Crash during test flight

ArduCopter Copter 4.5
1

I had a crash recently and am trying to determine the cause. If anyone has time to take a look it would be greatly appreciated.

Build
• Cube Black copter v4.5.7
• Here2 GPS
• Quad
• Motor T-Motor MN4014 330KV
• ESC - TMotor F35A Dshot
• Prop - 15”

Short history

  1. I was flying but it was not very stable and was particularly an issue in RTL. (Separate thread) Turned out it was not RTL but the tune. I didn’t have DShot set up correctly.
  2. I set up DShot (I think correctly but maybe not) and after a short test flight vibrations were much better. I was not using any notch filter yet.
  3. I wanted to get bidirectional telemetry working on DShot to try to use RPM based notch filter.
    a. The only 2 additional parms I changed were SERVO_BLH_BDMASK = 3940 and SERVO_BLH_POLES = 24 The MN4014 motor is 18N24P
    b. I bench tested motors they seemed fine.
    c. I didn’t see RPM in the quick data view but thought it might be too low.
    d. Went to do a test flight and after arming and lift off it rocketed up became very unstable and came down hard.

After the crash when booting the cube it was saying “EKF3 IMU0 forced reset” I also see some IMU message in the log just before it crashed. I am replacing the cube black with an Orange Plus and the HERE2 to a HERE3.

My question is if the last parameter change I made could cause this or did the IMU fail causing it or something else, was DShot still set up incorrectly? If it is a general parameter setup issue I don’t want to repeate the problem and destroy the new orange but it it was the cube itself then the orange may fix it.

Log File – 2025-02-05 16-25-56_Crash.bin - Google Drive

Last Parameter File - T650SParms2025-02-05AfterCrash.param - Google Drive

2

I see no evidence that CubeBlack supports Bdshot so configure for just Dshot*. Which you were already set for it looks like.

*I say this because in the HWDEF file for Cube Black it uses fmuv3 not fmuv3-bdshot This doesn’t sound right but that’s what’s in there.

Good idea.

3

Thanks Dave,

I had first followed the DShot set up in - DShot ESCs — Copter documentation

After that I was following the set up in
ESC Telemetry — Copter documentation. It seemed to indicate with newer BLHeli32 (like 32.9) I could get rpm over the DShot signal line. I thought provided I was using the AUX outputs (ch9-12) and not he main ones I could get the telemetry.

I’ll set that back to zero till I can find a small esc with a seperate telemetry line if one exists :slight_smile:

Owen