Today I flew my Twinstar with APM in the hotseat. It's the second flight I've had with it wired in, but yesterday I was only using the stabilise mode. It's been a couple of great days from a weather and wind point of view, so ideal for testing. The Stabilise mode is lovely. The Twinstar (mine has a stock power system) when it is trimmed up is a super stable platform anyway, so I'm not too surprised that stabilise didn't have a massive impact, but it was certainly noticeable and very pleasant to fly! The plane does have about a 5 degree nose down pitch when hands off (in stabilise) and I don't know how to fix this, can it just be trimmed out with the radio? I thought the AP would compensate for any trimming I did to the control surface, and the fact that it has a nose down attitude is probably an autopilot config issue.
Return to launch was interesting. I took off in stabilise mode and flew fairly straight away into the wind gaining a bit of altitude. I then changed mode to RTL and took my hands of the control for the next few minutes. The plane held attitude well, and executed well controlled turns. However, you couldn't in all honesty describe what it was doing as a circle overhead the launch site. Figures of eight perhaps, it seemed to be hunting for something. It certainly seemed to be controlled and comfortable in the sky, I wasn't too worried. I still don't understand it's behaviour though.
I would like to share the log file with you, but I can't. For some reason this flight wasn't logged. The previous two were and I have the KML and log files for those (not huge files, probably about 3-4mins flying each). Log three only shows one 'page' of data.
I will fully admit that this may all be my own fault. I'm still learning, but in my excitement and the heady sense of progress, I havn't run the tests and tuning using FBW_A that the manual suggests that I should do. I've not got my head around PID settings, and I suspect that this is the root cause of the issues i was seeing with RTL. I'm guessing the AP couldn't hit it's mark to begin the orbit.
If the weather holds I'll be out again tomorrow to diligently follow the FBW_A tuning guide!