The failsafe's first choice was refused: falling back to RTL or Land
What ArduPilot says:
- Trying Land Mode
- Trying RTL Mode
A failsafe is set to “mission landing or RTL” (value 6) or “Brake or Land” (7), and the first choice could not start. “Trying RTL Mode”: the mission has no DO_LAND_START or DO_RETURN_PATH_START to jump to (“Mode change to AUTO RTL failed: …” comes right before it), so the copter tries RTL, and Land if RTL is refused too. “Trying Land Mode”: Brake needs a position estimate and there is none, so the copter lands after a 4 s pause, drifting with the wind unless you hold it with the sticks.
What to do, most likely first
The mission in the copter has no landing sequence, though a failsafe is set to use one.
CheckRead the mission back from the copter and look for
DO_LAND_STARTbefore the landing commands;FS_THR_ENABLE,FS_GCS_ENABLEor a battery action is 6.FixPut
DO_LAND_STARTin front of the landing part of every mission flown with this setting, or choose plain RTL as the failsafe action.There was no position estimate when the failsafe came, so Brake could not start.
CheckLook in the log for “EKF variance”, “GPS Glitch or Compass error” or a lost GPS fix shortly before the line.
FixFind why the position was lost (GPS, compass and EKF messages before the failsafe). Without a position estimate a copter can only land or hold its height.
Parameters to look at
| Parameter | What it is |
|---|---|
FS_THR_ENABLE | Throttle Failsafe Enable |
FS_GCS_ENABLE | Ground Station Failsafe Enable |
BATT_FS_LOW_ACT | Low battery failsafe action |
BATT_FS_CRT_ACT | Critical battery failsafe action |
FS_DR_ENABLE | DeadReckon Failsafe Action |
Where to do it:Failsafe ExplainerMission Energy CheckSetup & Tuning Guide
The code that sends it
Trying Land Mode
ArduCopter/events.cpp Copter::set_mode_brake_or_land_with_pause() · Open in ArduPilot Copter-4.7.1
Trying RTL Mode
ArduCopter/events.cpp Copter::set_mode_auto_do_land_start_or_RTL() · Open in ArduPilot Copter-4.7.1