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AF 447 Search to resume (part2)

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AF 447 Search to resume (part2)

Old 2nd May 2011, 11:34
  #521 (permalink)  
 
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Fdr/cvr data recovery

@ Noske
BEA spent a whole month on unsuccessful attemps to read the memory cards and then gave up. From the report: "They were examined at Honeywell, manufacturer of the recorders, in the United States on 5 and 6 January 2009 in the context of an International Commission of Inquiry. Some short-circuits were discovered on the cards. Eliminating the short-circuits allowed a complete read-out of the data."
Thanks for that.

Interesting that the BEA had problems with memory cards and Honeywell found shorts on the board. Sounds like it could have been shock vibration damage to the die connection wires rather than water ingress.

The recovered memory unit housing we see from yesterday's recovery looks in remarkably good shape to me - the indent does not seem to extend beyond the weld seam, and although there is a bit of rust, the seam appears to be intact. If the seal is compromised, then the integrated memory circuit packages will eventually get exposed to 400atmos pressure, and it's possible that the void inside the chip package will collapse onto the micro circuit die. In the past, Aerospace or Mil parts have used ceramic packaging for integrated circuits, with plastic, which is a lot cheaper to fabricate, the norm for commercial applications. There has been some use of plastic in mil aerospace apps in recent years, but one of the problems with plastic packages is that they are porous and allow water to penetrate the void. So, for either package, the void could collapse and crack the die. Or, on the other hand, a plastic package could be subject to a slow increase in pressure gradient (leak through a micro crack in the cylindrical metal containment housing), and it could fill with water and expose the die to corrosion. There are a few manufacturers around who will put die into ceramic packages, but not that many, and usually the cost is hugely expensive compared with plastic. If there is any moisture present around the die, then any application of voltage will cause an electrolyses effect and irreversible damage. So, If there is any suspicion that water has penetrated, the most like course of action is for a trip back to the manufacturer for the top of the package to be removed under controlled conditions and a session of drying and cleaning of corrosive deposits in the hope that maybe something useful can be recovered. Of course, It's quite possible that the CVR/FDR manufacturer has either obtained a special package for the FLASH ram, or has encapsulated the devices in some form of epoxy resin to cover the contingency of water ingress.

It's also interesting that the BEA allowed Honeywell to dig into the electronics. In section 2.4.1 of the EUROCAE document: MINIMUM OPERATIONAL PERFORMANCE SPECIFICATION FOR CRASH PROTECTED AIRBORNE RECORDER SYSTEMS, it states:

NOTE 1: Microscopic examination of the surface characteristics of memory
devices is not acceptable as means of data recovery.

NOTE 2: The repair of individual memory devices is not permitted.......


Seems a rather restrictive policy considering that all measures need to be applied to discover the truth - maybe it's a legal issue...

On a more hopeful note, we know from the interim report that the G forces experienced for the majority of passengers (front to rear of aircraft) was in the range 100 to 200G (from pathology), so it is therefore reasonable to say that the FDR and CVR experience something similar or less, and was then subjected to 400atmos pressure for 2 years. Given that these devices must pass certification at 3400 G (6.5ms) and also be able to resist 600 atmos (up to 30 days to pass certification test), I think it reasonable to assume that the contents have survived even after all this time. However, I'm not so confident about the FADEC's and the other 12 or 13 subsystems with non-volitile memory devices which would have minimal, if at all, protection from pressure.
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Old 2nd May 2011, 11:54
  #522 (permalink)  
 
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BEA and the Yemenair A310-300 accident at Moroni, Comores

noske and rotor12,

As you know, the BEA was only one of the participants in the Yemenair accident investigation, which protocols dictate was the responsibility of the tiny state where the A310 crashed: Comores. Their agency, ANACM (Agence Nationale de l’Aviation Civile et de la Météorologie) has not closed its deliberation.

The logistical and political difficulties faced by expert accident investigators working abroad in third-world countries were the subject of a recent programme on BBC Radio4:

BBC - BBC Radio 4 Programmes - File on 4, Air Crashes
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Old 2nd May 2011, 12:04
  #523 (permalink)  
 
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BJ-ENG

On a more hopeful note, we know from the interim report that the G forces experienced for the majority of passengers (front to rear of aircraft) was in the range 100 to 200G (from pathology), so it is therefore reasonable to say that the FDR and CVR experience something similar or less, and was then subjected to 400atmos pressure for 2 years. Given that these devices must pass certification at 3400 G (6.5ms) and also be able to resist 600 atmos (up to 30 days to pass certification test), I think it reasonable to assume that the contents have survived even after all this time. However, I'm not so confident about the FADEC's and the other 12 or 13 subsystems with non-volitile memory devices which would have minimal, if at all, protection from pressure.
Given that this is a technical forum I wonder if one could explain the following:

How does 100-200gs on a persons body equate to G loadings on a CVR/FDR? innards

How does 200 atmos pressure at the bottom of the sea cause damage to a memory chip in a module if it is exposed to water intrusion?
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Old 2nd May 2011, 12:08
  #524 (permalink)  
 
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Recorded parameters

RR_DNB,
The chances to UNDERSTAND everything with readable FDR and CVR are near 100%.
I fear you are being far too optimistic. Although I expect all of the data to be recoverable, the recorded capacity is limited. The Honeywell 4X Unit has a max recording rate of 256 words/sec, probably only enough to record a couple of hundred or so parameters at a reasonable rate, out of the many thousands of data items flashing between systems. The data recorded will typically be validated data, not necessary reality, not diagnostic data and not 'raw' data; it should be sufficient to identify the system(s) that are contributory, but not why a particular system 'went wrong'. A typical example in point is QF72; both recorders are available, as well as a bunch of expert witnesses, but "everything" is still far from understood.
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Old 2nd May 2011, 12:25
  #525 (permalink)  
 
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Information gold mine

BJ-ENG,

If there is any moisture present around the die, then any application of voltage will cause an electrolyses effect and irreversible damage. So, If there is any suspicion that water has penetrated, the most like course of action is for a trip back to the manufacturer for the top of the package to be removed under controlled conditions and a session of drying and cleaning of corrosive deposits in the hope that maybe something useful can be recovered.
Considering the careful way the whole issue is being handled we could expect they would avoid any risk in loosing the valuable information we hope is still present at both CSMU´s.

The non tangible (and tangible) value of the info after it´s analysis is "immensurable".
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Old 2nd May 2011, 13:05
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"Everything"

VicMel,

In the meaning of "what is really important" to understand what went wrong so dramatically to make a "complex System" fail in that way.

The ultimate goal is to learn how to avoid similar cases, addressing all issues involved.

The synergy between FDR and CVR info normally allow a very good UNDERSTANDING.

But i agree with you that we will be trying to understand the "reaction" of a complex System (in the sense an A/B is a "flying System").

We hope the 4X recorder with it´s (uncompressed) 37 MB could shown what we need.

Indeed a fascinating issue to many of us.

PS

IMO we will understand. Bu i´m not so confident that A/B will be able to learn everything to make their Systems perfect.

Reagan´s SDI (complex system) lack "Testability". Complex Systems are intrinsically unpredictable.

I prefer K.I.S.S. solutions with more "human touch" and involvement.

This trend makes me feel "too much alert" to situations i could not even understand when they arise.

A/B flying Systems has an history of "complex behavior" impossible to be solved IN TIME by the crew...
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Old 2nd May 2011, 13:10
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Nevertheless BEA spent a whole month on unsuccessful attemps to read the memory cards and then gave up.
Noske, if memory serves me well, BEA gave up after a couple of attempts. The "whole month" was spent on negotiating with the US authorities on how to maintain French judicial custody of the unit while shipping it to Honeywell during the Christmas/New Year time period.
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Old 2nd May 2011, 13:36
  #528 (permalink)  
 
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RR NDB

Forgive me, please, but this statement from you:

"A/B flying Systems has an history of "complex behavior" impossible to be solved IN TIME by the crew..."

...only rings true to me if you add "... "Impossible" because the crews didn't have an adequate understanding of the rather complex system they were piloting."

Or am I missing some incidents/accidents where more knowledge wouldn't have helped the crew solve their particular complex behavior issue?
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Old 2nd May 2011, 14:00
  #529 (permalink)  
 
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Is there any information on when we may expect to hear if the data on the FDR is good or has been lost?
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Old 2nd May 2011, 14:08
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Effects of water pressure

lomapaseo Post #522 How does 200 atmos pressure at the bottom of the sea cause damage to a memory chip in a module if it is exposed to water intrusion?
It might not be so much pressure as the rate of increase of water pressure.

I am thinking "water hammer" if the leak is sudden.
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Old 2nd May 2011, 14:32
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THL,

more knowledge wouldn't have helped the crew solve their particular complex behavior issue?
Knowledge always is necessary. But remember the crews that faced and unsolved "different behavior" (i replaced complex by different) were trained in SIM, by all the required Standards and they failed.

I don´t think what happened in many cases was just an issue related to complex systems they piloted. It involved much more, like issues later improved by software updates, hardware improvements, etc.

Even in a perfect complex System the "real world" presents new situations.

And our capabilities are much more dependable on what we learned before a "completely unusual situation". When they arise in complex Systems our capability to solve it (with the several steps since the start of the issue to the adequate solution) IN TIME as you know, is LIMITED.

As a Designer i am not contrary to new solutions, automation, etc.

But i understand the limitations of Systems in the hands of "normal professionals" in "real world environment".

And i respect the K.I.S.S. design approach and threat´s of Murphy´s law.

The crew never of Northwest Airlines 727-25 N26 4US near Thiells Dec 1, 1974 never understood in time what happened to their "simple" a/c in the ferry flight.

Where a simple interlock could have prevented the unreliable air speed that triggered the accident.

Last edited by Jetdriver; 2nd May 2011 at 16:41.
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Old 2nd May 2011, 14:57
  #532 (permalink)  
 
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Mac

Thanks for the response RR NDB, I believe I understand your point. I guess what I'm trying to say is that while the a/c become more complex, the knowledge required to successfully operate them takes more study and training than it used to.... Training departments, and Pilots MUST keep up!
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Old 2nd May 2011, 15:01
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What RR_NDB is referring to is N274US, a Northwest 727-25 on a ferry to Buffalo, that crashed after stalling following near simultaneous freezing of all three independent pitot systems. The pitot heating was not selected because the 3 crew members got tangled up in the pre-flight checklist.
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Old 2nd May 2011, 15:02
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info update BEA

Information, 2 May 2011


"2nd May 2011 briefing

The Remora 6000 made a further dive yesterday evening. The search operations are continuing in order to localize the Cockpit Voice Recorder (CVR).
After the Flight Data Recorder (FDR) was raised, the BEA, as agreed, asked the French Navy to send a patrol boat to transport the recorders to Cayenne (French Guyana), from where they will be transferred by airplane to the BEA in Le Bourget.
The BEA Investigator-in-Charge, an officer from the French judicial police and an investigator from CENIPA (the Brazilian equivalent of the BEA) will be present during the transfer from the Ile de Sein to the BEA, which should take around ten days.
At present, there are 69 people on board the ship, an officer from the Brazilian Navy having joined last Friday (29 April). "
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Old 2nd May 2011, 16:00
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BEA, with their dubious track record, will doubtless try to put a 'spin' on the FDR evidence so that Air France and AI will not be unduly embarrassed. Difficult to imagine how they will get away with this one, but try they shall.
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Old 2nd May 2011, 16:10
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Frozen pitots

Quote from deSitter:
What RR_NDB is referring to is N274US, a Northwest 727-25 on a ferry to Buffalo, that crashed after stalling following near simultaneous freezing of all three independent pitot systems. The pitot heating was not selected because the 3 crew members got tangled up in the pre-flight checklist.

Hope you will not mind me adding some words of explanation for those not familiar with pitot-probes or the above accident (even I was young then), since freezing of pitot tubes is presumed to be material to AF447.

The tubes froze completely at some stage in the climb, trapping the current dynamic pressure on the dynamic side of each (mechanical) pressure capsule. Because the aircraft was climbing, the static pressure continued to fall steadily, transmitted to the static side of each aneroid (pressure) capsule from the (unfrozen) static ports. The increasing differential pressure across each capsule led to a steady increase in the IAS reading on the cockpit ASIs, even to the point of an overspeed warning. The PF allegedly flew indicated speed in preference to attitude, with a stall being the inevitable result. (Unlike its British T-tail counterparts, the B727 did not have a stall-ident/stick-pusher system, although it did have a stick shaker.)

It appears that the scenario was dependent on the whole of each pitot head being frozen, including the small water drain-hole which is normally placed near the aft end of a pitot tube. If that hole remains open, the dynamic pressure is able to dissipate; leading to an under-reading, or zero-reading, of airspeed.

In the case of AF447, history of previous anomalies on A330s and A340s suggests that the drain holes may have remained open. Also, when maintaining a pressure altitude, the static pressure remains constant by definition (although an automatic altimeter correction for speed-related errors at the static ports may complicate the issue slightly). The result may have lead to an under-reading of airspeed. However, I'm not aware that the BEA has discussed publicly the issue and/or effects of drain holes being frozen or remaining unfrozen. It would certainly be crucial during climb or descent.


PS
In those days (the early 1970s), US jet transports like the B727 and B707/720 were still being certificated with scratch-foil flight-recorders capable of handling fewer than 10 parameters. Their British counterparts (BAC 1-11, VC10 and Trident) had analogue, wire-recording FDRs with many times the number of parameters. They paved the way for what became the SESMA programme, which monitors crew/aircraft performance on all flights. I think the Americans can lay claim to having caught up with the Brits by now...

Last edited by Jetdriver; 2nd May 2011 at 16:39.
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Old 2nd May 2011, 16:26
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Neptunus Rex posted :

"BEA, with their dubious track record, will doubtless try to put a 'spin' on the FDR evidence so that Air France and AI will not be unduly embarrassed. Difficult to imagine how they will get away with this one, but try they shall."

I understand that some forum members are sceptical about the independence of the BEA and that they believe that there is a conspiracy of some kind afoot .

Can we now take that viewpoint as a given rather than have it tiresomely repeated every few pages?

Additionally I noticed a reference by a poster to this thread being 'fun'. It is certainly intellectually challenging and of huge interest - not least to me as a frequent flier to Brasil and a past user of AF447 (the last time on a Friday the 13th!).

With reference to the circumstances however, and numbers reading posts, might I suggest that use of the word 'fun' may not be wholly appropriate?

I'm truly sure that nothing inappropriate was intended, just an unfortunate use of the word.

Back to SLF lurking!
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Old 2nd May 2011, 16:48
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Cool

Hi,

French politician at work ...........

Google Vertaling

Thierry Mariani, the Secretary of State for Transport, said that never in aviation history has it been possible so far to "recover the wreckage of a plane at such a depth.
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Old 2nd May 2011, 16:59
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Cool

Hi,

Knowledge always is necessary. But remember the crews that faced and unsolved "different behavior" (i replaced complex by different) were trained in SIM, by all the required Standards and they failed.
Standards in force BEFORE the accident
AF reviewed the standards of training for such "different behavior" some months after the AF447 tragedy and all AF pilots were send again to the sim !
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Old 2nd May 2011, 17:13
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Neptunus Rex

BEA, with their dubious track record, will doubtless try to put a 'spin' on the FDR evidence so that Air France and AI will not be unduly embarrassed. Difficult to imagine how they will get away with this one, but try they shall.
Its interesting to note that even if the BEA is not sucessful in their nefearious deed that they will have been deemed to at least tried
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