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AF 447 Search to resume (part2)

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AF 447 Search to resume (part2)

Old 4th May 2011, 16:52
  #661 (permalink)  
 
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@jcjeant
Concretions on the CVR pinger ..... indication of a crack ?
I think this may be galvanic action where the aluminium housing of the pinger is acting as an anode and is corroding rather than the ferrous cylinder. Further evidence of this is that there appears far less rust on the CVR cylinder than the FDR which has lost its pinger, and hence no sacrificial anode to stop it rusting. There needs to be an electrical path between pinger and cylinder for the effect to occur, which I assume is there somewhere.

Galvanic anode - Wikipedia, the free encyclopedia

Sacrificial protection on the hull of a ship using a Zinc anode.

Zinc anodes protect the steel parts of the hull | Flickr - Photo Sharing!
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Old 4th May 2011, 16:54
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bearfoil,
What's a 'guppy' in your neck of the woods?

In my world, the 'Guppies' are blown-up Stratocruisers and A300s with faulty cabin pressure regulators.... LOL.
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Old 4th May 2011, 16:54
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The only suggestion of independent power supply that has emerged was after SR111 and that was the voice recorder.
Airbus CVR designs currently record 4-channels - the Capt, F/O and 3rd occupant crew mic signals, and the CVR area mic. Since the crew microphones within modern aircraft are all 'powered' (electret), these will be lost if electrical power is lost. The dedicated CVR microphone could be powered from an internal supply sourced from a battery supply, so that would remain active.
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Old 4th May 2011, 16:59
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Might be an American or 'company' thing, Chris, a guppy is a 737. Alas, they are all gone, victims of the 320. (Not that there's anything wrong with that!!)

 
Old 4th May 2011, 17:06
  #665 (permalink)  
 
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Corrosion on pingers ?

If it's corrosion on the pingers, it is probably galvanic corrosion ( occurs between metals of different potentials in seawater).
But since the waranty ends after 30 days at sea, I don't think the designers cared about this.

Last edited by DJ77; 4th May 2011 at 17:11. Reason: Ooops, BJ-ENG fired first.
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Old 4th May 2011, 17:07
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Originally Posted by ChristiaanJ
Even without a vertical tail, the rear end of the fuselage provides some "weathervane" stability, ...
Modern Airliners are not realy designed like a "weathervane". Large part of the fusalage is ahead of the CG as opposed to e.g. the B52. The lateral drag of the fuselage that incurs ahead of CG generates a destabilizing yaw moment, the lateral drag aft of CG generates a stabilizing moment. I.e. the larger the part of the fusalage aft of CG, the better the a/c will fly without VS.

A swept wing without a fuselage doesn't need a VS to fly:
Horten Nurflugels
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Old 4th May 2011, 17:09
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Caygill,
"If you lose all power on a modern aircraft..."
Rare... since there are batteries, and inverters to generate some essential AC from the 28V DC battery bus.

Us engineers are not quite as stupid as you seem to think.
RTFD... and so far I've seen almost nothing about the A330 system.

RR_NDB has a few points.
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Old 4th May 2011, 17:09
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OleOle


Define "Fly"......
 
Old 4th May 2011, 17:13
  #669 (permalink)  
 
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Originally Posted by GarageYears View Post
The dedicated CVR microphone could be powered from an internal supply sourced from a battery supply, so that would remain active.
And what tells you that's not already the case?
Unless you have the full WDM for the A330 at hand....
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Old 4th May 2011, 17:22
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Define "Fly"......
Something like seen here ?

YouTube - Horten Ho-2 Flying Wing Test Flight 1935
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Old 4th May 2011, 17:26
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Originally Posted by bearfoil View Post
Might be an American or 'company' thing, Chris, a guppy is a 737. Alas, they are all gone, victims of the 320. (Not that there's anything wrong with that!!)
[offtopic]
OK, bear, never heard that term for the 737...
Saw 'Fat Albert' a few times, then found that that particular 'sobriquet' had shifted to the C-130....
I like the 737, less of a noisy flying Coke can than the A320 family, from the SLF point of view.
[/offtopic]
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Old 4th May 2011, 17:28
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OleOle

I flew a Manta 'Wing' in the seventies, so am familiar. Just a little fun poked at Jack Northrop and his obsession. At a billion dollars a copy, the B-2 is less a flying wing than an airborne Bank, or money sewer, depending on one's pov.



ChristiaanJ

Then there is the BUFF. Boeing gets the familiars, eh??
 
Old 4th May 2011, 17:28
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And what tells you that's not already the case?
Unless you have the full WDM for the A330 at hand....
Which I do...

18V DC is derived for the CVR area mic preamp, from the 115V AC supply delivered to the CVR.
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Old 4th May 2011, 17:29
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Trying to keep some VS effect for a minimum of "airworthiness "

ChristiaanJ,

The separation of VS in both cases (AA587 and AF447) occurred at its "coupling" to the fuselage. This "coupling" in EADS design appears to be the "point" that fail when the loads exceed the specs. The "connection" between "conventional metal" to "new materials" advanced VS structure.

Question:

Wouldnt be better/safer to have a "tapered design" with greater "Fault Tolerance" and "Graceful Degradation".

I mean:

Considering the main reason for a big VS is for take off * why not to have a tapered (strength) design?

To keep some VS effect even after exceeding specs limits (due any reason)

(*) Exceptions: Windy and cross wind Landing

Rationale:

Redundancy, fault tolerance and graceful degradation are "defense lines" against our "nightmare": Murphys law.



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Old 4th May 2011, 17:35
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Mac, you made your point.
Once the entire VS comes off, all bets are off too, one could say.
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Old 4th May 2011, 17:36
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Very long New York Times article on the finding of AF 447.

What Happened to Air France Flight 447? - NYTimes.com

There is a lot of history, and some theorizing. Quite a bit of information on the autopsies, with the doctor indicating that he couldn't rule out that some might have survived the initial impact.
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Old 4th May 2011, 17:41
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RR NDB

"Sequential Failure". A time worn concept, whether "crumple zone", or ablative skin.

The problem is at least "twofold". One is the almost unavoidable problem of mating plastic to metal, mechanically (1), or bonded (2).

On the Airbus VS it is mechanical. This presents the "focal energy" obstacle. A concentration of stress in Epoxy/Reinforced structures is counter intuitive to the material's strong point. Thus a dowel, pin, or clevis, bracket system focuses failure sums of energy on an assembly whose design is related to stress/spread for maximum load areas. Note the A350 has gone to 5 (five) saddle/pin systems.

The second, bonded, is universally avoided unless some spread can be attained.

The most important consideration is the fact that this most critical assembly is "surface mounted". This concentrates virtually all Stresses on an inescapably small area. The VS/Rudder is vertically cantilevered, a swell looking and very efficient way to alleviate drag from external wetted areas.

However.......


edit... I cannot locate the "lateral rods" on the bare aft fuse of the 587 A300. These were added to later a/c....... There are pictures of these rods on the VS (447). After the fact design, hmmm.......

edit... Disregard, I did find a remnant of the "Lateral Rod" on aft bracket.
sorry...
 
Old 4th May 2011, 17:42
  #678 (permalink)  
 
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Originally Posted by RR_NDB View Post
ChristiaanJ,

The separation of VS in both cases (AA587 and AF447) occurred at its "coupling" to the fuselage.
No it didn't. In AA587 as shown in your images, the VS structure was torn off the couplings.

In contrast, in AF447 the couplings did not fail and were still attached to the VS along with bits of the fuselage. The rear fuselage itself failed. BEA first report has images (P39): http://www.bea.aero/docspa/2009/f-cp...90601e1.en.pdf
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Old 4th May 2011, 17:53
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Bear

Think you got your numbers mixed up, it isn't a 737, it is a 377 Super Guppy

http://upload.wikimedia.org/wikipedi...SA_landing.jpg
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Old 4th May 2011, 18:07
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Quote:
Originally Posted by RR_NDB
ChristiaanJ,

The separation of VS in both cases (AA587 and AF447) occurred at its "coupling" to the fuselage.
No it didn't. In AA587 as shown in your images, the VS structure was torn off the couplings.

In contrast, in AF447 the couplings did not fail and were still attached to the VS along with bits of the fuselage. The rear fuselage itself failed. BEA first report has images (P39): http://www.bea.aero/docspa/2009/f-cp...90601e1.en.pdf
Precisely! One shows a fuselage with bits of fin attached, and the other shows a fin with bits of fuselage attached. Huge difference!
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