The weather was not too bad yesterday morning, so I zipped out to the airport for an RV-8 flight. I got an hour of engine break-in and autopilot testing done before some snow showers started to approach the airport. It wasn't clear how bad it was going to get, so I landed. It turned out that the snow never really hit the airport, but it is a lot better to be on the ground wishing you were flying than the other way around.

I tweaked the autopilot gains a bit more, and managed to make some improvement. It works well in level flight, and the altitude hold performance in turns is better than before. It still isn't working as well as I would like during climbs or descents, so I'll focus on that on the next flight.

I tested the automatic 180 degree turn mode, and that works well. It is designed for the case where you are flying VFR and inadvertently enter cloud. You press and hold the engage button for the lateral or vertical servo, and the autopilot executes a level 180 degree turn. The turn is to the left if you push the button for the lateral servo (which is on the left side of the control head), and it is to the right if you used the vertical servo button (on the right side of the control head). I hope to never need this mode, but it is a nice safety feature, assuming the pilot can remember how to engage a mode that he probably only ever used during the initial testing.

I'm finding the interface for the vertical modes confusing, just as I had expected from reading the manual. The basic operation is very simple - it always engages in altitude hold mode when you engage the vertical servo. This might not be what you want, but it is at least very predictable, and the active ALT HLD mode is clearly indicated on the control head. The confusion starts when you want to do a climb or descent to a selected altitude. You need to make just the right sequence of "V MODE" button pushes and rotary knob turns and pushes. If you get it right, the autopilot climbs or descends to the desired altitude. If you get out of sequence and push the rotary knob when you should be pushing the "V MODE" button, you cancel the climb or descent and go back to altitude hold mode. And, if you got it all right, the LEDs are flashing during the climb or descent. Most people would associate flashing with a problem, but not on this autopilot in this specific circumstance (the autopilot does use flashing to indicate a problem in other circumstances). This is definitely not a good user interface. I'm going to write up a Cheat Sheet and add it to my printed checklist.

I've got some ideas for clearer mode selection and indication logic, and I'll send them to the designers as suggested improvements after I have some more time using the autopilot.