PX4 User Guide

# Altitude Mode (Multicopter)

Altitude mode is a relatively easy-to-fly RC mode in which roll and pitch sticks control vehicle movement in the left-right and forward-back directions (relative to the "front" of the vehicle), yaw stick controls rate of rotation over the horizontal plane, and throttle controls speed of ascent-descent.

When the sticks are released/centered the vehicle will level and maintain the current altitude. If moving in the horizontal plane the vehicle will continue until any momentum is dissipated by wind resistance. If the wind blows the aircraft will drift in the direction of the wind.

Tip Altitude mode is the safest non-GPS manual mode for new fliers. It is just like Manual/Stabilized mode but additionally locks the vehicle altitude when the sticks are released.

The diagram below shows the mode behaviour visually (for a mode 2 transmitter).

Altitude Control MC - Mode2 RC Controller

# Technical Summary

RC/manual mode like Manual/Stabilized (MC) mode but with altitude stabilization (centered sticks level vehicle and hold it to fixed altitude).

  • 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.
  • Takeoff:
    • When landed, the vehicle will take off if the throttle stick is raised above 62.5% percent (of the full range from bottom).

Note

  • Manual input is required (RC controller, or gamepad/thumbsticks through MAVLink).
  • The altitude is normally measured using a barometer, which may become inaccurate in extreme weather conditions. Vehicles that include a LIDAR/range sensor will be able to control altitude with greater reliability and accuracy.

# Parameters

The mode is affected by the following parameters:

Parameter Description
MPC_Z_VEL_MAX_UP Maximum vertical ascent velocity. Default: 3 m/s.
MPC_Z_VEL_MAX_DN Maximum vertical descent velocity. Default: 1 m/s.
RCX_DZ RC dead zone for channel X. The value of X for throttle will depend on the value of RC_MAP_THROTTLE. For example, if the throttle is channel 4 then RC4_DZ specifies the deadzone.
MPC_XXXX Most of the MPC_xxx parameters affect flight behaviour in this mode (at least to some extent). For example, MPC_THR_HOVER defines the thrust at which a vehicle will hover.

← Manual/Stabilized Mode (MC) →