Need help with the dreaded TBE (Toilet Bowl Effect)

[DanMan32]

I believe I saw my P3 TBE once a distance away. I was flying somewhat low over water. It beelined back to me when I hit RTH. I believe the issue was conflict between VPS tracking water currents like a treadmill thinking it was stationary, but GPS saying it was moving so it moves back to original GPS coordinates.

 

[sar104]

I believe I saw my P3 TBE once a distance away. I was flying somewhat low over water. It beelined back to me when I hit RTH. I believe the issue was conflict between VPS tracking water currents like a treadmill thinking it was stationary, but GPS saying it was moving so it moves back to original GPS coordinates.

Right - but that's not going to cause TBE, which results from a 90° heading error. You can think of it a bit like an orbiting satellite where the force (gravity) is always orthogonal to the direction of motion. With TBE the 90° heading error has a similar effect - the aircraft applies thrust that is 90° off the direction that it really wants, which drives it in a circular path.

 

[BIGDAVE]

LOVE IT

I have recently encountered the TBE, but ONLY in Sport mode. I have performed multiple compass calibrations to no avail. I have NOT calibrated the IMU, but of all the threads I've read on this problem, re-calibrating the IMU was not mentioned, even though this seems to be the only other component that could affect the TBE issue. The real question is why is this happening to me ONLY in Sport mode. Any thoughts or suggestions would be appreciated.

UPDATE: PROBLEM SOLVED -- IT JUST NEEDED A STICK CALIBRATION.

Gove it when someone UPDATES the question.[emoji106][emoji4]

 

[DanMan32]

Right - but that's not going to cause TBE, which results from a 90° heading error. You can think of it a bit like an orbiting satellite where the force (gravity) is always orthogonal to the direction of motion. With TBE the 90° heading error has a similar effect - the aircraft applies thrust that is 90° off the direction that it really wants, which drives it in a circular path.

I later checked the flight path that day in the app playback. It definitely was going in circles without me telling it to. Most of it the P3 was facing the same direction rather than following its odd course direction. From pure VLOS, it looked like it was going back and forth, as you can't easily see front to back motion from a distance. Since it was over water, that's what concerned me. All I'd need is a full compass or IMU error without kicking into ATTI and it might bank right into the water. Even in ATTI, it could have drifted into an island of trees before I could react.

 

[BudWalker]

I later checked the flight path that day in the app playback. It definitely was going in circles without me telling it to. Most of it the P3 was facing the same direction rather than following its odd course direction. From pure VLOS, it looked like it was going back and forth, as you can't easily see front to back motion from a distance. Since it was over water, that's what concerned me. All I'd need is a full compass or IMU error without kicking into ATTI and it might bank right into the water. Even in ATTI, it could have drifted into an island of trees before I could react.

It would be interesting to see the log file for this. It's probably too much to hope the .DAT still exists. But, the .txt will have data where we can compare GPS weighted position vs position computed mostly from accelerometer and gyro data.

I didn't quite understand the comment about VPS. The P3 doesn't have a vision system that will estimate position.

Your description fits TBE - especially the part where Yaw is constant while it circles.

 

[DanMan32]

Yes, P3, at least A/P, does have VPS. It's only one camera for vision, and ultrasonic for range/distance.

I should be able to get the txt as I never cleared any of the logs from the cloud, and may even have the DAT. I may have a post about the incident, though no logs, over on PhantomPilots.