Drone Drifting in Loiter Mode During Radio Failsafe

ArduCopter
1

Dear ArduPilot Community,

First of all, I apologize if my English is not perfect as I am not a native speaker.

I am facing an issue where my drone starts moving slowly (about 1 m/s) instead of staying stationary when I switch to Loiter mode via Mission Planner during a Radio Failsafe (FS) condition. The GPS status was “RTK Fixed,” so I believe there are no GPS-related issues. I confirmed that RCIN1-4 was in a neutral state when the transmitter is turned off.

This behavior was observed under various FS_THR_ENABLE settings “always RTL”,“always Land”, and “always Brake or Land”. When, FS_THR_ENABLE is “disabled”, the behavior wasn’t occured.
The ArduCopter versions I tested are V4.5.7 and V4.3.7.

Could you please let me know what the problem is?
Below, I have provided detailed flight logs and the steps I performed during testing.

Flight Logs and Observations -----------------------------

Flight 1 (flt1)
FS_THR_ENABLE : Always RTL

  • 11:41:00 ~ : While flying in Loiter, switched to RTL via Mission Planner, then back to Loiter via the transmitter. The drone remained stationary. (Transmitter was always turned on)
    *11:41:50 ~ : While flying in Loiter, switched to RTL via Mission Planner, then back to Loiter via Mission Planner. The drone remained stationary. (Transmitter was always turned on)
    *11:43:25 ~ : While flying in Loiter, turned off the transmitter. FS triggered RTL. Switched back to Loiter via Mission Planner. The drone started moving.

Flight 2 (flt2)
FS_THR_ENABLE : Always RTL

  • 11:45:30 ~ : While flying in Loiter, turned off the transmitter. FS triggered RTL. Switched to Brake mode via Mission Planner. The drone remained stationary.
  • 11:46:40 ~ : While flying in Loiter, turned off the transmitter. FS triggered RTL. Switched to Brake mode via Mission Planner, then back to Loiter. The drone started moving.
  • 11:49:20 ~ : While flying in Loiter, turned off the transmitter. FS triggered RTL. Switched back to Loiter via Mission Planner. The drone started moving.

Flight 3 (flt3)

  • Triggered Battery FS by increasing FS voltage threshold. Switched to Loiter via Mission Planner. The drone flew stationary.

Flight 4 (flt4)

  • Triggered Battery FS by increasing FS voltage threshold. Switched to Loiter via the transmitter. The drone flew stationary.

Flight 5 (flt5)
FS_THR_ENABLE: Disabled

  • 14:35:06 ~ : Turned off the transmitter and tested RTL and Land modes. Both worked as expected.
  • 14:37:00 ~ 14:38:00: At some point during this timeframe, turned off the transmitter. The drone remained stationary.
  • 14:37:25 ~ 14:38:45: Turned off the transmitter while RC1 (Roll) was actively inputted. Despite the FS settings on the transmitter, RCIN1 values remained fixed.

Flight 6 (flt6)
FS_THR_ENABLE: Disabled

  • Turned off the transmitter, then switched to RTL via Mission Planner, and subsequently to Loiter. The drone remained stationary.

Flight 7 (flt7)
FS_THR_ENABLE: Always Land

  • Turned off the transmitter. FS triggered Land mode as expected. Switched to Loiter via Mission Planner. The drone started moving.

Flight 8 (flt8)
FS_THR_ENABLE: Always Brake or Land

  • Turned off the transmitter. FS triggered Brake mode. The drone remained stationary.
  • Switched to Loiter mode via Mission Planner. The drone started drifting.
  • Repeated this test five times, and the behavior was reproducible.

Thank you very much for your support!

Best regards,

2

The link doesn’t work.

3

I’m sorry. The access settings was wrong. I fixed it, so could you please check it?

4

Looks like velocity target isn’t set to 0 correctly. We probably should improve rejecting pilot modes when there is no valid pilot input.

PS IIRC Mission Planner warns against setting pilot control modes when in RC failsafe.

1 Like
5

Thank you for your response.
I understand that setting the loiter mode during RC failsafe is not specifically intended and can lead to unexpected behavior.
I will make sure not to set the pilot control mode during RC failsafe.

1 Like