Estimating aircraft performance loss in windshear from Doppler radar

The Terminal Doppler Weather Radar (TDWR) is currently being deployed at 45 major airports across the United States. Designed to detect hazardous windshear events such as microbursts, the algorithms currently in use create products that do not readily translate to the performance loss an aircraft may suffer should it penetrate the hazard. Such a capability is crucial to preventing false alarms. A recognized performance parameter for such purposes is the F-factor. A crude way of estimating F from Doppler radar data was presented by Elmore and Sand (1989). This paper investigates an updated version with improving the TDWR hazard detection algorithm as the ultimate goal. F-factor quantifies aircraft performance as a dimension-less parameter. F is essentially a measure of the performance reserve an aircraft has and may be generically defined as (thrust - drag)/weight. While F is somewhat configuration-dependent it is a parameter recognized and used by airframe manufacturers and can easily be determined for any aircrat. In the Summer of 1992, the National Center for Atmospheric Research (NCAR) participated with the National Aeronautics and Space Administration /-Langley Research Center (NASA) in developing an airborne Doppler system for windshear detection. As part of thid program, NASA flew their instrumented Boeing 737 through numerous microburst events in the Denver area, as determined by the Mile High Radar TDWR testbed. Such penetrations provide us with a unique opportunity to verify Doppler radar-derived parameters with in situ measurements. This paper investigates a method for recovering F directly from single Doppler radar data.