I am trying to simulate multi vtol simulation in GZ with ROS2
I am using following gazebo_terrain_generator for the GZ world.
world and model spawn successfully, but as soon as the model touches the ground, it shows
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array, which is of size 4
here is terminal output
mubashir@mubashir:~/PX4-Autopilot$ PX4_GZ_MODEL_POSE="0,-1" ./build/px4_sitl_default/bin/px4 -i 1
INFO [px4] instance: 1
INFO [px4] working directory /home/mubashir/PX4-Autopilot/build/px4_sitl_default/rootfs/1
______ __ __ ___
| ___ \ \ \ / / / |
| |_/ / \ V / / /| |
| __/ / \ / /_| |
| | / /^\ \ \___ |
\_| \/ \/ |_/
px4 starting.
INFO [px4] startup script: /bin/sh etc/init.d-posix/rcS 1
env SYS_AUTOSTART: 4001
INFO [param] selected parameter default file parameters.bson
INFO [param] importing from 'parameters.bson'
INFO [parameters] BSON document size 370 bytes, decoded 370 bytes (INT32:15, FLOAT:4)
INFO [param] selected parameter backup file parameters_backup.bson
INFO [dataman] data manager file './dataman' size is 1208528 bytes
INFO [init] Gazebo simulator 8.10.0
INFO [init] Starting gazebo with world: /home/mubashir/PX4-Autopilot/Tools/simulation/gz/worlds/prayag.sdf
INFO [init] Starting gz gui
INFO [init] Waiting for Gazebo world...
Dbg DART Bullet heightfield AABB: min = {-1154.87, -1148.88, -260}, max = {1154.87, 1148.88, 260} (will be translated by z=260)
INFO [init] Gazebo world is ready
INFO [init] Gazebo model pose: 0 -1 0 0 0 0
INFO [init] Spawning Gazebo model
Warning [Utils.cc:132] [/sdf/model[@name="standard_vtol"]/link[@name="base_link"]/sensor[@name="imu_sensor"]/gz_frame_id:/home/mubashir/PX4-Autopilot/Tools/simulation/gz/models/standard_vtol/model.sdf:L134]: XML Element[gz_frame_id], child of element[sensor], not defined in SDF. Copying[gz_frame_id] as children of [sensor].
Warning [Utils.cc:132] [/sdf/model[@name="standard_vtol"]/link[@name="base_link"]/sensor[@name="air_pressure_sensor"]/gz_frame_id:/home/mubashir/PX4-Autopilot/Tools/simulation/gz/models/standard_vtol/model.sdf:L193]: XML Element[gz_frame_id], child of element[sensor], not defined in SDF. Copying[gz_frame_id] as children of [sensor].
Warning [Utils.cc:132] [/sdf/model[@name="standard_vtol"]/link[@name="base_link"]/sensor[@name="magnetometer_sensor"]/gz_frame_id:/home/mubashir/PX4-Autopilot/Tools/simulation/gz/models/standard_vtol/model.sdf:L206]: XML Element[gz_frame_id], child of element[sensor], not defined in SDF. Copying[gz_frame_id] as children of [sensor].
Warning [Utils.cc:132] [/sdf/model[@name="standard_vtol"]/link[@name="base_link"]/sensor[@name="navsat_sensor"]/gz_frame_id:/home/mubashir/PX4-Autopilot/Tools/simulation/gz/models/standard_vtol/model.sdf:L232]: XML Element[gz_frame_id], child of element[sensor], not defined in SDF. Copying[gz_frame_id] as children of [sensor].
INFO [gz_bridge] world: prayag, model: standard_vtol_1
INFO [lockstep_scheduler] setting initial absolute time to 4184000 us
INFO [init] Setting camera to follow standard_vtol_1
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
INFO [init] Camera follow offset set to -2.0, -2.0, 2.0
Warning [Utils.cc:132] [/sdf/model[@name="standard_vtol"]/link[@name="base_link"]/sensor[@name="imu_sensor"]/gz_frame_id:<data-string>:L188]: XML Element[gz_frame_id], child of element[sensor], not defined in SDF. Copying[gz_frame_id] as children of [sensor].
Warning [Utils.cc:132] [/sdf/model[@name="standard_vtol"]/link[@name="base_link"]/sensor[@name="air_pressure_sensor"]/gz_frame_id:<data-string>:L201]: XML Element[gz_frame_id], child of element[sensor], not defined in SDF. Copying[gz_frame_id] as children of [sensor].
Warning [Utils.cc:132] [/sdf/model[@name="standard_vtol"]/link[@name="base_link"]/sensor[@name="magnetometer_sensor"]/gz_frame_id:<data-string>:L223]: XML Element[gz_frame_id], child of element[sensor], not defined in SDF. Copying[gz_frame_id] as children of [sensor].
Warning [Utils.cc:132] [/sdf/model[@name="standard_vtol"]/link[@name="base_link"]/sensor[@name="navsat_sensor"]/gz_frame_id:<data-string>:L229]: XML Element[gz_frame_id], child of element[sensor], not defined in SDF. Copying[gz_frame_id] as children of [sensor].
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
INFO [commander] LED: open /dev/led0 failed (22)
WARN [health_and_arming_checks] Preflight Fail: ekf2 missing data
WARN [health_and_arming_checks] Preflight Fail: system power unavailable
WARN [health_and_arming_checks] Preflight Fail: No connection to the GCS
INFO [tone_alarm] home set
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
INFO [uxrce_dds_client] init UDP agent IP:127.0.0.1, port:8888
INFO [mavlink] mode: Normal, data rate: 4000000 B/s on udp port 18571 remote port 14550
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
INFO [mavlink] mode: Onboard, data rate: 4000000 B/s on udp port 14581 remote port 14541
INFO [mavlink] mode: Onboard, data rate: 4000 B/s on udp port 14281 remote port 14031
INFO [mavlink] mode: Gimbal, data rate: 400000 B/s on udp port 13031 remote port 13281
INFO [logger] logger started (mode=all)
INFO [logger] Start file log (type: full)
INFO [logger] [logger] ./log/2026-02-18/22_36_11.ulg
INFO [logger] Opened full log file: ./log/2026-02-18/22_36_11.ulg
INFO [mavlink] MAVLink only on localhost (set param MAV_{i}_BROADCAST = 1 to enable network)
INFO [mavlink] MAVLink only on localhost (set param MAV_{i}_BROADCAST = 1 to enable network)
INFO [px4] Startup script returned successfully
pxh> Warning [Utils.cc:132] [/sdf/model[@name="standard_vtol"]/link[@name="base_link"]/sensor[@name="imu_sensor"]/gz_frame_id:<data-string>:L188]: XML Element[gz_frame_id], child of element[sensor], not defined in SDF. Copying[gz_frame_id] as children of [sensor].
Warning [Utils.cc:132] [/sdf/model[@name="standard_vtol"]/link[@name="base_link"]/sensor[@name="air_pressure_sensor"]/gz_frame_id:<data-string>:L201]: XML Element[gz_frame_id], child of element[sensor], not defined in SDF. Copying[gz_frame_id] as children of [sensor].
Warning [Utils.cc:132] [/sdf/model[@name="standard_vtol"]/link[@name="base_link"]/sensor[@name="magnetometer_sensor"]/gz_frame_id:<data-string>:L223]: XML Element[gz_frame_id], child of element[sensor], not defined in SDF. Copying[gz_frame_id] as children of [sensor].
Warning [Utils.cc:132] [/sdf/model[@name="standard_vtol"]/link[@name="base_link"]/sensor[@name="navsat_sensor"]/gz_frame_id:<data-string>:L229]: XML Element[gz_frame_id], child of element[sensor], not defined in SDF. Copying[gz_frame_id] as children of [sensor].
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
[Err] [MulticopterMotorModel.cc:529] You tried to access index 4 of the Actuator velocity array which is of size 4
WARN [health_and_arming_checks] Preflight Fail: No connection to the GCS
