Airspeed sensors are highly recommended for fixed-wing and VTOL frames. They are so important because the autopilot does not have other means to detect stall. For fixed-wing flight it is the airspeed that guarantees lift not ground speed!
Recommended digital airspeed sensors include:
MEAS Spec series (e.g. MS4525DO)
EagleTree Airspeed MicroSensor V3 (eagletreesystems)
- Sensirion SDP3X Differential Pressure Sensor
- Holybro Digital Air Speed Sensor
All the sensors are connected via the I2C bus/port.
PX4 setup information can be found in: Basic Configuration > Airspeed.
- Airspeed drivers (source code)