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AF 447 Search to resume

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AF 447 Search to resume

Old 26th Aug 2010, 00:29
  #1981 (permalink)  
 
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GreatBear;

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

mm43
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Old 26th Aug 2010, 00:49
  #1982 (permalink)  
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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

Last edited by bearfoil; 26th Aug 2010 at 01:13.
 
Old 26th Aug 2010, 01:17
  #1983 (permalink)  
 
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Regarding the BAC 1-11 superstall accident and other such accidents and likely true for AF447, Davies' comments still ring true, “There is no point in discussing the irrecoverable case any further, except perhaps to say that those aeroplanes which have been lost in such manoeuvres finally reached the ground substantially level laterally, having defied all efforts to roll or spin them out of the stabilized condition; only slightly nose down in pitch, with little or no forward speed; at an extremely high incidence; rotating only very slowly in yaw; with (in one case) all the engines flamed out because of being exposed to such massive angles of incidence; and finally with an enormous vertical velocity.”
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.
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Old 26th Aug 2010, 01:37
  #1984 (permalink)  
 
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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.
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Old 26th Aug 2010, 01:46
  #1985 (permalink)  
 
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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
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Old 26th Aug 2010, 01:48
  #1986 (permalink)  
 
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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?
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Old 26th Aug 2010, 01:51
  #1987 (permalink)  
 
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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.
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Old 26th Aug 2010, 01:56
  #1988 (permalink)  
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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.

edit
JD-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?

Last edited by bearfoil; 26th Aug 2010 at 03:05.
 
Old 26th Aug 2010, 04:06
  #1989 (permalink)  
 
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Bearfoil
You are putting words into my keyboard.
Apologies! I have enough trouble with my own keyboard, let alone playing tunes on yours.

Cheers
mm43
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Old 26th Aug 2010, 04:08
  #1990 (permalink)  
 
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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.
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Old 26th Aug 2010, 05:33
  #1991 (permalink)  
 
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Old 26th Aug 2010, 07:04
  #1992 (permalink)  
 
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"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
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Old 26th Aug 2010, 08:49
  #1993 (permalink)  
 
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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.
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.
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Old 26th Aug 2010, 13:25
  #1994 (permalink)  
 
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This article appeared today in IEEE spectrum:

IEEE Spectrum: Beyond the Black Box

There was discussion about this in this thread, so...
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Old 26th Aug 2010, 14:28
  #1995 (permalink)  
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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

Last edited by bearfoil; 26th Aug 2010 at 21:50.
 
Old 26th Aug 2010, 22:55
  #1996 (permalink)  
 
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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}
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Old 26th Aug 2010, 23:18
  #1997 (permalink)  
 
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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.

{^_-}
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Old 26th Aug 2010, 23:18
  #1998 (permalink)  
 
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JD-EE
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.

mm43
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Old 27th Aug 2010, 01:39
  #1999 (permalink)  
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mm43

Hello again. I think a discussion of Tail strike protection would be fruitful. The first consideration is to spread focal stress as the tail hits and the VS wants to keep going. With a pitch sufficient to hit tail first ~17 degrees, the Hinge axis of the rudder is roughly 34 degrees off vertical and the arm restraint would be roughly 90 degrees to the deck, so the effort seems to point to protection of the Rudder from deforming the hinge plates from a linear alignment (all seven). If the hinges deform from line, the Rudder will Bind, and not perform, an expensive fix. In this way I think the arm makes sense. OldEngineer points out the increasing danger of arm failure as the attach point decreases in size, specifically Bolt Size. The other way to express this is to say that as the attach points increase, not in mass, but in bedded area, the forces are attenuated with less structure and less risk of breakage. In arm 36g, the bolt subtracts substantial cross section from the arm, such that a failure such as we see in 447 is not surprising. Without sounding arrogant, I think rather than an arm, with its attachment vulnerability to tension, perhaps another way to address the "drop" of the Rudder relative to the VS, to protect the Rudder hinges would be to fasten plates to the spar and the Rudder Pinion, such that rather than focal (tension) strength, the area is protected by a more familiar shear solution. This would be addressed by a composite of sufficient cross section to carry the load away from the hinges, and load the Aft Spar of the VS spanwise to the Rudder Pinion(s).

It may be that the arm is after all not intended to "Balance" the shear forces of the two control surfaces under landing and tail strike events, so I have to wonder what the purpose of featuring the picture of the arm is meant to convey. At first I assumed the Picture and the numbers were included for people to make of it what they may. BEA makes no actual finding re: this arm, so does anyone have a more evolved take on the Arm issue?

Edit. Whatever people may think of my continued presence here, including those I perhaps offend regularly, my passion is genuine and my purpose is to find out the truth. I relish responses from every single person here, and could not begin to single out folks at which to direct my admiration. I am here to learn. I write no drafts, and I post without even editing for spelling and grammar. I do not even know how to drag a quote, and my prose may get brash or conceited. In person I am quite sociable, but in text, especially here, I sometimes cannot hide my feelings still. My family does much business in France, and travels regularly on Air France, a grand and enjoyable Airline to most of us, some of us like the Old Blue "Murican" legacy, no accounting for taste.

Cheers, and may the recorders be found.

bear
 
Old 27th Aug 2010, 03:22
  #2000 (permalink)  
 
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On the note on recorders, an interesting paper was published this year on Recovering Data and Voice Recorders Following At-Sea Crashes.

I can't link the paper, but i'm posting the abstract below. If anyone wants to read the whole thing, send me a PM and i'll email it to you.

Abstract – The international aviation safety community has
concluded that existing methods of blackbox localization and
recovery are not effective in deep ocean situations, and
occasionally not effective even in relatively shallow water when
the acoustic pinger is buried or covered in debris. The majority
of these pingers are provided by two companies, Teledyne
Benthos and Dukane, according to pre-determined form and
function, and these devices are essentially “built to spec.” The
purpose of this paper is to identify the shortcomings in the
existing, decades-old functionality and to recommend the
introduction of acoustic modem technology to provide orders of
magnitude improvement in blackbox localization and data
recovery.
Fundamental ocean physics clearly indicates that the
following conceptual changes should be considered:
1. The current pinger technology operates at nearly 40 kHz
frequency. Simply reducing the frequency to perhaps 12
kHz will substantially increase range in seawater and
even improve performance when the device is covered in
sand or debris.
2. The devices use very short sinusoidal tones (usually
called tonals) as their signals. Ocean propagation often
is highly selective in frequency due to the constructive
and destructive alignment of propagation paths – some
frequencies are supported, others are canceled.
Furthermore, it is difficult to transmit sufficient energy
into the water with these signals.Tonals are very poor
candidates for robust, reliable ocean signaling.
In addition to fundamental issues, the current system
operates by a water-activated commencement of repetitive
transmissions (pings) of these short tonals the moment the device
enters the water – even though no listening devices are present.
This is a waste of energy.
In this paper, we provide a brief overview of acoustic
propagation from the perspective of its differences with more
commonly understood radio frequency (RF) propagation. We
follow that with our suggestions for substantial changes in
operational concept, specifically arguing for wider bandwidth
waveforms with more sophisticated receiver processing.
However, given the effort to utilize more complex systems, we
recommend they be further adapted to support underwater
acoustic communications (acomms). This will provide blackbox
and crash recovery far more effectively than is now possible, and
can support data recovery when the devices themselves cannot be
recovered. In particular, acomms modems can be used in support
of long-range, accurate position estimation by either manned or
unmanned platforms. Our proposed system will be somewhat
larger than the present system, but it will significantly enhance
the ability to find a submerged black box.
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