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AF 447 Search to resume

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AF 447 Search to resume

Old 22nd Dec 2009, 14:41
  #161 (permalink)  
 
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Think I need to bite at this one, although my better conscience tells me not to.

1) We are long past the days of "tape" in a modern flight recorder.

2) In the whole history of aviation there have only been a handful of broken or irrecoverable recorders.

3) To transmit data every 15 minutes is hopeless, It is usually the last 15 minutes of data that are the most important and under this ludicrous idea that would all be lost.

4) Have you any idea of how much data transfer via satellite link really costs? Most of this huge amount of data would be totally useless.

5) Do you have any idea how it would be possible to maintain an uplink in severe weather conditions and unusual aircraft angles?

6) Yes we do use the internet to transfer data, predominantly via cables/fibre networks and after that via GSM networks, I don't recall passing any GSM towers in the mid Atlantic, but possibly I should look more carefully next time.

7) Please read all the other post regarding this point.

tex

Last edited by Tex37; 22nd Dec 2009 at 14:42. Reason: sp
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Old 22nd Dec 2009, 15:28
  #162 (permalink)  
 
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Thanks Tex37!
Makes my answer simpler!

Originally Posted by memyself View Post
You clearly (I hope) know more about nuts & bolts engineering that you do about electronic engineering and IT system analytics. As such I understand fully your preference for metal boxes and tape reels.

It just so happens that, before retiring, one of the last things I designed and got to work was an ATE for the FDRs we manufactured.

Your electronic and IT experience clearly ended with the Commodore 64 and programs on cassette tape.

CJ
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Old 22nd Dec 2009, 23:31
  #163 (permalink)  
 
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Has there ever been a cost/benefit study of CVR and FDR? Hauling 50-100 lb of hardware and wire for the lifetime of every airplane is no small cost.

GB
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Old 23rd Dec 2009, 00:12
  #164 (permalink)  
 
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Originally Posted by Graybeard View Post
Has there ever been a cost/benefit study of CVR and FDR? Hauling 50-100 lb of hardware and wire for the lifetime of every airplane is no small cost.
GB
Interesting question, GB ....

What is the cost? Fuel to haul the equivalent of a couple of extra suitcases and some duty-free, or one more empty seat, for the lifetime of the aircraft, plus the cost of maintaining the CVR and FDR.
Less than the cost of carrying diversionary fuel, which is mostly not used... to put the weight in perspective.

What is the benefit? More difficult, because it is very difficult to assess how much and how often CVR/FDR data from a given crash have prevented further crashes (hence more hull losses and more loss of life).

Almost worth a separate thread, to avoid "polluting" this one.

CJ
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Old 23rd Dec 2009, 10:34
  #165 (permalink)  
 
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ChristiaanJ
It should be quite possible to scope the total bandwidth that would be required for a continuous uplink system to cover e.g. the Atlantic. I'm sure that it has already been done many times and that the answer is not currently feasible, but I haven't seen it documented.

From your experience with FDR's, what is the peak data rate that a typical large aircraft records?
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Old 23rd Dec 2009, 11:49
  #166 (permalink)  
 
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The French are "confident" that the recorders will be found, this new article says, but the reporter "could" be slightly wrong about the search area:

an international team of experts will reduce the search area to 2,500 square meters (26,910 square feet) a fifth the size of previous efforts.
France confident of finding Air France black boxes - thestar.com

Square kilometers would be better
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Old 23rd Dec 2009, 16:52
  #167 (permalink)  
 
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I was thinking about this yesterday. For crashes on land where the a/c remains relatively intact (or in one place) the current FDR designs work pretty well - they're hardened and are relatively easy to locate.

What is needed is data redundancy for when the ADR can't be found. An uplink would be a not very reliable, not very high bandwidth, not very cheap form of it.

A better idea would be to have 2 or 3 small auxiliary hardened FDR memory units which are slaved off the main FDR and attached to pieces of the aircraft that are more likely to float or be readily recovered in the event of a water impact/breakup. e.g. the tail assembly, or even attached to a float. They wouldn't have to be as large (they don't need any of the input processing etc.) or as hardened as the main FDR, just watertight and impact resistant enough to survive e.g. a water impact.
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Old 23rd Dec 2009, 17:45
  #168 (permalink)  
 
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Originally Posted by XB70_Valkyrie View Post
... small auxiliary hardened FDR memory units.... They wouldn't have to be as large (they don't need any of the input processing etc.) ... as the main FDR....
This is not a comment on your idea as such.
But most present-day FDRs don't do any input processing.
Their input processing is done by a separate FDAU (flight data acquisition unit) which then sends the data in digital format (ARINC 717, usually) to the hardened FDR.

CJ
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Old 23rd Dec 2009, 18:07
  #169 (permalink)  
 
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Originally Posted by Sallyann1234 View Post
ChristiaanJ
From your experience with FDR's, what is the peak data rate that a typical large aircraft records?
My experience dates a few years, so I did a bit of "informed Googling"...
The data rate tends to vary widely, depending on the age and the size of the aircraft.
64 and 128 12 bit words per second sounds familiar to me, but it's now up to 256 wps, with 1024 wps on the horizon.
That translates to about 12 kbps raw data, and for robust transmission via satellite I would say you would have to double that (more checksums, more labels, more sync).

Doesn't sound too bad, until you multiply it by the number of aircraft in the air at any one time (about 10000, of which roughly 5000 over the US, so presumably several hundred over the Atlantic).

Not to mention there is no infrastructure to handle any of this sort of data, or assure a continuous and robust second-by-second data stream...
As mentioned already, packets every 15 seconds are useless, a lot happens in 15 seconds.

Also there is no mention of the CVR in this context, which would easily account for another 12 kbps for the recording to be of any use.

CJ
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Old 23rd Dec 2009, 19:16
  #170 (permalink)  
 
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Thank you Christiaan.
So to build a system that is reasonably future-proof you will need 100kbps per aircraft, 1000 aircraft over the Atlantic, total 100 Megabits.

The challenge will be to design and build a robust satellite-based TDMA system that can control and synchronise the individual transmissions. And an entirely new radio fit in all aircraft (with appropriate redundancy of course because the radio link will always be less reliable than an on-board recorder).

It's not impossible - given vast resources and general agreement from all the relevant national and international organisations - none of which is about to happen any time soon.

I think this puts the idea to bed.
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Old 23rd Dec 2009, 20:43
  #171 (permalink)  
 
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Originally Posted by Sallyann1234 View Post
Thank you Christiaan.
So to build a system that is reasonably future-proof you will need 100kbps per aircraft, 1000 aircraft over the Atlantic, total 100 Megabits.
Of course 100Mbs is nothing... it's about one 2nd-generation Ethernet link, no?
So when we talked about just bandwidth, we were barking up the wrong tree.
"The truth is elsewhere"...

You already ponted to some of the other issues...
The challenge will be to design and build a robust satellite-based TDMA system that can control and synchronise the individual transmissions. And an entirely new radio fit in all aircraft (with appropriate redundancy of course because the radio link will always be less reliable than an on-board recorder).
And a huge infrastructure on the ground everywhere, to recover these data, save them, distribute them, etc. etc.

I just used my imagination a moment...
Can little "AZ Airlines", trying to operate half a dozen second-hand regional jets conscientiously on a shoe-string budget (yes, they exist and try to survive), even afford to subscribe to such a service (they never could do it on their own)? Or can they be relied on to have the facilities to receive and store the data reliably?
Their half-dozen aircraft will carry FDRs, they have to, and they're likely to maintain them as they do the rest of their equipment.
Not to mention that if they're clever, they have already tied them in with QARs etc.
What is their interest in a system that "maybe" recovers a few more data from an extremely rare accident, where the FDR itself is not recovered?????

I think this puts the idea to bed.
I can think of many more reasons..... like the one already mentioned... the posited "data link" breaking down because the aircraft is in a vertical dive, for instance.

The idea mentioned by XB70_Valkyrie would be nice... were it not that a few more FDR memory units would be equally impossible to locate as the original wreckage.

Personally, I still like the dye markers.... and the improvements suggested to the ELBs and ULBs, and possibly adding more of those.

Contray to the suggestions about adding FDR units (which would mean major aircraft system modifications), they would mean minor, and largely system-independent and aircraft-independent, improvements.

CJ
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Old 23rd Dec 2009, 22:26
  #172 (permalink)  
 
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Of course 100Mbs is nothing... it's about one 2nd-generation Ethernet link, no?
Unfortunately, no.
100Mbs from one aircraft would be easy.
But we don't have that, we have 1,000 separate data streams sent up to the satellite receiver. The transmissions can't be sent up blind from each aircraft, they would have to be synchronised and controlled from the satellite base station just as mobile phones are controlled by their network. It's a much more complex requirement. And synchronising high-speed data over long and variable-length paths from fast-moving vehicles is very difficult. Not quite impossible, but extremely difficult to do with the required 99.9999% reliability.
Only then can you combine all these data received in the satellite into a single stream to send down to the ground stations for distribution to the surface infrastructure you correctly identified.

edit: I still like the dye markers too!
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Old 23rd Dec 2009, 22:46
  #173 (permalink)  
 
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Sallyann1234
I may not have been 100% clear in my reply.
But I think we're already 99.9999% on the same wavelength.

CJ
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Old 23rd Dec 2009, 23:22
  #174 (permalink)  
 
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But I think we're already 99.9999% on the same wavelength.
Perhaps even quasi-synchronous
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Old 24th Dec 2009, 12:39
  #175 (permalink)  
 
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A satellite uplink is only needed when there is just one aircraft in the neighbourhood. In this case the aggregate data rate for the neighbourhood is that of a single aircraft. Where there are multiple aircraft then each can broadcast its data to its neighbours. Since it is unlikely that the neighbouring aircraft would also crash, they do not need to keep the received data in hardened memory; they can store it on a regular PC and upload it to the Internet on arrival.

Arguably, the only really vital data to be transmitted are the GPS coordinates. If these were updated every 5 seconds then locating the crash site would be easy and the rest of the data could be retrieved from the black boxes. If the data were available in real time survivors could be found quicker too. The badwidth required would be much lower.

However, as already noted higher performance pingers would be a much simpler solution.
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Old 24th Dec 2009, 16:53
  #176 (permalink)  
 
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Originally Posted by dtyedytgerdy View Post
The bandwidth required would be much lower.
As already said, the bandwidth is not the key problem.
Your solution too would need a brand-new, very elaborate and very robust infrastructure, which currently doesn't exist.
However, as already noted, higher performance pingers would be a much simpler solution.
As indeed already mentioned in the latest DGAC report.

CJ
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Old 26th Dec 2009, 15:26
  #177 (permalink)  
 
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dtyedytgerdy Where there are multiple aircraft then each can broadcast its data to its neighbours. Since it is unlikely that the neighbouring aircraft would also crash, they do not need to keep the received data in hardened memory; they can store it on a regular PC and upload it to the Internet on arrival.
Sallyann1234 100Mbs from one aircraft would be easy.
The above started me daydreaming of a simple system.

Could one have a "buddy system", where each aircraft is paired with a buddy? i.e. two aircraft on the same or nearby routes maybe 10 to 30 minutes away from each other are "paired". Each aircraft has its own DFDR as normal, but each also transmits its full DFDR data stream to its buddy, which records it.

On landing and confirming that its buddy is safely on the ground, the received data is deleted. Gone.

Advantages include:

(a) No other infrastructure is required. No satellites or central data handling is needed. No massive amounts of data is stored. The cost is distributed between all airlines and countries

(b) The full data stream of the downed aircraft is available immediately. Also, it might be possible to transmit just the last known position to emergency services even before the receiving aircraft lands.

(c) While I hesitate to mention this, it does cross my mind that the buddy aircraft will most times be from a different airline and maybe a different country, minimizing the possibility of any funny business in withholding, delaying, massaging, or losing the data.

There will some routes where there will be no buddy within range, but maybe only 1% of routes.

Just daydreaming.
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Old 26th Dec 2009, 16:03
  #178 (permalink)  
 
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PickyPerkins,

Think it through.....

- There is no equipment in current aircraft capable of transmitting, or receiving and recording, a continuous 10 to 20 kb/sec data stream over a distance of a few hundred miles, omni-directionally.

- The FDR data in the aircraft (usually between FDAU and FDR) are perfectly useless for broadcasting... they would need additional time-stamps, sync, labels, etc. .... i.e., your scheme would require another piece of equipment for the re-coding, which currently doesn't even exist.

I can think of several other points why your scheme is impractical....

Only incremental improvements of existing equipment (such as the pingers) or very cheap add-ons (such as the dye markers) have any chance of being accepted to solve what is a very rare problem.

CJ
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Old 26th Dec 2009, 23:29
  #179 (permalink)  
 
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4000m is a long way down. In terms of design modifications to achieve retention and transmission of information, it's all fixable ... for a price. Wreckage location: simple buoy to be released following g measurement exceeding preset level (crash). Buoy contains GPS receiver/data logger and beacon, retrieve buoy and download data logger to locate release point. ELF receiver to trigger further buoy release (assuming USN ELF system is still in operation?), ELF signal to be sector specific (but I doubt if ELF can reach to 4000m). Buoys may contain flight data loggers, data to be stored on (several) SD cards or similar.

All adds weight/cost.
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Old 27th Dec 2009, 00:38
  #180 (permalink)  
 
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Originally Posted by Mike7777777 View Post
4000m is a long way down. In terms of design modifications to achieve retention and transmission of information, it's all fixable ... for a price. Wreckage location: simple buoy to be released following g measurement exceeding preset level (crash). Buoy contains GPS receiver/data logger and beacon, retrieve buoy and download data logger to locate release point. ELF receiver to trigger further buoy release (assuming USN ELF system is still in operation?), ELF signal to be sector specific (but I doubt if ELF can reach to 4000m). Buoys may contain flight data loggers, data to be stored on (several) SD cards or similar.
All adds weight/cost.
Mike,
Nearly all your suggestions mean new and currently non-existing equipment.

Wreckage location: simple buoy to be released following g measurement exceeding preset level (crash). Buoy contains GPS receiver/data logger and beacon, retrieve buoy and download data logger to locate release point.
Yes, this has been suggested and wouldn't cost that much. Sticking a few more, and more sophisticated, ELBs (emergency location beacons) on the airframe.

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....

And no, ELF doesn't work that far down.

CJ
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