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RickSolana
05-13-2019, 09:10 AM
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
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

airguy
05-15-2019, 01:31 PM
Just an observation here...

The Dynon autopilot, when flying a coupled approach, pays attention ONLY to the needles (guidance) delivered to it from the certified navigator (of whatever form) through the ARINC-429. If the autopilot flies an LPV approach flawlessly, then the autopilot is functioning fine. The problem necessarily belongs to the receiver and/or the type of nav signal being used by the receiver at that point.

RickSolana
05-15-2019, 01:52 PM
So combining Greg and Carl?s comments, if my needle is accurate on my glide slope and I can follow it smoothly down uncoupled, but my plane is flying above and below that needle when coupled (with healthy airspeed changes), that suggests the problem is not in the 650. Does that sound right?

Carl Froehlich
05-15-2019, 02:13 PM
Perhaps.

As you are manually smoothing out the error signal (the needles) that still leaves the possibility the error signal noise from the GTN-650 is causing your problem in the coupled approach mode.

Again recommend testing the autopilot itself. Does the autopilot function properly without the GTN-650 input as in track mode? Altitude hold mode - with manual dialing in of a new altitude to verify autopilot response? Are you using the default autopilot setting as a starting point?

Here a careful monitoring of the GPS signal page on the GTN-650 may help to figure out what what is working and what is not.

Carl

airguy
05-15-2019, 02:44 PM
So combining Greg and Carl’s comments, if my needle is accurate on my glide slope and I can follow it smoothly down uncoupled, but my plane is flying above and below that needle when coupled (with healthy airspeed changes), that suggests the problem is not in the 650. Does that sound right?

If you can keep the airspeed steady, as in +/- 5 knots, then the autopilot should be able to fly the glideslope just fine. If you let the airspeed vary more than that, then of course it's going to have trouble.

Asking the autopilot to follow a glideslope with "healthy airspeed changes", then observing the autopilot fail to do so, is NOT a failure of the autopilot. It's a failure of the pilot to provide proper application of power for a stabilized descent.

If you set the autopilot up to descend at a constant rate (say 800 fpm) and then proceed to jack the throttle all over the place, the autopilot will, of course, fail to maintain the target vertical speed. Any autopilot in any aircraft will exhibit the same behavior. You have to give it a fighting chance...

RickSolana
07-17-2019, 10:07 AM
I have gotten my Dynon autopilot on my RV10 tuned really well, with the help of David Brown in Australia! Here is a detailed description of the solution, in case it is useful to someone. The autopilot is now performing outstanding with only a half bar-width deviation on final approach. David and I now have almost identical settings, having come from different directions.

SOLUTION:
? Slop must be removed. Mine was coming from a cracked capstan. Slop is easy to check if you set the autopilot on ?level? and manipulate the elevator to see how much play you have.
? There are two important trim settings that must be addressed before dealing with autopilot settings (thanks to David Brown for identifying these and getting our two planes on the same page):
1. The trim tab set up should be checked and set according to the procedure posted in Matronics on 2006.
2. The TRIM speed settings must be right to allow the autopilot auto-trim to be fast enough and not fight the autopilot. The settings David gave me (for both pitch and roll) are:
 105 Kts ? 100%
 130 Kts ? 35%
? Then I re-ran the in-flight tuning (for the millionth time), resulting in sensitivity 13, pitch gain 1.5, altitude gain 0.9. This was fine enroute, but terrible on LPV glide slope (VNAV setting).
? Finally I flew many LPV approaches, testing pitch sensitivities from 13 to 20. For each, I would then test pitch gain until I found the maximum gain that would fly an approach without any oscillations. To do that, I would push the stick to try to induce oscillations at each gain setting. Pitch sensitivity of 17 worked best for me, with a pitch gain of 1.5, and altitude gain has been set at 0.9 from the tuning results. All other numbers are default. David is now at 16, 1.5, 0.9 (only one digit off); he is planning on trying my settings 17, 1.5, 0.9. Nonetheless, we were very far apart and now we are almost identical in our settings.

OBSERVATIONS:
? The autopilot is a completely different animal as soon as VNAV engages, so flying some VNAV coupled LPV final approaches is a necessary part of in-flight tuning.
o Meeting the in-flight tuning criteria alone results in a sloppy coupled approach
o Setting the autopilot pitch just short of ?twitchy? (in in-flight tuning) results in a rough, oscillating coupled approach.


Here are the settings David and I are using:
Dynon default Rick David
ROLL
sensitivity 10 14 14
gain 0 0 0.3
PITCH
sensitivity 10 17 16
gain 2 1.5 1.5
altitude gain 0.6 0.9 0.9
pull rate 1 1 1
VSI gain 1.5 1.5 1.5
g-error gain 1 1 1
g-error limit 0.25 0.25 0.25


Rick Solana
RV10, N804RS

RickSolana
07-30-2019, 03:26 PM
Sorry for the formatting problem of the numbers. There are three numbers in each line, separated by spaces. They follow the titles in the first line, so the first number is Dynon default, the second is My (Rick?s) setting, and the third are David?s setting. So for roll try a sensitivity of 14, and gain between 0 and 0.3.

I can?t seem to line the columns up in the forum posts.

Rick

Cumulo
08-04-2019, 10:31 PM
More better?
Here are the settings David and I are using:

Dynon default Rick David
ROLL
sensitivity 0 14 14
gain 0 0 0.3
PITCH
sensitivity 10 17 16
gain 2 1.5 1.5
altitude gain 0.6 0.9 0.9
pull rate 1 1 1
VSI gain 1.5 1.5 1.5
g-error gain 1 1 1
g-error limit 0.25 0.25 0.25

Rick Solana
RV10, N804RSRon

RickSolana
08-05-2019, 05:11 AM
Thanks Ron! Much better.

olyolson
08-05-2019, 09:31 AM
Just started flying the RV-8 with an upgrade to the AFS 5500 with touchscreen & the Skyview network. I have the A/P screen controls and the external A/P control (so I could have auto pitch trim). Using a GTN 650 IFR navigator with the Dynon Airinc and Dynon servos.

Anyone have some ballpark numbers for an RV-8?

rleffler
08-05-2019, 12:34 PM
Just started flying the RV-8 with an upgrade to the AFS 5500 with touchscreen & the Skyview network. I have the A/P screen controls and the external A/P control (so I could have auto pitch trim). Using a GTN 650 IFR navigator with the Dynon Airinc and Dynon servos.

Anyone have some ballpark numbers for an RV-8?

Check the AFS install manual. rob used to put reference numbers for all the rvs. I haven?t checked recently, since I?ve been flying for awhile.