This DJI S1000 platform with a Pixhawk fc has done about 20 uneventful flights ranging from manual takeoffs to at least 10 full auto takeoff to landing missions. On the flight of the crash all preflights were performed as normal and no alerts or errors were shown in mission planner. Upon launching using an auto mission takeoff command, the aircraft immediately started violently pitching and rolling and yawing in all directions. It ascended up for a few seconds before the GCS operator triggered RTL, which caused the aircraft to begin climbing while violently oscillating (up to 90 degrees in each direction). At about 15 seconds after launch the aircraft was in RTL mode and violated a polygon geofence with the RTL/Land action enabled. It kind of keeled over to one side and dropped straight down ~75 feet onto the ground. The airframe is a loss and unfortunately the dual sensor EO/IR gimbal is also destroyed.
What I am trying to figure out at this point is why the flight controller caused this action. All the motors were spinning and the props were fully unfolded and torqued to spec.
The aircraft had flown around 5-6 flights with this ~800g payload without any anomalies.
After looking at the on-board logs it looked like the aircraft was violently yawing, while also oscillating on the pitch and roll axis. The camera feed, although stabilized on a gimbal did confirm the yawing motion. Any idea what would cause this from the logs? We have launched from this same location many times without any issue.
One note is that with our Pixhawk equipped S900 and S1000, sometimes when doing auto mission execution from a remote GCS (arming and do action -> mission start), the aircraft will have one or two motors spool up a tiny bit ahead of the other motors which will sometimes cause it to lurch and wobble once or twice as it climbs above the ground. It has always stabilized and corrected for these sudden lurches on launch until this flight. This flight the aircraft was unable to correct for the lurch and just made it worse over time.
If required I have a cellphone video of the wobble I am talking about on Auto launch. If anyone has any idea how to resolve that it would be greatly appreciated as well!
Here is a replay visualization of the aircraft from the onboard logs. The visual observers have confirmed that this is what they saw the platform do.