Groundspeed/Airspeed Differences as a Wind Shear Indicator and Flight Evaluation of a DME-Derived System to Determine Groundspeed.

The use of groundspeed in conjunction with airspeed as a wind shear indicator is discussed. It is shown that a satisfactory indication of headwind can be obtained using indicated airspeed and a low-cost groundspeed measurement device. This report describes the flight test and evaluation of a distance measuring equipment DME range-rate derived system for measuring airplane groundspeed. The system consists of a specially developed airborne unit operating in conjunction with unmodified very high frequency omnidirectional radio range VORDME ground stations. Operating at ranges up to 50 nautical miles in level flight directly toward or away from the ground station, the root mean square RMS groundspeed error is 3 to 5 knots. In landing approaches or climbout, the RMS error is 4 to 8 knots. Author