My previous post has the pictures so skip this if you don’t care for technical details.
I got to the venue a little early to set up. Unpacking the equipment and assembling the quad took about 25 minutes. I decided to start with the two 3s 4000mAh nano-tech batteries hooked up in parallel. Telemetry and video link were solid and GPS was getting 9 satellites in view. Takeoff was smooth and I had fun tooling around in stabilize mode. Altitude hold mode proved to be more stable for general video pans. I never got a chance to use circle mode.
My flight path imported into Google Earth. Each color represents a switch in flight mode. Yellow is altitude hold, green is loiter, purple and red is stabilize, and blue is land.
As you can see, the flight controller switched into land mode at the very end. I had a battery failsafe setup to land when the voltage fell below 10.4V which is 3.5V per cell.
When I saw the voltage start to drop I flew back to the starting point and was preparing to land when all of a sudden I lost all stick inputs and the copter accelerated into a smooth descending arc and went straight into the side of the building.
You can see my stick inputs in red and the flight controller’s motor outputs in green. They track pretty well up until the end where it just ignores me. This is actually normal for failsafe modes. What is not normal is the acceleration and the huge arc that you see in the next two images.
I have not had time to reassemble the copter since then. I had never tried land mode before and I want to see if it works correctly or has a glitch. Perhaps the low battery voltage caused the glitch. The GPS had a solid lock and all other sensors, altimeter, magnetometer, gyro, were all functioning correctly according to the log file. In any case I would like to recreate the events that led to the crash.