Optical Air Data Systems (OADS).
The system employs laser Doppler velocimetry, a variant of lidar. By measuring the wavelength shift induced by the scattering effect of natural particulates like ash and sand in the air, the technique is said to be able to deliver accurate airspeed information in three axes at low and even negative airspeeds. This range of capability is not possible with pitot tubes, the longstanding industry standard for airspeed sensors.
The OADS system can measure airspeeds as low as 20 knots, to an accuracy of better than 2 knots over the entire flight. In comparison, standard pitot tubes do not work below airspeeds of around 30 knots.
In addition, it is able to monitor the air 50-60 meters away from the aircraft. This factor is especially significant in rotary wing applications, where airspeed measurements may be affected by the downwash effect.
But as well as measuring airspeed around an aircraft, the OADS technology is also able to monitor wind and turbulence several thousand feet above and below – in principle providing pilots with the ability to select the most favorable altitude for a flight, saving fuel and offering a smoother ride.
As a result, the technology's capability in collecting wind data for “tactical
en route and strategic flight planning over extended periods of time is examined.
Another important factor is that the optical system is not affected by icing - a dangerous condition during which ice can form in the sensor openings of pitot tubes, blocking their ability to accurately measure airspeed.