Autoland Aborted at 3m AGL – Unexpected RTL Triggered Mid-Landing

Hi everyone,

I recently attempted an autoland with my fixed-wing aircraft, and while the approach phase went very smoothly — good alignment with the runway and a gentle descent — something went wrong during the final moments.
At around 3 meters above ground level, the autopilot suddenly considered the mission complete and switched to RTL. This resulted in a sharp right bank that almost led to a crash.

I’m using both a Lidar for altitude and an airspeed sensor, and as far as I can tell, both are working correctly. There were no obvious failsafes or anomalies reported during the flight.

Has anyone experienced a similar issue or have suggestions on what might have caused this behavior? Any help would be appreciated!

Log of the Flight (.bin)

The plane did exactly what it was told (maybe not what you wanted).

From the wiki:

Plane will RTL unless the last mission item is unlimited loiter or turns, or a landing.

2025-05-10 09:24:04.340 Mission: 13 WP
2025-05-10 09:24:10.540 Passed waypoint #13 dist 1m
2025-05-10 09:24:10.540 Mission: 14 WP
2025-05-10 09:24:10.740 Reached waypoint #14 dist 41m
2025-05-10 09:24:10.740 Mission complete, changing mode to RTL
WP 13 was at 0m AGL  -- Was this supposed to be LAND? 
WP 14 was at 100m AGL.  -- Perhaps this should have been a Land command at 0m, rather than another waypoint.

The plane finished it’s last waypoint and because there was nothing else it began the RTL.

If you will be regularly flying auto missions you can use ARMING_MIS_ITEMS to make sure you always have a landing or RTL set as required.

Also a good idea to set ARMING_CHECK,1

2 Likes

Thank you again for your help. One thing I still don’t understand is why the autopilot considered it had reached WP14, even though it was actually 41 meters away from the waypoint. The waypoint radius was set to 25 meters, if I remember correctly.

Aside from that, I really appreciate all your support!

In the log I looked at WP_RADIUS is 60m, and may of the waypoints were triggered around the 40m mark.

2025-05-10 09:22:37.040 Mission: 1 WP
2025-05-10 09:22:47.340 Reached waypoint #1 dist 56m
2025-05-10 09:22:47.340 Mission: 2 WP
2025-05-10 09:22:57.540 Reached waypoint #2 dist 40m
2025-05-10 09:22:57.540 Mission: 3 WP
2025-05-10 09:23:10.040 Reached waypoint #3 dist 41m
2025-05-10 09:23:10.040 Mission: 4 WP
2025-05-10 09:23:22.540 Reached waypoint #4 dist 8m
2025-05-10 09:23:22.540 Mission: 6 WP
2025-05-10 09:23:24.540 Reached waypoint #6 dist 28m
2025-05-10 09:23:24.540 Mission: 7 WP
2025-05-10 09:23:30.040 Reached waypoint #7 dist 45m
2025-05-10 09:23:30.040 Mission: 8 WP
2025-05-10 09:23:40.840 Reached waypoint #8 dist 45m
2025-05-10 09:23:40.840 Mission: 9 WP
2025-05-10 09:23:47.840 Reached waypoint #9 dist 40m
2025-05-10 09:23:47.840 Mission: 10 WP
2025-05-10 09:23:57.640 Reached waypoint #10 dist 5m
2025-05-10 09:23:57.640 Mission: 11 WP
2025-05-10 09:23:58.440 Reached waypoint #11 dist 41m
2025-05-10 09:23:58.440 Mission: 12 WP
2025-05-10 09:24:04.340 Reached waypoint #12 dist 6m
2025-05-10 09:24:04.340 Mission: 13 WP
2025-05-10 09:24:10.540 Passed waypoint #13 dist 1m
2025-05-10 09:24:10.540 Mission: 14 WP
2025-05-10 09:24:10.740 Reached waypoint #14 dist 41m
1 Like

Thanks a lot for all the help!