Today I was testing (the third test flight) my HJ Y3 tricopter (AC3.5.5 on PixRacer, Beitian BN-880 GPS, APM power module, BLHeli 30A ESC with BEC, SkyRC X2830/950kV motors, 4S 25C 3500mAh battery, Matek MicroPDB). The previous two flights were successful (the second one was an Autotune session that never completed and I had to abort it due to low voltage). Here are some pictures of the frame showing how the PixRacer is mounted (using a vibration damper base):
This is my first ever tricopter, in the past I had great success with ArduCopter on quadcopters (an S500 and a CX-20 which I upgraded to a PixRacer).
On the third flight - while at PosHold mode - about 4 minutes after taking off, the tricopter entered an uncontrolled yaw state that made it spin frantically. The battery was fully charged and new (less than 3 charge cycles). It forced me to use the kill motors switch to bring it down (no damage done as I was flying over a football field, less than 10 meters from the surface). A quick check of the dataflash log did not show any indications of extreme vibrations (excluding the actual crash, FC vibrations are well within the advised limits).
I was hoping that someone with more experience with tricopters and ArduCopter in general could check my dataflash log and provide an explanation what went wrong (and some advice); I am really afraid to fly it again because I cannot understand what went wrong, even if it is still flying like before the crash.
I am attaching my dataflash log and my parameters file.
Thank you very much in advance.