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-   -   Dynon SkyView autopilot performance poll (https://vansairforce.net/community/showthread.php?t=171476)

RickSolana 05-13-2019 09:10 AM

Dynon SkyView autopilot performance poll
 
The question for the poll is:
Do you have a steady glide slope tracking with needle centered, or do you have constant deviations above and below (mine is 1/4 scale deflections) with resulting airspeed fluctuations.

A follow up question: Are you flying with default autopilot settings or did you go through the Dynon in-flight autopilot tuning guide?

I am asking because I am trying to see if my 2 year problem is specific to my system or if it is in all Dynon SkyView systems. This will help focus the troubleshooting.

Thanks!

Rick Solana
RV10
Dynon SkyView HDX

airguy 05-13-2019 09:52 AM

I'm flying with the standard autopilot settings, and what I see is also an artifact of the signal received for feeding commands to the autopilot. I'm using a 430W to feed the ARINC 429.

For instance on an RNAV coupled approach, it flies like it's on rails, as long as I manage the throttle to keep the airspeed steady. Very tight coupling to the needles. On an ILS it's a bit looser, and frequently approaches 1/4 scale before correcting on the glideslope. The localizer seems to perform a fair bit better than the glideslope and stays tight. A VOR approach, on the other hand, is just about useless and I would say is borderline dangerous to perform as a coupled approach in my airplane - it wanders all over the place. I hand-fly VOR approaches or use Heading Mode and adjust it based on the indicator rather than try to couple them.

My IFR instructor said he has seen the same thing with several other airplanes, and attributes it (rightly or wrongly, I don't know) to a less-accurate signal or slower time resolution of the signal variation on the VOR. The ILS is a little better but the GPS has them both beat.

RV10inOz 05-14-2019 03:20 AM

Rick,

I have about 1500 hours on ours, and I do not suffer your problem.

Can I suggest we discuss via face time, I will send you details by PM.

When we work out your issues then come back and post the results here for the benefit of others.

But in short, Sensitivity and gain values are the likely problem. Perhaps your speed control. Maybe mechanical linkage stuff.

It will work fine you just need to get the bug squashed!

RickSolana 05-14-2019 08:27 AM

autopilot fix
 
David,

I'd love to take you up on your offer! Even better to share the solution if we get it fixed!

Thanks,

Rick

miyu1975 05-15-2019 06:02 AM

I have the same problems/out comes as Airguy mentioned. It will fly a GPS approach great, both LAT and Vertical... An ILS, not so much. It will hold the localizer fine, but has hard time tracking down the glideslope. I usually have to help it a lot and will hear and see (on screen) the pitch AP slipping..and it is cranked up to 100% torque. It will then lose the glideslope but its all over with. I pretty much know that on an ILS I use VS mode at about 600 FPM one the GS is intercepted.

9GT 05-15-2019 08:03 AM

I have spent hours in the air helping my buddy with his Cozy MKIV equipped with a Dynon Skyview Touch with Dynon AP system and a Garmin 430 non WASS trying to get the thing to work right. Using the manual, we went through the calibration/settings process starting at the lowest settings and adjusted/tested all the way up to the max settings. Bottom line is it will not follow the approach close enough to consider dependable. It also will not hold altitude well, sometimes dropping 100' or more in level straight flight. It requires constant attention, disconnecting to correct heading and altitude. The closest we could get to following an approach, it would over shoot the turn and put us 20* or more off course, but it would never try to correct itself after leveling out. I am hoping I don't have problems like this with my G3X Touch with Garmin AP.

Carl Froehlich 05-15-2019 09:11 AM

I note the common thread - the SkyView EFIS and autopilot is ?on rails? when following a GPS LP approach, but not when on a non-gps approach.

The SkyView coupled approach is only as good as the input is it getting - from a GTN-650, 430 or whatever.

I started flying with a dual SkyView and GTN-650 install in 2012. The SkyView autopilot was dirt simple to configure and would hold the plane on course and altitude with amazing precision. Even dialing in a new altitude it would follow the chosen VS better than I could. On a GPS LP approach it would hold the GS & CDI needles dead center. I too however noticed it was not as accurate on non-GPS approaches. As I demonstrated the autopilot working properly I attributed this to the inherent difference with the non-GPS approach and the GTN-650.

I suspect I could have gone into the GTN-650 to tweak non-GPS error rates, but it worked well enough for me and I did not want to screw up the GPS functionality.

My recommendation - do what I did and first verify the autopilot does what it should, then go look at whatever you are using to feed the ARINC module.

Carl

DakotaHawk 05-15-2019 10:02 AM

While on GPS navigation, my auto pilot will keep the needles centered all the way down to minimums.

However, on VOR/ILS navigation, I had a real bad issue with the needle being all over the place, and the autopilot was unable to fly a coupled approach. After troubleshooting, I found the center pin of the coax from the signal splitter to the NAV radio had broken off and was only making momentary contact with the center conductor. Man! That lead to some wild rides trying to follow that nav signal!!!

As soon as I replaced the BNC connector, the autopilot can follow the VOR/ILS with less than one dot of variation.

RickSolana 05-15-2019 11:37 AM

I should add, in response to Carl?s post, that my issues on glide slope are on an LPV approach. The navigator is a Garmin 650, and I have swapped out the 650 with a loaner to find that the problem was the same (so not the 650).

Carl Froehlich 05-15-2019 01:15 PM

Ok - got it.

As I posted, my SkyView/GTN-650 RV-10 install did the LPV approach with needles centered, every time.

So what could be the issue:
- Autopilot tuning? I?m using the default settings (RV-10) and never found a need to change. You may need to do some adjusting.
- Is the GTN-650 doing it?s job? I had a massive issue on my GTN-650 on initial install, later finding out that it suffered from a ?known problem?. What happened was when transmitting on the GTN-650 radio it would loose GPS signal during the LPV approach. Signal would come back after I let go the PTT switch. It took awhile to relate this cause and effect. The feed I got back from Garmin (via the avionics shop where I purchased the unit) was the GTN-650 radio had harmonics that feed back via other avionics not transmitting but in the plane that degraded the GPS antenna, I was told the most common being the ELT antenna. I fixed this. I recommend you look at the GPS satellite display transmitting and not transmitting to see if you have any degradation of satellite reception. I note that my experience is the GTN-650 GPS antenna is more sensitive to mounting location than any other GPS antenna I have used.

Good luck,
Carl


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