We need help in figuring out why the drone crashed. We flew a quad, with firmware Copter 3.5.5 in a mission flight ( auto mode). After 10 minutes of flight, at height of 40 meters, the drone switched to alt hold. At this moment, the drone started to spin around itself and descend till it crashed on the ground. We use a sonar rangefinder for landing, and we set:
EK2_ALT_SOURCE = 0, EK2_RNG_USE_HGT = -1, and FS_EKF_ACTION = 2 ( AltHold).
We set rangeinder max_cm = 100 meters. We don’t use optical flow. In previous flights we got bad ekf terrain altitude variance messages. I’m attaching the log file, the parameters, and two graphs. We see a sudden spike in SS parameter (NKF4) before it changed to althold. What is exactly SS?
link for params:
Thanks a lot!