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B-747 in Flight during Vortex Study B-747 in Flight during Vortex Study

Photo Number: ECN-4242
Photo Date: September 20, 1974

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In this 1974 NASA Flight Research Center photograph, a Boeing B-747 jetliner is shown taking part in the trailing wake vortex study. In the photograph, the two wing tip vortex trails, being the strongest, stay in tight cylindrical rolls. The "strength" of the vortices decreases toward the midspan of each wing, and the trails become less defined.

In 1974 the NASA Flight Research Center (later Dryden Flight Research Center, Edwards, California) used a Boeing 747 as part of the overall NASA study of trailing vortices. Trailing vortices are the invisible flow of spiraling air that trails from the wings of large aircraft and can "upset" smaller aircraft flying behind them. The 747 that NASA used was on loan from the Johnson Space Center where it was part of the Space Shuttle Program.

The data gathered in the 747 studies complemented data from the previous (1973-74) joint NASA Flight Research Center and Federal Aviation Administration (FAA) Boeing 727 wake vortices study.

Six smoke generators were installed under the wings of the 747 to provide a visual image of the trailing vortices. The object of the experiments was to test different configurations and mechanical devices on the747 that could be used to break up or lessen the strength of the vortices. The results of the tests could lead to shorter spacing between landings and takeoffs, which, in turn, could alleviate air-traffic congestion. For approximately 30 flights the 747 was flown using various combinations of wing air spoilers in an attempt to reduce wake vortices. To evaluate the effectiveness of the different configurations, chase aircraft were flown into the vortex sheets to probe their strengths and patterns at different times. Two of the chase planes used were the Flight Research Center’s Cessna T-37 and the NASA Ames Research Center’s Learjet. These aircraft represented the types of smaller business jets and other small aircraft that might encounter large passenger aircraft on approach or landings around major airports or in flight.

Tests without the 747’s wing spoilers deployed produced violent "upset" problems for the T-37 aircraft at a distance of approximately 3 miles. From the magnitude of the problems found, distances of as much as ten miles might be required if spoilers were not used. With two spoilers on the outer wing panels, the T-37 could fly at a distance of three miles and not experience the "upset" problem. The wake vortex study continued even after the 747 was returned to its primary mission of carrying the Space Shuttle.

NASA Photo by: NASA

Keywords: 747; 727; Boeing; wake vortex (vortices) study; NASA; NASA Flight Research Center; Dryden Flight Research Center; Ames Research Center; Johnson Space Center; FAA; Space Shuttle; Cessna T-37; Learjet; Federal Aviation Administration.

Last Modified: February 6, 2002
Responsible NASA Official: Marty Curry
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