Michael Braukus<br />Headquarters, Washington August 19, 2003<br />(Phone: 202/358-1979)<br /><br /><br />Kathy Barnstorff<br />Langley Research Center, Hampton, Va.<br />(Phone: 757/864-9886)<br /><br /><br />RELEASE: 03-271<br /><br /><br />SCIENTISTS LISTEN IN ON SOUNDS OF AIRCRAFT WAKE SIGNATURES<br /><br /><br /> Tests starting this week in Denver will help scientists <br />determine if sound can be used to detect, track and predict <br />hazards from aircraft wake turbulence.<br /><br /><br />Researchers, including some from NASA's Langley Research <br />Center (LaRC) in Hampton, Va., will spend more than three <br />weeks collecting acoustic data at Denver International <br />Airport. They will be using precisely calibrated microphone <br />arrays to measure sound generated by airplane wake vortices. <br />Two laser radars (lidars) will record the actual position, <br />track, and vortex strength, so scientists and engineers can <br />look for subtle characteristics within the wake acoustic <br />signal.<br /><br /><br />"The purpose of the test is to acquire the best data ever <br />collected on the wake acoustic phenomena," said Wayne Bryant, <br />LaRC Wake Vortex Projects Manager. "We hope to establish <br />whether an acoustic-based wake vortex sensor is operationally <br />feasible for the airport environment. One of the key items we <br />will be looking for is a relationship between the recorded <br />acoustic signal and the hazard the wake represents. Estimates <br />of this hazard level will be provided by the lidar systems in <br />our test," he said.<br /><br /><br />Aircraft produce wake vortices when they fly, much like two <br />small horizontal tornadoes trailing behind the wing tips. <br />Larger, heavier aircraft produce stronger wakes. Small <br />aircraft following larger ones can encounter a wake vortex, <br />if they are too close. Turbulence can be severe enough to <br />cause a plane to crash.<br /><br /><br />Wake vortex detectors, such as lidar or possibly a wake <br />acoustic sensor, are envisioned as important parts of a Wake <br />Vortex Avoidance System. Such a system may be able to give <br />pilots advance warning of the location and nature of <br />hazardous wake turbulence.<br /><br /><br />The technology could also increase runway capacity, because <br />air traffic controllers would have a better idea where wakes <br />are and how they decay. Controllers could use that <br />information to efficiently separate aircraft.<br /><br /><br />The Denver test will also provide an opportunity to evaluate <br />recent modifications to a laser-based wake acoustic sensor <br />being developed by Flight Safety Technologies and Lockheed-<br />Martin. The Sensors for Characterizing Ring-eddy Atmospheric <br />Turbulence Emanating Sound (SOCRATES), projects low power <br />laser beams across open space onto a reflector device, which <br />reflects the beams back to a receiver. Developers say the <br />system then measures the changes in the laser beams, which <br />reveal the existence of sound.<br /><br /><br />Participants in the wake acoustics test include NASA; the <br />Department of Transportation Volpe National Transportation <br />Systems Center; OptiNav/Microstar/Titan, Coherent <br />Technologies, Inc.; MIT Lincoln Laboratories; United <br />Airlines; Florida Atlantic University; Flight Safety <br />Technologies; Lockheed-Martin; and the German Aerospace <br />Research Center.<br /><br /><br />For information about NASA and aerospace on the Internet, <br />visit:<br /><br /><br />http://www.nasa.gov