I maidened my Bixler today with an APM2 running flight software 2.74b and had a couple issues. The setup is running an external uBlox GPS and 3DR Telemetry radios. I've got APMs on two multicopters, but this is my first time using it on a fixed wing plane.
Some background - from when I first got the software setup, when I was testing it on the bench, whenever I switch to Loiter or RTL mode (the only flight modes I have setup that use GPS) the 3DR telemetry radio would freeze up. The green and red lights on both radios would continue blinking, but updates in the Planner would stop. If I switched flight modes using my transmitter back to Manual or Stabilize the plane would act normally so I assumed (maybe wrongly) that this was an issue with Mission Planner or running it in a VM on my Mac.
Question #1 - Has anyone else seen this lockup behavior with the 3DR radios after using GPS modes?
My first flight started out very well - I took of in manual mode and the plane flew fairly well. It was super-twitchy and if I fly in that mode much I'll set up some D/R and Expo with my transmitter for it. After I was up in the air and happy with the trims I switched to Stabilized Mode and that worked very well. I then switched to FBWA and though it was sluggish, and took a LOT of stick to change course, it performed as advertised.
Feeling good about things, I thought I'd give RTL a shot. Sure enough, it turned the plane around and headed back to home. When it got close by, I switched to Loiter and though the loiter circle was very large, it did indeed make a nice big circle above my power-on point. I then switched back to Stabilize and things got weird - my motor speed went very low. I tried switching around to all different modes and though I still had control of roll, pitch, and yaw, I had no throttle control in any mode. Luckily I had space and was able to glide the plane in for a decent landing.
Question #2 - Why would I have no throttle control after leaving Loiter mode?
I checked then checked the plane over and everything seemed OK. By hand I verified the stabilization was working and the throttle seemed to be working fine on the ground. I did not power down the system (in retrospect a mistake). I took off OK in manual mode, switched to Stabilize when I was just a few feet up, and immediately lost throttle again. I tried switching modes around, nothing worked and I didn't have enough time or speed to land safely. I ended up going in nose first, smashing the front of the craft and breaking off a wing.
Question #3 - Why would Stabilize cut throttle?
After all this, I was anxious to look at the logs. Unfortunately the TLogs stopped recording when I switched to RTL back in the beginning so I had no interesting information there. Even more unsettling, the flash logs seem to have stopped recording then too. So I have no log info after switching out of Loiter.
Question #4 - Am I just unlucky? Why would flash logging stop? Especially when it seemed like everything was working fine.
I've got some repairs to do, but am anxious to get back out flying again. I really liked stabilize mode and I can sure see how RTL would be useful. And of course Auto will be fun. But I don't like loosing control of the throttle.