ELT testing

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GDBall

ELT testing

Post by GDBall »

I was reading the ELT replacement thread, and I saw a comment or two about only being able to test 121.5 reception using an aircraft frequency VHF. I thought I would mention that for $25 or less you can buy an SDR-RTL dongle (USB) that plugs into your laptop and can receive 406 MHz. Can even use it as a scanner to listen to the game or CTAF or whatever in the hanger if you want - they are pretty broad band receivers and the software is free. Could use it to check any of your transmitters, including ADSB decoding or satellite weather with the right plugins.
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Steve
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Re: ELT testing

Post by Steve »

I don't think that you want to radiate 406 MHz when testing your ELT. That will get the Rescue folks calling you. The ELT won't start radiating 406 MHz until 50 seconds after activation, which is plenty of time to receive a couple of 121.5 MHz sweeps.
GDBall

Re: ELT testing

Post by GDBall »

That’s totally fair and sensible.

If there is any doubt though, is there a means to notify them of a one time test?

Maybe my thinking has been colored. I work with too many systems and I’m conditioned to expect some sort of issue until an installation has been thoroughly tested. In my normal professional life I would never assume that one mode working correctly guarantees the other. In fact I’d rather like the call to know that their DB is updated correctly with my information. How do you know the GPS coordinates are feeding correctly, etc..

If verifying the correct installation of a new piece safety gear that you may stake your life on offends them... that would feel to me like a different conversation needs to happen.

Regards,
Greg
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Re: ELT testing

Post by Steve »

Hi Greg:

The 406 MHz signal can be tested, including position data, but requires special test gear. If your installation is done by an avionics shop, they should be able to do this. In my situation, I have verified that the GPS data does get to the ELT, and that the G-switch functions and that the ELT radiates on 121.5 MHz. This test is done at each Annual Inspection. This is what the ICAW requires for the E-04.

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Re: ELT testing

Post by Rich »

GDBall wrote: Thu Sep 24, 2020 2:25 am That’s totally fair and sensible.

If there is any doubt though, is there a means to notify them of a one time test?

Maybe my thinking has been colored. I work with too many systems and I’m conditioned to expect some sort of issue until an installation has been thoroughly tested. In my normal professional life I would never assume that one mode working correctly guarantees the other. In fact I’d rather like the call to know that their DB is updated correctly with my information. How do you know the GPS coordinates are feeding correctly, etc..

If verifying the correct installation of a new piece safety gear that you may stake your life on offends them... that would feel to me like a different conversation needs to happen.

Regards,
Greg
It's more than "offends them". Some excerpts from a 2018 AOPA article (emphasis mine):

In 2017, there were 8,898 406 MHz ELT activations in the AFRCC area of responsibility and about 98% of those alerts were false alarms. Just 122 of the alerts in 2017 were actual distress cases. For each false alert, AFRCC specialists put in considerable research and manhours to track down the ELT and owner. Each activation is treated as an emergency so each false alert is a distraction and negatively affects other search and rescue missions. About 90% of false alerts occur because of beacon mishandling during the testing and maintenance of these systems.

It's also worth perusing the SARSAT web site to see how the system works. It's a bit out of date, as the satellites no longer utilize 121.5/243.0 MHz.

From my recent experience, they may handle things differently when the aircraft is found to be located at an airport, especially the home airport. The first thing they will do is call the primary phone number.

Recently there was an article I read (I think on AvWeb) that indicates the process now is utilizing additional sources for locating, such as ADS-B/FlightAware and even Aerion. The latter actually receives and processes signals from 1090ES non-diversity aircraft, though somewhat more sporadically.
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GDBall

Re: ELT testing

Post by GDBall »

Rich wrote: Thu Sep 24, 2020 3:05 pm Each activation is treated as an emergency so each false alert is a distraction and negatively affects other search and rescue missions. About 90% of false alerts occur because of beacon mishandling during the testing and maintenance of these systems. [/i]
Thank you very much for sharing the data. To me that argues more strongly that a conversation is needed. For other systems we give notice to any monitoring systems of an 8 hour window or whatever in which maintenance is being performed. During that window all alerts are ignored. Seems like for the price of a web page/form, they’d save a bunch of time and as you say benefit other SAR missions.

I never want to discount the benefit or expertise of an avionics shop, but still also true that what used to take highly specialized equipment is more accessible to the owner than maybe once was. From engine monitors to SDR...

I’m still kinda blown away that once someone realized a laptop at running 2 gig could easily decode data at much lower radio frequencies... all the tools that they came up with. I hope for a day when vhf frequencies aren’t a thing per say - if they want to hand you off from controller A to controller B - they just do it with no knob fiddling on your part. Some kind of virtual channel trunking system maybe? Seems like there is some not reasonable dreaming we could do.
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Re: ELT testing

Post by Rich »

I can't get overly excited about testing every possible function. It only proves that it works that time, that day. I monitor the Aviation Safety Network for various kinds of accidents. Inevitably they have a link to FlightAware that, low and behold, shows the flight termination within a mile. In addition, those who are really concerned are now carrying Personal Locator Beacons, some with emergency text transmission and whatnot.

The FAA isn't all that religious about the 406 MHz deal, anyway. If you currently have just a 121.5/243.0 ELT you're good to go for the rest of your life, even though you will no longer be in the population of potentially immediately known to have had an incident.
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Re: ELT testing

Post by ultraturtle »

GDBall wrote: Fri Sep 25, 2020 9:54 pm..I hope for a day when vhf frequencies aren’t a thing per say - if they want to hand you off from controller A to controller B - they just do it with no knob fiddling on your part. Some kind of virtual channel trunking system maybe? Seems like there is some not reasonable dreaming we could do.
That's kind of happening already with CPDLC (see http://code7700.com/communications_cpdlc.htm). Properly equipped aircraft operating over the oceans normally request, receive, and acknowledge clearances via datalink with the simple press of a button, no knob fiddling for primary contact, although they also must dial in and maintain HF voice as a backup. Kansas City Center and Indianapolis Center are also using the system for clearances as well as issuing VHF frequency changes, although pilots are required to check in on the new frequency using voice.
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