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As part of the overall National Aeronautics and Space Administration (NASA) study of trailing vortices -- the invisible flow of spiraling air that trails from the wings of large aircraft and can "upset" smaller aircraft flying behind -- the NASA Flight Research Center (FRC) borrowed a Boeing 747 jetliner for testing. The B-747 had been purchased by NASA for the space shuttle program and assigned to the Johnson Space Center. Six smoke generators were installed under the wings of the B-747 to provide a visual image of the trailing vortices.
Additional Information
The objective of the flights was to test different configurations and mechanical devices on the B-747 that could be used to break up or lessen the strength of the vortices. This could lead to shorten spacing between landings and take-offs, thereby helping to alleviate air traffic congestion. Over 30 flights the B-747 aircraft was flown using combination of wing spoilers in an attempt to reduce wake vortices. To evaluate the effectiveness of the different configurations chase aircraft were introduced into the vortex sheets to probe their strengths and patterns at different times. Two of the chase airplanes used were the FRC's Cessna T-37 and the NASA Ames Research Center's Learjet. These aircraft were representative of the business jets and smaller aircraft which might encounter large passenger carrying aircraft on approach or landings around major airports, or in flight.
Tests without the B-747 wing spoilers deployed produced violet "upset" problems for the T-37 aircraft at a distance of around three miles. From the magnitude of the problems found, distances of as much as ten miles may be required if spoilers were not employed. With two spoilers on the outer wing panels used, the T-37 could fly at a distance of three miles and not experience an "upset" problem. The wake vortex study continued even after the B-747 was returned to its primary mission of carrying the Space Shuttle Orbiter.
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