VTOL Land Detector Airspeed Question

PX4 Autopilot VTOL 🚁
1

Fixed wing landing for VTOL was previously being considered as an option and is currently unsupported. The code for get landed state (in VTOL Land Detector) returns ‘false’ if not in rotary wing mode. However the logic still takes into account airspeed as a determining factor in whether landing state can be achieved. It appears this may result in the state being stuck in “Maybe Landed” with the implication being the aircraft does not disarm.

Potential issues arise in winds greater than 16 knots or when faced with wind gusts. Alternatively, a failure to calibrate, properly calibrate, or other general failure of the airspeed sensor may result in being unable to transition to “Landed” state thereby preventing auto disarm.

My question is whether or not the check for airspeed being less than LNDFW_AIRSPEED_MAX should only be performed if the vehicle status is not rotary wing? (i.e. fixed wing)

I am unsure if this is a defect or by design and request clarification of the intent of the airspeed check.

This also impacts v1.6.5 which does not have the check for rotary wing, but still appears that it should only be check if the vehicle status is not rotary wing as it appears to strictly be applicable to fixed wing landings.

2

A specific example which resulted into my looking into this logic is that my VTOL aircraft was not disarming upon landing. Log analysis indicated that there was an issue with the airspeed sensor / calibration. Additionally, the airspeed never we below 10 m/s, primarily due to the issue with the airspeed sensor ( all data was essentially junk ).

The result was landing but the aircraft never disarmed, it appeared to be stuck in the “maybe landed” state.

3

The current code is intentional, but was a short term compromise. We need to carefully consider how this should work overall.

The land detector is basically split into MC and FW implementations. Ideally I think we’d want to switch back and forth, with some special consideration during transitions.

FYI @sanderux