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Thread: Which Dynon Servos?

  1. #1

    Join Date
    Mar 2010
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    Default Which Dynon Servos?

    I'm thinking of adding an auto pilot to my Model IV. I have had a Dynon D10A since first flight so I will be using Dynon servos. I've seen some installations on the forum that look interesting but am confused regarding servo choice. I think what I am hearing is that an SV32 is sufficient for roll (which may be all I install) but it may slip when used for pitch. That makes sense as my controls are very light in roll but I am definitely glad that I installed the electric pitch trim as the force is much greater. So, which Dynon servos are working well?

    Thanks!

  2. #2
    Senior Member Eric Page's Avatar
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    Default Re: Which Dynon Servos?

    I'm bumping this thread because I have the same question. I plan to use a Dynon system in my Series 5, and I'd like to buy the right servos the first time.

    Can anyone with a working Dynon installation offer guidance on which servos work well for roll and pitch? As Henry mentioned above, there seems to be some lore that the SV32 slips in the pitch application, but I haven't found anyone saying the SV42 doesn't slip. The Dynon servo application guide suggests using the SV32 for both roll and pitch, but the table says this suggestion is not "known to work."

    For anyone with a Garmin autopilot setup, can you please post the torque settings you use for roll and pitch? [For those unfamiliar, the Garmin GSA 28 servo is software adjustable up to 60 in/lbs. I asked the factory what settings they use, but they declined to answer.]

    Thanks.
    Eric Page
    Building: Kitfox 5 Safari | Rotax 912iS | Dynon HDX
    Member: EAA Lifetime, AOPA, ALPA
    ATP: AMEL | Comm: ASEL, Glider | ATCS: CTO
    Map of Landings

  3. #3

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    Default Re: Which Dynon Servos?

    Well, I guess I can answer my own question now.

    I installed an SV32 for roll and an SV42 for pitch in my Model IV. The install went really well. Just by luck I guess, the regular servos have exactly the amount of movement that I needed. The regular servos have 2.6 inches of travel at the hole furthest from the shaft. The roll servo is mounted behind the pilot seat and is connected along with the push rod from the control stick where it connects to the flaperon system. The pitch servo is under the seat center and forward. It connects with the push rod connection between the two control sticks. At both places, the existing AN3 bolts were replaced with longer bolts. No drilling or modification of the control system was required. I purchased one of the Dynon servo wiring kits as it has plenty of wire and used molex connectors at the servos. Also bought two of the $25.00 generic mechanical connect kits. The servo installations are such that it is absolutely impossible to have an "over center" condition. The servo arms are at 90 degrees to the connecting push rods when the controls are centered. I had to remake one of the push rods to get this just right.

    The system works GREAT! It couples to my Dynon D10A that has been in the aircraft since first flight. I changed out the pilot control stick grip so I have an engage/disengage button along with a PTT on the stick. There is a pulllable circuit breaker on the panel to remove power from the servos if needed. Calibration was very easy and I did play with the roll settings a bit in flight to get it just right. Not too jerky but still pretty quick in turbulence.

    Do they slip? Yes, on occasion in turbulence but that is normal according to Dynon. I only notice it if I have my hand on the stick and I will feel it. I'm not sure if the SV42 is required for pitch but when I move the altitude bug the plane will climb or descend without having to re trim. I have it set for 500 fpm. If I disengage the autopilot with my hand on the stick during these climbs/descents I can feel the control force that the servo was holding to perform the maneuver. I'm not sure if the SV32 would be able to do climb/descend without pitch trimmadjustment or power changes. That said, even with the SV42 I do sometimes get the "trim" annunciation on the Dynon display telling me which direction to re trim the A/C. I have the electric trim in my plane. Placing the engage/disengage button on the panel is an option in the install manual but I WOULD NOT do it. I want my hand on the stick when I disengage or it things could get interesting! The Dynon does not complain about trim until the forces are fairly hefty.

    I find the best way to use the autopilot is to just fly the plane from takeoff until established on my first leg and then engage it after setting power and trim by holding the stick button for three seconds. That locks me on my current heading and altitude. I can then make changes at the Dynon display. I have my iFly 740 coupled to the Dynon and the AP will track my course so if I have a flight plan entered in the iFly I change the roll axis from "Heading" to "Nav". I also tweak the altitude bug if needed. If I ever need to take a quick break while hand flying I can just press the button for three seconds and on release it will hold heading and altitude.

    I don't know why I waited 7 years to do this!

    Henry

  4. #4
    Senior Member Eric Page's Avatar
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    Default Re: Which Dynon Servos?

    Thanks for following up with your experience, Henry. That's a VERY helpful post!
    Eric Page
    Building: Kitfox 5 Safari | Rotax 912iS | Dynon HDX
    Member: EAA Lifetime, AOPA, ALPA
    ATP: AMEL | Comm: ASEL, Glider | ATCS: CTO
    Map of Landings

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