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
      • Recommended Hardware/Setup
      • Toolchain Installation
        • MacOS Setup
        • Ubuntu Setup
        • Windows Setup
        • Visual Studio Code IDE
        • Other/Generic Tools
      • Building the Code
      • Writing your First Application
      • Application/Module Template
    • Concepts
      • PX4 Architecture
      • PX4 Flight Stack Architecture
        • Controller Diagrams
      • Events Interface
      • Flight Modes
      • Flight Tasks
      • Control Allocation
      • PWM limit state machine
      • System Startup
      • SD Card Layout
    • Simulation
      • jMAVSim Simulation
        • Multi-Vehicle Sim with JMAVSim
      • Gazebo Simulation
        • Vehicles
        • Multi-Vehicle Sim
      • Gazebo Classic Simulation
        • Vehicles
        • Worlds
        • Multi-Vehicle Sim
      • FlightGear Simulation
        • FlightGear Vehicles
        • Multi-Vehicle Sim with FlightGear
      • JSBSim Simulation
      • AirSim Simulation
      • Multi-Vehicle Simulation
      • Simulate Failsafes
      • HITL Simulation
      • Simulation-In-Hardware
    • Hardware
      • Flight Controller Reference Design
      • Manufacturer’s Board Support Guide
      • Flight Controller Porting Guide
        • PX4 Board Configuration (kconfig)
        • NuttX Board Porting Guide
      • Serial Port Mapping
      • Airframes
        • Adding a New Airframe
      • Device Drivers
      • Telemetry Radio
        • SiK Radio
      • Sensor and Actuator I/O
        • DroneCAN
        • I2C Bus
        • UART/Serial Ports
          • Port-Configurable Serial Drivers
      • RTK GPS (Integration)
    • Middleware
      • uORB Messaging
      • uORB Graph
      • uORB Message Reference
        • ActionRequest
        • ActuatorArmed
        • ActuatorControlsStatus
        • ActuatorMotors
        • ActuatorOutputs
        • ActuatorServos
        • ActuatorServosTrim
        • ActuatorTest
        • AdcReport
        • Airspeed
        • AirspeedValidated
        • AirspeedWind
        • AutotuneAttitudeControlStatus
        • BatteryStatus
        • ButtonEvent
        • CameraCapture
        • CameraStatus
        • CameraTrigger
        • CellularStatus
        • CollisionConstraints
        • CollisionReport
        • ControlAllocatorStatus
        • Cpuload
        • DebugArray
        • DebugKeyValue
        • DebugValue
        • DebugVect
        • DifferentialPressure
        • DistanceSensor
        • Ekf2Timestamps
        • EscReport
        • EscStatus
        • EstimatorAidSource1d
        • EstimatorAidSource2d
        • EstimatorAidSource3d
        • EstimatorBias
        • EstimatorBias3d
        • EstimatorEventFlags
        • EstimatorGpsStatus
        • EstimatorInnovations
        • EstimatorSelectorStatus
        • EstimatorSensorBias
        • EstimatorStates
        • EstimatorStatus
        • EstimatorStatusFlags
        • Event
        • FailsafeFlags
        • FailureDetectorStatus
        • FollowTarget
        • FollowTargetEstimator
        • FollowTargetStatus
        • GeneratorStatus
        • GeofenceResult
        • GimbalControls
        • GimbalDeviceAttitudeStatus
        • GimbalDeviceInformation
        • GimbalDeviceSetAttitude
        • GimbalManagerInformation
        • GimbalManagerSetAttitude
        • GimbalManagerSetManualControl
        • GimbalManagerStatus
        • GpioConfig
        • GpioIn
        • GpioOut
        • GpioRequest
        • GpsDump
        • GpsInjectData
        • Gripper
        • HealthReport
        • HeaterStatus
        • HomePosition
        • HoverThrustEstimate
        • InputRc
        • InternalCombustionEngineStatus
        • IridiumsbdStatus
        • IrlockReport
        • LandingGear
        • LandingGearWheel
        • LandingTargetInnovations
        • LandingTargetPose
        • LaunchDetectionStatus
        • LedControl
        • LogMessage
        • LoggerStatus
        • MagWorkerData
        • MagnetometerBiasEstimate
        • ManualControlSetpoint
        • ManualControlSwitches
        • MavlinkLog
        • MavlinkTunnel
        • Mission
        • MissionResult
        • ModeCompleted
        • MountOrientation
        • NavigatorMissionItem
        • NormalizedUnsignedSetpoint
        • NpfgStatus
        • ObstacleDistance
        • OffboardControlMode
        • OnboardComputerStatus
        • OrbTest
        • OrbTestLarge
        • OrbTestMedium
        • OrbitStatus
        • ParameterUpdate
        • Ping
        • PositionControllerLandingStatus
        • PositionControllerStatus
        • PositionSetpoint
        • PositionSetpointTriplet
        • PowerButtonState
        • PowerMonitor
        • PpsCapture
        • PwmInput
        • Px4ioStatus
        • QshellReq
        • QshellRetval
        • RadioStatus
        • RateCtrlStatus
        • RcChannels
        • RcParameterMap
        • Rpm
        • RtlTimeEstimate
        • SatelliteInfo
        • SensorAccel
        • SensorAccelFifo
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        • SensorGyroFft
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        • SensorsStatusImu
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        • TaskStackInfo
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        • TelemetryStatus
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        • VtolVehicleStatus
        • Wind
        • YawEstimatorStatus
      • MAVLink Messaging
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    • Modules & Commands
      • Autotune
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        • Airspeed Sensor
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On this page
  • Arming Gesture
  • Arming Button/Switch
  • Auto-Disarming
  • Pre-Arm Checks
  • Arming Sequence: Pre Arm Mode & Safety Button
  • Default: COM_PREARM_MODE=Safety and Safety Switch
  • COM_PREARM_MODE=Disabled and Safety Switch
  • COM_PREARM_MODE=Always and Safety Switch
  • COM_PREARM_MODE=Safety or Disabled and No Safety Switch
  • COM_PREARM_MODE=Always and No Safety Switch
  • Parameters
  1. Advanced Configuration

Prearm/Arm/Disarm Configuration

PreviousLand Detector ConfigurationNextIMU Factory Calibration

Last updated 1 year ago

Vehicles may have moving parts, some of which are potentially dangerous when powered (in particular motors and propellers)!

To reduce the chance of accidents, PX4 has explicit state(s) for powering the vehicle components:

  • Disarmed: There is no power to motors or actuators.

  • Pre-armed: Motors/propellers are locked but actuators for non-dangerous electronics are powered (e.g. ailerons, flaps etc.).

  • Armed: Vehicle is fully powered. Motors/propellers may be turning (dangerous!)

:::note Ground stations may display disarmed for pre-armed vehicles. While not technically correct for pre-armed vehicles, it is "safe". :::

Users can control progression though these states using a on the vehicle (optional) and an , , or MAVLink command on the ground controller:

  • A safety switch is a control on the vehicle that must be engaged before the vehicle can be armed, and which may also prevent prearming (depending on the configuration). Commonly the safety switch is integrated into a GPS unit, but it may also be a separate physical component.

    :::warning A vehicle that is armed is potentially dangerous. The safety switch is an additional mechanism that prevents arming from happening by accident. :::

  • An arming switch is a switch or button on an RC controller that can be used to arm the vehicle and start motors (provided arming is not prevented by a safety switch).

  • An arming gesture is a stick movement on an RC controller that can be used as an alternative to an arming switch.

  • MAVLink commands can also be sent by a ground control station to arm/disarm a vehicle.

PX4 will also automatically disarm the vehicle if it does not takeoff within a certain amount of time after arming, and if it is not manually disarmed after landing. This reduces the amount of time where an armed (and therefore dangerous) vehicle is on the ground.

PX4 allows you to configure how pre-arming, arming and disarming work using parameters (which can be edited in QGroundControl via the ), as described in the following sections.

:::tip Arming/disarming parameters can be found in (search for COM_ARM_* and COM_DISARM_*). :::

Arming Gesture

By default, the vehicle is armed and disarmed by moving RC throttle/yaw sticks to particular extremes and holding them for 1 second.

  • Arming: Throttle minimum, yaw maximum

  • Disarming: Throttle minimum, yaw minimum

  • Mode 2:

    • Arm: Left stick to bottom right.

    • Disarm: Left stick to the bottom left.

  • Mode 1:

    • Arm: Left-stick to right, right-stick to bottom.

    • Disarm: Left-stick to left, right-stick to the bottom.

Parameter
Description

Time that RC stick must be held in arm/disarm position before arming/disarming occurs (default: 1 second).

Arming Button/Switch

A two-position switch can also be used for arming/disarming, where the respective arm/disarm commands are sent on switch transitions.

:::tip Two-position arming switches are primarily used in/recommended for racing drones. :::

Parameter
Description

RC arm switch channel (default: 0 - unassigned). If defined, the specified RC channel (button/switch) is used for arming instead of a stick gesture. Note: - This setting disables the stick gesture! - This setting applies to RC controllers. It does not apply to Joystick controllers that are connected via QGroundControl.

Auto-Disarming

By default vehicles will automatically disarm on landing, or if you take too long to take off after arming. The feature is configured using the following timeouts.

Parameter
Description

Time-out for auto disarm after landing. Default: 2s (-1 to disable).

Time-out for auto disarm if too slow to takeoff. Default: 10s (<=0 to disable).

Pre-Arm Checks

To reduce accidents, vehicles are only allowed to arm certain conditions are met. Arming is prevented if:

  • The vehicle is not in a "healthy" state. For example it is not calibrated, or is reporting sensor errors.

  • The current mode requires an adequate global position estimate but the vehicle does not have GPS lock.

  • Many more ...

Arming Sequence: Pre Arm Mode & Safety Button

  • Disabled: Pre-arm mode disabled (there is no stage where only "safe"/non-throttling actuators are enabled).

  • Safety Switch (Default): The pre-arm mode is enabled by the safety switch. If there is no safety switch then pre-arm mode will not be enabled.

  • Always: Prearm mode is enabled from power up.

The sections below detail the startup sequences for the different configurations

Default: COM_PREARM_MODE=Safety and Safety Switch

The default startup sequence is:

  1. Power-up.

    • All actuators locked into disarmed position

    • Not possible to arm.

  2. Safety switch is pressed.

    • System now prearmed: non-throttling actuators can move (e.g. ailerons).

    • System safety is off: Arming possible.

  3. Arm command is issued.

    • The system is armed.

    • All motors and actuators can move.

COM_PREARM_MODE=Disabled and Safety Switch

The startup sequence is:

  1. Power-up.

    • All actuators locked into disarmed position

    • Not possible to arm.

  2. Safety switch is pressed.

    • All actuators stay locked into disarmed position (same as disarmed).

    • System safety is off: Arming possible.

  3. Arm command is issued.

    • The system is armed.

    • All motors and actuators can move.

COM_PREARM_MODE=Always and Safety Switch

The startup sequence is:

  1. Power-up.

    • System now prearmed: non-throttling actuators can move (e.g. ailerons).

    • Not possible to arm.

  2. Safety switch is pressed.

    • System safety is off: Arming possible.

  3. Arm command is issued.

    • The system is armed.

    • All motors and actuators can move.

COM_PREARM_MODE=Safety or Disabled and No Safety Switch

The startup sequence is:

  1. Power-up.

    • All actuators locked into disarmed position

    • System safety is off: Arming possible.

  2. Arm command is issued.

    • The system is armed.

    • All motors and actuators can move.

COM_PREARM_MODE=Always and No Safety Switch

The startup sequence is:

  1. Power-up.

    • System now prearmed: non-throttling actuators can move (e.g. ailerons).

    • System safety is off: Arming possible.

  2. Arm command is issued.

    • The system is armed.

    • All motors and actuators can move.

Parameters

Parameter
Description

Condition to enter prearmed mode. 0: Disabled, 1: Safety switch (prearm mode enabled by safety switch; if no switch present cannot be enabled), 2: Always (prearm mode enabled from power up). Default: 1 (safety button).

Circuit breaker for IO safety.

RC controllers will have different gestures (as controller mode affects the sticks used for throttle and yaw):

The required hold time can be configured using .

An arming button or "momentary switch" can be configured to trigger arm/disarm instead of (setting an arming switch disables arming gestures). The button should be held down for () one second to arm (when disarmed) or disarm (when armed).

The switch or button is assigned (and enabled) using , and the switch "type" is configured using .

Arm switch is a momentary button. - 0: Arm switch is a 2-position switch where arm/disarm commands are sent on switch transitions. -1: Arm switch is a button or momentary button where the arm/disarm command ae sent after holding down button for set time ().

:::note The switch can also be set as part of QGroundControl configuration. :::

The vehicle has a that has not been engaged.

The vehicle has a that is unhealthy or otherwise not ready

A VTOL vehicle is in fixed-wing mode ().

The current failed checks can be viewed in QGroundControl (v4.2.0 and later): .

Note that internally PX4 runs arming checks at 10Hz. A list of the failed checks is kept, and if the list changes PX4 emits the current list using the . The list is also sent out when the GCS connects. Effectively the GCS knows the status of prearm checks immediately, both when disarmed and armed.

:::details Implementation notes for developers The client implementation is in :

QGC implementation: . :::

PX4 also emits a subset of the arming check information in the message (see ).

The arming sequence depends on whether or not there is a safety switch, and is controlled by the parameters (Prearm mode) and (I/O safety circuit breaker).

The parameter defines when/if pre-arm mode is enabled ("safe"/non-throttling actuators are able to move):

If there is a safety switch then this will be a precondition for arming. If there is no safety switch the I/O safety circuit breaker must be engaged (), and arming will depend only on the arm command.

The default configuration uses safety switch to prearm. From prearm you can then arm to engage all motors/actuators. It corresponds to: (safety switch) and (I/O safety circuit breaker disabled).

When prearm mode is Disabled, engaging the safety switch does not unlock the "safe" actuators, though it does allow you to then arm the vehicle. This corresponds to (Disabled) and (I/O safety circuit breaker disabled).

When prearm mode is Always, prearm mode is enabled from power up. To arm, you still need the safety switch. This corresponds to (Always) and (I/O safety circuit breaker disabled).

With no safety switch, when COM_PREARM_MODE is set to Safety or Disabled prearm mode cannot be enabled (same as disarmed). This corresponds to (Disabled/Safety Switch) and (I/O safety circuit breaker engaged).

When prearm mode is Always, prearm mode is enabled from power up. This corresponds to (Always) and (I/O safety circuit breaker engaged).

Flight Mode
remote ID
Fly View > Arming and Preflight Checks
Events interface
libevents
libevents > Event groups
health_and_arming_checks.h
HealthAndArmingCheckReport.cc
SYS_STATUS
MAV_SYS_STATUS_SENSOR
COM_RC_ARM_HYST
gesture-based arming
nominally
RC_MAP_ARM_SW
COM_ARM_SWISBTN
COM_PREARM_MODE
CBRK_IO_SAFETY
COM_PREARM_MODE
CBRK_IO_SAFETY
COM_PREARM_MODE=1
CBRK_IO_SAFETY=0
COM_PREARM_MODE=0
CBRK_IO_SAFETY=0
COM_PREARM_MODE=2
CBRK_IO_SAFETY=0
COM_PREARM_MODE=0 or 1
CBRK_IO_SAFETY=22027
COM_PREARM_MODE=2
CBRK_IO_SAFETY=22027
COM_RC_ARM_HYST
parameter editor
arming switch/button
arming gesture
based on their mode
safety switch
safety switch
Parameter Reference > Commander
by default
COM_RC_ARM_HYST
RC_MAP_ARM_SW
COM_ARM_SWISBTN
COM_DISARM_LAND
COM_DISARM_PRFLT
COM_PREARM_MODE
CBRK_IO_SAFETY