Flight Modes

Flight Modes define how the autopilot responds to user input and controls vehicle movement. The tables below summarizes flight modes for fixed wing and copter (table key is below). Note that this is the "high level" default behaviour, and may vary based on vehicle parameters. The linked topics (sidebar) provide more detailed information about individual modes, including their tuning parameters.

A beginner friendly explanation of all flight modes is provided in Getting Started > Flight Modes.

Fixed Wing

Modes Roll & Pitch Yaw Throttle Position Sensors Summary
Position

S+ S+ S+

RC mode where centered sticks put vehicle into straight and level flight where vehicle posture/attitude, altitude, and the straight line vehicle path are maintained against wind (and other forces).

  • Centered RC RPY sticks – level flight that follows a straight line ground track in the current direction against any wind.
  • Outside center:
    • Pitch stick controls altitude (same as Altitude).
    • Roll stick controls roll angle. Autopilot will maintain coordinated flight (same as Stabilized).
    • Throttle sets airspeed (same as Altitude).
    • Roll, pitch and yaw are all angle-controlled (so it is impossible to roll over or loop the vehicle).
    • Yaw stick actuates the rudder (signal will be added to the one calculated by the autopilot to maintain coordinated flight). This is the same as Stabilized.

Altitude

S (roll)

S+(pitch)

M S+

RC mode like Stabilized mode but with altitude stabilization (centered sticks put vehicle into straight and level flight and maintain current altitude). The vehicle course is not maintained, and can drift due to wind.

  • Centered RPY sticks (inside deadband):
    • Autopilot maintains altitude with wings also level.
    • Throttle stick controls the airspeed of the aircraft if an airspeed sensor is connected (without airspeed sensor, the user cannot control throttle).
  • Outside center:
    • Pitch stick controls altitude.
    • Throttle stick controls the airspeed of the aircraft (as for centred RPY sticks).
    • Yaw stick actuates the rudder (signal will be added to the one calculated by the autopilot to maintain coordinated flight). This is the same as Stabilized.

Stabilized

S M M

RC mode where centered RP sticks levels vehicle attitude (roll and pitch). The vehicle course and altitude are not maintained, and can drift due to wind.

  • Pitch stick controls pitch angle.
  • Roll stick controls roll angle. Autopilot will maintain coordinated flight.
  • Throttle stick controls throttle.
  • Yaw stick actuates the rudder (signal will be added to the one calculated by the autopilot to maintain coordinated flight).
Acro

Srate Srate M

RC mode for performing acrobatic maneuvers e.g. rolls, flips, stalls and acrobatic figures.

RPY stick inputs are translated to angular rate commands that are stabilized by autopilot. Throttle is passed directly to the output mixer.

Manual

M M M

RC mode where stick input is sent directly to the output mixer (for "fully" manual control).

This is the only mode that overrides the FMU (commands are sent via the safety coprocessor). It provides a safety mechanism that allows full control of throttle, elevator, ailerons and rudder via RC in the event of an FMU firmware malfunction.

Takeoff Auto Vehicle initiates the takeoff sequence using either catapult/hand-launch mode or runway takeoff mode (in the current direction).
Land Auto Vehicle initiates the fixed-wing landing sequence.
Hold Auto Vehicle circles around the GPS hold position at the current altitude.
Return Auto Vehicle ascends to a safe height and then returns to its home position and circles.
Mission Auto Vehicle executes a predefined mission/flight plan that has been uploaded to the flight controller.

Multicopter

Modes Roll & Pitch Yaw Throttle Position Sensors Summary
Position

S+ Srate S+

RC mode where RPT sticks control speed in corresponding directions. Centered sticks level vehicle and hold it to fixed position and altitude against wind.

  • Centered RPT sticks hold x, y, z position steady against any wind and levels attitude.
  • Outside center:
    • Roll/Pitch sticks control speed over ground in left-right and forward-back directions (respectively) relative to the "front" of the vehicle.
    • Throttle stick controls speed of ascent-descent.
    • Yaw stick controls rate of angular rotation above the horizontal plane.

Altitude

S Srate S+

RC mode like Manual/Stabilized mode but with altitude stabilization (centered sticks level vehicle and hold it to fixed altitude). The horizontal position of the vehicle can move due to wind (or pre-existing momentum).

  • Centered sticks (inside deadband):
    • RPY sticks levels vehicle.
    • Throttle (~50%) holds current altitude steady against wind.
  • Outside center:
    • Roll/Pitch sticks control tilt angle in respective orientations, resulting in corresponding left-right and forward-back movement.
    • Throttle stick controls up/down speed with a predetermined maximum rate (and movement speed in other axes).
    • Yaw stick controls rate of angular rotation above the horizontal plane.

Manual/ Stabilized

S Srate M

RC mode where centered sticks level vehicle (only - position is not stabilized).

  • Centered RP sticks level vehicle.
  • Outside center:
    • Roll/Pitch sticks control tilt angle in those orientations, resulting in corresponding left-right and forward-back movement.
    • Throttle stick controls up/down speed (and movement speed in other axes).
    • Yaw stick controls rate of angular rotation above the horizontal plane.

Rattitude

S or Srate Srate M

RC mode that allows pilots to fly using Manual/Stabilized flight most of the time, but still perform Acro mode-style flips and tricks when desired. Centered sticks level vehicle.

  • Sticks within mode's threshold (like Manual/Stabilized mode).
    • Centered RP sticks level vehicle. Roll/Pitch sticks control tilt angle in those orientations, resulting in corresponding left-right and forward-back movement.
  • Sticks outside threshold (like Acro mode):
    • RPY stick inputs control the rate of angular rotation around the respective axes.

Acro

Srate Srate M

RC mode for performing acrobatic maneuvers e.g. flips, rolls and loops.

RC RPY stick inputs control the rate of angular rotation around the respective axes. Throttle is passed directly to the output mixer. When sticks are centered the vehicle will stop rotating, but remain in its current orientation (e.g. possibly inverted) and moving according to its current momentum.

Takeoff Auto Vehicle ascends to takeoff altitude and holds position.
Land Auto Vehicle lands at the position where the mode was engaged.
Hold Auto Vehicle hovers at the current GPS position and altitude.
Return Auto Vehicle ascends to a safe height and then returns to its home position and lands.
Mission Auto Vehicle executes a predefined mission/flight plan that has been uploaded to the flight controller.
Follow Me Auto Vehicle autonomously follows a user using an Android phone/tablet running QGC.
Offboard Auto Vehicle obeys a position, velocity or attitude setpoint provided over MAVLink (often from a companion computer connected via serial cable or wifi).

VTOL

VTOL vehicles support both fixed-wing and multicopter flight modes, executing them based on the current vehicle mode (MC or FW).

VTOL supports Offboard mode in either configuration.

Key

Key for understanding the table is as follows:

Symbol Description
M Manual control via RC sticks. RC input is sent directly to the output mixer.
S Assistance from autopilot to stabilize the attitude. RC input is required. Position of RC stick maps to the orientation of vehicle.
Srate Assistance from autopilot to stabilize the attitude rate. RC input is required. Position of RC stick maps to the rate of rotation of vehicle in that orientation.
S+ Assistance from autopilot to hold position or altitude against wind. RC input is required.
Auto This mode is automatic (RC control is disabled by default except to change modes).
Sensor(s) that measures position/height needed e.g. optical flow, GPS+barometer, visual-inertial odometry.
Sensor(s) that measures height/altitude needed e.g. barometer, rangefinder.
   Flight mode difficulty (easy/medium/hard).

Abbreviations:

  • RPY: Roll, Pitch, Yaw
  • RPT: Roll, Pitch Throttle
© PX4 Dev Team. License: CC BY 4.0            Updated: 2018-09-19 03:49:20

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