NTSB Flight-Data and Cockpit-Voice Recorder Lab Tour - Page 1
Forum section: electronics / general

author: sonicj
author_rank: Frequent Contributor
timestamp: November 03, 2014, 03:53:18 am
content: An interesting behind the scenes tour of the NTSB flight-data and cockpit-voice recorder laboratories in Washington, DC. The tour only addresses solid state devices. I'm not sure if magnetic & mechanical recovery are in a separate facility or if those devices are just no longer in use... But yea, Definitely worth the watch if you're into electronics and/or aviation!

author: Unknown
author_rank: Unknown
timestamp: November 03, 2014, 04:41:42 am
content: Fascinating stuff! This reminds me of a data extraction we did at work years ago. It involved a flight recorder which was badly burnt in a post-crash fire. I think from memory the data was stored on CompactFlash media. Despite the CF card being damaged, the contents of the memory was intact.One thing I've never understood is why Americans pronouncesolderas "sodder".

author: djacobow
author_rank: Super Contributor
timestamp: November 03, 2014, 05:14:47 am
content: Very interesting. It looks like these guys' jobs would be a lot easier if there were some standards for information format for these devices. It looks like every manufacturer, aircraft, model, software revision, etc, has a different system. There's got to be a better way than that. Even something like a multiple redundant flash cards each with a SQLite file on them would be better. Then the NTSB could just read out the names of the variables from the file itself. For the cost of flash these days, they could be many-ways redundant. In fact, they could even have multiple data stores; one each in the front, rear, and both wingtips would increase the odds of at least one not being incinerated.Quote from: sonicj on November 03, 2014, 03:53:18 am

author: pickle9000
author_rank: Super Contributor
timestamp: November 03, 2014, 06:00:12 am
content: Very interesting, be neat to see some actual work in progress.

author: sonicj
author_rank: Frequent Contributor
timestamp: November 03, 2014, 06:32:48 am
content: Quote from: djacobow on November 03, 2014, 05:14:47 amThey have been known to hand transcribe binary on damaged magnetic tape through a microscope... I don't think they are worried about it...With support from the manufacturer, they can map out the data quickly. Leaving it open to the manufacturer's and operator's discretion, as long as they meet specified minimums, allows the manufacturer's and operator's to increase sensors & sample rates as they see fit without compromise to meet some protocol standard.I do think diversifying data collection would be useful though. Breakaway, floating enclosures, etc. Many planes are already equipped with external data logging via Quick Access Recorders, FADEC logs, etc.ADS-B adds some very basic data parameters that could be potentially useful in the event of a accident with loss of flight recorders/airplane. ie: ADS-B logging buoys. ADS-B data is currently being crowdsourced for realtime flight tracking sites/apps.

author: djacobow
author_rank: Super Contributor
timestamp: November 03, 2014, 07:59:19 am
content: Yeah, I'm not buying. I can easily imagine a protocol that would allow manufacturers to add sensors and change sample rates. Heck, they could write the "standard protocol" in addition to whatever proprietary hoo-ha they want.What these devices all have in common is that their data formats are not self-describing, thus requiring external documentation to be decoded. I guess that's fine for airliners, as nobody flies airliners from defunct manufacturers (at least nobody who is going to be investigated by the NTSB), but to me it looks like a bit of a jobs program for avionics designers. It's a good thing FDRs are not required in the GA world, because this approach would crash and burn very quickly.ADS-B is never going to downlink the amount of data captured by a FDR. ADS-B 1090-ES, as used by airliners and everyone outside the US I believe only allows for < 50 parameters, most of which are navigational in nature: aircraft id and type, current position, next waypoint, yadda yadda. It's not like you're going to see the fuel pressure in engine 3 that way. ADS-B UAT has more bandwidth (mostly for uplink, maybe not that much more for downlink?), but it's just a US GA thing at this point.Overall, FDRs are cool, and the people who can extract the data from them are clearly skilled and resourceful. But it's hard to look at one of those things and not see ways it could be improved.Quote from: sonicj on November 03, 2014, 06:32:48 am

author: Howardlong
author_rank: Super Contributor
timestamp: November 03, 2014, 08:50:22 am
content: Quote from: djacobow on November 03, 2014, 05:14:47 amAs you might imagine, avionics is controlled by heavy regulation and type acceptance and certification, and the cost of certification is enormous because typically the devices have to be certified in dozens and dozens of jurisdictions separately for a global market. The result is that a given piece of avionics will have a shelf life of decades, so things like glass cockpits and GPS have taken a very long time to gain acceptance, and it's still very common to find steam gauges in commercial transports. Indeed, in the UK, and many other countries, dead reckoning is still the primary navigation method taught for initial pilot training, and you'd be failed if you used a GPS.The use of redundancy by doubling up or otherwise being dependent on multiple identical units has its place, but it doesn't protect you from common mode failure. As an example, IBM, back in the early 90s, introduced RAID arrays which suffered a failure where the heads on the badly designed disks stuck on the platter after a power down, rendering your RAID array dead. Corrective action was percusive, with just the right tongue angle, a hammer, and a prayer. Also, storing the RAID config on the single controller card was another idiotic thing to do.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 03, 2014, 09:28:06 am
content: Quote from: Halon on November 03, 2014, 04:41:42 am... or frequently say "We'll go ahead and...."

author: SeanB
author_rank: Super Contributor
timestamp: November 03, 2014, 05:52:31 pm
content: Moving tape recorders have been around so long that some that are still in use use whale oil as a tape lubricant. Those actually run essentially until the plane is only extant as museum displays, as the oil does not degrade with time. The later formulations have major life issues, such that often the FDR and CVR data on tape is unusable as the tape has degraded and shed so much oxide onto the tape path and heads that it actually no longer records on the tape. As there is no verify on the tape this means it is blank. This is always an issue on older recorders, as the fault detector really only will show up a jammed tape or a snapped one.

author: djacobow
author_rank: Super Contributor
timestamp: November 03, 2014, 06:25:20 pm
content: Quote from: Howardlong on November 03, 2014, 08:50:22 amOh, I get it. I'm a pilot myself (not airline) and even worked a short stint for the FAA. I'm just saying that the regulations could be better. And believe, me, if you have ever read the US FARs you will agree. Feast your eyes on these:http://www.ecfr.gov/cgi-bin/text-idx?c=ecfr&tpl=/ecfrbrowse/Title14/14tab_02.tpl. Also not saying that old equipment should necessarily be forced into redesign, but, come on, you don't think new equipment could do better than a constant series of proprietary one-offs?Pilots are taught to dead reckon, of course, but it is not the "primary" method. The primary method for VFR flight is pilotage," otherwise known as looking out the window. :-). For IFR in IMC, dead reckoning comes into play, but it's more for when the sh*t hits the first compressor stage.Personally, I prefer to fly by steam gauges and VOR needles; it's how I learned. When I use all the GPS whiz-bang, it just feels like cheating. But it's amazing stuff. There is more capability in a modern tablet than in the state-of-the-art glass cockpit from not too many years ago. Perversely perhaps, that probably discourages airlines from retrofitting their cockpits to new avionics. Just maintain the cockpit with the minimal set of certified avionics necessary for the type of flight and any new whiz-bang beyond that you probably want in an uncertified device in the pilot's chart case.

author: SeanB
author_rank: Super Contributor
timestamp: November 03, 2014, 06:56:32 pm
content: Just remember in the all singing all dancing cockpit you still have the standby magnetic compass, the standby altimeter and ASI, along with the standby gyro and a tilt indicator. Has saved a few pilots where they had a major failure of the power bus, like the Gimli Glider.I worked on helicopters where the only electrical connections on the instrument panel was for lighting and warning lights. I do not think any of the pilots wanted to ever fly a non VFR approach.

author: Howardlong
author_rank: Super Contributor
timestamp: November 03, 2014, 09:00:30 pm
content: Quote from: djacobow on November 03, 2014, 06:25:20 pmWell dead reckoning also refers to the use of the wizz wheel, which is fundamental to pre-flight planning under VFR training. When I did my IMC training, I had to dust off the wheel again for that too when preparing for the tests here in the UK. All the planning I do for real life though is done on a computer, and I take a tablet with me loaded with the plan in the cockpit, although I print out the plog and take paper enroute charts and paper approach plates, I still don't trust the technology. My Cherokee is nearly as old as I am, 1966, and is of course steam gauges but is IFR equiped, not that that will mean all that much soon, VORs are gradually being taken down here, soon it'll be difficult to take an enroute IFR test unless GPS is allowed!

author: djacobow
author_rank: Super Contributor
timestamp: November 03, 2014, 11:59:24 pm
content: The whizz-wheel is just a calculator, nothing more or less. It can be used for any math problem. You can use it for dead reckoning, or you can use it to calculate a wind correction angle, time to next waypoint, fuel remaining at destination, whatever. Dead reckoning usually refers specifically to estimating one's position from a starting position and a series of speeds, times, and courses. When I was working on my IFR rating, it was the very last technique in the toolbox. I needed to know it, of course, but I definitely don't remember having to demonstrate it on my checkride.Here in the states, they are talking about decommissioning the VORs, and they have a schedule to do it, but they seem to find ways to not actually pull the plug. Maybe somebody at the FAA understands the weakness of an all-GPS nav system. VORs are simple and robust. Also, it is possible for a computer to calculate a position on its own by rapidly scanning and IDing VORs and comparing that to a database. I think airline FMSs will actually do that. I'm not sure why such a gadget or backup has not found its way into GA, but I think it would be a nice backup for GPS.As for paper charts, I still carry VFR charts, but I finally dropped the paper IFR stuff. It weighed a ton and was a huge pain in the ass. The procedures now are in the box in the panel and on two tablets: one on the yoke running Garmin Pilot, the other as plain pdfs on a tablet in my bag. That's plenty of redundant for me. I guess if there's an nuclear electromagnetic pulse, I'm screwed, but I'm comfortable with that risk. :-)Quote from: Howardlong on November 03, 2014, 09:00:30 pm