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ORICHETTI
11th Mar 2014, 11:33
Hi,

I have a few questions about the ELT.

A plane crashes and then the ELT automatically begins sending a signal, ok.

But somebody has to be listening actively that signal in order to find the plane? or that signal is send it to somebody?

I mean, of course with the malasyan plane, i guess everybody is actively monitoring on 121,5 to see if they can listen up the elt.

but is this signal specifically from that plane?
if an small plane has an accident in the alaska tundra, but no body advert it, will somebody go and look for them?

Dave Sharpe
11th Mar 2014, 11:54
The current generation of commercial units --as most aviators will know use 406 which is monitored on a continous basis by sat coverage--121.5 can be used by an asset tasked for search to get a directional fix in a local area--the early ELTS has a very high rate of spurious alarms with a low (relatively) automatic activation in a real emergency-thus continuos monitoring of 121.5 was abandoned--having used 121.5 for training/demo purposes in east Anglia(UK) the response was immediate!----121.5 still has its place alongside the newer technology!

awblain
11th Mar 2014, 15:29
As David Sharpe says, 406MHz distress beacon signals are watched by receivers on geostationary satellites.

But radio waves from a smashed beacon trapped in debris on the seabed do not escape to the surface.

island_airphoto
11th Mar 2014, 20:38
The 406 MHz beacons will be picked up anywhere and are coded with your boat/plane name, owners name, and contact info. If you buy one and register it, you can expect a call within about 5 minutes of turning it on.

sardak
11th Mar 2014, 20:56
The 406 beacons are also monitoried by low Earth orbiting satellites (LEOSAR). The next generation of monitors are being installed on navigation satellites (GLONASS, GPS and Gallileo), some of which are already in orbit for the MEOSAR system, set for initial operational capability in 2018.


All you want to know about the international Cospas-Sarsat system (Sarsat = Search and Rescue Satellite Aided Tracking, Cospas = equivalent in Russian) is here: International Cospas-Sarsat Programme (http://www.cospas-sarsat.org/index.php)

ampclamp
11th Mar 2014, 23:46
ELTs are not infallibe. The MH one may not have activated automatically (if the circumstances required its activation) and even if it did, there's no guarantee it worked as advertised. If it is under water it maybe shielded or the antenna / skin where it is mounted may have been torn away in any catastrophic event. The ELT maybe transmitting into a short length of coax that could be physically shorted or now water logged. Some signal maybe transmitted but it would be highly compromised as they are pretty low power anyway at about 5 watts. All speculation of course but a few things that may account for non receipt of a distress beacon signal.

Phalconphixer
12th Mar 2014, 02:59
We installed 406Mhz ELT's on our Falcons; always struck me as odd that our (CAA approved) design allowed the unit to be installed in the tail cone of the aircraft while the antenna was installed in the Dassault approved location at the base of the fin forward of the tailcone...
Given that the tailcone is a removable section of the airframe, in some cases a crash followed by an aircraft break-up and tailcone detachment would almost certainly result in the antenna feeder ripping out of its connector, thus rendering the installation useless...

Oktas8
12th Mar 2014, 04:14
Helicopter crashed near NZRA a few years ago. Wreckage rolled on impact into a small gully and lay there inverted.

It took (from memory) about a year to find the wreckage, as the trees & shrubs had closed over the wreckage and the 121.5MHz signal could not escape the metal and soil lying on top of it. This was in a low density populated rural area, not wilderness.

So there you go. ELTs in general, 121.5 or 406, are very useful indeed after a forced landing, but dubious after a serious crash.

NigelOnDraft
12th Mar 2014, 07:14
A plane crashes and then the ELT automatically begins sending a signal, ok.I raised this on the MH370 thread, but we never got an answer.

It is my understanding that there is no requirement for all airliners to have crash ('g') activated ELTs. Many have ELTs in the rear cabin that rely on crew removing and activating them after an accident.

The more modern variants do have (additional) 'g' activated ELTs, albeit the 787 ones were deactivated / removed post the LHR incident, and I do not know if they have been reactivated. Partly comes down to requirements of the country of registration.

So whether the MH370 777 had one I open to ideas?

wiggy
12th Mar 2014, 08:00
NOD

Partly comes down to requirements of the country of registration.

AFAIK it may also be a requirement for overflight of some countries - I seem to recall (can't find definitive source) that we had to have hull mounted ELT's installed in "our" 777's because they became mandatory for overflight of the CIS (or remote parts thereof).

SMOC
12th Mar 2014, 12:23
Unfortunately for MH370, 406 lasts 24hrs & 121.5 lasts 50hrs so they are of no use, debris will be the only thing now. Don't think the black boxes have much range but at least once the location is found they should still be pinging away for the next 3 weeks.

ORICHETTI
12th Mar 2014, 12:24
Thanks a lot for your answers. So next time i hear an ELT on 121.5, better don´t say anything by the freq? because somebody will perfectly now from who is that signal coming?

the process is the same with that breitling watch?

island_airphoto
12th Mar 2014, 13:01
Please DO report 121.5 MHz ELTs! That is the only way they are discovered now. I have reported a few over the years. In the USA at least the CAP or USCG will hunt them down.

NeoFit
12th Mar 2014, 13:24
@ SMOC
...the black boxes .... should still be pinging away for the next 3 weeks.

Or not! Remember 447 pingers . One disappeared (dauphin/shark/ other ?) and it seems that the other one (recovered) never worked.
But, AFAR I did not see recommendation from French BEA for mandatory periodic controls of these beacons.

SMOC
13th Mar 2014, 00:41
Anyone know what g force is required to set an applicable ELT off?

Had a quick search but no actual figure found.

Sawbones62
13th Mar 2014, 02:33
The questionable utility of an ELT mounted inside the fuselage is an old issue.

Years ago a solution for remote and oceanic crashes was developed called the "Crash Position Indicator" - essentially an ELT that is mounted in a protective "tumbling airfoil" outside the aircraft. On impact the ELT flies away from the aircraft and can float or have a better chance of not being burned/buried. Some were even connected to the CVR/FDR.

It was a technical success and is still found on some aircraft, especially in the RCAF.

Commercially it was a failure, but events like AF447 and MH370 suggest the CPI may need another look.

Crash position indicator - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Crash_position_indicator)

ORICHETTI
14th Mar 2014, 18:22
and adding to this post, do black boxes have a signal also? or elt is mounted together?

sardak
14th Mar 2014, 23:04
^^^The black boxes, as in CVR and FDR, have acoustic pingers for underwater search, but not a radio beacon. An ELT is generally not mounted near them.

Anyone know what g force is required to set an applicable ELT off? Had a quick search but no actual figure found.For current generation 406 MHz beacons, the activation threshold is 2.3 +/- 0.3 G, with a change in velocity (delta V) of 4.5 +/- 0.5 ft/sec (1.4 m/sec +10%). There is also an impulse curve (acceleration vs time) which must be complied with.

For the US, the requirements are contained in FAA TSO C-126b, "406 MHz Emergency Locator Transmitter, (ELT)" which references for specific requirements, document RTCA/DO-204A "Minimum Operational Performance Standards for 406 MHz Emergency Locator Transmitters (ELT)."

Per RTCA, DO-204A is harmonized with EUROCAE ED-62, "Minimum Operational Performance Specification for Aircraft Emergency Locator Transmitters on 406 MHz AND 121.5 MHz (Optional 243 MHz)" The above numbers were taken directly from DO-204A and ED-62.

Regarding carriage of ELTs, the Cospas-Sarsat program, referenced earlier, publishes document C/S S.007 "Handbook of Beacon Regulations" which "...provides a summary of regulations issued by Cospas-Sarsat Participants regarding the carriage of 406 MHz beacons. It also includes practical information on coding and registration requirements in each country, where such information was made available to the Cospas-Sarsat Secretariat." http://www.cospas-sarsat.org/images/stories/SystemDocs/Current/cs_s007_sept2013.pdf

LeadSled
14th Mar 2014, 23:22
Folks,
From Australian research of actual accidents, fixed ELT have a better than 95% failure to broadcast a useable signal, most commonly because the aerial or aerial cable is damaged in the crash sequence.
For aircraft that go into the water, the failure rate is 100%, the frequencies used for ELT do not propagate any useful distance in water.
Fixed ELT are a total waste of money.
This is why Australian does not mandate the carriage of fixed ELT, although it mandates an ELT on any aircraft traveling more than 50nm.

ORICHETTI
15th Mar 2014, 10:54
I am totally sure this "accident" will make mandatory some sort of gps localizer. They should have done it after the Air France 5 years ago.

SMOC
15th Mar 2014, 12:30
LeadSled,

Can you PM or post some linked reports to back this up as I'm interested in following it up with our company.

a926da41119f5579e192
15th Mar 2014, 12:35
I'm truly amazed that no technology exists to eject an emergency locator beacon (E.L.B.) in the event of ditching on the high seas the device could be ejected using a similar device to a vehicle airbag,aft of the pressure bulkhead of course and the device could be on the surface, within seconds if not minutes,and preferably with solar cells to keep the transmitter active as long as possible,finally if the E.L.B had a tether to the structure of the aeroplane
once (the beacon) had surfaced the ditched aeroplane could be located fairly quickly under the waves. I know about the underwater ping type beacon,
but if there is a transmitter atop the the waves, then everybody should know about it's location within a short space of time.

island_airphoto
15th Mar 2014, 12:39
ACR ELECTRONICS AquaLink® 406 GPS Personal Locator Beacon | West Marine (http://www.westmarine.com/personal-locator-beacons/acr-electronics--aqualink-406-gps-personal-locator-beacon--11046612)


This is what would work in any crash with people still alive and able to move.

sardak
15th Mar 2014, 16:52
I'm truly amazed that no technology exists to eject an emergency locator beacon (E.L.B.) in the event of ditching on the high seas...There are ejectable ELTs, currently in service, as described earlier in this thread by Sawbones62 here: http://www.pprune.org/tech-log/535756-elt-doubts.html#post8370773

Mike

SalNichols94807
17th Mar 2014, 01:51
I find it curious that the 406 EPIRB, hanging a mere 6' behind my head will automatically deploy and begin transmitting my position to any COSPAS/SARSAT equipped satellite, and in less than 45 seconds, the USCG will know where to come looking for me....like they did a few years back when a whale sunk my friends boat 800 mi. North of Oahu.

How in the hell do I get this kind of technology, that I've carried with me on 5 trips to and from Oahu...and we're still trying to figure out where the hell this plane went down?

Seriously, 30 years in aerospace, and I just don't understand this. Its freaking inexcusable.

Sawbones62
17th Mar 2014, 03:02
Here's an example for the USAF C-141 original CPI, including multiple damage sensors throughout the aircraft and provision for a tape recorder for the CVR AN/URT-26 Crash Position Indicator (http://c141heaven.info/dotcom/training_materials/section_6_20_elt.pdf)

Other offshore industry and military examples can be found on Google.

The extra cost over ELTs made the CPI unpalatable for regulators and airlines, but that may change...with modern electronics it can be a very much smaller device using the 406Mhz technology and solid-state memory for FDR/CVR:
http://www.hr-smith.com/images/stories/503-CPI.pdf

HAWK21M
17th Mar 2014, 12:53
Both types of ELTs can be on board.....Impact type that transmits on exceeding 5g impact and water activated type, that transmits on touching water.