I was testing the Auto Commands for ArduCopter 2.9.1 using APM 2.5 with MTK GPS and something strange happened.
I had been doing successful auto flights (takeoff, waypoint, RTL) for about a week and I was starting to change some parameters for RTL. I changed two parameters and then did an auto mission but instead of landing the quad dove toward the ground at around 4 m (during the RTL landing phase). I switched back to my default parameter, but the same thing happened. I also noticed that it twitches in auto flight but not in stabilize flights. I tried to fix the twitch by changing the PPM encoder (as it is listed in the wiki) and this stopped the motor spin ups (which were happening while it was flying successfully) but the twitch remains.
So, I thought that RTL was the problem and I started using waypoint with land instead of RTL. I also reflashed the firmware on it to 2.9.1b. I got one good flight out of it. When I went to fly it a second time the quad took off, flew to the first waypoint (this is into the wind) fine and was on its way to the second waypoint (wind at its back) when it dove out of the sky. Both times it looked like a motor stopped spinning.
I have attached the .tlog for the last flight (I can find the others if you want to see them). I noticed that there is a throttle spike (went to 100) right before the quad started to lose altitude.
I thought that this might be a hardware problem, but shouldn't the motor cut out in stabilize flights as well?
I'm going to look at all of its solder joints and all the hardware connections on Monday. Any ideas for places to look for faults (in the hardware or the log)?