Drucella Andersen Headquarters, Washington, D.C. August 7, 1991 (Phone: 202/453-8613) H. Keith Henry Langley Research Center, Hampton, Va. (Phone: 804/864-6120) RELEASE: 91-125 NASA TESTS NEW WINDSHEAR WARNING SYSTEM Results from a NASA flight test program show that new sensor technology may provide airline flight crews with advance warning of "microbursts" that sometimes harbor potentially dangerous windshears. A microburst is an intense downdraft that produces strong divergent winds near the ground, typically for a short duration and over a relatively small area. When an airliner is taking off or landing, a microburst can force the plane into the ground before the flight crew can take proper corrective action. NASA's Boeing 737 Transport Systems Research Vehicle is equipped with a number of instruments intended to detect hazardous windshear in time for the aircraft to avoid it. NASA and the Federal Aviation Administration (FAA) are most interested in sensors that will provide a minimum of 20-40 seconds advance warning of microburst windshear conditions. Although airlines are in the process of equipping their planes with windshear detection systems, these commercial systems are designed to alert the flight crew that the aircraft is experiencing hazardous windshear. The FAA has mandated that airlines must select and install an approved microburst detection system on their aircraft by the end of 1995. The NASA 737 flight tests represent the final phase of a joint NASA/FAA windshear research program started in 1986. The FAA determines the requirements for the program, while NASA is developing the technology for airborne sensors. Researchers believe the combination of ground-based and airborne detection will give commercial airline pilots precious extra seconds to avoid or escape a microburst. - more - - 2 - NASA's 737 recently completed two series of test flights. The first was in the Orlando, Fla., area, June 9-21. The second series of flights took place in the Denver area, July 7-25. Orlando often has moisture-filled microbursts and Denver experiences relatively dry microbursts, making the areas excellent candidates for studying the full range of microburst conditions. The flight test program was highly successful. Conditions in the Orlando area allowed the aircraft to make many microburst windshear penetrations after the storms had been measured by the forward-looking sensors. Denver weather during the deployment period did not produce the expected dry microbursts, but did allow strong gust front penetrations and other storm measurements. The NASA 737 also conducted radar surveys of terrain and ground traffic around the Orlando and Denver airports. Both airports have experimental ground-based Doppler radars designed to spot windshear. Information from these radar systems was used in the studies to direct the aircraft toward microbursts. For safety, the aircraft flew 750 to 1,100 feet above the ground at 210 knots (about 240 statute mph). This summer, the NASA 737 research aircraft carried the forward-looking remote sensors, one based on radar technology and one based on infrared technology. The radar sensor, a modified aircraft weather radar, detects sudden, large changes in raindrop velocities in a storm cell ahead of the airplane. NASA modifications to the otherwise off-the-shelf radar filter out false indicators like cars moving in opposite directions near the airport, allowing windshear readings near ground level. The infrared sensor is a passive instrument that measures temperature changes usually produced by microbursts. The flight tests also demonstrated a Langley-developed data link between ground weather radar and the 737 and the feasibility of deriving a windshear alert from that data and displaying it in the aircraft. Warnings from ground weather radar today are typically relayed by voice. The only way to ensure that these advanced instruments operate reliably is for the test aircraft to fly into a variety of shears and compare the instruments' performance with what the plane actually encounters. Researchers at Langley have developed a real-time computer program that accurately determines what the 737 detected. The 737 and the NASA team are based at Langley Research Center, Hampton, Va. - end - NOTE TO EDITORS: Still photos to illustrate this release are available to media representatives by calling 202/453-8375: Color: 91-HC-530 B&W: 91-H-628 Also, a 1 minute, 27 second edited video clip and 9 minute, 40 second resource footage is available by calling 202/453-8594.