PX4 User Guide
  • Introduction
  • Getting Started
    • Basic Concepts
    • Vehicles/Frames
    • Flight Controllers
    • Sensors
    • Radio Systems
    • Flight Modes
    • Vehicle Status Notifications
      • LED Meanings
      • Tune/Sound Meanings
      • Preflight Checks
    • Payloads & Cameras
    • Flight Reporting
  • Basic Assembly
    • Mounting the Flight Controller
    • Mounting the GPS/Compass
    • Vibration Isolation
    • Cable Wiring
    • CUAV Pixhawk V6X Wiring QuickStart
    • CUAV V5+ Wiring Quickstart
    • CUAV V5 nano Wiring Quickstart
    • Holybro Pixhawk 6C Wiring Quickstart
    • Holybro Pixhawk 6X Wiring Quickstart
    • Holybro Pixhawk 5X Wiring Quickstart
    • Holybro Pixhawk 4 Wiring Quickstart - Discontinued
    • Holybro Pixhawk 4 Mini Wiring Quickstart - Discontinued
    • Holybro Durandal Wiring Quickstart
    • Holybro Pix32 v5 Wiring Quickstart
    • Cube Wiring Quickstart
    • Pixracer Wiring Quickstart
    • mRo (3DR) Pixhawk Wiring Quickstart
  • Standard Configuration
    • Firmware
    • Airframe
    • Sensor Orientation
    • Compass
    • Gyroscope
    • Accelerometer
    • Airspeed
    • Level Horizon Calibration
    • Radio Setup
    • Joystick Setup
    • Flight Modes
    • Battery
    • Safety
      • Failsafe Simulation
    • ESC Calibration
    • Actuators
    • Autotune
  • Vehicle Types & Setup
    • Multicopters
      • Multicopter Config/Tuning
        • MC Filter/Control Latency Tuning
        • MC PID Tuning (Manual/Basic)
        • MC PID Tuning Guide (Manual/Advanced)
        • MC Setpoint Tuning (Trajectory Generator)
          • MC Jerk-limited Type Trajectory
        • Multicopter Racer Setup
      • X500 v2 (Pixhawk 6C)
      • X500 v2 (Pixhawk 5X)
      • X500 (Pixhawk 4)
      • S500 V2 (Pixhawk 4)
      • DJI F450 (CUAV v5+)
      • DJI F450 (CUAV v5 nano)
      • QAV250 (Pixhawk4 Mini) - Discontinued
      • DJI F450 + RTK (Pixhawk 3 Pro)
      • QAV250 (Pixhawk Mini)
      • QAV-R 5" Racer (Pixracer)
      • Omnicopter
    • Planes
      • Fixed Wing Config/Tuning
        • Fixedwing PID Tuning Guide
        • Fixedwing Advanced Tuning Guide
        • Fixedwing Trimming Guide
      • Reptile Dragon 2 (ARK6X)
      • Turbo Timber Evolution (Pixhawk 4 Mini)
      • Wing Wing Z84 (Pixracer)
    • VTOL
      • VTOL Config/Tuning
        • QuadPlane Configuration
        • Back-transition Tuning
        • VTOL w/o Airspeed Sensor
        • VTOL Weather Vane
      • Standard VTOL
        • FunCub QuadPlane (Pixhawk)
        • Ranger QuadPlane (Pixhawk)
        • Falcon Vertigo QuadPlane (Dropix)
      • Tailsitter VTOL
        • Build: TBS Caipiroshka Tailsitter Build (Pixracer)
      • Tiltrotor VTOL
        • Build: Convergence Tiltrotor (Pixfalcon)
    • Airships (experimental)
    • Autogyros (experimental)
      • ThunderFly Auto-G2 (Holybro pix32)
    • Balloons (experimental)
    • Helicopter (experimental)
      • Helicopter Config/Tuning
    • Rovers (experimental)
      • Traxxas Stampede
    • Submarines (experimental)
      • BlueROV2
    • Airframes Reference
  • Flying
    • First Flight Guidelines
    • Flying 101
    • Missions
      • Package Delivery Mission
    • GeoFence
    • Safety Point Planning
    • Flight Modes
      • Position Mode (MC)
      • Altitude Mode (MC)
      • Manual/Stabilized Mode (MC)
      • Acro Mode (MC)
      • Orbit Mode (MC)
      • Position Mode (FW)
      • Altitude Mode (FW)
      • Stabilized Mode (FW)
      • Acro Mode (FW)
      • Manual Mode (FW)
      • Takeoff Mode
      • Land Mode
      • Return Mode
      • Hold Mode
      • Mission Mode
      • Follow Me Mode
      • Offboard Mode
    • Terrain Following/Holding
  • Flight Log Analysis
    • Log Analysis using Flight Review
    • Log Analysis using PlotJuggler
  • Advanced Configuration
    • Finding/Updating Parameters
    • Full Parameter Reference
    • ECL/EKF Overview & Tuning
    • Flight Termination Configuration
    • Bootloader Flashing onto Betaflight Systems
    • Land Detector Configuration
    • Prearm/Arm/Disarm Configuration
    • IMU Factory Calibration
    • Sensor Thermal Compensation
    • Compass Power Compensation
    • Advanced Controller Orientation
    • Static Pressure Buildup
    • Serial Port Configuration
    • MAVLink Telemetry (OSD/GCS)
    • PX4 Ethernet Setup
    • Bootloader Update
  • Hardware (Drones&Parts)
    • Complete Vehicles
      • ModalAI Starling
      • PX4 Vision Kit
      • MindRacer BNF & RTF
        • MindRacer 210
        • NanoMind 110
      • Holybro Kopis 2
      • Bitcraze Crazyflie 2.1
    • Flight Controllers (Autopilots)
      • Pixhawk Series
        • Silicon Errata
      • Pixhawk Standard Autopilots
        • CUAV Pixhawk V6X (FMUv6X)
        • Holybro Pixhawk 6X (FMUv6X)
        • Holybro Pixhawk 6C (FMUv6C)
        • Holybro Pixhawk 6C Mini(FMUv6C)
        • Holybro Pix32 v6 (FMUv6C)
        • Holybro Pixhawk 5X (FMUv5X)
        • Holybro Pixhawk 4 (FMUv5) - Discontinued
        • Holybro Pixhawk 4 Mini (FMUv5) - Discontinued
        • Drotek Pixhawk 3 Pro (FMUv4pro)
        • mRo Pixracer (FMUv4)
        • Hex Cube Black (FMUv3)
        • mRo Pixhawk (FMUv3)
        • Holybro Pixhawk Mini (FMUv3) - Discontinued
      • Manufacturer-Supported Autopilots
        • AirMind MindPX
        • AirMind MindRacer
        • ARK Electronics ARKV6X
        • CUAV X7
        • CUAV Nora
        • CUAV V5+ (FMUv5)
        • CUAV V5 nano (FMUv5)
        • CUAV Pixhack v3 (FMUv3)
        • CubePilot Cube Orange+ (CubePilot)
        • CubePilot Cube Orange (CubePilot)
        • CubePilot Cube Yellow (CubePilot)
        • Holybro Kakute H7v2
        • Holybro Kakute H7mini
        • Holybro Kakute H7
        • Holybro Durandal
        • Holybro Pix32 v5
        • ModalAI Flight Core v1
        • ModalAI VOXL Flight
        • ModalAI VOXL 2
        • mRobotics-X2.1 (FMUv2)
        • mRo Control Zero F7)
        • NXP RDDRONE-FMUK66 FMU
        • Sky-Drones AIRLink
        • SPRacing SPRacingH7EXTREME
        • ThePeach FCC-K1
        • ThePeach FCC-R1
      • Experimental Autopilots
        • BeagleBone Blue
        • Raspberry Pi 2/3 Navio2
        • Raspberry Pi 2/3/4 PilotPi
          • PilotPi with Raspberry Pi OS
          • PilotPi with Ubuntu Server
      • Discontinued Autopilots/Vehicles
        • Drotek Dropix (FMUv2)
        • Omnibus F4 SD
        • BetaFPV Beta75X 2S Brushless Whoop
        • Bitcraze Crazyflie 2.0
        • Aerotenna OcPoC-Zynq Mini
        • CUAV v5
        • Holybro Kakute F7 (Discontinued)
        • Holybro Pixfalcon
        • Holybro pix32 (FMUv2)
        • mRo AUAV-X2
        • 3DR Pixhawk 1
        • Snapdragon Flight
        • Intel® Aero RTF Drone (Discontinued)
      • Pixhawk Autopilot Bus (PAB) & Carriers
        • ARK Electronics Pixhawk Autopilot Bus Carrier
    • Flight Controller Peripherals
      • ADSB/FLARM (Traffic Avoidance)
      • Air Traffic Avoidance: ADSB/FLARM
      • Air Traffic Avoidance: UTM
      • Airspeed Sensors
        • TFSlot Airspeed Sensor
      • Barometers
      • Camera
      • Distance Sensors (Rangefinders)
        • Lightware SFxx Lidar
        • Ainstein US-D1 Standard Radar Altimeter
        • LeddarOne Lidar
        • Benewake TFmini Lidar
        • Lidar-Lite
        • TeraRanger
        • Lanbao PSK-CM8JL65-CC5
        • Avionics Anonymous Laser Altimeter UAVCAN Interface
      • ESCs & Motors
        • PWM ESCs and Servos
        • DShot ESCs
        • OneShot ESCs and Servos
        • DroneCAN ESCs
          • Zubax Telega
          • PX4 Sapog ESC Firmware
            • Holybro Kotleta
            • Zubax Orel
        • VESC
      • TBS Crossfire (CRSF) Telemetry
      • FrSky Telemetry
      • Gimbal (Mount) Configuration
      • GPS/Compass
        • ARK GPS
        • Holybro DroneCAN M8N GPS
        • LOCOSYS Hawk A1 GNSS
        • Hex Here2
        • Holybro M8N & M9N GPS
        • Sky-Drones SmartAP GPS
      • Grippers
        • Servo Gripper
      • Optical Flow
        • ARK Flow
        • PMW3901
        • PX4FLOW (Deprecated)
      • Precision Landing
      • Parachute
      • Power Modules/PDB
        • CUAV HV pm
        • CUAV CAN PMU
        • Holybro PM02
        • Holybro PM07
        • Holybro PM06 V2
        • Holybro PM02D (digital)
        • Holybro PM03D (digital)
        • Pomegranate Systems Power Module
        • Sky-Drones SmartAP PDB
      • Satellite Coms (Iridium/RockBlock)
      • Telemetry Radios
        • SiK Radio
          • RFD900 (SiK) Telemetry Radio
          • HolyBro (SIK) Telemetry Radio
        • Telemetry Wifi
          • ESP8266 WiFi Module
          • ESP32 WiFi Module
          • 3DR Telemetry Wifi (Discontinued)
        • Microhard Serial Telemetry Radio
          • ARK Electron Microhard Serial Telemetry Radio
          • Holybro Microhard P900 Telemetry Radio
        • CUAV P8 Telemetry Radio
        • HolyBro XBP9X - Discontinued
      • RTK GPS
        • ARK RTK GPS
        • RTK GPS Heading with Dual u-blox F9P
        • CUAV C-RTK
        • CUAV C-RTK2 PPK/RTK GNSS
        • CUAV C-RTK 9Ps
        • Femtones MINI2 Receiver
        • Freefly RTK GPS
        • Holybro H-RTK-F9P
        • Holybro H-RTK-M8P
        • Holybro H-RTK Unicore UM982 GPS
        • Locosys Hawk R1
        • Locosys Hawk R2
        • Septentrio AsteRx-RIB
        • Septentrio mosaic-go
        • Trimble MB-Two
        • CubePilot Here+ (Discontined)
      • Remote ID
      • Smart Batteries
        • Rotoye Batmon Battery Smartification Kit
      • Tachometers (Revolution Counters)
        • ThunderFly TFRPM01 Tachometer Sensor
      • I2C Peripherals
        • I2C bus accelerators
        • TFI2CADT01 I2C address translator
      • CAN Peripherals
      • DroneCAN Peripherals
        • PX4 DroneCAN Firmware
        • ARK CANnode
    • Companion Computers
      • Pixhawk + Companion Setup
        • RasPi Pixhawk Companion
      • Companion Computer Peripherals
      • Holybro Pixhawk RPI CM4 Baseboard
      • Auterion Skynode
      • Computer Vision
        • Obstacle Avoidance
        • Safe Landing
        • Collision Prevention
        • Path Planning Interface
        • Motion Capture (MoCap)
        • Visual Inertial Odometry (VIO)
          • Realsense T265 Tracking Camera (VIO)
      • Video Streaming
  • Development
    • Getting Started
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    • Concepts
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      • PX4 Flight Stack Architecture
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    • Hardware
      • Flight Controller Reference Design
      • Manufacturer’s Board Support Guide
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        • NuttX Board Porting Guide
      • Serial Port Mapping
      • Airframes
        • Adding a New Airframe
      • Device Drivers
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          • Port-Configurable Serial Drivers
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    • Middleware
      • uORB Messaging
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On this page
  • Failsafe Actions
  • QGroundControl Safety Setup
  • Low Battery Failsafe
  • RC Loss Failsafe
  • Data Link Loss Failsafe
  • Geofence Failsafe
  • Return Mode Settings
  • Land Mode Settings
  • Other Failsafe Settings
  • Position (GPS) Loss Failsafe
  • Offboard Loss Failsafe
  • Mission Feasibility Checks
  • Traffic Avoidance Failsafe
  • Quad-chute Failsafe
  • Failure Detector
  • Attitude Trigger
  • External Automatic Trigger System (ATS)
  • Emergency Switches
  • Kill Switch
  • Arm/Disarm Switch
  • Return Switch
  • Other Safety Settings
  • Auto-disarming Timeouts
  • Further Information
  1. Standard Configuration

Safety

PreviousBatteryNextFailsafe Simulation

Last updated 1 year ago

PX4 has a number of safety features to protect and recover your vehicle if something goes wrong:

  • Failsafes allow you to specify areas and conditions under which you can safely fly, and the that will be performed if a failsafe is triggered (for example, landing, holding position, or returning to a specified point). The most important failsafe settings are configured in the QGroundControl page. Others must be configured via .

  • on the remote control can be used to immediately stop motors or return the vehicle in the event of a problem.

Failsafe Actions

When a failsafe is triggered, the default behavior (for most failsafes) is to enter Hold for seconds before performing an associated failsafe action. This gives the user time to notice what is happening and override the failsafe if needed. In most cases this can be done by using RC or a GCS to switch modes (note that during the failsafe-hold, moving the RC sticks does not trigger an override).

The list below shows the set of all failsafe actions, ordered in increasing severity. Note that different types of failsafe may not support all of these actions.

Action
Description

None/Disabled

No action. The failsafe will be ignored.

Warning

A warning message will be sent (i.e. to QGroundControl).

The vehicle will enter Hold mode. For multicopters this means the vehicle will hover, while for fixed/wing the vehicle will circle.

The vehicle will enter Land mode, and lands immediately.

Disarm

Stops the motors immediately.

If multiple failsafes are triggered, the more severe action is taken. For example if both RC and GPS are lost, and manual control loss is set to and GCS link loss to , Land is executed.

:::tip The exact behavior when different failsafes are triggered can be tested with the . :::

QGroundControl Safety Setup

The QGroundControl Safety Setup page is accessed by clicking the QGroundControl icon, Vehicle Setup, and then Safety in the sidebar). This includes the most important failsafe settings (battery, RC loss etc.) and the settings for the triggered actions Return and Land.

Low Battery Failsafe

The low battery failsafe is triggered when the battery capacity drops below one (or more warning) level values.

The most common configuration is to set the values and action as above (with Warn > Failsafe > Emergency). With this configuration the failsafe will trigger warning, then return, and finally landing if capacity drops below the respective levels.

The settings and underlying parameters are shown below.

Setting
Parameter
Description

Failsafe Action

Battery Warn Level

Percentage capacity for warnings (or other actions).

Battery Failsafe Level

Percentage capacity for Return action (or other actions if a single action selected).

Battery Emergency Level

Percentage capacity for triggering Land (immediately) action.

RC Loss Failsafe

The RC Loss failsafe may be triggered if the RC transmitter link is lost.

Additional (and underlying) parameter settings are shown below.

Parameter
Setting
Description

RC Loss Timeout

Time after RC stops updating supplied data that the RC link is considered lost. This must be kept short because the vehicle will continue to fly using the old RC data until the timeout triggers.

Failsafe Reaction Delay

Delay in seconds between failsafe condition being triggered (COM_RC_LOSS_T) and failsafe action (RTL, Land, Hold). In this state the vehicle waits in hold mode for the RC system to reconnect. This might be set longer for long-range flights so that intermittent connection loss doesn't immediately invoke the failsafe. It can be to zero so that the failsafe triggers immediately.

Failsafe Action

Disabled, Loiter, Return, Land, Disarm, Terminate.

RC Loss Exceptions

Set the modes in which RC loss is ignored: Mission, Hold, Offboard.

Data Link Loss Failsafe

The settings and underlying parameters are shown below.

Setting
Parameter
Description

Data Link Loss Timeout

Amount of time after losing the data connection before the failsafe will trigger.

Failsafe Action

Disabled, Hold mode, Return mode, Land mode, Disarm, Terminate.

Geofence Failsafe

The Geofence Failsafe is a "virtual" cylinder centered around the home position. If the vehicle moves outside the radius or above the altitude the specified Failsafe Action will trigger.

Setting
Parameter
Description

Action on breach

None, Warning, Hold mode, Return mode, Terminate, Land.

Max Radius

Horizontal radius of geofence cylinder. Geofence disabled if 0.

Max Altitude

Height of geofence cylinder. Geofence disabled if 0.

The following settings also apply, but are not displayed in the QGC UI.

Setting
Parameter
Description

Geofence altitude mode

Altitude reference used: 0 = WGS84, 1 = AMSL.

Geofence counter limit

Set how many subsequent position measurements outside of the fence are needed before geofence violation is triggered.

Geofence source

Set whether position source is estimated global position or direct from the GPS device.

Preemptive geofence triggering

(Experimental) Trigger geofence if current motion of the vehicle is predicted to trigger the breach (rather than late triggering after the breach).

Circuit breaker for flight termination

Enables/Disables flight termination action (disabled by default).

Return Mode Settings

The settings and underlying parameters are shown below:

Setting
Parameter
Description

Climb to altitude

Vehicle ascend to this minimum height (if below it) for the return flight.

Return behaviour

Choice list of Return then: Land, Loiter and do not land, or Loiter and land after a specified time.

Loiter Altitude

If return with loiter is selected you can also specify the altitude at which the vehicle hold.

Loiter Time

If return with loiter then land is selected you can also specify how long the vehicle will hold.

Land Mode Settings

The settings and underlying parameters are shown below:

Setting
Parameter
Description

Disarm After

Select checkbox to specify that the vehicle will disarm after landing. The value must be non-zero but can be a fraction of a second.

Landing Descent Rate

Rate of descent (MC only).

Other Failsafe Settings

Position (GPS) Loss Failsafe

The Position Loss Failsafe is triggered if the quality of the PX4 position estimate falls below acceptable levels (this might be caused by GPS loss) while in a mode that requires an acceptable position estimate.

  • 0: Remote control available. Switch to Altitude mode if a height estimate is available, otherwise Stabilized mode.

  • 1: Remote control not available. Switch to Land mode if a height estimate is available, otherwise enter flight termination.

The relevant parameters for all vehicles shown below.

Parameter
Description

Delay after loss of position before the failsafe is triggered.

Position control navigation loss response during mission. Values: 0 - assume use of RC, 1 - Assume no RC.

Parameters that only affect Fixed-wing vehicles:

Parameter
Description

Loiter time (waiting for GPS recovery before it goes into land or flight termination). Set to 0 to disable.

Fixed roll/bank angle while circling.

Offboard Loss Failsafe

The Offboard Loss Failsafe is triggered if the offboard link is lost while under Offboard control. Different failsafe behaviour can be specified based on whether or not there is also an RC connection available.

The relevant parameters are shown below:

Parameter
Description

Delay after loss of offboard connection before the failsafe is triggered.

Failsafe action if RC is available: Position mode, Altitude mode, Manual mode, Return mode, Land mode, Hold mode.

Mission Feasibility Checks

A number of checks are run to ensure that a mission can only be started if it is feasible. For example, the checks ensures that the first waypoint isn't too far away, and that the mission flight path doesn't conflict with any geofences.

Traffic Avoidance Failsafe

The relevant parameters are shown below:

Parameter
Description

Set the failsafe action: Disabled, Warn, Return mode, Land mode.

Quad-chute Failsafe

The parameters that control when the quad-chute will trigger are listed in the table below.

Parameter
Description

Maximum quad-chute height, below which the quad-chute failsafe cannot trigger. This prevents high altitude quad-chute descent, which can drain the battery (and itself cause a crash). The height is relative to ground, home, or the local origin (in preference order, depending on what is available).

Altitude loss threshold for quad-chute triggering during VTOL transition to fixed-wing flight. The quad-chute is triggered if the vehicle falls this far below its initial altitude before completing the transition.

Minimum altitude above Home for fixed-wing flight. When the altitude drops below this value in fixed-wing flight the vehicle a quad-chute is triggered.

Absolute roll threshold for quad-chute triggering in FW mode.

Absolute pitch threshold for quad-chute triggering in FW mode.

Failure Detector

The failure detector allows a vehicle to take protective action(s) if it unexpectedly flips, or if it is notified by an external failure detection system.

Attitude Trigger

The failure detector can be configured to trigger if the vehicle attitude exceeds predefined pitch and roll values for longer than a specified time.

The relevant parameters are shown below:

Parameter
Description

Flight termination circuit breaker. Unset from 121212 (default) to enable flight termination due to FailureDetector or FMU loss.

Maximum allowed pitch (in degrees).

Maximum allowed roll (in degrees).

External Automatic Trigger System (ATS)

Parameter
Description

Enable PWM input on AUX5 or MAIN5 (depending on board) for engaging failsafe from an external automatic trigger system (ATS). Default: Disabled.

The PWM threshold from external automatic trigger system for engaging failsafe. Default: 1900 ms.

Emergency Switches

This section lists the available emergency switches.

Kill Switch

A kill switch immediately stops all motor outputs (and if flying, the vehicle will start to fall)! The motors will restart if the switch is reverted within 5 seconds. After 5 seconds the vehicle will automatically disarm; you will need to arm it again in order to start the motors.

Arm/Disarm Switch

The arm/disarm switch is a direct replacement for the default stick-based arming/disarming mechanism (and serves the same purpose: making sure there is an intentional step involved before the motors start/stop). It might be used in preference to the default mechanism because:

  • Of a preference of a switch over a stick motion.

  • It avoids accidentally triggering arming/disarming in-air with a certain stick motion.

  • There is no delay (it reacts immediately).

  • Manual mode

  • Acro mode

  • Stabilized

For modes that do not support disarming in flight, the switch is ignored during flight, but may be used after landing is detected. This includes Position mode and autonomous modes (e.g. Mission, Land etc.).

Return Switch

Other Safety Settings

Auto-disarming Timeouts

You can set timeouts to automatically disarm a vehicle if it is too slow to takeoff, and/or after landing (disarming the vehicle removes power to the motors, so the propellers won't spin).

Parameter
Description

Timeout for auto-disarm after landing.

Timeout for auto disarm if vehicle is too slow to takeoff.

Further Information

The vehicle will enter Return mode. Return behaviour can be set in the (below).

Turns off all controllers and sets all PWM outputs to their failsafe values (e.g. , ). The failsafe outputs can be used to deploy a parachute, landing gear or perform another operation. For a fixed-wing vehicle this might allow you to glide the vehicle to safety.

It is also possible to set the Failsafe Action to warn, return, or land when the failsafe level is reached.

Warn, Return, or Land based when capacity drops below , OR Warn, then return, then land based on each of the level settings below.

:::note PX4 and the receiver may also need to be configured in order to detect RC loss: . :::

The QGCroundControl Safety UI allows you to set the and . Users that want to disable the RC loss failsafe in specific automatic modes (mission, hold, offboard) can do so using the parameter .

The Data Link Loss failsafe is triggered if a telemetry link (connection to ground station) is lost when flying a .

:::tip PX4 separately supports more complicated GeoFence geometries with multiple arbitrary polygonal and circular inclusion and exclusion areas: . :::

The settings and underlying are shown below.

:::note Setting GF_ACTION to terminate will kill the vehicle on violation of the fence. Due to the inherent danger of this, this function is disabled using , which needs to be reset to 0 to really shut down the system. :::

Return is a common that engages to return the vehicle to the home position. This section shows how to set the land/loiter behaviour after returning.

:::note The return behaviour is defined by . If negative the vehicle will land immediately. Additional information can be found in . :::

Land at the current position is a common that engages . This section shows how to control when and if the vehicle automatically disarms after landing. For Multicopters (only) you can additionally set the descent rate.

This section contains information about failsafe settings that cannot be configured through the QGroundControl page.

The failure action is controlled by , based on whether RC control is assumed to be available (and altitude information):

Fixed-wing vehicles and VTOLs in fixed-wing flight additionally have a parameter () that defines how long they will loiter (circle with a constant roll angle () at the current altitude) after losing position before attempting to land. If VTOLs have are configured to switch to hover for landing () then they will first transition and then descend.

As these are not strictly speaking "failsafes" they are documented in .

The Traffic Avoidance Failsafe allows PX4 to respond to transponder data (e.g. from ) during missions.

Failsafe for when a VTOL vehicle can no longer fly in fixed-wing mode, perhaps due to the failure of a pusher motor, airspeed sensor, or control surface. If the failsafe is triggered, the vehicle will immediately switch to multicopter mode and execute the action defined in parameter .

:::note The quad-chute can also be triggered by sending a MAVLINK message with param2 set to 1. :::

Quad-chute action after switching to multicopter flight. Can be set to: , , , .

Uncommanded descent quad-chute altitude threshold. In altitude controlled modes, such as , , , or , a vehicle should track its current "commanded" altitude setpoint. The quad chute failsafe is triggered if the vehicle falls too far below the commanded setpoint (by the amount defined in this parameter). Note that the quad-chute is only triggered if the vehicle continuously loses altitude below the commanded setpoint; it is not triggered if the commanded altitude setpoint increases faster than the vehicle can follow.

During flight, the failure detector can be used to trigger if failure conditions are met, which may then launch a or perform some other action.

:::note Failure detection during flight is deactivated by default (enable by setting the parameter: ). :::

During takeoff the failure detector invokes the if the vehicle flips (disarm kills the motors but, unlike flight termination, will not launch a parachute or perform other failure actions). Note that this check is always enabled on takeoff, irrespective of the CBRK_FLIGHTTERM parameter.

The failure detector is active in all vehicle types and modes, except for those where the vehicle is expected to do flips (i.e. , , and ).

Time to exceed for failure detection (default 0.3s).

Time to exceed for failure detection (default 0.3s).

The , if , can also be triggered by an external ATS system. The external trigger system must be connected to flight controller port AUX5 (or MAIN5 on boards that do not have AUX ports), and is configured using the parameters below.

:::note External ATS is required by . One example of an ATS device is the . :::

Remote control switches can be configured (as part of QGroundControl ) to allow you to take rapid corrective action in the event of a problem or emergency; for example, to stop all motors, or activate .

The arm/disarm switch immediately disarms (stop) motors for those that support disarming in flight. This includes:

:::note (e.g. via ) are independent of the arm/disarm switch - ie even if the switch is armed the timeouts will still work. :::

A return switch can be used to immediately engage .

The are shown below:

mission
Flying > GeoFence
ADSB transponders
MAV_CMD_DO_VTOL_TRANSITION
flight termination
parachute
Acro mode (MC)
Acro mode (FW)
Manual (FW)
ASTM F3322-18
FruityChutes Sentinel Automatic Trigger System
flight modes
Return mode
relevant parameters
QGroundControl User Guide > Safety Setup
Battery Failsafe Level
failsafe action
RC Loss timeout
COM_RCL_EXCEPT
CBRK_FLIGHTTERM
Return mode
failsafe action
Land Mode
failsafe action
Safety Setup
COM_QC_ACT
CBRK_FLIGHTTERM=0
attitude trigger
disarm action
failure detector
enabled
Flight Mode Setup
Return mode
Auto disarm timeouts
COM_DISARM_LAND
Hold mode
Return mode
Land mode
Flight termination
Hold mode
Position mode
Altitude mode
Mission mode
Return Home Settings
Battery Failsafe Level
Warning
Return
Land
Hold
FD_FAIL_P
FD_FAIL_R
Radio Setup > RC Loss Detection
Mission Mode > Mission Feasibility Checks
Failsafe State Machine Simulation
action
Safety Setup
parameters
Safety switches
Return mode
Land
Return mode
Safety Setup(QGC)
Safety - Battery (QGC)
Safety - RC Loss (QGC)
Safety - Data Link Loss (QGC)
Safety - Geofence (QGC)
Safety - Return Home Settings (QGC)
Safety - Land Mode Settings (QGC)
COM_FAIL_ACT_T
geofence parameters
RTL_LAND_DELAY
COM_POSCTL_NAVL
FW_GPSF_LT
FW_GPSF_R
NAV_FORCE_VT
PWM_MAIN_FAILn
PWM_AUX_FAILn
COM_LOW_BAT_ACT
BAT_LOW_THR
BAT_CRIT_THR
BAT_EMERGEN_THR
COM_RC_LOSS_T
COM_FAIL_ACT_T
NAV_RCL_ACT
COM_RCL_EXCEPT
COM_DL_LOSS_T
NAV_DLL_ACT
GF_ACTION
GF_MAX_HOR_DIST
GF_MAX_VER_DIST
GF_ALTMODE
GF_COUNT
GF_SOURCE
GF_PREDICT
CBRK_FLIGHTTERM
RTL_RETURN_ALT
RTL_DESCEND_ALT
RTL_LAND_DELAY
COM_DISARM_LAND
MPC_LAND_SPEED
COM_POS_FS_DELAY
COM_POSCTL_NAVL
FW_GPSF_LT
FW_GPSF_R
COM_OF_LOSS_T
COM_OBL_RC_ACT
NAV_TRAFF_AVOID
COM_QC_ACT
VT_FW_QC_HMAX
VT_QC_ALT_LOSS
VT_QC_T_ALT_LOSS
VT_FW_MIN_ALT
VT_FW_QC_R
VT_FW_QC_P
CBRK_FLIGHTTERM
FD_FAIL_P
FD_FAIL_R
FD_FAIL_P_TTRI
FD_FAIL_R_TTRI
FD_EXT_ATS_EN
FD_EXT_ATS_TRIG
COM_DISARM_LAND
COM_DISARM_PRFLT