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AF 447 Search to resume (part2)

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AF 447 Search to resume (part2)

Old 14th May 2011, 10:17
  #1321 (permalink)  
 
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gums,

Here in Europe on the morning after, looking at my previous post, I think something else needs to be said. For reasons we can easily understand, these AF447 threads have attracted a wide range of experts and/or enthusiasts whose combined contributions I doubt have been bettered on any other PPRuNe topic.

These discussions would have been very limited indeed if the only contributors had been airline pilots, Airbus or otherwise.

Last edited by Jetdriver; 14th May 2011 at 21:00.
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Old 14th May 2011, 11:35
  #1322 (permalink)  
 
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From the BEA, as quoted by HN39 above:
Les déformations des cadres montrent qu’ils se sont rompus dans un mouvement vers l’avant avec une légère composante en torsion vers la gauche.

HN39,
So, do you infer that the R/H side struck the water first?
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Old 14th May 2011, 11:55
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Chris,

yes, my reasoning is that the V/S inertia tends to let it move forward without twisting. It is the fuselage violently veering to the right which 'twists' the frames.
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Old 14th May 2011, 13:01
  #1324 (permalink)  
 
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infrequentflyer789,

Everyone on the flight has already been declared dead by an official accident investigation. Even if that isn't recognised in Brazil, then there will be jurisdictions where it is, and AF & AB have a lot of presence around the world - plenty of places to sue them.
This is not so straightforward. Some brazilian relatives already tried to sue Airbus in the USA, but the american judges refused that (link in portuguese). Besides, I think each jurisdiction is sovereign to accept or not accept the "official declaration" by BEA.

There is also a juridical thesis affirming that as most brazilians victims bought their tickets in Brazil, AF and AB must be sued under brazilian legislation. And here, if you can´t have a death certificate derived from the identification of a body, you must have a "presumed death certificate", that is a considerably longer and bureaucratic procedure.

PS: I´m not a victims´ relative.
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Old 14th May 2011, 13:22
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auv-ee, the spreading or square law loss is about 20 log10( 1700 ) if we use 1700 meters as the ultimate range. That's only 65dB (pulling it off a calculator rather than my semi-memorized log tables.) Add in a generous 10dB for the extra attenuation of H2O at that frequency - as somebody else cited, and you get slightly less than 75dB. So gives about 86 dB above 1 micro Pascal. If the noise level is only 36dB give or take a few dB we still have about 50 dB more attenuation to cover. We are working one way rather than radar range calculations that raise exponents.

That extra 50dB comes from ???? Antenna loss and other properties are figured in already on the sensitivity and sound pressure at 1 meter figures.
That hints the range at noise floor is about 300 times 1700 meters.

Ah, I had not allowed for bandwidths. I presume the figures you gave are in the traditional 1Hz bandwidth. If we use 100Hz FFT that's 20dB of the 50 dB right away. If we use 100kHz bandwidth and simply look for an amplitude change that could account for the full 50 dB and why Thales may have figured post processing with say a 1kHz set of FFT windows should bring it right out.

(That was a stupid omission in my original analysis. Learning the actual measurement method would probably lead to better answers, too. I bet that would take a REAL lot of digging.)

For the onlookers:

It's called square law or spreading loss because the signal has to cover more area on the surface of a sphere as the signal expands out from the source. The area of the surface of a sphere is an r^2 or range squared function. So the power drops with the range squared.

Noise is usually figured in decibels, 10 log10( power ratio), and are a logarithmic ratio with no units. A very handy measurement when dealing with signals in noise is the amount of noise at the frequency you are operating in a known bandwidth, usually 1Hz. Since the noise is usually incoherent noise doubling the bandwidth doubles the power.

So we end up with a "20 log10( distance ratio) + 10 log10( power ratio) + incidental numbers" sort of calculation. I hope that filled in gaps for most people.
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Old 14th May 2011, 13:26
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bearfoil, I have long contemplated an upset or intentional rapid dumping of altitude with the crew in control or back in control before the splash. They may have been trying to goose the engines hard enough to get them back flying after the altitude loss and simply ran out of sky. I'm not sure there is near enough data to fully support that scenario. I am not sure there is enough data to rule it out. That's why I've not harped on it.
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Old 14th May 2011, 13:31
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HN39,

Just to clarify: you have the aircraft yawing to the right on impact, so the rear fuselage and VS swing left? When the APU detaches, it might be thrown to the forward-left even more than the fin?

We know about the THS screw-jack, but I wonder what happened to the THS itself. Or should we treat the L/H and R/H elements separately?
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Old 14th May 2011, 13:38
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Centrosphere, under what theory would an accident that happened on a French plane, on a flight from Brazil to France, that happened over international waters in the Atlantic ocean fall under the jurisdiction of a US court? We're not THAT arrogant that we think we should have world wide court jurisdiction.
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Old 14th May 2011, 13:49
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Chris;

All I wanted to say is that, if I have to choose between left wing low and right wing low, I vote right. At or after the impact of the rear fuselage, that's where the flight ends for me.
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Old 14th May 2011, 13:53
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Originally Posted by takata
Second, you'll need a bunch of incompetent designers (for all those unreliable flight envelope protection systems)
No question, these guys are very competent designers, but the more complex the design , the more chance something unexpected and/or foreseen will eventually present, sooner or later.
The flight envelope protection systems are reliable as long as the numerous sensors send the accurate and real information and also that this information is processed as designed by the different computers ...

Originally Posted by sensor_validation
Don't you find the evidence posted by BEA compelling.
Not at all.
Still trying to figure out why the BEA did omit the tracks of IB6024 and LH507 ?!
They have crossed the full red too, but as HN39 wrote much earlier : always keep in mind that the big systems seen by satellites don't necessarily show up like that on an aircraft's weather radar.
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Old 14th May 2011, 14:30
  #1331 (permalink)  
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Salute!

Nuts is onto the original reason I joined the fray here two years ago.

Having flown the first "operational" full FBW system, I was a non-volunteer test pilot, as were all of us in those days ( 1979 and a few years thereafter). We only had a few hundred flights by then, and most were by Edwards "golden arms" and highly experienced fighter pilots. When we increased the sortie rate by an order of magnitude, we discovered flight conditions unforeseen by the engineers and the "golden arms". So we were flying several hundred flights a month versus the several hundred flown from 1974 to 1979 during F-16 development and testing.

We clever pilots can find ways to "beat the system". We can do things that the engineers and others never envision ( see Perpignan, for example, or the first crash with a high-time pilot making a low pass for public relations). Then there are actual flight conditions that the engineers have not planned for with all their control laws, limiters, reversion sequences.

Let's face it. The Viper has an operational envelope that waters your eyes compared to the 'bus. We had and have different priorities on our flight control logic, and gee was the easiest to implement. It was and still is the aero that causes problems. Our great engineers never envisioned us zooming up at extreme pitch attitudes, then trying to roll at max rate below 150 knots or so. NOBODY DID THAT!!! Simply because they couldn't until then. So now we have a jet that feels good, handles better than anything flying and we get spoiled. We "go where no man has gone before", heh heh. Hence, we discovered that exceeding the flight control laws wasn't all that hard. Especially with respect to the AoA protection. Then we discover that at 50 or 60 degrees AoA that we run outta nose down pitch authority. Well, hell Kemo Sabe, what are you doing at 50 deg AoA? The limiter was supposed to keep you from exceeding 25 degrees. So see the Code One article and read what we discovered and how to get outta a bad situation.

So my personal observation is that this accident will be found to be in the category of "unplanned flight conditions", possibly complicated by one or two sensor failures.

I also see a few modifications coming for the 'bus control laws. It's digital, right? So not a lotta hardware needed, just some good flight tests with modified control laws/reversion sequences.

Last edited by gums; 14th May 2011 at 15:39.
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Old 14th May 2011, 14:30
  #1332 (permalink)  
 
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JD-EE, seem to me your numbers about transmission losses are about right. However, since the source frequency is 37.5 ± 1 kHz, I think we can safely assume that the bandwidth of the TPL reciever is at least 2 kHz. Counting only sea state noise (7 to 10 kt, no rain) we have about 34 dB re 1 uPa / 1Hz wich gives a 67 dB noise level. Using your numbers for transmission losses this leaves 160 - 75 - 67 = 18 dB available for detection @ 1700 m, a value considered minimal for simple detection (learned from auv-ee).

By the way, I am wondering if the towed array the french navy submarine dragged was really a usefull asset. Theese things may not be efficient at all at 37.5 kHz even using DSP.
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Old 14th May 2011, 15:17
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JD-EE,

Centrosphere, under what theory would an accident that happened on a French plane, on a flight from Brazil to France, that happened over international waters in the Atlantic ocean fall under the jurisdiction of a US court? We're not THAT arrogant that we think we should have world wide court jurisdiction.
Yes, it sounds like poor juridical reasoning to me also, but it was attempted. The "justification", it seems, was the fact that the plane had american components. You must be aware that there is an indemnization industry, and in cases like that, lawyers try to seduce people to sue in america due to the widespread belief in Brazil that US courts are more though.

In any case I was just trying to say to infrequentflyer that despite his argument about the "wide international presence" of AB and AF, I think that from the point of view of the brazilian victims´relatives the "forum shopping" should be restricted to brazilian and french courts.
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Old 14th May 2011, 15:46
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CONFiture said:
Still trying to figure out why the BEA did omit the tracks of IB6024 and LH507 ?!
They have crossed the full red too, but as HN39 wrote much earlier : always keep in mind that the big systems seen by satellites don't necessarily show up like that on an aircraft's weather radar.
As a curious SLF, I wondered if satellite images of weather systems might be useful to pilots, as a supplement to what they can get from their own weather radars? Would it be prohibitive in terms of bandwith to download a localised image every couple of minutes? Or do the weather satellites track in a way that wouldn't be useful?

As a passenger, it would alarm me a little to know that the pilots were trying to pick their way through a maze with only an educated guess as to the layout.
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Old 14th May 2011, 16:15
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Hi,

Originally Posted by CONF iture
No question, these guys are very competent designers, but the more complex the design , the more chance something unexpected and/or foreseen will eventually present, sooner or later.
The flight envelope protection systems are reliable as long as the numerous sensors send the accurate and real information and also that this information is processed as designed by the different computers ...
But exactly the same thing can be said about the human way of processing informations. Our brain is far more "complex" than computers at analysing those informations transmitted by our senses, and our senses can be abused exactly the same way by any false/distorded information.

Moreover, as far as flying an aircraft is concerned, those basic informations can not be acquired by our senses alone without relying on instrumentation (which may display good or wrong data in particular cases). Consequently, ergonomy (human-machine interface) and crew training are the most important factors as for retrieving any compromised situation where everyone (human and machine) can end confused by unexpected environmental factors.

The only false idea is if one will claim that we could make flying an aircraft "100% safe" in every possible situations. Automatisms would make them "safer" in most situations... but not extreme ones.
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Old 14th May 2011, 16:17
  #1336 (permalink)  
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overthewing

Chris Scott explained it quite well. The time to avoid weather is well before one enters. Large commercial a/c are built (designed) to cruise, not to manouver. As gums has said, his a/c has a different mission, and it is not his personal comfort or peace of mind.

Radar has been discussed already, and the volume of opinion affirms the perception that much is left to guesswork. Any technology that is admittedly improving over time is an admission that the current kit is insufficient.

The auto pilot disconnects when it cannot keep up with the a/c. Turbulence and airstream impacts cause the slow to react airframe to lose "response", ie, it doesn't have sufficient time to complete an aspect change before the environment comes up with a new and different challenge.

I would board an A330 from Rio tomorrow. There is no increase of worry. What happened to AF447 will become known, and there will likely be no "new" gremlins to fear, only old ones to re-assess. My fear has to do with gum's eloquent statement. It is likely the FlightCrew will be burdened with the lion's share of responsibility. My hope is that in this new world of intercomm, those who have traditionally owned the forum will be fearful of appearing less than forthcoming, or even sly.

Where do you sit?? Since I left the cockpit, I sit Port abeam the engines.

happy skies,
bear

But takata, you speak of the solution in your post, one I think may never change. A computer can calculate, extremely accurately, and super fast. It cannot, as yet, display judgment, a "balance" of inputs, an abstract weighting of data, and a trained reaction to an uncommon situation.

For auto flight, abstract thought is a negative, it consumes energy and creates ennui. In the corners, where dwell the demons, the box is out of its domain. Here comes the seasoned pilot(s) to assess, entrain, and command. Your word, interface, plus an exhaustively trained segregation of appropriate domain, has been, and will remain the solution, No?? Further, I would not mind flying behind two sleeping pilots, with a tested system that allocated rem sleep to each, and had a sense of what may be ahead, sufficiently to collect a safe "get" and alertness. It is flight envelope that commands the choice of PIC, not simply the passage of time airborne. With this accident, I have the insistent feeling there was "surprise". Surprise is bull goose demon, imo.

Last edited by bearfoil; 14th May 2011 at 18:54.
 
Old 14th May 2011, 18:42
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Tracks & Pitots

CONF iture said:

Not at all.
Still trying to figure out why the BEA did omit the tracks of IB6024 and LH507 ?!
They have crossed the full red too, but as HN39 wrote much earlier : always keep in mind that the big systems seen by satellites don't necessarily show up like that on an aircraft's weather radar.
Tracks: My understanding is that LH507 was on the exact same track (UN866) as AF447 except they were at least 30 minutes ahead (20 minutes difference at TO from Rio). I don't know what track IB6024 was on. However, in some manner LH507 recognized a weather situation ahead and altered their track ~12 miles to the West. By the time AF447 got to the weather, the storm cells congealed into one with the worst part being towards the Eastern end. Originally, it was four separate cells. I am wondering if LH507 approached in time and picked their way through before the storm congealed? Also, by altering their course Westward, did they passed through a more mundane area? On the other hand, AF447 approached a congealed storm and turned Westward only 3 miles off track, timing of turn unknown but perhaps late?

Pitot tubes: I read somewhere about other A330/A340 problems relating to speed errors, i.e., pitot tube abnormalities. What I remember (not from the BEA reports) was that one crew thought the pitots might be icing, and at some point through the episode, switched the pitot tube heating setting from "automatic" to "on". Then everything settled back down and the flight proceeded normally. What exactly is the difference between the automatic setting and the setting regarding pitot tube heating?
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Old 14th May 2011, 19:01
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Hi,

No question, these guys are very competent designers, but the more complex the design , the more chance something unexpected and/or foreseen will eventually present, sooner or later.
The “testability issue” in complex designs is a big, complex and crescent challenge.

The flight envelope protection systems are reliable as long as the numerous sensors send the accurate and real information and also that this information is processed as designed by the different computers ...
"Accurate and real information" : Again a testability issue

"processed as designed" : The loss of IR1,2 and 3. Could a system like this one be designed to afford faults of this type? Or was a "black swan" like event, for EADS evolution?

But exactly the same thing can be said about the human way of processing informations. Our brain is far more "complex" than computers at analysing those informations transmitted by our senses, and our senses can be abused exactly the same way by any false/distorded information.
But our brain can “invent a new algorithm” and immediately apply it when required. And succeed, despite CRM issues during "extreme" situations.

The only false idea is if one will claim that we could make flying an aircraft "100% safe" in every possible situations. Automatisms would make them "safer" in most situations... but not extreme ones.
"but not extreme ones": Mostly if your design is highly optimized. And at extremes can present an unexpected "toll" for the operator. Just to remember us optimization is not "free".

Last edited by Jetdriver; 14th May 2011 at 20:59.
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Old 14th May 2011, 19:20
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Hi,
Originally Posted by RR_NDB
"processed as designed" : The loss of IR1,2 and 3. Could a system like this one be designed to afford faults of this type? Or was a "black swan" like event, for EADS evolution?

RR_NDB
, if I were you, I would refrain from the use of bold/colors in my postings as it doesn't make them either more sensical and/or authoritative this way. Where the hell did you see "the loss of IR1, 2 and 3" in AF447 case?
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Old 14th May 2011, 20:00
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Originally Posted by Turbine D
Pitot tubes: I read somewhere about other A330/A340 problems relating to speed errors, i.e., pitot tube abnormalities. What I remember (not from the BEA reports) was that one crew thought the pitots might be icing, and at some point through the episode, switched the pitot tube heating setting from "automatic" to "on". Then everything settled back down and the flight proceeded normally. What exactly is the difference between the automatic setting and the setting regarding pitot tube heating?
In auto mode, the amount of heat provided by the heaters is modulated following what the "probes" themselves are sensing. When anti-ice is selected ON, full heating is provided, whatever the "probes" are sensing. It makes sense if you are considering that the "probes" are freezing because the heaters were not delivering the correct amount of heat at the first place.

In fact, it seems that those probes freezing at cruise are not related to temperature (really) changing but to those specific (very small) ice particles melting when such conditions are encountered (mostly in tropical weather). Hence, TAT will increase very fast and reach a level close to 0°C (iced particles temp melted on the TAT probes). The drawback is that you can not fly with anti-ice ON all the time as it can also damage all the systems by overheating the probes. Hence, it should be selected on purpose.
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