The low airspeed sensor is driven around by a small motor, and it gives very accurate information when the helicopter is below 40 KIAS. It gives side and rear wind, and for a helicopter that hovers over the water in the middle of the night, is nearly essential.. .Every helicopter that flies IFR, and probably every other helicopter should have such a system, but we don't because we've never had them before, so we think we don't need them.. .Bit of a pet peeve of mine - I used it to very good effect on the HH-65 when I was instructing at the Naval Test Pilot School to show hover performance. . .Since it calculates the side and rear wind components and feeds them in to the navigation computer, it gives very accurate wind calculations.