Ads-b, Acro and GPS

So I got 2020 compliant ADS-B setup (GTN 650 feeding Dynon transponder). Interesting thing is that when I do acro, the GPS signal is lost (mostly when going inverted.)

Right now I am not worried but not sure if I'd be made to address such failure cases in future (i.e. in 2020).

Are others experiencing loss of GPS signal while doing acro? Shall I be fixing installation issues? (The GPS lock is pretty quick and solid when upright, so it has never been an issue).

Nothing magic there, when the GPS antenna is blocked by structure it can't see the sky so you lose the signal. The "fix" for that don't do acro in controlled airspace

Mode C veil?

Walt said:

Nothing magic there, when the GPS antenna is blocked by structure it can't see the sky so you lose the signal. The "fix" for that don't do acro in controlled airspace

Click to expand...

What about Mode C veil? So I need ADS-B within the 30 nm veil but I think we also can do acro as long as clear of lateral Class B/C/D limits.

Airzen said:

So I got 2020 compliant ADS-B setup (GTN 650 feeding Dynon transponder). Interesting thing is that when I do acro, the GPS signal is lost (mostly when going inverted.)

Right now I am not worried but not sure if I'd be made to address such failure cases in future (i.e. in 2020).

Are others experiencing loss of GPS signal while doing acro? Shall I be fixing installation issues? (The GPS lock is pretty quick and solid when upright, so it has never been an issue).

Click to expand...

yes when I check my dynon log I loose coverage in every loop as my GPS is on top of the airplane. reacquires really quickly though. Actually in the process right now of putting a second GPS in the wing tip that one should work inverted as I want to use that to plot my loops... . I figure if I put enough GPSs on my RV-8 eventually I will have enough logs Now the once I use are 50$ each (66 channel 10HZ WAAS) so they won't help you with your ads-b issue

Airzen said:

So I got 2020 compliant ADS-B setup (GTN 650 feeding Dynon transponder).

Click to expand...

FYI: As of today this combination (GTN 650 feeding Dynon transponder) is not a 2020 compliant ADS-B setup. However DYNON is working on the paperwork so hopefully it will, eventually, be compliant.

yes when I check my dynon log I loose coverage in every loop as my GPS is on top of the airplane. reacquires really quickly though. Actually in the process right now of putting a second GPS in the wing tip that one should work inverted as I want to use that to plot my loops...

Click to expand...

You're kidding, right?

I wasn't kidding... .

I just installed my GPS-2020 in the wingtip and pulled a report with the FAA. Now the good news is that it does work during loops and inverted flight. The bad news is that in one steep turn it seems to have lost accuracy if I understand the Dynon logs correctly. That gave me a fail on the NIC metric (missed 24 seconds). Need to go back and do some more flying to figure out the exact attitude... .

The way I interpreted the Dynon logs is that I assumed a "NO ADS-B OUT: GPS LOST" message in the alert log relates to the event the FAA report picked up. I then checked the matching user log for flight attitude etc... . Interesting is that the user log still shows GPS Fix quality as 1 with 7 satellite. Not sure how to reconcile that. Would be nice if the Dynon logs would show the info reported by the transponder so you could correlate faults with what you were doing ... .

Now my question is if that will cause a problem with the FAA. I am unlikely to do either of those maneuvers while in an airspace which requires ADS-B out. However, I also heard that the FAA will audit the data they collect and warn none compliant airplanes. I don't want to get a warning every time I am having some fun... .

Thx

Oliver

GalinHdz said:

FYI: As of today this combination (GTN 650 feeding Dynon transponder) is not a 2020 compliant ADS-B setup. However DYNON is working on the paperwork so hopefully it will, eventually, be compliant.

Click to expand...

This is new - perhaps there is something I don't understand.

I got a fully compliant report from the FAA on my GTN-650 and Dynon Transponder set up.

Carl

Carl Froehlich said:

This is new - perhaps there is something I don't understand.

I got a fully compliant report from the FAA on my GTN-650 and Dynon Transponder set up.

Carl

Click to expand...

Just FYI the post you responded to is over a year old. As I had more info on the topic I added it to this thread... . I guess I should have started a new thread to avoid confusion.... .

Oliver

Oliver,
The TSO for ADS-B position sources only requires it to work in low dynamic situations. It's about 0.5G to 1.5G if I remember right, and even less on lateral accelerations. Our GPS 2020 works well beyond that, but it's not a requirement.

If you read the FAR's, it says you must have ADS-B equipment, and it must be operating when in ADS-B required areas. It does not say that it must have a 2020 compliant lock the whole time. In fact, the equipment is doing exactly what it's supposed to by reporting that it is unsure of position when you maneuver aggressively. I don't believe that there is any issue with this in the FAA's eyes or the language of the FAR.

If you pull a compliance report and want to use it to know if your system is working, that flight needs to be a pretty normal flight with almost only IFR type maneuvers. It's fully expected that it will have some missing data if you were out trying to shake that lost wrench loose

As a note, a GPS fix of 1 is the minimal fix we can have (2D). It's not 3D, nor is it with integrity and WAAS. Look at bit deeper at the logs and you'll see fixes of 3 or higher and that's when your ADS-B is valid.

--Ian @ Dynon

Thanks! Exactly the information I was looking for. Will do a "gentle" flight next and see... .

Are you sure about the meaning of the GPS fix number in the dynon logs?

When I have the 1 I still have GPS altitude information in the log. I also see that more frequently (often with 10 satellites) so ADS-B out must still be working otherwise I would have had more then 24 seconds missing in my report. Also never saw a 3.

I know 1 means 2D in some of the NEMA sentences but it means 3D in others. I couldn't find a description of the log field anywhere so I am not sure how to interpret it in the logs... .

Thx

Oliver