37KHz from Black Box - Page 1
Forum section: electronics / projects

author: mfeinstein
author_rank: Contributor
timestamp: April 07, 2014, 03:41:06 am
content: Hey Dave, watching so many of your videos I know you worked for a long time with sonar buoys and other seismography related equipment for the navy, right?With all the lastest news of the missing malasian flight, I keep hearing that the pinger inside the Black (orange) Box, sends a signal of 37KHz when it's under water...the thing that gets my curiosity is why 37KHz? Is it a "magic" number? Does signals in this frequency go further in the ocean? Does anyone has a knowledge why they chose this particular frequency as a standard?Thanks!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 07, 2014, 03:59:37 am
content: About 37kHz exactly, I don't know, but extremely low frequencies do propagate further in water. Military submarine channels go all the way down to 50-90Hz I think. Think of it this way: salt water is a conductor, and therefore exhibits skin effect; high frequencies are absorbed easily, or bounce right off altogether.Tim

author: mfeinstein
author_rank: Contributor
timestamp: April 07, 2014, 04:05:30 am
content: Quote from: T3sl4co1l on April 07, 2014, 03:59:37 amYes, that's exacly my point! I know as low frequency as you get, the further you can go...so why 37KHz? I think it's quite ""high frequency"" for this kind of application, isnt it?

author: pickle9000
author_rank: Super Contributor
timestamp: April 07, 2014, 04:08:14 am
content: Have a look here, bottom of the page.https://www.eevblog.com/forum/chat/twenty-passengers-on-missing-flight-370-worked-for-freescale-semiconductors/360/

author: Fsck
author_rank: Super Contributor
timestamp: April 07, 2014, 04:14:43 am
content: I'd guess it's a frequency selected to not interfere or affect the ecosystem otherwise the tree huggers would be on a rampage, not used for long range deep sea communications to avoid interference and low enough to not get screwed by the physics of communication through the ocean.

author: bench_knob
author_rank: Regular Contributor
timestamp: April 07, 2014, 04:19:28 am
content: Quote from: mfeinstein on April 07, 2014, 03:41:06 amwww.radiantpowercorp.com/dk-series-underwater-locator-beacons.aspxwww.radiantpowercorp.com/dk-180-airframe-locator-beacon.aspx

author: pickle9000
author_rank: Super Contributor
timestamp: April 07, 2014, 04:21:53 am
content: The frequency and repetition rate was selected because it's not naturally occurring and therefore easier to find.

author: mfeinstein
author_rank: Contributor
timestamp: April 07, 2014, 04:23:35 am
content: Quote from: pickle9000 on April 07, 2014, 04:08:14 amWhich part? I dont see any part where someone explain why they picked this particular frequency for this purpose...

author: mfeinstein
author_rank: Contributor
timestamp: April 07, 2014, 04:24:32 am
content: Quote from: Fsck on April 07, 2014, 04:14:43 amWell it could be...I mean it could be 1000 things and people could especulate about it in here for agesbut if someone knows for sure, it will be nice to share

author: mfeinstein
author_rank: Contributor
timestamp: April 07, 2014, 04:28:33 am
content: Quote from: bench_knob on April 07, 2014, 04:19:28 amThanks for sharing the specifications, but I dont see where it says WHY they chose this particular frequency, and not like 100Hz or 20KHz or 40KHz or 30KHz or even 35Khz or even 37KHz, but 37,5KHz :0 it sounds too magical for me...maybe they flip a coin, but i rather ask then speculate

author: Wytnucls
author_rank: Super Contributor
timestamp: April 07, 2014, 04:55:19 am
content: 37.5kz is not the best frequency. There is a push to change that to a lower frequency to increase the detection range.Today, aircraft are equipped with Flight Recorders with Underwater LocatorBeacon (ULB). The range of the current used Flight Recorder ULB’s is limiteddue to the used frequency of 37.5 kHz.An initiative has been founded to investigate in Wreckage LocalizationTechnology where among other things, a Low Frequency ULB transmitting on afrequency between 8 to 9 kHz was proposed.In 2012 SAE Aerospace has published an Aerospace Standard (AS6254) tocover the Minimum Performance Standard for Low Frequency UnderwaterLocating Devices (LF-ULB) transmitting on a frequency of 8.8 kHz ±1 kHz.ICAO published its annex 6 amendment 36 (Nov 2012), stating that a LF-ULBshall be installed on all aircraft with a maximum take-off mass of over 27,000 kg,operating over water at particular distances to land suitable for making anemergency landing.This ICAO requirement is currently in the process to become national rules bylocal Airworthiness Authorities.

author: zapta
author_rank: Super Contributor
timestamp: April 07, 2014, 04:56:57 am
content: IIRC Sonar range goes down by the square of the frequency but lower frequencies require larger hydrophones so it's a balance act.

author: vk6zgo
author_rank: Super Contributor
timestamp: April 07, 2014, 05:01:50 am
content: Quote from: mfeinstein on April 07, 2014, 04:28:33 amIt is probably a convenient division of a standard crystal frequency.If it comes to it,why are receiver I.Fs the weird frequencies they are?

author: mfeinstein
author_rank: Contributor
timestamp: April 07, 2014, 05:06:11 am
content: Quote from: Wytnucls on April 07, 2014, 04:55:19 amThat makes lots more of sense! It's still a frequency that doesnt require big hydrophones, but still can cover a lot more space...

author: Wytnucls
author_rank: Super Contributor
timestamp: April 07, 2014, 05:21:53 am
content: It may be in addition to the current system.It is also important to use a frequency free from interference from other transmitters.

author: zapta
author_rank: Super Contributor
timestamp: April 07, 2014, 05:29:28 am
content: Quote from: Wytnucls on April 07, 2014, 04:55:19 amIIRC this is, the standard frequency for underwater voice commutation, 8.75 SSB or something like that. Used by submarines, divers, etc.

author: VK5RC
author_rank: Unknown
timestamp: April 07, 2014, 08:14:56 am
content: Don't you get better direction finding (phase difference between 2 separated mikes) at higher frequencies, note the range went only to 3.6km in specs, it's in close to 4.5km of water depth.

author: dannyf
author_rank: Super Contributor
timestamp: April 07, 2014, 10:24:18 am
content: QuoteBingo!

author: David Hess
author_rank: Super Contributor
timestamp: April 07, 2014, 05:43:13 pm
content: Quote from: vk6zgo on April 07, 2014, 05:01:50 amReceiver IF frequencies are chosen to place their image and fundamental frequencies out of the way.

author: MartinX
author_rank: Regular Contributor
timestamp: April 07, 2014, 09:18:55 pm
content: 37kHz is convenient because it is easy to make a reasonably cheap and small piezo electric transducer using existing technology from depth sounders and sonar, I wonder what they will use if they change to 8kHz it seems a bit low but maybe there is no problem, I am only speculating.

author: mfeinstein
author_rank: Contributor
timestamp: April 07, 2014, 09:21:34 pm
content: I was expecting to hear from Dave by now... I dont see him replying much in the blog... I wonder what is he up to nowdays....

author: Zero999
author_rank: Super Contributor
timestamp: April 07, 2014, 10:02:17 pm
content: Quote from: Wytnucls on April 07, 2014, 05:21:53 amQuote from: T3sl4co1l on April 07, 2014, 03:59:37 amThere seems to be a lot of confusion here. It has nothing to do with the conductivity of the water or the electromagnetic spectrum. The black box produces an acoustic signal, i.e. sound, not an electromagnetic wave. Lower frequency sound travels further than higher frequencies but larger transducers are required and it's probably less easy to locate the signal.

author: Wytnucls
author_rank: Super Contributor
timestamp: April 08, 2014, 05:37:51 am
content: Doh, of course, forgot it was an acoustic signal.Is it not a possibility electromagnetic signals could interfere with the ship's detection equipment though?I suppose the shielding is pretty good inside a big ship, but perhaps not so much on a Chinese inflatable.

author: dexters_lab
author_rank: Unknown
timestamp: April 08, 2014, 09:32:55 am
content: Quote from: mfeinstein on April 07, 2014, 09:21:34 pmup to his eyes in uCurrents?

author: dexters_lab
author_rank: Unknown
timestamp: April 08, 2014, 09:34:57 am
content: ultrasonic bath cleaners work around this frequency too... must be more to it than random choice

author: vk6zgo
author_rank: Super Contributor
timestamp: April 08, 2014, 11:05:27 am
content: Quote from: David Hess on April 07, 2014, 05:43:13 pmIt was a rhetorical question--I know why!IF frequencies aren't set in stone,though --some older radios use 465kHz rather than 455kHz--some were 262kHz at one time.The 10.7MHz frequency is sometimes replaced by 10.68 MHz,or 11 or 9 MHz.Australian analog TV sound IF is 5.5Mhz,in the USA it is 4.5MHz,& in the UK,6.5MHz.

author: zapta
author_rank: Super Contributor
timestamp: April 08, 2014, 02:32:28 pm
content: Quote from: mfeinstein on April 07, 2014, 09:21:34 pmFixing the Tapatalk plugin of course, or on a beach in Hawaii posting prerecorded videos, or in a dark cell due to a DUI... This could be an interesting Where Is Dave thread. ;-)As for the topic at hand, here is an interesting video from Mikehttp://youtu.be/mQehX0rVYuY

author: mfeinstein
author_rank: Contributor
timestamp: April 09, 2014, 07:14:58 am
content: Quote from: zapta on April 08, 2014, 02:32:28 pmI should have linked mike's video on my first post, really good one Mike!

author: bench_knob
author_rank: Regular Contributor
timestamp: April 10, 2014, 06:30:21 am
content: Quote from: mfeinstein on April 07, 2014, 04:28:33 amYep.I forgot to mention in my post that this manufacturer is the actual maker of the two ultrasonic-beacons that were mechanically installed on the OUTSIDE of one end of each of the two 'black-boxes'. Apparently the two black-boxes are located at each end of the airplane, the tail box isn't pinging, which is consistent with the plane depleting its fuel, as apparently, the plane stalls, and goes in tail-first. Physically the beacons are housed inside cylinders that are mounted on the long-side of the cylinder, so while the emitted wave-shape from the transducer on one end (likely piezocrystal) is nearly lambertian (80%), due to the beacon mechanical mounting arrangement the effective pattern is likely somewhat isotropic.In addition to all the other dynamic (moving) variables one likely sees in such an environment along with the black-boxes being carried along with the currents, its just another variable that likely affects the detection 'beam-corridor'. Three minutes of signal + 20hrs of silence, 15 seconds of signal + 11hrs of silence, 7 minutes of signal, etc, and then the battery is past the 30 day spec (mininum) and is apparently diminishing as anticipated, yet another anticipated verifiable characteristic. I suspect that its likely that some engineer (if there is any think'n happening) has attempted to verify the anticipated signal level drop rate / signal variance characteristics against the manufacturer's battery depletion curve for the beacon models deployed. Its simply another verification physik that need fit the characteristics of acoustic-beacon unit. Individually each of this seemingly unrelated poor quality data-point...things, are not very good evidence, but collectively, it shows that the aircraft wreckage area has very likely been located. Then couple those few points of which the public is aware (the authorities have many more, hopefully), with the fact that in that area of the world's oceans, there's not much happening, no buoys, no oil-platforms, no research vessels, no islands, AND its the long-way around the world so there's not much aircraft traffic either, so what's the likelihood of finding a non-naturally occurring 37.5KHz emitter source there? Its another speck of paint from the overall painting, while being unable to see the actual picture. Those poor people.. . .in any case, finding that airplane...its a crapshoot in my opinion. Unlike the Titanic, which was very large and essentially went down intact (two big peices), the airplane likely disintegrated upon impact, so there ain't gonna be large descernable chunks lying about and then the ocean currents have been moving all that aircraft grade aluminum, scattering it here and there. Unlike the Titanic, it may never be found. And the bodies? 30 days in an environment where a single eye-dropper of ocean water contains uncountable hungry animals, (radiolarians etc)....yep yep yep. Its a pipe dream.I was not able to directly discern the specific model deployed, but rather found a range of models that basically fit the minutia that has been revealed by the talking-heads of the American news-media.Re; the 'magic-number'. Quite true, however, my reason for citing the mfr's (marketing) specs, was simply because folks had nothing other than Clueless Network News for information among all of their wild-a.ss guessing (but their marketers sold lots of juicy advertising slots).Ad rem, here are a few pointers to the answer to your specific question, about the frequency selectionbeing a magic-number or having been selected via a flip-of-the-coin...some juicy tidbits to succulate while sipping a JD with a WD40 spritzer splash in da workshop! Hah!Underwater Acoustics physicshttp://en.wikipedia.org/wiki/Underwater_acoustics"Acoustic-Impedance is the relationship of how much sound pressure is generated by the vibration of molecules of a particular acoustic medium at a given frequency."Transducer matching to the medium:http://en.wikipedia.org/wiki/Acoustic_impedanceAnd then here's a bit about how to transduce the acoustic-vibrations:Hydrophonehttp://en.wikipedia.org/wiki/Hydrophonebench knob

author: mfeinstein
author_rank: Contributor
timestamp: April 10, 2014, 06:43:28 am
content: Excessive quoting removed, see previous post for what was quoted.Thanks for all the links! I was expecting a more stragiht foward answer than have to read all this technical stuff about sound underwatercould you make it short, maybe? I dont have time (at least not in the coming weaks) to read it all, and looking at it quickly, I couldnt find anything related to 37,5KHz.

author: bench_knob
author_rank: Regular Contributor
timestamp: April 10, 2014, 07:51:11 am
content: Quote from: mfeinstein on April 10, 2014, 06:43:28 amAwwww, ya hurt my feelin's <<snip>> <<snip>> all my yak'n! Heh heh.However...its all in the physics...the math. You said ya wanna know why they chose that frequency, the only way to know that info definitively, is to ask the Dukane-SeaCom design engineer....info that DSC may not tell ya, or ya can back-track to the likely reason, by doing the physics math. Its very unlikely that they just flipped a coin.bench knob

author: KedasProbe
author_rank: Frequent Contributor
timestamp: April 10, 2014, 08:12:13 am
content: Why isn't it modulated, then it could even send info like how deep it is or the strength of the signal so the distance can be calculated.or its last (or current if possible) GPS location.Makes it also a lot easier to verify that the signal is from the black box and not some other source.

author: VK5RC
author_rank: Unknown
timestamp: April 10, 2014, 11:52:43 am
content: Isn't it, with a very simple binary modulation, I thought the KISS principle is pretty important.

author: eurofox
author_rank: Unknown
timestamp: April 10, 2014, 12:46:45 pm
content: Maybe I miss something here1/ reception of those beacons is max lets say 3000 m2/ from surface to bottom of the sea in this area +/- 4000 m3/ they should be almost on the vertical of the beacon to detect something but they got signal from different spots quite far away from each other4/ I can imagine that all is according hydrophone and quality of amplifier but this beacon send a quite limited in amplitude signal and there is so much "parasite noise"5/ they need 6-8 hours to turn this big boat, why not use a small one? Maybe they got a long cable to have the hydrophone already 1000 m or more under water level.eurofox

author: dannyf
author_rank: Super Contributor
timestamp: April 10, 2014, 01:39:22 pm
content: QuoteDo they have to listen on the surface? Cannot they drop the listening device deep into the water, like maybe 2 - 3000m deep?QuoteI am not so sure.

author: David Hess
author_rank: Super Contributor
timestamp: April 10, 2014, 01:41:04 pm
content: Quote from: eurofox on April 10, 2014, 12:46:45 pmSalinity, temperature, and pressure gradients can cause refraction and reflection of the sound waves in water moving the apparent position and bearing of the transmitter.QuoteThe hydrophone is certainly operating below the thermocline.http://en.wikipedia.org/wiki/Sonar#Sound_propagation

author: eurofox
author_rank: Unknown
timestamp: April 10, 2014, 02:32:15 pm
content: Quote from: dannyf on April 10, 2014, 01:39:22 pmWaves (quite low frequency), dolphins who use ultra sound to navigate ....I know the technology of sonar's, I build one from scratch a very long time ago, ultrasonic transducer generating a pulse, the echo was visible on a neon that was spinning on a disk spinning with a motor. The "look" of the neon light was reflecting the size of the echo.eurofox

author: bench_knob
author_rank: Regular Contributor
timestamp: April 11, 2014, 07:33:59 am
content: Quote from: KedasProbe on April 10, 2014, 08:12:13 amIt is modulated, according to the manufacturer (Dukane-SeaCom), the beacon 'pulse' is a once per second, 10 ms (10 thousandths of a second) gated (turns it on and then off) 37,500 cycle (37.5 KHz) ultrasonic 'tone'. That works out to be a short 2.66 cycle 'pulse' at 37.5KHz during the gate 'ON' time, once per second. The likely reason they chirp it, is to magnify the pulse-power while prolonging the battery life. In other words, doing so, allows the release of a significant tone blast (very short power 'on' time) without rapidly draining the battery. With a fresh battery, the chirp power is 157 dB.QuoteHowever your point is 'why isn't the beacon transmitting a lot of telemetry data, info such as depth and GPS style position info?' To do the answer justice requires a fairly complicated answer, however, breifly, the DK120 (Dukane-SeaCom) beacon is designed to be survivable during a transient extremely violent event; be active for a relatively long period of time; and be fairly 'loud' over a long range in an incredibly, yet similar type signal, noisy environment, while remaining functional at extreme pressure depth, at low temperatures, and be battery operable inside a relatively small mass container. As one of the fellows here in the EEVblog succinctly said, 'KISS' or more verbosely, 'keep it simple Sue'. And because the beacon works in ocean water, and as I stated before, the environment is incredibly noisy and then the oceanic physics constrain the quantity and type of data that can be reliably recognized and that one point is a **BIGGIE** and then just simply, GPS does not work underwater. It would be very difficult if not impossible to make such a gadget as you ask about.QuoteTough to do in ocean, as the media is so variable and without also transmitting internal health and likely precision time information, the distance info would only be relative at best. But the enviornment is so noisy and the bandwidth is so constrained, that the data transmission would need be long, in order to reliably sequence (and be recognizable) the intra-message symbols, but in of itself renders it unreliable as evidenced by the actual 'ping' durations being detected in the suspected MH370 search area.However, there is always, seemingly, an alternative possible strategy available. A retired (US) NTSB investigator/engineer interviewed by US CluelessNetworkNews, early on, made an interesting suggestion which he emphatically re-embraced several times. His suggestion may in my opinion and obviously his, address several of the points raised. However, from an engineering perspective, some of the desired characteristics involve possibly significant practical engineering challenges in of themselves. The retired aircraft accident investigator (whose name I do not recall :[ ...), suggested that upon aircraft (assuming water) impact, that a satellite beacon would be released and deployed, that floats on the water, and being microwave enabled (exposed to atmosphere), it would be capable of wide-bandwidth transmission. Taking the idea a bit further, I speculate that such a device could be powered all the time, taking GPS location readings while the aircraft is in normal flight, but not transmitting, but just storing the data, so as not to add any more to the already congested RF spectrum. And then, God Forbid, when impact-trigger-released, the microwave-satellite-beacon would mechanically disconect, and also switch to internal, fully charged, battery power, and having stored a record of waypoints and at least the impact point if not post-impact position data. It would be able to uplink significant useful location data. The battery would not need to endure as long either, as the data would be immediately uplinked and likely received. However, this satcom-beacon would shock-burst the buffered data, periodically uplinking to conserve battery life, in any case. One of the challenges is how to deploy the beacon so that it doesn't become enmeshed in the wreckage tangle, possibly sinking uselessly to the bottom, or be so encumbered to lose line-of-sight with the sky overhead. Another challenge is how to prevent the beacon, floating on the surface, from being too far removed by surface currents from the initial impact point, but this may not actually be an issue, considering the several areas that were searched, each 'block' avg'g around 43,0002Km/(27,0002Mi),because of the bad data given by the Malaysian 'authorities'.In comparison±200 hundred miles is like painting a target-icon on the impact point.bench knob

author: Wytnucls
author_rank: Super Contributor
timestamp: April 11, 2014, 10:00:36 am
content: The trigger for the ejection of a data and ELT capsule before a crash would be easy. If the landing gear is not down by say, 200 feet (radio altimeter), a launch would happen. Most of the logic is in place already in the GPWS (Ground Proximity Warning System).

author: VK5RC
author_rank: Unknown
timestamp: April 11, 2014, 10:29:38 am
content: If the plane hits hard (at full flight speed) say 1000km/Hr vertically (~300m/s) if the ejection were to occur at 200 feet altitude AGL that would give the data system only 0.3 of second to clear the plane and it potential impact site.

author: dannyf
author_rank: Super Contributor
timestamp: April 11, 2014, 10:54:33 am
content: QuoteIndeed, as long as we don't have to engineer an actual solution for it.

author: EEVblog
author_rank: Unknown
timestamp: April 11, 2014, 12:17:33 pm
content: Quote from: KedasProbe on April 10, 2014, 08:12:13 amAs someone who has also worked on ocean depth sensors, that is not something you want to integrate into such a product where the priorities are simplicity and reliability.QuoteIt's already practically guaranteed to be not from another source, the official public uncertainly is just politics.

author: KedasProbe
author_rank: Frequent Contributor
timestamp: April 11, 2014, 12:31:31 pm
content: Maybe we are concentrating to much on the black box, if we just make it impossible for an airplane to hide its location while flying then you know where the black box will be. (last received position will always be very close too the crash site)How hard can it be to activate an isolated standalone transmitter when it can't detect its normal position broadcast info anymore.

author: Wytnucls
author_rank: Super Contributor
timestamp: April 11, 2014, 12:46:42 pm
content: Quote from: VK5RC on April 11, 2014, 10:29:38 amCommercial aeroplanes can't fly that fast at low altitude. 350kts (650 km/hr or 180m/s) is about the maximum before they start falling apart. In a stall, they come down at about 50m/s. Electrical signals travel fast enough to initiate a small explosive charge in the unpressurized part of the tail and eject in time, at a safe distance, whatever needs to be recovered later for analysis.

author: dannyf
author_rank: Super Contributor
timestamp: April 11, 2014, 12:54:25 pm
content: QuoteBingo!Like mandatory ACARS - like services at all times. If we can isolate the last known position to even 10s of miles, it would have greatly aided search and rescue efforts.The other solutions discussed (explosive charges in an airplane?) are great, as long as those airplanes are not meant to fly.

author: Wytnucls
author_rank: Super Contributor
timestamp: April 11, 2014, 01:20:31 pm
content: Martin Baker has done it successfully with explosive charges for many years, to the relief of many pilots in distress.Compressed air would probably do the job too. We'll see what the FAA and ICAO come up with.ACARS is always on and already installed in commercial aeroplanes, but a failure of the system is always possible.CPDLC and ADS-C are also mandatory in most remote airspaces, but can malfunction too.Adding another layer is fine, but failure of that extra communication system is also possible.'Always on' systems,with no means of disconnectionfrom the electrics are bringing a host of safety problems by themselves and are unlikely to be approved.

author: dannyf
author_rank: Super Contributor
timestamp: April 11, 2014, 02:10:01 pm
content: QuoteAre any of those Martin Baker systems automatically triggered?Quoteso being always on, ACARS is not approved to use on airplanes?QuoteIf the possibility of failure is sufficient to ban the use of a system, we should use no system of any kind, and the only way for humans to fly is to jump off a cliff.

author: mfeinstein
author_rank: Contributor
timestamp: April 11, 2014, 07:49:11 pm
content: Quote from: EEVblog on April 11, 2014, 12:17:33 pmAnd here he is!this solves one of the puzzles hahaha

author: mfeinstein
author_rank: Contributor
timestamp: April 11, 2014, 07:58:00 pm
content: Quote from: KedasProbe on April 11, 2014, 12:31:31 pmI was watching CNN the other day, and they asked the same question....apparently this idea was raised after 9/11 because the black boxes were ruined in the fire, so there is no data of the airplane to help in the investigations...so people starting to talk about continuos streaming to a ground location...but then came the politics guys and shut the idea off, concerned with "invasion of privacy", since there will be too much information being transmitted to the ground (let's remember black boxes do record audio).... I remember this was explained by some US transportation autority, and she said she has hopes that now this ideia will come back to life, with just maybe less data to dont step into privacy issues.I think a floating beacon is cool, but straming of GPS and Telemetry is a lot simpler and easier to do, specially because it wont need some new device outside the airplane, connected to the airplane's main computer... AFAIK, this can genarate loooots of trouble (reliability, costs, installation) and goes away of our good and classic KISS

author: mfeinstein
author_rank: Contributor
timestamp: April 11, 2014, 07:58:54 pm
content: Out of curiosity, Wytnucls do you work in the Aviation Industry?

author: dannyf
author_rank: Super Contributor
timestamp: April 11, 2014, 08:52:40 pm
content: QuoteAbsolutely. Streaming audio data for thousands of airplanes (flying at any point in time) is not feasible right now, nor necessary - commercial jets are big and slow and we just need to know their general position at any point in time.

author: eurofox
author_rank: Unknown
timestamp: April 11, 2014, 10:28:44 pm
content: Quote from: dannyf on April 11, 2014, 08:52:40 pmLast 5 or 10 minutes of audio could be automatically compressed and in case of detection of problem (could be for example away from airport and below 1000 feet) streamed to a ground station using satellite.Aircraft technical condition could be streamed every x or xx seconds. Bandwidth should not be an issue with the actual technology.I suppose everybody know this link that show aircraft online in the air:http://www.flightradar24.com/51.58,1.1/8eurofox

author: bench_knob
author_rank: Regular Contributor
timestamp: April 12, 2014, 08:14:36 am
content: Quote from: Wytnucls on April 11, 2014, 10:00:36 amYep, that's good.bench knob

author: bench_knob
author_rank: Regular Contributor
timestamp: April 12, 2014, 09:01:37 am
content: Quote from: eneuro on April 12, 2014, 06:22:20 amThere are two different types of 'pings' being yakked about on the (entertainment-biz) news channels, because they are clueless, yet their mouths are still moving. Wise people speak when they have something to say, and yakkers speak because they hav'ta say somethin'.Ad rem, the ACARS system wasn't 'pinging' in the true sense of the original meaning of the SONAR idea of ping, but from the perspective of a Unix TCP/IP 'ping' as the ACARS unit was being data-packet queried, in that sense, it was being pinged...got any data?Then there is the Acoustic-Beacon which is not physically nor electrically manufactured as a component of the so-called 'black-box'. The ABs (Acoustic-Beacons) are mechanically attached externally to the black-boxes, beyond screws, there are no other connections to the black-box. These so-called 'pingers' do not share data, power or any other form of electrical connection, nor any data-telemetry with their mechanical host...the black-box.The reason that the Acoustic-Beacon is called a 'pinger', I speculate, is owing to the intensity of the 2 cycles of 37,500 ultrasonic 'carrier' tone. When one aurally listens or hears the tone, sans frequency-shift conversion, for Human hearing convenience, via a loud-speaker, it sounds like a short duration 'pop', occurring once per second. The continually repeating, 2PPS repetition rate of the pop is part of the intended 'message'. That 'message' is that its not a natural sound in the ocean. While many animals in the oceans communicate using ultrasonics, annunciating whistles, clicks, pops, et cetera, none of them do so at 37.5KHz tone, and none of them do so continuously at a 2PPS rate. That's the identifying 'signature' of the Acoustic-Beacon locating 'pinger'.Could the pinging be from another DK120 Acoustic-Beacon? Could be, but there have been no other aircraft that have crashed, that carried these type locaters in that area of the world. And due to the battery life period, it couldn't be from an old crash. As according the Dukane-SeaCom spec sheet, the beacon battery is only rated for 30 daysminimumat the full 157dB output, and rated at 40 days maximum to .LTE. 5 dB...depleted battery output. In other words, these gadgets are rated for a mininum of 30 days of full power output, but actually continue to output a continuously diminishing signal for an additional 10 day span....and that's period that is transpiring now.Nope, they have found crash area. But where is the floatsom?Pointless conspiracy theory deleted.The question I have, maybe WytNucls or maybe the Board's Fearless-Leader, can answer this, how many waypoints can be programmed into the autopilot navigation controller on a B777? If only one, well...heh heh, that's the end of that theory!Deletedbench knob

author: SeanB
author_rank: Super Contributor
timestamp: April 12, 2014, 03:00:26 pm
content: Having an ejection system for a beacon is nice, but has difficulty. Compressed gas has the release problem, with rotting neoprene seals or sticking metal seals, and if you have a bursting disc then you might as well use an azide charge in any case to provide the needed gas pulse. Plus leaks and the need for monitoring make it unreliable unless you need a few minutes of operation, like emergency stored oxygen systems.Explosive powered release is both simple, reliable and rugged. Ejection seats rarely malfunction as they are typically well maintained, plus also have 2 redundant initiating charges, 2 initiation triggers and 2 delay fuses to trigger the separate actions, while also having dual ejection charges for rail systems or 2 rocket motors for others. As well they can operate even if the secondary cockpit separation system does not operate, unless you are in a helicopter which will turn you into meat slices if the gearbox fragmentation charges do not operate. Biggest problem is false actuation by people rather than seat failure. Thank Martin Baker and the brave test pilots in the 1950's that volunteered to sit in test seats and get blown out of a dummy plane in various conditions. Also you have to wonder at the Soviet design bureau that made ejection seats with bottom eject. Too low and you made your own grave. Best was the development of the Zero Zero seat, which worked safely even on the ground. Saved a lot of pilots that did. I know of one that decided leaving was good when he looked up and saw the trees above the canopy. He landed next to the pyre 10cm shorter.Anyhow, in any crash ejecting the data pack is nice, and nicer still if it floats even if severely damaged, from either impact or from the release. Unfortunately making this doable needs a lot of float with multiple cells, and this then makes the hole needed in the plane bigger, and restricts further where you can put it, and reduces cargo capacity as well, along with interfering with flight control operator placement. The current recorders fit well in the space, make them double the dimension in all axes and also having a gas generator to pop them out means a redesign of the whole rear of the plane. Triggering as well needs to be reliable, so you will need both a barometric sensor ( trigger close to sea level with varying pressure and keeping accuracy is hard to do so without a compensation for weather) that has a pressure sensing static input along with both gear down detection and proximity input. All there but will need a lot of work to get the barometric switch to operate reliable at this low altitude, most operate at 10 000 feet to trigger a parachute or provide oxygen supply to a pilot who has ejected. There an error of 1% of total span is not a worry, but at 300ft that total error might mean you are under water before trigger, and in pieces.

author: Wytnucls
author_rank: Super Contributor
timestamp: April 12, 2014, 05:35:04 pm
content: The existing ELT is well suited for ejection, being long, narrow and cylindrical. It floats and will emit automatically once immersed in water. One would only have to add a solid-state memory card inside it, to hold a copy of the FDR and CVR tapes. There is no need to eject the whole recorder shebang.Commercial aircraft already carry compressed gasses in fire extinguishers for engines and cargo holds. If need be, the rear hold canisters, or even closer, the APU fire extinguisher bottle, could be used for ejection propellant.Lots of parameters could trigger an ejection: low RA altitude, unusual aircraft attitude, loss of electrical power, all detected by existing aircraft systems.That's just an idea, anybody can come up with their own version. I'm sure somebody somewhere is working on an official solution.(There is an ELT on board already, strapped in the roof of the rear cabin, on some aircraft)http://eandt.theiet.org/magazine/2014/03/flight-mh370-emergency.cfm

author: Seg
author_rank: Regular Contributor
timestamp: April 13, 2014, 09:35:52 pm
content: Quote from: dannyf on April 11, 2014, 08:52:40 pmWhat decade do you live in? Getting voice quality real time streams from tens of thousands of aircraft istotallydo-able with current tech. Cell phones! Remember those?Lets be really generous, and figure a classic 56kbit voice stream. (Modern codecs need less) That's 7kbyte/s per aircraft. A generous estimate for aircraft in the sky worldwide at any one time seems to be about 20,000. That's ~138mbyte/s or ~1 gigabit/sec, ~11 terabytes a day. That is completely feasible, have you seen the HD video people are streaming these days? Mind you this would be spread out worldwide, among satellites and/or ground stations.The tech is there, making it happen is just a simple matter of money and politics...

author: mfeinstein
author_rank: Contributor
timestamp: April 14, 2014, 07:35:25 pm
content: Quote from: Seg on April 13, 2014, 09:35:52 pmExcelent answeralthough I am not familiar with all this numbers on voice stream, I also thought the same thing "What decade do you live in?"

author: KedasProbe
author_rank: Frequent Contributor
timestamp: May 12, 2014, 06:53:38 pm
content: Thetechnology is already in placeon 90% of the world’s commercial fleet. for free tracking and paid"black box in the sky" service.http://news.sky.com/story/1259842/how-global-plane-tracking-system-will-workQuoteQuoteblack box in the sky:QuoteThis also means that we don't know where MH370 is because they thought paying (now free) for this (existing) service was wasted money.

author: ve7xen
author_rank: Super Contributor
timestamp: May 13, 2014, 10:48:58 am
content: Quote from: Seg on April 13, 2014, 09:35:52 pmRemember this needs to cover (most of) the planet. It cannot depend on terrestrial infrastructure like the communications technologies you're thinking of. So yes, it's doable, but I don't think the current satphone infrastructure can support it, and most other satcomm deployments are not designed for low power ground->air use, moving targets, and global coverage. You'd probably have to launch an entire constellation of birds to support this, or take over Inmarsat and reengineer it or something. Even if the infrastructure does exist, buying up that amount of satellite bandwidth is going to cost an absolute fortune. Just to aid investigating the very infrequent cases where planes crash and can't be found or recovered easily.A triggered approach makes a hell of a lot more sense, and avoids the privacy problems too.

author: Wytnucls
author_rank: Super Contributor
timestamp: May 13, 2014, 11:16:34 am
content: Inmarsat has offered aircraft tracking to their client airlines already, at no extra cost. It seems that they can use the existing SATCOM system, without much modifications, if any.http://www.theguardian.com/business/2014/may/12/inmarsat-free-airline-tracking-service-mh370

author: amyk
author_rank: Super Contributor
timestamp: May 13, 2014, 01:18:01 pm
content: http://www.dailymail.co.uk/news/article-2626106/No-MH370s-Satellite-firm-used-search-missing-plane-offers-low-cost-tracking-prevent-flight-disappearing.htmlhttp://www.mirror.co.uk/news/world-news/mh370-black-box-pings-actually-3511000

author: KedasProbe
author_rank: Frequent Contributor
timestamp: May 13, 2014, 02:19:29 pm
content: Some signals could have been from tagged whales...This one below is laughing with our intelligence after they told him that: