Dynon AP Servo Selection

flickroll · #1 05-30-2009, 09:38 PM

I have a Dynon AP in my -8. As recommended by Dynon, I have the SV32 servo installed for both pitch and roll. However, I am seeing the slip indicator light up at times on both servos, even though each has the torque cranked up to 100%. I am thinking I need the SV42 servo, which is capable of more than 50% more torque than the SV32. Has anyone else seen this issue? If so, did a more powerful servo fix the problem? Thanks

rvmills · #2 05-31-2009, 06:00 PM

Jim,

Just a data point for you, as my first thought was torque settings, but you have them at 100%, so I'm scratching my head along with ya.

I have SV-32's with torque set to 100% in my Super Six, and have never seen them slip in flight, even near max GW and with some bumps in the air.

Sensitivity is at 15 for pitch, 10 for roll. Not sure if having the sensitivity turned way up will help induce servo slips (and not sure where yours are set), but I've run them up high for testing, and did not see slips there either.

I know that Jaime P was having pitch oscillation issues, and was looking at SV-42s before going to TT, but don't know if he saw slipping with either Dynon servo.

Hope you get some more info and a fix!

Cheers,
Bob

flickroll · #3 05-31-2009, 08:42 PM

Installed 5.1 today and went for a ride to check out the install of the upgrade. The EFIS and the EMS worked fine, but saw a LOT of slippage on the pitch servo, and some on the roll servo. It was a mildly bumpy day. If I slow down it does a lot better, but if I'm cruising at 160+ kts, the pitch servo indicator stays yellow a LOT. Think I need to call Dynon

rvator51 · #4 05-31-2009, 09:05 PM

Are you using the outside hole on the control arm of the servo? If so, you can move down to using the 2nd hole from the top instead and it will give you more torque. You just have to make sure you dont hit the control stops on either side as the control arm will move further in both directions.

flickroll · #5 06-01-2009, 06:00 AM

I am going to look at that as an option since you do get more torque. IF the control feel with the AP disengaged would be the same with the higher torque SVS42 servo compared to the SVS 32 I would prefer the 42 since it would give more options to hone in the control parameters.

Dynon, I know you monitor this board.....can you provide feedback?

Thanks

flickroll · #6 06-01-2009, 04:30 PM

I called Dynon today and once again, true to form, I received EXCELLENT customer service. After talking to Robert in sales/marketing and Mike in tech support we decided I probably need the SV42 for the pitch servo while the SV32 MAY be OK for the roll servo. They're sending me two SV42's, and I'll immediately replace the pitch servo with one of them. I'll do more adjusting/fiddling with the AP setup and decide if I want to keep the 32 for the roll servo or go to the 42. I'll report back my results after I make the pitch servo swap.

flickroll · #7 06-07-2009, 03:23 PM

Went from SV32 to SV42 servos for both pitch and roll servos. The SV32's that I removed had a lot of slop between the output shaft and shaft bushing. Not shear screw slop but main shaft slop. The SV42's are much tighter. I had earlier production run servos for the SV32's, don't know if Dynon changed anything here or not. I suspect the slop in the output shaft was causing some of the performance issues that I was having before.

The pitch servo I have set at 85% torque, sensitivity 15, VS at 600 ft/min. The roll servo is at 60% torque, 7 sensitivity, and 40 deg bank angle max. I have not finished playing around with the roll servo settings yet and MAY go back to a NEW SV32 servo with a shaft that's not so sloppy. The SV42 does however give me more setup flexibility so at the end of the day may just stay with the SV42.

Today while testing in smooth air, the altitude would hold within 10'-20', and the roll would hold within a degree or two. It does GPS and Nav tracking very well too. So....this system is performing extremely well. The next test will be in turbulent air. I suspect I may have to increase the torque on both servos a little in turbulent air. FWIW in the Bonanza that I had until last summer, its high dollar AP (King KFC-200) performed in a similar fashion to the Dynon (i.e. 10'-20' altitude deviation, +/- 1-2 degrees heading deviation. The King did have auto trim which was nice, but then again the Dynon system is about 10% of the price of a King system. In turbulent air, the King was +/- 50'-100', and about +/- 4-5 deg heading deviation. It will be interesting to see what the Dynon will do in similar conditions.

Dynon, you have produced a great system. After system tweaks my Dynon autopilot is performing solidly. Thanks!!