Precision Landing (PLND) on VTOL fixed-wing drone

JG_Drohne · August 20, 2025, 8:25am

Hi everyone,

I’m working on precision landing for a VTOL-plane-drone (tilt-rotor style). The drone can take off and land vertically like a multicopter, then transition midair to fixed-wing flight by tilting the rotors.

For landing, I’m using visual detection of ArUco markers on the ground with a companion computer. The setup and parameters are the same ones I successfully used before with a regular ardupilot hexacopter, where the precision landing worked flawlessly!

Current setup:

Landing mode: QLand
PLND enabled
All other PLND parameters configured sameway as with the hexacopter
Companion computer sending vision-based landing target data (tested)

Problem:
On the VTOL, the system does not react at all to the visual landing target. It just behaves as if no precision landing data was available. Mission PLanner shows massages saying “Target found” “Initializing Complete” but when we want to land, it doe not position itself to the target.

Has anyone experienced a similar issue with precision landing on VTOLs, fixed-wing, or plane-drones? Is there something specific about the transition/QLand implementation that prevents or overwrites PLND from working?

Any hints, or recommendations would be greatly appreciated.

Thanks in advance!

Marcus_Hartman · August 22, 2025, 4:08pm

I am actually working through the same issues using an IrLock MarkOne with a VTOL fixed wing using plane 4.6.0. Precision Landing was just added in 4.5.0 for plane. Maybe it just isn’t fully mature yet? We are going to explore using a companion computer now.

Marcus_Hartman · August 23, 2025, 12:32am

I finally got mine to work today. I had to also run the Precision Landing Lua Script to get it to track to the target. Im on 4.6.0 and used the 4.5.0 commit lua script. Are you doing that?

JG_Drohne · August 25, 2025, 10:55am

Hello,

we are also using the 4.6.0 ArduPilot firmware. Our setup is a Raspberry Pi with the Raspberry Pi camera module, detecting ArUco markers. The Pi sends angles and other information via the MAVLink command LANDING_TARGET over UART to the telemetry port of the Orange Cube.

We haven’t used the Lua script – I’m not exactly sure what that is or where to find it. Could you point me to some documentation or examples on how to use the Precision Landing Lua script with Plane?

Thanks a lot for the hint!

Marcus_Hartman · August 25, 2025, 11:47am

Plane Precision Landing

This script implements a precision landing system for VTOL fixed wing aircraft (quadplanes).

Precision positioning over a landing sensor is supported in QLOITER, QLAND, QRTL and AUTO landing.

Parameters

Beyond the normal PLND parameters the script adds 2 additional parameters to control it’s behaviour. The parameters are:

PLND_ALT_CUTOFF

This is an optional altitude in meters below which the precision landing system will stop correcting the landing position. Many precision landing sensors have poor performance at low altitudes, so setting this to around 5 meters is advisable. A value of zero disables this cutoff.

PLND_DIST_CUTOFF

This is a maximum horizontal distance in meters that will be accepted for a landing corrections. If this parameter is greater than zero and the precision landing subsystem gives a distance beyond this distance then precision landing correction will stop and the last landing position will be used.

Operation

You should first install and configure a precision landing sensor as described here:

then you should enable the precision subsystem and install the lua script in the APM/scripts folder of your flight controller.

The script will start adjusting the landing position only when in the descent phase of an automatic VTOL landing. The PPLD log message can be used to analyse the performance of the precision landing.

It is advisable to have a manual pilot able to take over control in a mode such as QLOITER for instances where the precision landing system may malfunction.

Moving Target

If the PLND_OPTIONS bit for a moving target is enabled then the vehicle will be set to track the estimated target velocity during descent

Precision QLoiter

To enable precision position hold in QLOITER you will need to use auxiliary function 39 (PRECISION_LOITER) on an R/C switch or via GCS auxiliary switch buttons. When enabled the vehicle will position itself above the landing target. Height control is under user control.

github.com/ArduPilot/ardupilot

libraries/AP_Scripting/applets/plane_precland.lua

Plane-4.5

--[[
 support precision landing on quadplanes

 This is a very simple implementation intended to act as a framework
 for development of a custom solution
--]]

local PARAM_TABLE_KEY = 12
local PARAM_TABLE_PREFIX = "PLND_"

local MAV_SEVERITY = {EMERGENCY=0, ALERT=1, CRITICAL=2, ERROR=3, WARNING=4, NOTICE=5, INFO=6, DEBUG=7}

local MODE_QLAND = 20
local MODE_QLOITER = 19

local AUX_PRECLOITER = 39

local precloiter_enabled = false

-- bind a parameter to a variable

This file has been truncated. show original

If you enable SCR_ENABLE then you can use mavftp to load in the lua script. Thats what finally got the q plane to move to the landing target for me.

JG_Drohne · October 22, 2025, 12:24pm

“Thanks a lot @Marcus_Hartman!
After applying the Lua-Script and tuning the parameters, it finally worked.
We successfully managed to land our fixed-wing aircraft vertically as a quadcopter in PLND mode . Really appreciate your support!”