basically planks, no airfoil. The Wing appeared to be machined out of billet, but I have seen working drawings, they are rib spar and skin, (Very thick skin relative to thickness of the wing overall). As I recall, the reason for so much anhedral was the airframe was too stable in roll, so the pilot was busy staying level. A lazy pilot of this thing was a dead pilot.

Hope to see you on t'other thread, I haven't lost my marbles, and my theory has more to do with nomenclature than one may assume at first. Oh, yeah, the rumor was that a living 104 jock had tattoos on the inner eyelids, "Speed is Life".
 
Old 27th Aug 2010, 22:09
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bearfoil,
See you on the other thread, before I go off-topic on the F-104... she who climbs like an angel, and glides like a brick....

CJ
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Old 28th Aug 2010, 01:00
  #2027 (permalink)  
 
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ChristiaanJ
As to all these discussions about a detached V/S behaving even vaguely like a wing.... anybody here made up a model with about the same shape and roughly the same mass distribution and tossed it off a 10-story building? If not, why not? It would give you some real ideas about the weird and wonderful things a shape like that can do when falling through the air.
Hi ChristiaanJ, Yes did the experiment with a piece cut from paper small enough to not significantly distort from the Q loads. Reynolds number is way low of course, but it did just what I expected and fluttered down like a leaf. I really don't think there are any stable non-rotating modes for a single surface with relatively uniform mass distribution.
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Old 28th Aug 2010, 01:15
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hi Machinbird

I think a slow spiral is possible bottom first, I don't consider the mass to be at all evenly distributed, with taper at the top edge, much more massive root and attached structure.

Now I must build a model, I'm thinking a meter or more in height, and rigid, meaning styrofoam, and a floppy TE. Probably more height at launch, too, to allow stability to "set" (perhaps wishful thinking.)

17:45 local. 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. More drops and notice a peculiar thing. It falls in fidelity with the aspect I drop it with. Top down release, top down all the way. Bottom down release, bottom down all the way. Perhaps a third of a square foot in total area with a weight of 50 grams, the weight may need to decrease, there has to be something wrong with the stability I'm seeing. It is too stable. GreatBear of great animation, are you interested in some unpaid work?

bear

Last edited by bearfoil; 28th Aug 2010 at 01:50.
 
Old 28th Aug 2010, 03:00
  #2029 (permalink)  
 
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mm43
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I believe somebody some time ago pointed out the part's part number was 36g? Or did I miss that getting refuted.
Arm 36g was so named due to a requirement in the regulations, and its part name is directly related to the moment it was designed to handle. HazelNuts39 found the appropriate reference, and though I haven't done a search, the original discussion on the subject is spread through pages 20 ~ 30 in this thread. I believe that OE's analysis of Arm 36g is probably correct, and tail strike protection of the rudder is probably the prime reason for its existence.
Nonetheless, are we missing the point that "36 times the acceleration of gravity" is not a force? What is it that gets accelerated and what is the actual force vector that widget is supposed to handle?

When we know that we can address bearfoil's well meaning if persistent insistence on a specific loss of VS type scenario. 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. The tail strike in that situation would put the tail underwater first with very heavy drag and the elevators providing sufficient force to peel the tail assembly upwards damaging the nose of the VS and breaking the attachments in the manner shown. That seems low probability. It seems to explain the particular damage to the plane, especially if the tail assembly as a whole is also torn off. It does not explain the mostly level attitude, though. What attitude of such a plane produces a tail strike while it is still on the runway? I presume a somewhat lower angle would strike the tail first before the main part of the fuselage with no landing gear down.

This all hinges, pun intended I suppose, on the meaning of the 36g, the vector of that acceleration, and the design strength of the widget. It also is important whether that part's strength is intended for tail strike protection. 36 times the acceleration of gravity is one hellacious jolt. The passengers might not survive it even if the VS did.
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Old 28th Aug 2010, 03:17
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GreatBear for what it is worth I do remember some intensive search in that general area. It was postulated at the time on the old list that they were trying to make it to one of the two slightly inhabited virtually invisible on GoogleEarth islands in the area.
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Old 28th Aug 2010, 03:21
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MucMuc, you're quite right on postulating eddies and the like. The other thing to consider from FluidFlow's analysis is that it does not account for the bodies probably being underwater, perhaps at a non-negligible depth, for the first few days coming up to the surface after decay had generated enough gas to bloat the bodies.

So two things are needed, the underwater current profiles and the unknowable depth to which the bodies sank. His analysis is a good line on which to search. And with the sinkage in mind that puts the likely crash site pretty close to where the slick was found, does it not?
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Old 28th Aug 2010, 03:24
  #2032 (permalink)  
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JD-EE

At impact, I think there was very little "sinking" happening. It is virtually certain the tail left the a/c (the entire tail), and the cabin interior started to spill right away.

"10g's". Layman wise, that means a 200 pound pilot is "pulling" 10 g's, and "weighs" the equivalent of 2,000 pounds. Same for the Rudder. If it weighs 200 pounds, 36g's mean it "effectively" weighed 7200 pounds. 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! Rulebook notwithstanding, from an engineering consideration perspective, WTF? I still think that because at the most predicted deck angle of the a/c for a tail strike, the "36g" arm is 90 degrees to the deck, suspiciously looking like it was designed as OldEngineer would have it. I think he's right. If the Rudder does weigh 200 pounds, I consider it extremely "light" (meaning strength to weight, here), and sufficiently attached with the seven hinges (which look like they could be salvaged and re-used), to keep the Rudder in pristine condition throughout its challenges, and as I have said before, strong well in excess of the considered forces encountered in the crash, and demonstrably to the detriment of the a/c. "Lose a Rudder, keep a Fin".

bear

Last edited by bearfoil; 28th Aug 2010 at 03:38.
 
Old 28th Aug 2010, 03:26
  #2033 (permalink)  
 
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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. Perhaps it would show a tendency to spiral nose down much like a maple leaf, even though the shape is radically different.

Building a rude and crude model out of a business card cut to a triangular shape plus some dabs of modeling clay or library paste on the leading edge and along the "bottom" of this pseudo-VS structure.
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Old 28th Aug 2010, 03:42
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bearfoil, it appears it was specifically designed to withstand a force of 36 times the weight of the rudder parallel to the rudder's hinge line. That sounds like tail strike to me. What else would put that specific load on the widget?

That came from just a few messages earlier by mm43.

And something to consider in your tests - the rudder probably flops around pretty easily. That will upset any airfoil situation, won't it?
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Old 28th Aug 2010, 04:01
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Bearfoil

With no hydraulics the rudder is "free"- about +/- 35 degrees. It will obviously follow any movement of the V/S and could compound a tumbling type scenario.

JD-EE

Thanks for drawing attention to my earlier post re "arm 36g". With the subjects jumping around, stuff tends to get missed.

mm43

Last edited by mm43; 28th Aug 2010 at 04:15.
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Old 28th Aug 2010, 04:11
  #2036 (permalink)  
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Not long ago I posted what I think is the solution to what you propose. The Rudder is not powered, it deflects, and in doing so removes energy from the system; it has no impetus to hold anything but centered, more energy outside the system, meaning stability, not chaos. The airstream wants to bully the panel, not the reverse. There can be no "helicoptering", like a pine seed spinning slowly down in the forest, the "tips" are way out of mass, drag, and inertia to maintain that image. In fact, they are so incongruent, what I am getting with my second iteration is a slick plummet, no chaos, no "low speed". The higher I go before dropping it, the faster it drops. I'm working on getting some video, that will take time, but my sis is a CG professor, and maybe I can have a chat with her. I'd need help posting the images anyway.

Done for the day I am. All the best mm43
 
Old 28th Aug 2010, 04:23
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Bearfoil

I've read your posts on the "Bernoulli was a plumber" thread, and believe you are right when saying the rudder will center and follow. I'm reminded of the laws of nature - the blunt end always comes first, be it giving birth, the LE of a wing or the LE/base of the V/S and its child - the rudder!

mm43
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Old 28th Aug 2010, 04:34
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JD-EE

The Hinge Line is the pivot edge of the Rudder. The Hinge Plane, is the Sweep of the Rudder. The rule is for the Plane, the Tail Strike is what is assumed by me to be the design consideration of the Arm. Someone is confused, it may well be me at this point, but I will still say that BEA got it wrong if Plane is what they meant to demonstrate. You are correct if tail strike is what you are saying also.

mm43

Noted, and thanks.

bear
 
Old 28th Aug 2010, 06:31
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Has the investigation report come out yet?
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Old 28th Aug 2010, 06:45
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AF447 - current search status

Andy98 wrote:-

Has the investigation report come out yet?
The short answer is no. There have been two interim reports issued by the BEA, but without the flight data recorders the final report remains on-hold.

Published today in the Edmonton Journal is a piece attributed to the Waitt Institute, which along with the Woods Hole Oceanographic Institution were responsible for the supply/operation of two of the AUVs used in the Phase 3 search. Gives an insight into the terrain encountered and the bumps and scrapes suffered in the process, and a prognosis that the search will resume.

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