Last week I flew the initial tests of my new Tru Trak Digiflight VSGV coupled to my GRT EFIS, and found that everything worked, right out of the box! It?s hard to believe that I got all the wires going to the right places the first time, but I?ll take success when I can get it. This past weekend, I flew up to Dallas and back, which gave me a chance to play with the system a little bit, and I was extremely impressed ? twiddle the knobs on the EFIS for altitude and heading, and watch the airplane go. In fact, when I got to my destination, I remarked to a friend that it didn?t seem like I had been flying ? it seemed more like a simulator session!
One thing I did play with, however, is gain tuning. When I first engaged the pitch channel during testing (in a climb) I got some noticeable hunting behavior in GPSV mode (EFIS driving the autopilot). When I asked Mark at GRT about this, he was up front and said the gains in the EFIS were what I probably needed to adjust, to leave the autopilot alone. He also said he really didn?t have any suggestions on numbers to try, (since he hadn?t tuned the system, for an RV-8 before), except to slowly increase or decrease and then see what I get. That?s a reasonable and normal way to do it, so on the cross-country, I played around a little with the climb and altitude hold gains a bit. I was surprised that very small variations made a positive difference. Since it seemed a bit too lively, I reduced both gains from the default ?1.00? to ?0.95?, and the hunting behavior went away in both climb and hold. Now, the air was smooth as glass, so it?s probably not fair to say that I have them nailed ? just working better.
I?m curious if anyone else with the set-up in an -8 has numbers to share?
Paul
One thing I did play with, however, is gain tuning. When I first engaged the pitch channel during testing (in a climb) I got some noticeable hunting behavior in GPSV mode (EFIS driving the autopilot). When I asked Mark at GRT about this, he was up front and said the gains in the EFIS were what I probably needed to adjust, to leave the autopilot alone. He also said he really didn?t have any suggestions on numbers to try, (since he hadn?t tuned the system, for an RV-8 before), except to slowly increase or decrease and then see what I get. That?s a reasonable and normal way to do it, so on the cross-country, I played around a little with the climb and altitude hold gains a bit. I was surprised that very small variations made a positive difference. Since it seemed a bit too lively, I reduced both gains from the default ?1.00? to ?0.95?, and the hunting behavior went away in both climb and hold. Now, the air was smooth as glass, so it?s probably not fair to say that I have them nailed ? just working better.
I?m curious if anyone else with the set-up in an -8 has numbers to share?
Paul