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AF 447 Search to resume

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AF 447 Search to resume

Old 27th Dec 2009, 07:59
  #181 (permalink)  
 
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This thread is heading for banishment to Tech Log, so I might as well contribute to its demise.

The kind of data the FDR records is called State of Health data, on spacecraft at least. It is generally boringly repetitious and compresses nicely (losslessly, of course) sometimes using algorithms that insert values (for each channel, or parameter) only when they change by a meaningful amount. More dynamic parameters may be recorded by inserting differences between consecutive values into the data stream, each difference taking fewer bits than stating the whole value would. There's a popular silicon-based encoder (popularly called Rice encoding after one of the designers) that choses the best algorithm on the fly, no pun intended. And all this stuff exists in boxes with 1553 interfaces, since that's become popular at higher altitudes, so to speak.

I don't look at FDR data so am guessing, but would be pretty surprised if 10:1 compression wasn't a piece of cake. The costly bit would be making the box and uplink robust enough to survive a nearby explosion long enough to deliver the last message. While the normal data rate would be low, a serious event would generate full values for each parameter at the system's normal sample rate, for the duration of the event, and that would have to be preserved and uplinked perhaps over a period of several seconds.

CVR data needn't be lossless. I have nothing special to contribute in that arena, but we all realize that a minute of good-fidelity music becomes something like 1MB of mp3 data. Voice quality would be much less than that. As with FDR data, in normal flight there would be next to nothing to send.

I know nothing about what happens next, but note that Hughes and others operate geosync spacecraft with transponders dedicated to providing internet service to hopefully more than 500 customers (cited earlier as the number of transoceanic flights in some area). They're happy to support megabyte data rates for their users - far greater than needed except for mayday situations. Afaik no such service exists in the right place for oceanic monitoring, but that doesn't mean one of the maritime birds wouldn't mind providing such a capability. Hughes gets around USD80 per month per user, btw, and per the TOS doesn't appear to get annoyed until users start using hundreds of MB in a short period. I'm assuming that uplink and downlink are symmetrical for them, unless they do a lot of common-data caching on board the spacecraft. That's unlikely.

What to do with the data seems to bother people. Clearly the system would be operated by a central authority like ARINC, who could simply store it in a disk array at the satellite ground station - a giant FDR.

The thing I haven't mentioned is the uplink, because I truly know zilch about that. Hughes/Directway uplink antennae tend to be dishes around a meter dia, I think.
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Old 27th Dec 2009, 11:51
  #182 (permalink)  
 
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Has it been confirmed that one FO, recent to the type, was alone in the cockpit at the time of the incident?
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Old 27th Dec 2009, 14:26
  #183 (permalink)  
 
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That can't possibly be confirmed, ever, unless the CVR is found and there happens to be a message from whoever was on the FD speaking aloud "Well, it's just me on my ownsome" or similar......
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Old 27th Dec 2009, 15:37
  #184 (permalink)  
 
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Payscale,
Seems highly unlikely, given that they were heading into some nasty weather.
Even the least-experienced flying crew member had 807 hrs on type and nearly 3000 hrs TT.
Rockhound
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Old 27th Dec 2009, 17:25
  #185 (permalink)  
 
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The true engineering spirit

But it's still as I said: "new and currently non-existing equipment", and the next aircraft going down will just happen to not yet have the equipment installed....
Which in itself is absolutely no excuse not to start working on a proper solution. I find it hard to accept that with the technology available today it seems nearly impossible to locate an airliner that went down into the ocean.

I also do not like the argument that a solution is not needed because "it does not happen very often". This accident could be a landmark accident in relation to the use of pitot tubes in high altitude adverse weather. Also: think about what happened to the BA 777 at Heathrow. Does the fact that the apparant ice accumulation in the oil-fuel heat exchanger only brought down one airliner make it any less important?
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Old 27th Dec 2009, 18:10
  #186 (permalink)  
 
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I also do not like the argument that a solution is not needed because "it does not happen very often".
No-one else likes it either.

But in a world where airlines are struggling to survive, it is simply unrealistic to expect them to spend huge amounts of capital and further commit to ongoing loss of revenue, in order to recover data from a one-in-a-billion accident.
It is even less realistic to expect agreement from airlines and administrations across the world on a single course of action. Their priorities are elsewhere at the moment, as can be seen in the headlines.
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Old 28th Dec 2009, 10:11
  #187 (permalink)  
 
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Not sure if its been covered but given the extreme depths that are likely involved the dye suggested may never actually make to the surface let alone anywhere near the prang.
There are thermal layers that affect acoustics I believe, so a dye solution may never appear .OK at shallows probably but them you would likely find the recorders anyway.It would certainly be helpful in many cases.
Anyone seen smoke from a large fire on a very calm day , sometimes the smoke appears to hit a glass ceiling and commence to spread out?

Given many airliners now use solid state recorders ie the fairchild 2100- series that are much lighter than the old models how about just adding to battery capacity ? All solutions will cost but suspect adding capacity in future maybe a relatively cheap option.

Live info squirts via satellite / acars for example maybe ok if they are only triggered by an event , ie engine out , manual ops by crew, excessive rate of descent, excessive g forces, loss of cab pressure etc.
Otherwise just too much info & too many flights to record.Much less to record / monitor if only triggered by an event.

Just brainstorming..
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Old 28th Dec 2009, 20:42
  #188 (permalink)  
 
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There´s no reason to abandon the present recorders for a wireless system since onboard recorders already are mandatory and the cost of having them already is calculated into the business model. Just have to make them easier to find, just like is being said here.
The Boeing 787 will have enhanced recorders (CVR plus FDR in a combined unit, times two) which will record many times the data of previous recorder models and one of them will have a ten minute independent power supply. The "only" problem is, they are designed differently and collect data directly from sensors in a fiber optics ethernet data stream, which makes it impossible to retrofit these enhanced recorders to older aircraft types. Read about it here:

http://dev.flightsafety.org/asw/jan0...n08_p47-48.pdf
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Old 28th Dec 2009, 22:32
  #189 (permalink)  
 
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Originally Posted by Finn47 View Post
.... Just have to make them easier to find, just like is being said here....
Hi Finn,
I was already becoming aware of ARINC 767 (mostly through this thread, I readily admit!).
However, ARINC 767 doesn't yet seem to address finding "lost" FDRs...
Or does it? The article you linked doesn't mention it.

Having two FDRs at 4000m under the ocean, rather than one, doesn't improve matters, if you can't find either of them....

CJ
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Old 29th Dec 2009, 04:26
  #190 (permalink)  
 
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Having two units, each with more data than ever before obviously will be a great improvement as such, but the French investigators seem to be the first to consider finding the boxes a problem worth looking into. Maybe there should be two improved ULB beacons per recorder? Provided there is enough physical free space available where the recorders are installed in the aircraft, of course.
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Old 4th Jan 2010, 12:53
  #191 (permalink)  
 
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Can I just put the satellite link to bed once and for all.

There will be noway of transmitting data up to a satellite and down to an SGS (Satellite Ground Station) for recovery or use in an inquiry. Yes, the technology exists, but there are just not enough satellites up in the sky to make any sort of inroads into the number of channels that would be required. I suspect nobody will put satellites up on behalf of the air industry, so they would have to fund it themselves. On average it costs about $500m to put a satellite up into orbit and maybes 200 more may be required up there. That cost (expensive even for airline budgets) would have to be passed onto the passengers, which would make flying extremely expensive.

Secondly, placing an omni-directional (which it would have to be) satellite dish on board and aircraft would cause an immense amount of pain for any aircraft manufacturer. Also, you cant hop from satellite to satellite (like mobile phone coverage) you need to know the specific upload/download speeds and upload/download freqs for any data transmission. Any satellite on board an aircraft would have to have auto-tracking and know exactly where and when it should be looking in the sky for a satellite. Most satellites up in the sky move around and do not stay in the same location, so the aircraft would have to constantly be looking for that movement, as well as counter acting its own movement.

Yes, info could be transmitted blind, hoping the satellite would pick it up, but what would be the point in that!
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Old 4th Jan 2010, 14:12
  #192 (permalink)  
 
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Rockhound, according to the latest interim report, the actual whereabouts of the Captain cannot be determined. His body was recovered and autopsied.

Perhaps a bit more strange, none of the several CC seats recovered were occupied at the time of impact.
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Old 4th Jan 2010, 15:12
  #193 (permalink)  
 
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Originally Posted by MATELO View Post
Can I just put the satellite link to bed once and for all.
I thought we already did?

Bandwidth as such isn't even the real problem, as we calculated earlier, it's the several thousands of individual little data streams, that have to be handled securely without any interruption. While technologically possible, the whole system would have to be designed and built from scratch.

As you say, the aerial is the other problem....
Satellite aerials are not omni-directional... even relatively wide-angle ones still need steering and locking on to the satellite.
Going down in an unusual attitude would most often mean losing the lock-on.
So would flying down a valley before crashing into a mountainside, unless the satellite happened to be right overhead.

So I agree with you.
Let's concentrate on finding the recorders themselves, come hell or high water (in the most literal sense...).

CJ
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Old 4th Jan 2010, 23:34
  #194 (permalink)  
 
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Satellite aerials are not omni-directional
Stricto senso this is incorrect.
Eg. Iridium, Orbcomm, Globalstar, Thuraya are satellites or constellations of satellites that are accessible by portable equipment with rubberduck type of antennas.
What matters is frequency band (L, C, Ku or Ka), what it is aiming for (in terms of bandwidth/speed, which correlates to satellite power and antennas' gains) and type of orbit and height (LEO, MEO or GEO, which correlates also to latency, a critical factor for some applications).
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Old 5th Jan 2010, 00:23
  #195 (permalink)  
 
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Originally Posted by iakobos View Post
Satellite aerials are not omni-directional
Stricto senso this is incorrect.
Eg. Iridium, Orbcomm, Globalstar, Thuraya are satellites or constellations of satellites that are accessible by portable equipment with rubberduck type of antennas.
What matters is frequency band (L, C, Ku or Ka), what it is aiming for (in terms of bandwidth/speed, which correlates to satellite power and antennas' gains) and type of orbit and height (LEO, MEO or GEO, which correlates also to latency, a critical factor for some applications).
iakobos,
Stricto senso you are right.
Which is why I said it's "technologically possible".... I already was thinking of that.

But none of those systems are capable of handling thousands of 100 kbit/sec data streams simultaneously, reliably.

And try to hold the rubberduck (I am familiar with the type of antenna) upside down under an aircraft and see what ERP you get towards the satellite(s) you are relying on for those last critical seconds/minutes of data.


Something passed through my mind...

Twenty-five years ago, being able to flip open a little 'StarTrek'-like communicator open nearly anywhere in the world, an talk to nearly anybody else on the planet, would have seemed a pipe dream. (Admittedly, there are still places where you need a sat-phone, but I think you get my point.)
Now it's almost normal.

Twenty-five years from now, we'll probably expect to be able to plug in our little communicator on a plane anywhere, and instantly get connected to anybody else on the planet.
FDR, CVR and a lot of other data could ride piggy-back onto such a service.

But while FDRs and CVRs now are slowly and steadily becoming mandatory on ever smaller aircraft, even if not not on your Cessna, how many of those "data transfer" systems would in in place (and not part of the MEL) even then?

Let's stick with FDRs and CVRs (and VCRs if they can be shown to be useful) powered by the essential bus, that will stay with the disaster until the last possible second.

CJ
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Old 5th Jan 2010, 06:23
  #196 (permalink)  
 
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unsafe condition

The inconsistency of measured speeds resulting from blockage of Pitot probe is "an event that can cause victims usually with the destruction of the plane! This event can lead pilots to excessive workload which does not allow them to perform their tasks accurately or completely! “

The FAA (USA) made that affirmation several times in a document* dated September 9, 2009 using just 2 words : "unsafe condition"!

The BEA has very kindly referred to the definition of an "unsafe condition" in his report of last December 17.

What the FAA said, the European Agency for Aviation Safety (EASA) has not wanted or dared to say ... but saying it anyway.

When, in August 2009, the elimination of the Pitot probe Thales AA, fitted to the A-330 flight AF 447, is considered mandatory, EASA issued an "airworthiness directive” (AD) but claiming that it was simply a precautionary measure.

An AD for a precautionary measure, it does not exist!

When the manufacturer and EASA detect a problem that is not an "unsafe condition" but that requires a response, EASA publishes a SAFETY INFORMATION BULLETIN (SIB).

Extract of EASA document** entitled "Continuing Airworthiness of Type Design (CAP)" (March 2008). Page 39:

Only when design related issues which may lead to unsafe condition are considered likely to exist or develop, issuance of an airworthiness directive is warranted.

And

Information may be available to EASA related to airworthiness concerns on aircraft under national registers, but for which insufficient evidence exists to qualify this as an 'unsafe condition'. In such a case, the PCM [1] may elect the publication of an SIB, containing information for the safe operation of the affected aircraft.

To remove the Pitot probe Thales AA, EASA issued an AD… not a SIB.

There was therefore an "unsafe condition" that required an answer (the elimination of the Pitot probe Thales AA) !

This response came very late because the pilots of flight AF 447 had not been advised of the existence of this potential "unsafe condition"!


They were asked to accommodate the lack of pitot probes Thales AA and ensure accountability of the "unsafe condition" by applying a checklist when it is defined that an "unsafe condition" may lead the pilots to excessive workload which does not allow them to perform their tasks accurately or completely!

* http://henrimarnetcornus.20minutes-b.../102670700.pdf

** http://henrimarnetcornus.20minutes-b...1239787795.pdf
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Old 5th Jan 2010, 23:27
  #197 (permalink)  
 
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ChristiaanJ, there is another little detail you may not have thought of. Communications does not have to be via satellite if an alternate link can be established. That greatly reduces the demand on satellite communications. An extended cell phone technology could handle large cells from the air. If the plane is too low and falls out of the large dedicated to aircraft cells you use regular cell phone towers. Only if they fail you fall back on satellite linkages.

Of course, who is going to pay for the development of the large communications cells when no worldwide frequency allocation exists for this purpose; and, getting it will likely be a more than one decade process given how often the international frequency allocation body meets.

It's all an expensive non-starter. It can be done. It'd he fun doing it. It'd be full of interesting challenges. And it would never "pay for itself".

{^_^}
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Old 6th Jan 2010, 10:49
  #198 (permalink)  
 
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Wake up Mods!

It's time this thread was locked, a new one opened for AF447 discussion only, and another in Jet Blast for impossible crackpot ideas.
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Old 6th Jan 2010, 15:05
  #199 (permalink)  
 
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There's always this one, SallyAnn.

http://www.pprune.org/tech-log/376433-af447-230.html

It seems to be the major repository of both crackedpottery and some good analysis. Let those with "ideas" for solutions mine that thread to see if they've presented anything new. For example, satellite FDR/CVR is very much "not a new idea." So far a cockpit video recorder linked to base by a satellite connection has not been proposed. So it's not THAT far "out there."

{o.o}
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Old 6th Jan 2010, 15:26
  #200 (permalink)  
 
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Sallyann1234,

There isn't really much in the way of news on the subject anyway, at the moment, so why not let it run, as most of those interested are monitoring it?

So far I've seen almost no comments on SPA83s posts, although he's pretty well succeeded in convincing me as to the "probable cause".

CJ
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