Help needed to understand crash log please

TRex 500 all stock except 4-blade head. Matek H743Mini running Aruducopter 4.2.2. The heli has flown for many years with a different FC, but this was its first flight with the Matek FC and Arducopter.

MP PreArm check was, and still is, clear. Arming and startup proceeded normally in Stabilise mode, though when it lifted off I felt it was not stabilised and, more to the point, it was leaning a lot to the right and perhaps a little bit forward. I landed, waited until the blades had almost stopped rotating, then took off again. In my attempt to correct the right lean I eventually got to full left throw on the Tx ‘roll’ stick before landing the second time. I thought I managed to land okay, but the heli then leaned over onto its right side, destroying the tail boom. Physical repairs and checks are ongoing, but I would appreciate it if someone could give me a clue as to why it went wrong. I see that vibe x, y, and z are very high, which I need to sort out, but could that alone be what caused the problem?

Below is a link to the flight’s log file, and a copy of the param file.

Hughes 500 parameters ATC_RAT_xxx_FLTD changed to 0.param (20.2 KB)

First I’m sorry to read that you had a crash. I will say though, if something doesn’t seem right then land and pull the log and look at what is happening. Don’t try again hoping it goes away. Ive also done this. It never turns out well.

Yes high vibrations could cause the attitude estimate to be wrong and result in uncommanded aircraft leaning. I haven’t looked at your log but if the attitude is changing to values you didn’t see while flying. For example the log shows roll attitude reaching 30 deg and you know it was never at 30 deg then the EKF was incorrectly estimating attitude.

Thank you Bill. I was almost taking your advice :smiley: But it crashed after it landed!! Damage was limited to the boom, and the main gear lost a couple of teeth. The expensive bits – 4 blades – survived without a mark.

The vibrations were in excess of 100 in each axis compared with about 10 which I see on my first TRex Arducopter. I’ll look at the log again to see what it tells me about attitude compared with what I actually observed during the flight. The good new is, during the stripdown to replace boom and main gear I’ve found the source of the vibration. The motor’s top bearing is completely shot – about 1mm play in all directions :unamused:

When I get a replacement motor, I’ll run the heli on the ground, without taking off, and check the log for vibration before I take it any further.