Jamie
Well Known Member
I'm at my wit's end. When I first flew my airplane last year it left the ground with a Trio EzPilot installed. For whatever reason I was never able to get the Trio to work right. In spite of everything I tried, the thing would just not track smoothly. I was using the SafeAir1 mounting kit with the servo mounted in the last bay of the right wing and a long pushrod connected from the servo to the aileron bellcrank. Anyway, I tried everything -- new servo, new head, wiring, etc. I have detailed this issue on other theads here on VAF, but I discuss it here only for back story, nothing else. I don't blame Trio for this issue, they tried to help, but there's only so much they can do remotely and so many dollars in avgas I can spend before I just gave up. I just sat down and added up the cost for me. It was > $500.00 in avgas diagnosing that Trio problem and I never came up with a solution. That $500.00 figure only includes flights specifically made to try new things with the Trio.
Well, as mentioned I gave up. When Dynon announced their autopilot I thought I would give it a try. I liked their ideas with their AP and I've been a happy customer with their EFIS and EMS in my panel.
I installed their autopilot (two-axis). The roll axis is perfect. It tracks extremely well. The only thing I don't understand is why when you tell it to fly a GPS ground track (i.e you set a track on the Dynon), it overshoots it every time. It doesn't make much sense to me. I also have an issue with the Dynon occasionally barking at me about losing the GPS signal and defaulting to magnetic heading mode. I never lose the HSI and if I go to the AP menu I can re-enable the NAV mode (so it tracks the GPS) with no problem. I've only done preliminary testing with this issue so for me this is lower priority.
The other thing (this is my big problem) is that the Dynon altitude hold is behaving badly. Tweaking the sensitivity settings, the best I can get the altitude hold to perform is +- 20 feet. I engage the altitude hold with the airplane trimmed and it will hold for about one minute or so and then begin an oscillation. The oscillation will grow larger and larger until it maxes at +-20 feet in altitude, but about +- 600fpm in rate. This is with the Dynon sensitivity setting set to the maximum value (25).
I pressure checked my static system and found no leaks.
I vented the Dynon static system to cabin air to ensure that I didn't have any fluctuations in my static system.
I flew the plane from 110kts to 170kts in increments of 10 knots, testing each speed to see if the pitch servo performed better or worse depending upon speed. The speed made little difference.
I pulled the baggage wall and noticed a little play in the mount. In other words, if I engaged the servo, then pushed/pulled on the pushrod until the servo slipped, I would see a little left/right (perpendicular to arm throw) flexing of the mount at the bottom. According to Dynon, the little flange on the bottom of the mount is optional. It's intended to be riveted to the floor. My plane is painted so I wanted to avoid putting drilling through the outter skins and risking chipping paint, etc, so I cut the flange off. In order to stop the flexing I put another fastener in the bottom of the mount. Now the mount is very rigid.
The Dynon support folks are fantastic and are helping me with this issue. Of course I understand that it is a new product and it will suffer growing pains. I fully expect to have some issues, but I'm truly at my wit's end and I'm beginning to believe that it was just never meant for me to have a functional autopilot in my airplane.
I spent all day today on this issue and I finished the day 20 gallons of avgas less, 8 hours without seeing my son and still no answer.
I basically wanted to post here at VAF to see if anyone has any ideas of what could possibly be causing this issue. Also, I know that there are a few Dynon AP beta testers here on VAF so I'm looking to them for ideas.
So, VAF...what say you. Where should I go from here?
Well, as mentioned I gave up. When Dynon announced their autopilot I thought I would give it a try. I liked their ideas with their AP and I've been a happy customer with their EFIS and EMS in my panel.
I installed their autopilot (two-axis). The roll axis is perfect. It tracks extremely well. The only thing I don't understand is why when you tell it to fly a GPS ground track (i.e you set a track on the Dynon), it overshoots it every time. It doesn't make much sense to me. I also have an issue with the Dynon occasionally barking at me about losing the GPS signal and defaulting to magnetic heading mode. I never lose the HSI and if I go to the AP menu I can re-enable the NAV mode (so it tracks the GPS) with no problem. I've only done preliminary testing with this issue so for me this is lower priority.
The other thing (this is my big problem) is that the Dynon altitude hold is behaving badly. Tweaking the sensitivity settings, the best I can get the altitude hold to perform is +- 20 feet. I engage the altitude hold with the airplane trimmed and it will hold for about one minute or so and then begin an oscillation. The oscillation will grow larger and larger until it maxes at +-20 feet in altitude, but about +- 600fpm in rate. This is with the Dynon sensitivity setting set to the maximum value (25).
I pressure checked my static system and found no leaks.
I vented the Dynon static system to cabin air to ensure that I didn't have any fluctuations in my static system.
I flew the plane from 110kts to 170kts in increments of 10 knots, testing each speed to see if the pitch servo performed better or worse depending upon speed. The speed made little difference.
I pulled the baggage wall and noticed a little play in the mount. In other words, if I engaged the servo, then pushed/pulled on the pushrod until the servo slipped, I would see a little left/right (perpendicular to arm throw) flexing of the mount at the bottom. According to Dynon, the little flange on the bottom of the mount is optional. It's intended to be riveted to the floor. My plane is painted so I wanted to avoid putting drilling through the outter skins and risking chipping paint, etc, so I cut the flange off. In order to stop the flexing I put another fastener in the bottom of the mount. Now the mount is very rigid.
The Dynon support folks are fantastic and are helping me with this issue. Of course I understand that it is a new product and it will suffer growing pains. I fully expect to have some issues, but I'm truly at my wit's end and I'm beginning to believe that it was just never meant for me to have a functional autopilot in my airplane.
I spent all day today on this issue and I finished the day 20 gallons of avgas less, 8 hours without seeing my son and still no answer.
I basically wanted to post here at VAF to see if anyone has any ideas of what could possibly be causing this issue. Also, I know that there are a few Dynon AP beta testers here on VAF so I'm looking to them for ideas.
So, VAF...what say you. Where should I go from here?
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