Land Speed when never flying above LAND_ALT_LOW

On a recent hover test, I was surprised at how quickly the copter descended when switching to LAND mode to land.

The copter had never been above the LAND_ALT_LOW (10 meters).

It made me wonder if the copter has to either be above LAND_ALT_LOW, or to have flown above it for that altitude during the flight - for the copter to switch to LAND_SPEED when below LAND_ALT_LOW on LAND mode. (or technically, RTL too)

Does anyone have any information about this?

Think it’s at WPNAV_SPEED_DN until it reaches 10m and then down at LAND_SPEED.

10 meters only if that’s the value of the LAMD_ALT_LOW parameter.

The question I’m wondering about is what happens if you never fly above that altitude? Which speed will be used for landing then?

I think LAND Mode is only controlled by those 2 parameters I noted. Do you have a Rangefinder on this craft?

Do you have a flight log you can share?

Follow Up:

Tested in simulation with AC4.3 and LAND_SPEED is used below LAND_ALT_LOW - regardless of if the descent starts above or below that threshold. For example, initiating LAND mode at 5m with a LAND_ALT_LOW set to 10m began a descent at LAND_SPEED.

Right. It’s not RTL we are talking about here it’s LAND Mode. I typically end a mission with a Land command rather than RTL to hit the deck quicker.

More specifically, a flight that only ever achieves 6m, never climbing above LAND_ALT_LOW (10m) prior to selecting LAND mode commences landing and touches down at LAND_SPEED. SITL quadcopter, 4.3.3.

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Regarding RTL, as I understand it, RTL has it’s own parameter for the “high speed”: descent rate of the landing phase. But once it reaches the LAND_ALT_LOW altitude for LAND mode, it then uses the slow speed descent rate, LAND_SPEED, that is defined for the LAND parameters.

So both LAND and RTL use the same parameters for the slow speed landing phase.