Ronald,

I felt the need to comment on this one…

The pitch and aileron trim in my Lancair IV-P is almost insignificant with speed change over the normal flight envelope, to the extent that if I notice a need for roll trim, I immediately know that I’ve generated a fuel imbalance between the wings. I have a noticeable pitch trim requirement with configuration changes (gear and flaps), but only a few clicks of the trim for speed changes between 150-210 KIAS. I do have a noticeable yaw trim change in this speed range however.

Due to reports from others about this while I was building, and speculation that it might be caused by a non-symmetrical or improperly offset vertical stab, I spent some time “profiling” my vertical. I discovered that it’s a long way from being symmetrical, but I’d already finished, sanded and prepped it for painting, So I decided I could “just live with it.”

After three years of otherwise superb flying in this magic carpet, I consider the vertical stab my biggest “dumb shit” error during building. I knew it was an issue but chose to ignore it… Unlikely that I’ll ever fix this, although I do have a set of vertical stab skins that I’d do better with if I ever have to replace the tail.

All this to say that at least on my airplane, the shape of the vertical significantly changes my yaw trim with speed (there are other factors such as engine power setting/torque that affect this also). You might want to check this out. As with any trim requirement, a manual or auto trim should fix you right up, at a slight increase in trim drag. After watching the experience of several Lancair owners with the yaw axis auto trim and damper systems available, I’m sticking with my manual rudder trim…works well.

Bob