Autopilot altitude hold performance - poll

[Alfio]

Hello,

I am starting to look at autopilots, and of course looking to the Dynon servos. I have read of a few people that had difficulty setting their units up, but am sure there are more success stories out there.

I would like to hear from people who have the servos for a while,  especially about the performance of the altitude hold, in calm, light turbulence, and mild turbulence. What kind of altitude excursions do you see?

I have an RV-9A with 160 hp engine, and would especially like to hear with people of similar configuration. I like to cruise anywhere  from 4K to 11K feet, so not sure if the performance of the autopilot differs at different altitudes.

Alfio

 

[PhantomPholly]

Alfio,

For what it is worth you should be aware that in the large scheme of things any answer you get today will not still be accurate by the time you buy and install an autopilot. Dynon's unit is still relatively new, and they are making changes frequently.

The upside is that Dynon's track record is terrific, and any issues today will doubtless be corrected in short order.

 

[N930RV]

Alfio,
After installation of 2 axis AP (on my 9A with 160 hp) and only initial adjustments on sensitivity I was able to hold altitude within +- 20ft in calm air and was seeing +-50 excersions in light to moderate turb.  Altitudes were between 3500' and 10500'.  This was on a 200 mile trip over the mountain and desert areas of the south west.

Bill

 

[rvmills]

My performance (RV-6/IO-540) has been similar to Bill's. SV-32 servos, set at 100% torque, and sensitivity at 15 pitch, 8 roll.

+/- 10-20 feet in smooth air, a bit more (maybe +/- 50+) in light chop or up/downdrafts, with a little twitchiness that can be alleviated by taking the sensitivity down a notch or two.

Cheers,
Bob

 

[Alfio]

Thanks for the feedback, guys.

I read in another forum (VAF) that an RV-8 builder swapped his SV32 servos for an SV42 servo because he needed more torque... it finally worked better for him.

Seems from previous post on this thread that the torque on an RV-9 is set to 100%. Would it not then be logical that the RV-9 should be using an SV42 as well? The RV-8 has probably lighter controls than the RV-9. You can always program the torque value down as needed.

 

[dynonsupport]

Servos set to 100% are not uncommon, and you don't necessarily have to go up to the next size if that 100% gets it just about right.

The generic reason not to go to the SV42 if you don't need to is the added weight (1lb more) and added residual drag of the bigger servo (not a huge deal, but why add more than you need to?)

Our RV-9 beta tester did experience better performance with the SV42, and we're thinking about switching the kitting of the mounting kit + servo packaging there. However, if you start with the SV32 and find they don't do the job, we'll happily swap them out for you. You can also buy the servo and mounting kits separately if you want to order the SV42s right off the bat. There is no difference in what you get whether you order the combination part numbers or break them up into separate kits and servos.

 

[shersha]

My altitude performance is similar to others. I have an RV-8 with SV-32's. In smooth air it's pretty good - about +/- 15 feet. In any turbulence however it's not nearly as good. It varies to +/- 40 feet and the altitude corrections to get back to the set altitude is rather abrupt. I've tried all different sensitivities and the best I can get is at 12 for my airplane.

Scott Hersha
RV-8

 

[dbiddle]

I upgraded D10 to D10A in order to use altitude hold. Now with about 25 hours using the altitude hold on my RV-6A, I do not like the pitch excursions of 300 to 400 vertical feet per minute up and down that the unit makes in trying to hold exact altitude. A "loose" mode would be nice. Something that is fine with an altitude band of maybe 100 feet plus and minus the set altitude. Vertical speed corrections kept to maximum 100fpm. I am still experimenting with settings but additional parameters such as a loose mode would make it more usable in my opinion.

 

[PhantomPholly]

Hey gang,

I don't have a Dynon AP but I do have a recommendation for you to try.

If you have plumbed in an "alternate static" source in your airplane, try switching to that source while airborne on a VFR day & flight, then engage the AP.

If the Altitude Hold is far superior, you can draw the following conclusion - there is too much air in your static line.

The same phenomenon happens with another popular AP but, when I switch to cabin air (I have a dashboard knob I can turn to switch between outside and cabin static) it becomes rock solid.

If you find that this is the problem, there IS something you can do. Replace all (or as much as possible) of your static tubing with the thinnest diameter you can. This will cause the whole system to equalize much faster as you transition from climb to descent, etc. This is because the static port holes are so tiny that it takes a finite moment to equalize the line with outside air. The duration will vary as a function of the volume of air in the tubes.

 

[dynonsupport]

Hi all,

We're for folks that have autopilots installed and flying, particularly D10/D100 series customers, who are running the latest firmware (5.3 currently), and have tried everything they can to dial in the autopilot - particularly in pitch - but aren't quite seeing the performance they would like. If this is you and:
-you're fairly technical - you understand how to use the Dynon Support Program to load firmware into your unit and you're comfortable with that process
-you're available to fly and iterate firmware and report back at least a few times over the coming weeks and months
-you're patient and fault-tolerant, and understand that testing "beta" firmware is an experimental thing

...then we want to hear from you. Please email betatest at dynonavionics dot com with the following information:
-airplane type
-dynon equipment, particularly, which servos you have
-roll axis setup:
servo type
short description of mounting method
all settings from the roll axis page in the ap setup menu
your performance notes/issues (in turbulence and smooth air if they're different)
what you've done so far (settings tweaked, results,etc) to try to dial it in
-pitch axis setup:
servo type
short description of mounting method
all settings from the roll axis page in the ap setup menu
your performance notes/issues (in turbulence and smooth air if they're different)
what you've done so far (settings tweaked, results,etc) to try to dial it in

Thanks!