ADS-B FAIL intermittently

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yyic
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ADS-B FAIL intermittently

Post by yyic »

Hey guys,

I was in the pattern and found “ADS-B FAIL” in the G1000 annunciator showed up intermittently. Any advice on how I can get this checked before sending it to an avionics shop?
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smoss
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Re: ADS-B FAIL intermittently

Post by smoss »

It may just be a GPS dead spot for you. There are a 2 isolated places I frequently get an ads-b fail, one on the ground at my home airport in the runup area, and one coming into KTOA about 500 ft AGL (about 1 out of 3 times). You may want to just sit on it a bit and see if the fails show up anywhere else.
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Tim H
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Re: ADS-B FAIL intermittently

Post by Tim H »

Same here. I get a ADS-B Fail just SW of Wilmington (KILN) enroute to Lunken (KLUK).

Thought I had an avionics issue but it turns out to be very repeatable in just that location.

Not to drift off the subject, on more than a handful of occasions I have have seen traffic (visually) that has not shown up on ADS-B. Need to keep your eyes outside looking for traffic as much as possible.

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Re: ADS-B FAIL intermittently

Post by haykinson »

My avionics shop believes this just means that I had flown into a dead zone for ADS-B reception. I've had the message pop up semi consistently at around the same place around my home airport, usually at around 1,100ft or so. And had it a few times at a few more airports, also around pattern altitude.
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Re: ADS-B FAIL intermittently

Post by CFIDave »

I've seen this on multiple DA40s with GTX345Rs where the original avionics shop that performed the 345R install "cheaped out" on the antenna, i.e., they simply added a signal splitter to an existing GPS antenna -- rather than adding a 3rd GPS antenna or installing a new combo VHF/GPS antenna for the GTX345R.
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Rich
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Re: ADS-B FAIL intermittently

Post by Rich »

It seems like there’s not enough information in such a message. Is it ADS-B out fail, triggered by a GPS problem? Or a problem receiving ADS-B in from towers? Or some kind of integrity deal about receiving direct traffic detected by some internal software? Some other deal?
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Re: ADS-B FAIL intermittently

Post by Boatguy »

In addition to the all the previous good suggestions, you can request a performance report of your ADSB this web site.

https://adsbperformance.faa.gov/PAPRRequest.aspx
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Re: ADS-B FAIL intermittently

Post by CFIDave »

Rich wrote: Mon Jan 11, 2021 1:20 am It seems like there’s not enough information in such a message. Is it ADS-B out fail, triggered by a GPS problem? Or a problem receiving ADS-B in from towers? Or some kind of integrity deal about receiving direct traffic detected by some internal software? Some other deal?
My understanding is that the "ADS-B FAIL" annunciation is caused by the GTX345R temporarily losing track of its GPS position.

Unlike newer G1000 NXi aircraft (and Legacy G1000 systems capable of running GDU Version 15 software) where the GTX345R obtains its GPS position from GIA63W or GIA64W units, most of the Diamond fleet requires a version of the GTX345R that has its own built-in GPS position source. If one of these GTX345R units experiences poor GPS antenna signal strength, the ADS-B unit no longer "knows where it is" and generates an "ADS-B FAIL" annunciation.
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Re: ADS-B FAIL intermittently

Post by Steve »

I have a GDL-82 in my airplane. It has a 'Fault Alert' output that can be wired to an annunciator light. According to the Garmin manual, 'Fault Alert' occurs when "System is not transmitting all FAA required ADS-B data". I didn't install an annunciator in my airplane, but I have periodically gotten the PAPR reports, and they always have been perfect. I'm not sure if the 'ADS-B FAIL' annunciation in the G1000 system indicates the same.
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Re: ADS-B FAIL intermittently

Post by Rich »

OK. The only time I see anything like this is if the avionics are fired up in the hangar for an extended period. My ADS-B transponder is fed from my 530W. Clears up when moved outside. The annunciation shows up on my KT74 display.
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