[Bug] Random land detection mid air, freefall detect not working

[FrankvVeelen]

Describe the bug

When testing our drone, we had a random land detect mid-air. When analysing we found out our MPC_THR_MIN is very close to our hover thrust estimate (25% vs ~29%). We think this could result in the random landing being detected.
However, after this a takeoff was detect (weird), but the motors didn't turn on again.
Freefall was also not detected. When looking at the land detection module we found that for a freefall to be detected the norm of the acceleration should be >2.0. We feel that this is quite tight, especially in more windy conditions where some lift might still be generated.

To Reproduce

Fly with MPC_THR_MIN set too high.

Expected behavior

We expected that a random land detection would not result in a full crash, but freefall detect saving the drone.

Screenshot / Media

No response

Flight Log

https://review.px4.io/plot_app?log=e2367fb6-f8de-46a3-b711-fcec82ce9968

Software Version

1.14.0

Flight controller

Holybro V6x

Vehicle type

Multicopter

How are the different components wired up (including port information)

No response

Additional context

No response

[bresch]

Why did you have to set MPC_THR_MIN so high? Default value is 12%

[FrankvVeelen]

Why did you have to set MPC_THR_MIN so high? Default value is 12%

We had some issues where landings were not detected with the previous version of our drone. We then switched to higher kV motors, but didn't set the parameter back. We realize that this is part of the issue, but we still think freefall detect should've detected an issue