Attached are the log files from 2 different drones that fell out of the sky, these both had AC4.0 and had 15" props.
Both had similar motors and T-Motor propellers
Both drones in excellent condition and flying fine before for many flights
Both had similar problems with motor 4 going to max output just before the crash.
These are both Quads using a 850mm carbon frame using HolyBro Pixhawk 4 flight controllers (mini in one)
Both about 2Kg TOW
high vibration could affect EKF measurement and could make problem like yours
VIBE message’s VibeX, VibeY and VibeZ values. These show the standard deviation of the primary accelerometer’s output in m/s/s. Maximum acceptable values appear to be below 30m/s/s.
Graph the Clip0, Clip1 and Clip2 values which increase each time one of the accelerometers reaches its maximum limit (16G). Ideally these should be zero for the whole flight but low numbers (<100) are likely ok especially if they occur during hard landings. A regularly increasing number through the log indicates a serious vibration problem that should be fixed.
That is really bad clipping. Setting up the dynamic notch will help a bit, but ultimately you need to find the root of the vibrations and deal with them.
Lots to unpack with this log, and lots of issues with your aircraft as far as I can tell. Your aircraft didn’t “fall out of the sky” they vibrated out of the sky! The main axis that’s having problems is the Z axis. How is your FC mounted?
You have thrust loss errors right before the crash. What sort of battery are you using? Also notable are the EKF primary failure and vibration compensation turning on.
Long story short, you’ve been really lucky this bird didn’t crash sooner. Did you follow the initial tuning wiki?
The main axis that’s having problems is the Z axis. How is your FC mounted?