PX4 accepts the takeoff command (vehicle arms and reports “takeoff detected”), but in Gazebo the drone does not receive effective upward thrust, so it stays on the ground.
In this state, PX4 logically transitions to takeoff, but the motors never execute a real climb command in the simulator.
Terminal Commands
udbhaw@udbhaw-LOQ-15IRX9:~$ cd ~/PX4-Autopilot
udbhaw@udbhaw-LOQ-15IRX9:~/PX4-Autopilot$ make px4_sitl gazebo-classic
[0/4] Performing build step for ‘sitl_gazebo-classic’
ninja: no work to do.
[3/4] cd /home/udbhaw/PX4-Autopilot/bu…w/PX4-Autopilot/build/px4_sitl_default
SITL ARGS
sitl_bin: /home/udbhaw/PX4-Autopilot/build/px4_sitl_default/bin/px4
debugger: none
model: iris
world: none
src_path: /home/udbhaw/PX4-Autopilot
build_path: /home/udbhaw/PX4-Autopilot/build/px4_sitl_default
GAZEBO_PLUGIN_PATH /usr/lib/x86_64-linux-gnu/gazebo-11/plugins::/home/udbhaw/PX4-Autopilot/build/px4_sitl_default/build_gazebo-classic
GAZEBO_MODEL_PATH /home/udbhaw/ardupilot_gazebo/models:/home/udbhaw/PX4-Autopilot/Tools/simulation/gazebo-classic/sitl_gazebo-classic/models
LD_LIBRARY_PATH /opt/ros/humble/opt/rviz_ogre_vendor/lib:/opt/ros/humble/lib/x86_64-linux-gnu:/opt/ros/humble/lib::/usr/lib/x86_64-linux-gnu/gazebo-11/plugins::/home/udbhaw/PX4-Autopilot/build/px4_sitl_default/build_gazebo-classic
empty world, setting empty.world as default
Using: /home/udbhaw/PX4-Autopilot/Tools/simulation/gazebo-classic/sitl_gazebo-classic/models/iris/iris.sdf
(gzserver:11795): GStreamer-App-CRITICAL **: 17:52:29.839: gst_app_src_push_internal: assertion ‘GST_IS_APP_SRC (appsrc)’ failed
(gzserver:11795): GLib-CRITICAL **: 17:52:29.840: g_main_loop_quit: assertion ‘loop != NULL’ failed
(gzserver:11795): GStreamer-App-CRITICAL **: 17:52:29.865: gst_app_src_push_internal: assertion ‘GST_IS_APP_SRC (appsrc)’ failed
(gzserver:11795): GStreamer-App-CRITICAL **: 17:52:29.869: gst_app_src_push_internal: assertion ‘GST_IS_APP_SRC (appsrc)’ failed
SITL COMMAND: “/home/udbhaw/PX4-Autopilot/build/px4_sitl_default/bin/px4” “/home/udbhaw/PX4-Autopilot/build/px4_sitl_default”/etc
| __ \ \ \ / / / |
| |/ / \ V / / /| |
| __/ / \ / /| |
| | / /^\ \ __ |
_| / / |_/
px4 starting.
INFO [px4] startup script: /bin/sh etc/init.d-posix/rcS 0
INFO [init] found model autostart file as SYS_AUTOSTART=10015
INFO [param] selected parameter default file parameters.bson
INFO [param] importing from ‘parameters.bson’
INFO [parameters] BSON document size 316 bytes, decoded 316 bytes (INT32:13, FLOAT:3)
INFO [param] selected parameter backup file parameters_backup.bson
INFO [dataman] data manager file ‘./dataman’ size is 7866640 bytes
etc/init.d-posix/rcS: 39: [: Illegal number:
INFO [init] PX4_SIM_HOSTNAME: localhost
INFO [simulator_mavlink] Waiting for simulator to accept connection on TCP port 4560
INFO [simulator_mavlink] Simulator connected on TCP port 4560.
INFO [lockstep_scheduler] setting initial absolute time to 2760000 us
INFO [commander] LED: open /dev/led0 failed (22)
WARN [health_and_arming_checks] Preflight Fail: ekf2 missing data
INFO [mavlink] mode: Normal, data rate: 4000000 B/s on udp port 18570 remote port 14550
Gazebo multi-robot simulator, version 11.10.2
Copyright (C) 2012 Open Source Robotics Foundation.
Released under the Apache 2 License.
[Msg] Waiting for master.
[Msg] Connected to gazebo master @ http://127.0.0.1:11345
[Msg] Publicized address: 192.168.1.48
INFO [mavlink] mode: Onboard, data rate: 4000000 B/s on udp port 14580 remote port 14540
INFO [mavlink] mode: Onboard, data rate: 4000 B/s on udp port 14280 remote port 14030
INFO [mavlink] mode: Gimbal, data rate: 400000 B/s on udp port 13030 remote port 13280
INFO [logger] logger started (mode=all)
INFO [logger] Start file log (type: full)
INFO [logger] [logger] ./log/2025-12-15/12_22_32.ulg
INFO [logger] Opened full log file: ./log/2025-12-15/12_22_32.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> INFO [tone_alarm] home set
[Wrn] [ModelDatabase.cc:212] Unable to connect to model database using [//database.config]. Only locally installed models will be available.
INFO [tone_alarm] notify negative
[Wrn] [Event.cc:61] Warning: Deleting a connection right after creation. Make sure to save the ConnectionPtr from a Connect call
INFO [commander] Ready for takeoff!
pxh> commander takeoff
pxh> INFO [commander] Armed by internal command
INFO [tone_alarm] arming warning
INFO [navigator] Using minimum takeoff altitude: 2.50 m
INFO [commander] Takeoff detected