Dynon auto pilot fault

Hi Guys,

Last weekend I was flying in moderate turbulence using the auto pilot and it was doing really well in all the thermals.

After about 1 hour I started getting pitch slip messages and shortly after that the auto pilot disengaged with a audible warning message.

When I tried to re-engage the auto pilot I got a pitch servo error and the auto pilot immediately disconnected.

What would cause this to occur?

Have I perhaps broken the shear pin on the pitch servo?

I tried to engage only the wing leveler but I could not get this to engage either.

Any suggestions on how to fault find this would be appreciated.

Cheers

Now that you are on the ground do the autopilot servo calibration (out of the install manual). If you have a servo problem this will tell you.

If you have consistent slip issues carefully verify that you have no control linkage binding (disconnect both servos to do this). Verify you installed the servo stops to prevent the servo arm from going over center. If good, then check you attached the linkage to the hole at the end of the servo arm. If already there, then get the next larger servo from Dynon.

Carl

The servos can fail. As Carl said, check to see if there are any obvious problems. If not, I sometimes get a servo error and just pulling and resetting the A/P breaker will fix it (rebooting the servo). The sheer screw wouldn't give you the error, or the slip, for that matter. It just wouldn't control the plane.

Thanks Carl,

I'll try the re-calibration to see what it tells me.

As far as slip goes, this was probably does to the amount of turbulence, so I can accept that warning message.

I am fairly sure that binding was not the reason for the autopilot going off line as it has been working fine for over 3.5 years now without any issues, but I'll recheck this again.

Cheers

Thanks Jesse,

I guess I'll know weather powering down has reset the servo and cleared the issue when I turn the Skyview on this coming weekend.

I didn't think of trying that when I got back to the airport as it had already been a very long hot bumpy day and I just wanted to get home and relax.


Cheers

Not on topic... but I didn't notice you were in Australia until I saw Long Hot Day..... We're in our frosty time of year over here burrr....

Please keep us posted as to what was the cause of the AP issue. I have dynon servos in my plane, so I am watching this thread with interest. One suggestion for a quicker answer (if you havent already), is to post this question on the Dynon Avionics forum.

As a side note for RV-10 builders, I first flew with the SV-42 for the pitch servo. It worked just fine except for the occasional slip in turbulence. Dynon came out with the SV-42T (linear actuator) to address this issue. They exchanged my two year old servo for free - and I have had no slip issues since replacing it.

Dynon continues to lead the market for after the sale service.

Carl

Hi Guys

I have posted on the Dynon forum as well and will post here when I get a reply...

If any of you are feeling a little to cool Sydney is currently a balmy 27 deg C at present.

I was coming back from Bendigo which is in Victoria where it was 37 deg C and getting uncomfortably hot.

Cheers

I have been asked by the Dynon person that manages the Dynon forums to contact Dynon support directly for advice on how to diagnose/resolve this issue.

I'll keep you updated on progress.

Cheers

To those that where interested in the reason for my auto pilot not re-engaging, here is the response from Dynon Technical support based on the diagnostics file I sent them, they are still investigating the issue.

The answers to the questions below;
No I did not have any metal or magnetic objects near the servos
The servos are not co-located;

The diagnostic files did turn up something weird.
I am having an engineer take a closer look at it.
The errors coming from the servo indicated that they had incorrect position readings each time you tried to engage the autopilot.
I am not sure what would cause it so we are looking a little deeper.

One thing that could would be magnetic interference with the servos.
Are they co-located and could there have been some steel, iron or magnets nearby them during that flight?
We use a magnetic hall effect sensor to determine position and it was not working properly.

Other flights were just fine and did not exhibit that error.

AP servo

All my many Dynon AP problems, including uncommanded turns, were solved by installing the next larger size roll servo. No problems in over 50 hours with new servo. Dynon folks great to work with - sometimes need to use your spurs on 'em.

Thanks Jerry I see what they come back with first ;-)

Cheers