How to make VTOL fixed wing AUTO belly land?

How to set ardupilot to make AUTO Belly-land a Tailsitter VTOL drone?
When planning an AUTO land as part of a mission the drone tries to transition to vertical flight by default (even without entering the “transition-to-copter” command). How to make it belly land?
Looks like the code for VTOL doesn’t allow for this (vertical takeoff, then belly land).
Is there a way to hack the ardupilot code to achieve this?
If yes, I’m willing to pay for someone who can help me with this.

Just to clarify, you want it to fly down to the ground and land on a runway or cleared grass strip as though it were not VTOL-capable?

I’m curious, why would you want VTOL takeoff but not VTOL landing?

Many of the tailsitter planes that I’ve seen would probably break something if belly-landed.

Hi Chris, tailsitters are not good in wind, and when windy it actually helps to shorten the landing. On our experience we have seen more than 90% of the field operations are okay with a belly landing, except if its maybe a dense jungle ;_0
Our design doesn’t get damaged by belly landing so it would be the simplest approach, whether is windy or not belly landing is just so simple too. But I have seen that when VTOL is enabled on arduplaneit won’t just belly land, except if I’m missing something. Someone suggested to change Q_ENABLE to “2” which I have yet to test.

I doubt setting Q_ENABLE to 2 would help. I suspect the code currently assumes that VTOL implies you want both takeoff and landing. In fact you’re looking for VTO without the L. :slight_smile:

Any TVBS can belly land as a fixed wing using RC Aux function 89 to force the motor tilt vertical at idle throttle…I takeoff VTOL (drifting backward as I climb to 15 ft for forward transition) and land fixed wing all the time in high wind
in normal wind I VTOL land

C1 Chaser, S800 , z84 all do it

that’s exactly what I believe the code has been made for, so the idea is to change this and make belly landing available anytime is required

but do you belly land in AUTO as part of a mission or do you do it manually? if in in AUTO, can you explain what parameters you have changed so that it doesn’t try Vertical landing everytime?

Hey, I think you have to set the Q_Option parameter option 3 to true : “Allow FW Land” and than program the end of the mission with a Land command at the specific coordinates. I do not think it will work if the mission ends with RTL since that will perform a Vtol land.

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no, that is for older GCS that did not support different VTOL and FW NAV_LAND commands…

while I have not flow a mission and belly landed, it should be easy to do:

  1. at the end of the mission set a NAV_LAND_CMD (fixed wind landing)…see wiki about setting up approaches, and parameters for an Automatic Landing
  2. setup the RCx_OPTION =89 on an unused RC channel…make sure that the TX sets this channel low (disabled)
  3. before the above NAV_LAND_CMD add a DO_AUX_FUNCTION (89,2) to activate the mid position of the flare aux function to tilt the motors up when the throttle is cut by the mission as it final flares…

this will VTOL takeoff…climb to 15m, transition, fly to WP2 and then WP 3, then proceed to approach to a fixed wing landing at WP5, but will tilt the motors up in the final flare when AP cuts the throttle

you can easily verify this in SITL

Note: image shows DO_AUX_FUNCTION using switch high (2), this will force the landing pitch…use (1) to allow AP to control the final flare pitch…sorry

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Thanks for taking the time to post this. My tailsitter does not have tilt motors. I have tried the same type of principle on the landing but without the DO_AUX_Function obviously, and it does not belly land, it attempts to go back to vertical flight and land.

there are two types of land waypoint commands…NAV_LAND and NAV_VTOL_LAND…which did you use?

also there is an option bit that makes NAV_LAND commands be interpretted as fixed wing LAND commands instead of NAV_VTOL_LAND…be sure its SET(bit 2 of Q_OPTIONS bitmask param)

I did use the Land command (without the VTOL of course).

actually at the same time you replied I was reading about this, how come didn’t see it before :-), thank you very much though, I think this is what I was looking for. I’ll test it next week and report.