Using an Airspeed Sensor

Plane supports the use of an airspeed sensor, which can help in windy conditions, slow flight and autonomous landings. It is not recommended for most new users, however, as it does require additional tuning and adds one more layer of control to set up.

The following sections explain how to wire sensors to the autopilot and set them up. After you install an airspeed sensor don’t forget to calibrate it!

ARSPD_USE
ARSPD_USE enables airspeed use for automatic throttle modes instead of TRIM_THROTTLE as the target throttle setting (altered by TECS (Total Energy Control System) for Speed and Height Tuning Guide as needed during altitude control) . The autopilot continues to display and log airspeed if set to 0, but only airspeed sensor readings are used for control if set to 1. It will only use airspeed sensor readings for control when throttle is idle, if set to 2 (useful for gliders with airspeed sensors behind propellers).

If an airspeed sensor is used, the throttle stick will set the target airspeed in CRUISE and FBWB, while maintaining altitude target. In AUTO and GUIDED, it will use the AIRSPEED_CRUISE value unless THROTTLE_NUDGE is enabled and throttle stick is used to alter it, or a MAVLink command to change speed is sent to the vehicle.

Airspeed Sensor Type
Airspeed sensors can be either analog or digital. The analog sensors connect to an A/D converter input pin on the autopilot, while digital sensors connect to the autopilot’s external I2C bus using the SDA and SCL external digital I/O pins or via DroneCAN. The type is set by the ARSPD_TYPE parameter. Analog sensors are type 2, DroneCAN sensors as type 8, and supported I2C bus digital sensors by other numbers.

If there is no sensor, be sure to set the ARSPD_TYPE to 0. ArduPilot calculates an sensor-less airspeed estimate that is used if no sensor is present or fails. ARSPD_TYPE must be set to zero in order to display this value if no sensor is present.