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View Full Version : Does your autopilot hold heading well?


andrew phillips
06-19-2009, 10:55 AM
I have the Trio set up. I was flying with my young son the other day and he complained that he was not feeling well. The autopilot and the alt hold were constantly wandering back and forth and up and down. I never gave it much thought before because there was usually some turbulence and I figured that was just what happened. This time I turned them off and we were in completely smooth air. The plane was so well trimmed that it flew better hands off than with the autopilot on. I went back to the instructions and turned the sensitivity down the next day. The heading still wanders left and right of track but the changes are not quite as abrupt. I have an AVmap driving the heading and wondered if it's slow refresh rate had anything to do with this. This is my first aircraft and the first time I ever had an autopilot. Is this as good as it gets?

scard
06-19-2009, 11:01 AM
This is not as good as it gets. My TruTrack is absolutely rock solid.

the_other_dougreeves
06-19-2009, 11:11 AM
Trutrak ADI Pilot II. Works great.

TODR

Sam Buchanan
06-19-2009, 11:15 AM
I have the Trio set up. I was flying with my young son the other day and he complained that he was not feeling well. The autopilot and the alt hold were constantly wandering back and forth and up and down. I never gave it much thought before because there was usually some turbulence and I figured that was just what happened. This time I turned them off and we were in completely smooth air. The plane was so well trimmed that it flew better hands off than with the autopilot on. I went back to the instructions and turned the sensitivity down the next day. The heading still wanders left and right of track but the changes are not quite as abrupt. I have an AVmap driving the heading and wondered if it's slow refresh rate had anything to do with this. This is my first aircraft and the first time I ever had an autopilot. Is this as good as it gets?

Andrew,

I have many hours of flying with all the Trio equipment in my RV-6 (along with a couple of other brands of autopilots). In smooth air you should expect your plane to fly "perfectly" provided there are no problems with the autopilot installation or setup.

It has been my experience the Trio system will hold altitude so precisely in smooth air the numbers on the Dynon altimeter will not change and the VSI tape will not appear. We are talking about +- less than ten feet. When pitch corrections are necessary due to turbulence, they should be smooth without feeling the servo kick in. It is, however, important that there be no friction in the elevator control system, no leakage in the pitot connections, and the gain setting should be appropriate for your airplane and typical CG.

Tracking performance should be similar. With all the production Trio units I've flown, the device will hold the aircraft within .03 mile or less, usually close to 0.00 mile deviation. Once again, if no installation problems, and if the gain settings are appropriate, you should not be able to detect the servo working.

Having said that, there have been a few instances of the Trio slowly oscillating +- 3-4 degrees in heading (about a 60 second period) as it held the aircraft very close to desired track (if I recall correctly, this has been almost exclusively in RV aircraft). This occurs only in smooth air. Even a tiny amount of chop will either render this characteristic undetectable or eliminate it. The Trio guys are familiar with this issue in a very small number of installations and are actively seeking a solution.

In my case, I never saw this behavior with any of the EZ-Pilot units, but the Pro Pilot I now fly shows a slight touch of this "feature" only in dead smooth air. Guess I'm just lucky ;) since none of the other beta testers saw this on their installations.

If you are convinced there are no installation problems that need addressing, I suggest you try a "soft" gain setting. I like 2,3 on the roll servo, and 30,30 on pitch. This is lower than the settings delivered from the factory, but I prefer to not feel the system working. If this doesn't help, by all means contact the Trio guys, their customer service is comprehensive and extremely individualized.

You mentioned the AvMap--I don't have experience with that device but I would think as long as it updates at least once a second it should be suitable. The Trio code is written with very tight filters that will reject any data that doesn't strictly meet high standards, so I assume this is not a problem since you are not getting a data error message on the Trio.

Build9A
06-19-2009, 12:01 PM
I had a similar problem and talked to EZ folks awhile back. Seems like they told me to be sure to turn the EZ Pilot on while on the ground while the GPS is booting up. Rather that turning on the EZ while in the air. That seemed to solve my problem. I only have the single axis unit and not alt. hold.