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Aviation Forum / Country Specific / Australian Group / September 2008Flight Data Recorders
I was reading this article about a Russian air crash - here is an excerpt... Russian investigators have discovered that the cockpit-voice recorder from the crashed Itek Air Boeing 737-200 contains no trace of the ill-fated jet's final flight. ... MAK adds that the quality of the flight-data recorder information is "unsatisfactory" because of partial thermal damage to its magnetic tape, caused by the intense fire which followed the crash. Which made me think: magnetic tape?! Surely we've come far enough that we can be using solid-state storage in flight data recorders? Does anyone know why FDRs would still be using what, to me, is archaic technology? >I was reading this article about a Russian air crash - here is an excerpt... > [quoted text clipped - 10 lines] >Which made me think: magnetic tape?! Surely we've come far enough that >we can be using solid-state storage in flight data recorders? Many are solid state. >Does anyone know why FDRs would still be using what, to me, is archaic >technology? There are even a few foil trace recorders still out there! The answer is in the regulatory requirements of different countries, particularly for domestic only operations, and in changes in the requirements over the years. A 200 series 737 would be quite old, between twenty and forty years old. The 100 and 200 series both started service in 1968, but the 200 series are the oldest 737 still in service. Solid State (Digital Flight Data Recorder(DFDR)) was not introduced until after the last of the -200s were made. Thus many, perhaps most, do not have DFDR. *Russian* ?? > I was reading this article about a Russian air crash - here is an > excerpt... > MAK adds that the quality of the flight-data recorder information > is "unsatisfactory" because of partial thermal damage to its [quoted text clipped - 5 lines] > Does anyone know why FDRs would still be using what, to me, is archaic > technology? >I was reading this article about a Russian air crash - here is an excerpt... > [quoted text clipped - 13 lines] >Does anyone know why FDRs would still be using what, to me, is archaic >technology? gee give them a chance! they've only just stopped using wire recorders. Michael Henry <michael.k.henry_nospam@gmail.com> wrote in news:00d3a924$0 $20321$c3e8da3@news.astraweb.com: > Which made me think: magnetic tape?! Surely we've come far enough that > we can be using solid-state storage in flight data recorders? > Does anyone know why FDRs would still be using what, to me, is archaic > technology? It's not all that archaic. Aviation trails the bleeding edge by a very long margin, and with good reason. The bleeding edge usually draws blood at some point! I was initially surprised to learn, in circa 1999, that the B767 didn't use GPS for navigation. I subsequently learned that they don't need it... GPS isn't really up to scratch. (I'm not gonna explain that here, that's fodder for another post!) The same might apply for solid state recording technologies. They're new, they're frightfully expensive (perhaps less so in aviation terms, but they're still expensive), and they wear out. You don't notice your USB flash memory drive wearing out, because they use some clever load-spreading smarts and so folks tend to lose them or physically break them before they wear. Flash memory isn't all that good in a long-term regularly overwritten situation though, because it does wear out. Combine wear with cost of replacement and tape starts to look good. Tape is as cheap as chips, well understood, and remarkably tolerant of bad environmental conditions. Tape wears out too, but it's tolerant of wear - you can still get useful data off of it in situations where equivalent data recorded digitally would be long gone. Tape beats other moving-parts recording technologies too. I have a mate who likes to strap a video camera to his motorcycle when he goes for a ride. He swears by MiniDV (a 'digital' tape format), and won't give time-of-day to the newer hard disk and DVD formats. Tape copes with vibration long after disks and DVDs have given up. Sure, tape is old when compared to what's available now, but tape ain't broken (whereas the newer technologies are), and so it don't need fixin'. GB  SignatureMy friend Steve is an atheist. He has a bumper sticker that reads "Honk if you love Jesus". When someone honks, he gives them the finger. > Michael Henry <michael.k.henry_nospam@gmail.com> wrote in news:00d3a924$0 > $20321$c3e8da3@news.astraweb.com: SNIP > It's not all that archaic. Aviation trails the bleeding edge by a > very long margin, and with good reason. The bleeding edge usually [quoted text clipped - 5 lines] > > GB GB You referring to INS? But they do now use GPS for 'local' navigation (SID, STAR, flextrack etc). Brian > You referring to INS? > But they do now use GPS for 'local' navigation (SID, STAR, flextrack > etc). Brian Yes I am, and yes I know. My (maybe badly made) point was that the new technology wasn't adopted for a very long time after it had become 'mainstream' in other fields. GB SignatureMy friend Steve is an atheist. He has a bumper sticker that reads "Honk if you love Jesus". When someone honks, he gives them the finger. >> You referring to INS? >> But they do now use GPS for 'local' navigation (SID, STAR, flextrack [quoted text clipped - 5 lines] > > GB No, not badly made, I was just wanting to check it was INS. I agree re aviation 'lagging' with technology - same philosophy as you, partly 'accreditation' of equipment, partly 100.1% safety requirement :) cheers Brian >> Michael Henry <michael.k.henry_nospam@gmail.com> wrote in >> news:00d3a924$0 $20321$c3e8da3@news.astraweb.com: [quoted text clipped - 14 lines] > But they do now use GPS for 'local' navigation (SID, STAR, flextrack > etc). Brian No, they use GPS to update the INS. Bertie >>> Michael Henry <michael.k.henry_nospam@gmail.com> wrote in >>> news:00d3a924$0 $20321$c3e8da3@news.astraweb.com: [quoted text clipped - 7 lines] > No, they use GPS to update the INS. > Bertie Bertie Can we call it one all? I'm talking of the derivation of the nav data - the GPS engine is used for local navigation data, how it gets to the display may well be via the INS but the GPS engine is still the source. cheers Brian >>> Michael Henry <michael.k.henry_nospam@gmail.com> wrote in >>> news:00d3a924$0 $20321$c3e8da3@news.astraweb.com: [quoted text clipped - 16 lines] > >No, they use GPS to update the INS. Aren't both sources integrated via a fast Kalman filter? GPS errors are rapid and errors tend to clump around an accurate position, whilst INS errors are slow and tend to drift away from an accurate position. Integrating the systems via a Kalman filter results in a far more accurate and precise position. >>>> Michael Henry <michael.k.henry_nospam@gmail.com> wrote in >>>> news:00d3a924$0 $20321$c3e8da3@news.astraweb.com: [quoted text clipped - 22 lines] > Integrating the systems via a Kalman filter results in a far more > accurate and precise position. No idea. Works well, lasts a long time. When we dont use GPS, we use radio update of another type, usually. VOR DME. Without it, even the best INS can drift appreciably over time. It's not uncommon to see an error of a couple of miles after a long flight, and errors of 20 miles are possible after an ocean crossing. Radio update pretty much eliminates this and I've never seen any map shift whatsoever on a GPS updated system. > Aren't both sources integrated via a fast Kalman filter? GPS errors > are rapid and errors tend to clump around an accurate position, whilst > INS errors are slow and tend to drift away from an accurate position. > Integrating the systems via a Kalman filter results in a far more > accurate and precise position. Be interested in the technicalities, having been obliged to use a 4th order Chebishev (sp?) filter for some DA years ago - got a URL ? (Too lazy to look atm :-) >> Aren't both sources integrated via a fast Kalman filter? GPS errors >> are rapid and errors tend to clump around an accurate position, whilst [quoted text clipped - 5 lines] >Chebishev (sp?) filter for some DA years ago - got a URL ? (Too lazy to >look atm :-) Chebyshev/Chebychev - ask the missus. ;) These books are worthwhile :- Global Positioning Systems, Inertial Navigation, and Integration, 2nd Edition http://www.wiley.com/WileyCDA/WileyTitle/productCd-0470041900.html Kalman Filtering: Theory and Practice Using MATLAB, 2nd Edition http://www.wiley.com/WileyCDA/WileyTitle/productCd-0471392545.html The wiki write up on Fast Kalman seems reasonable too. >>> Aren't both sources integrated via a fast Kalman filter? GPS errors >>> are rapid and errors tend to clump around an accurate position, whilst >>> INS errors are slow and tend to drift away from an accurate position. >>> Integrating the systems via a Kalman filter results in a far more >>> accurate and precise position. That really is a fascinating idea - sort of poor man's differential GPS..... If you kept track of the average position by the GPS and the difference from there to the inertial position, you'd be able calculate the inertial drift and thence correct the GPS to inertial accuracy :-) >>Be interested in the technicalities, having been obliged to use a 4th >>order >>Chebishev (sp?) filter for some DA years ago - got a URL ? (Too lazy to >>look atm :-) > > Chebyshev/Chebychev - ask the missus. ;) She wasn't available at the time or I woulda :-) Doubt if she ever used 'em herself though, as she was more into control theory (...yuk!). > These books are worthwhile :- > [quoted text clipped - 8 lines] > > The wiki write up on Fast Kalman seems reasonable too. Many thanks - I'll have a prowl...tho me and Matlab never really got on.... >>>> Aren't both sources integrated via a fast Kalman filter? GPS errors >>>> are rapid and errors tend to clump around an accurate position, whilst [quoted text clipped - 3 lines] > >That really is a fascinating idea - sort of poor man's differential GPS..... Yes, that order of precision and accuracy for navigation. >If you kept track of the average position by the GPS and the difference from >there to the inertial position, you'd be able calculate the inertial drift >and thence correct the GPS to inertial accuracy :-) That's about it. I thought it was used from scratch for aircraft systems with combined INS and GPS - the cost of the filter is a fraction of the cost of the system, particularly if their is already room available on the computing side of things to do it. Its certainly done with the PPS and SPS on military systems. However, on reflection, there are probably many aircraft where GPS has been added to an existing inertial based system and the integration only goes so far as to allow a position update to correct drift. >Many thanks - I'll have a prowl...tho me and Matlab never really got on.... Me two... >>That really is a fascinating idea - sort of poor man's differential >>GPS..... [quoted text clipped - 20 lines] > > Me two... Heh. Mentioned this to Her Indoors. She was mightily unimpressed. "Of course we were updating inertial nav - using radar - now do you want a cup of tea?" Friggin hell! :-) Mind you, her field was ICBMs, not IC domestic transport :-) (For those that tuned in late, my Missus was a fairly senior control systems engineer in the old USSR) Of the QF 767s all of them have GPS, but only in the last 3 (OGT, OGT, OGV) is it integrated with the nav system. All of the others use it for GPWS terrain avoidance only. Whilst it's nice to have, the updates that the system applied using nav aids were good enough for area and terminal navigation. Not for approaches, but even aircraft fitted with multiple integrated GPS aren't necessarily cleared for GPS based approaches...though I have no idea why. SignatureRead the latest aviation news at www.newsaviation.com > Of the QF 767s all of them have GPS, but only in the last 3 (OGT, OGT, > OGV) is it integrated with the nav system. All of the others use it for [quoted text clipped - 3 lines] > approaches, but even aircraft fitted with multiple integrated GPS aren't > necessarily cleared for GPS based approaches...though I have no idea why. JB, I asked the question of a crew en-route to Cairns from Sydney (I was on my way to Narita). I don't remember if the aircraft was a -200 or -300. They told me they had no GPS as all, and showed me how the INS updated with navaids worked. I was initially surprised to learn that there wasn't any GPS at all, but in hindsight I can see why it wasn't really necessary. This was circa 1999, IIRC. GB SignatureMy friend Steve is an atheist. He has a bumper sticker that reads "Honk if you love Jesus". When someone honks, he gives them the finger. >I was reading this article about a Russian air crash - here is an >excerpt... [quoted text clipped - 14 lines] > Does anyone know why FDRs would still be using what, to me, is archaic > technology? This occasionally happens, even though the FDR and CVR have considerable thermal inertia and are located in a part of the plane that is least frequently affected by both fire and mechanical damage. Also, the prose above suggests that there was some data recovered from the cocpit voice recorder and "some data" is probably more than they would have gotten from solid state memory. All the same, there has been a move from magnetic tape and metal foil to solid state memory in the 20+ years that I have been out of that industry. However, IMHO, that has been a case of obtaining more detailed data and information (most of the time) and greatly reduced maintenance cost (the frequent replacement of tapes and foils was shop maintenance) and accepting far less robust media in order to accomplish those goals. Personally, I can see more than one side of the arguments leading to these changes and I have mixed feelings regarding the wisdom of same. Peter Peter Dohm said the following on 7/09/2008 11:55 PM: > This occasionally happens, even though the FDR and CVR have considerable > thermal inertia and are located in a part of the plane that is least [quoted text clipped - 12 lines] > Personally, I can see more than one side of the arguments leading to these > changes and I have mixed feelings regarding the wisdom of same. There's no reason, except cost, why both can't be fitted. Solid state can potentially record most of a flight and, if it survives provide a considerable amount of data over an extended timeline. If the solid state doesn't survive then there's still the legacy FDR and CDR. A damaged hard disk might offer higher rates of recovery than a damaged solid state drive. However, I'm not sure how well a hard disk would tolerate mid air turbulence. Anyway, I think their ability to survive a fire might be a lot less than that of the older devices. > There's no reason, except cost, why both can't be fitted. Solid state > can potentially record most of a flight and, if it survives provide a > considerable amount of data over an extended timeline. If the solid > state doesn't survive then there's still the legacy FDR and CDR. I'd expect that newer aircraft have more capable recorders. The QARs already record hundreds of parameters, and virtually every switch position. As to whether the 'interested parties' would be all that keen on allowing CVRs that cover more than 2 hours is a completely different question. A recorder that could cover all of a flight (or multiple flights) would become a very attractive monitoring tool for big brother, and I doubt that it would take long before that started happening. The contents of existing recorders have already been used outside of the various laws and agreements covering them, so I doubt that anything would change there. The 2 hours covers pretty well any major event that you would want the recorder for. It didn't in this case, but they have both FDR and QAR, as well as the crew and aircraft, so I doubt that the investigation is really lacking very much. SignatureRead the latest aviation news at www.newsaviation.com >The 2 hours covers pretty well any major event that you would want the >recorder for. It didn't in this case, but they have both FDR and QAR, as >well as the crew and aircraft, so I doubt that the investigation is really >lacking very much. One wonders if there will be future protocols to pull the CVR breaker post-incident, pre-landing, to preserve the contents of the Time in Question. SignatureA host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433 David Lesher <wb8foz@panix.com> wrote in news:gajc42$gl0$4 @reader1.panix.com: > One wonders if there will be future protocols to pull the CVR breaker > post-incident, pre-landing, to preserve the contents of the Time in > Question. I suggest not. If the landing turns out to be an 'eventful' one, someone's gonna want data for that. GB SignatureMy friend Steve is an atheist. He has a bumper sticker that reads "Honk if you love Jesus". When someone honks, he gives them the finger. > David Lesher <wb8foz@panix.com> wrote in news:gajc42$gl0$4 > @reader1.panix.com: [quoted text clipped - 4 lines] > I suggest not. If the landing turns out to be an 'eventful' one, > someone's gonna want data for that. My (now out of date) experience was that the CVR could not be deleted or turned off unless the GPU was plugged in. > > David Lesher <wb8foz@panix.com> wrote in news:gajc42$gl0$4 > > @reader1.panix.com: [quoted text clipped - 7 lines] > My (now out of date) experience was that the CVR could not be deleted or > turned off unless the GPU was plugged in. No, but the aircraft does have to be on the ground for you to be able to erase it. It just sits there recording away, as long as the aircraft has any power on it...which means it's on just about all of the time. There is a CB. There would have to be, just in case the CVR turned out to be the cause of whatever problems you have...rather like the oxygen tank really. I can guarantee for you, that 'saving' the recording for posterity would never have reached the top of the 'to do' list, even if I'd thought about it. SignatureRead the latest aviation news at www.newsaviation.com >>> David Lesher <wb8foz@panix.com> wrote in news:gajc42$gl0$4 >>> @reader1.panix.com: [quoted text clipped - 10 lines] > erase it. It just sits there recording away, as long as the aircraft has > any power on it...which means it's on just about all of the time. Interesting - thanks for the update; F27 and V700 needed GPU to erase - but as I said "My (now out of date) experience" and it is somewhat of date. > MAK adds that the quality of the flight-data recorder information > is "unsatisfactory" because of partial thermal damage to its > magnetic tape, caused by the intense fire which followed the crash. >Which made me think: magnetic tape?! Surely we've come far enough that >we can be using solid-state storage in flight data recorders? >Does anyone know why FDRs would still be using what, to me, is archaic >technology? Co$t is why. And while flash-based systems may offer more survivable recording; consider the recent Qantas incident, where the depressurization itself was overwritten by subsequent flight. SignatureA host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433 >> MAK adds that the quality of the flight-data recorder information >> is "unsatisfactory" because of partial thermal damage to its [quoted text clipped - 9 lines] >recording; consider the recent Qantas incident, where the >depressurization itself was overwritten by subsequent flight. They could put in a bigger chip for longer recording. I thought most DRs were only about 1/2 hr looping? >>> MAK adds that the quality of the flight-data recorder information >>> is "unsatisfactory" because of partial thermal damage to its [quoted text clipped - 12 lines] > They could put in a bigger chip for longer recording. I thought most > DRs were only about 1/2 hr looping? The original CVRs were 1/2 hour looping, carying three channels (or tracks) of audio, and would erase the tape when the parking brake was applied at the destination gate. Part of that was due to a combination of technical necessity and convenience, and part was the dfproduct of negotiation between the interested parties. The reusult was robust, in the sense that the recovery of data did not depent upon any part of the equipment remaining operable I am not familiar with the newer equipment; but would expect that it would have been made functionally similar--with the possible addition of more channels of audio. The original FDRs contained a single use role of stainless steel foil, which was marked by stylii. The result was *extremely* robust, but even the second generation of such recorders had a very limited number of data channels and required frequent depot level maintenance to replace the foil rolls. Solid state memory simply does not have similar survivability and there is virtually no change that it will within the next 25 years. Therefore, solid state memory, in the event that it is actually in use, is simply a way to obtain more channels of data at less monetary cost in those cases where the data can still be recovered. So long as the purpose of the data is to detect failures which can then be resonably predicted, then it is probably a good trade. > Solid state memory simply does not have similar survivability I'm in two minds about this bit. Following the claims I made the other day re survivability, I'm having some second thoughts. It occurred to me that flash memory has some interesting capabilities wrt recovery. I don't claim to understand how the stuff works, but I've seen first hand some rather astonishing situations wrt recovering perceived to be lost data. I personally recovered data that was in the order of 180% (one-eight-zero-percent) of the stated capacity of a compact flash card on one occasion. I've no idea how, but some software I ran against it retrieved all the photos that had been recorded on it in the most recent use, and other sets of photos that the owner recognised, but said he'd copied and 'deleted' from the card in previous (much older) uses. I've no idea what was happening there, but it was quite interesting. Also, the capability for the memory to record and hold individual bits of data is quite seperate from the filesystem's ability to record what has been stored, and with appropriate recovery techniques and appropriately competent technicians, the stuff does seem to be quite good. Of course, Strange Things (tm) happen when heat and/or magnetism gets involved, dunno how the flash memory copes in hot/magnetic situations. Of course, price still remains a *substantial* issue. That Apple Computer has bought up HEAPS of the stuff (including future production I gather) for their iPods and iPhones makes that an even more profound problem. > and > there is virtually no change that it will within the next 25 years. With respect, I disagree. Professor Gordon Moore, broadly interpreted, might also have something to say on that point. We had the discussion in one of my classes a couple of weeks ago. A student asked my opinion, did I think that we'll hit a brick wall wrt technology, communications bandwidth, etc. I thought not - I've been lucky enough to live in technologically interesting times, and I've never seen the march of (computer) technology slow. It's amazing how far we've come in such a short time (circa 25 years). Stuff we take for granted now was unthinkable even 10 years ago. I'm not about to claim that I could even begin to guess at what computer technology I'll see 25 years from now. GB SignatureMy friend Steve is an atheist. He has a bumper sticker that reads "Honk if you love Jesus". When someone honks, he gives them the finger. Stuff we take for granted now was > unthinkable even 10 years ago. I'm not about to claim that I > could even begin to guess at what computer technology I'll see > 25 years from now. > > GB The famous example of how short sighted we can be is the famous set of quotes: "Nobody will ever need more than 640k RAM!" -- Bill Gates, 1981 "Windows 95 needs at least 8 MB RAM." -- Bill Gates, 1996 "Nobody will ever need Windows 95." -- logical conclusion > Stuff we take for granted now was >> unthinkable even 10 years ago. I'm not about to claim that I could [quoted text clipped - 9 lines] > "Windows 95 needs at least 8 MB RAM." -- Bill Gates, 1996 > "Nobody will ever need Windows 95." -- logical conclusion "You ain't goin' nowhere, son -- you ought to go back to drivin' a truck" Jim Denny, Sept. 25, 1954 as he fired Elvis Presley after one performance at the Grand Ole Opry. >> ... magnetic tape?! Surely we've come far enough that >> we can be using solid-state storage in flight data recorders? [quoted text clipped - 5 lines] > recording; consider the recent Qantas incident, where the > depressurization itself was overwritten by subsequent flight. I can see how solid state storage is more expensive than tape, but I would have thought that by the time you go through the whole certification process the cost of the actual medium is just a small fraction of the total cost... and if the solid state medium offers any benefits over tape than that small extra cost would certainly be justifiable. The other issue you raise really surprises me: the small amount of flight time for which recordings are kept. Some other posts have mentioned half-an-hour loop! Does anyone know what volume of data this entails? Regards, Michael P.S. A quick mental calculation: I can go to Officeworks (in Australia) and buy a 16 Gb memory stick for AU$100. OK, it's not going to meet the same fault-tolerance and quality standards, but let's ignore that for now :) For those of us in the iPod generation 16 Gb equates to around 300 hours of MP3 music. Obviously you would encode speech differently and fit a lot more than that, but let's not worry about that. Of course you also want to record other parameters (temperatures, pressures, position of controls, etc). I'm just pulling numbers out of the air but let's say you want to record 1,000 different parameters each sampled 10 times a second. Furthermore let's say the data for each parameter is stored as a 32-bit value, which comes out to 40kb of data per second or just under 150 Mb per hour. That's over 100 hours of parameters in our 16 Gb memory stick. Recording voice and data at the same time and I figure you can fit about 80 flight hours in a $100 USB stick. Not bad ;) I'm obviously missing out on some important bits but it has made me wonder: what would be the market for a really small, light, and cheap uncertified flight data recorder... > The other issue you raise really surprises me: the small amount of > flight time for which recordings are kept. Some other posts have > mentioned half-an-hour loop! Does anyone know what volume of data this > entails? I don't know the volume of data, but the CVR and FDR have different amounts of data in terms of time. 1/2 CVRs are old. New ones can record hours. btw - for older aircraft, the biggest cost of putting newer FDRs with (many) more channels is not the FDR itself, but all the sensors that have to be installed. SignatureBob Noel (goodness, please trim replies!!!) |
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