Johns Hopkins Laboratory To Study Wake Vortices At BWI Airport

September 09, 1996

Dangerous air currents created by large commercial aircraft will be studied this month by The Johns Hopkins University Applied Physics Laboratory (APL), Laurel, Md., on runway 33L at Baltimore Washington International Airport (BWI). The invisible air currents, known as wake vortices, have been identified as the cause of at least 51 aircraft accidents or incidents in the United States from 1983 to 1993, according to a report from the National Transportation Safety Board, yet no reliable detection system exists that can characterize these deadly air flows.

Wake vortices, a byproduct of the lift generated by the airplane1s wing, are tornado-like air currents that are particularly hazardous for small planes landing behind large aircraft. Last month, in hopes of reducing wake vortices-related incidents, the Federal Aviation Administration instituted new landing regulations that require a six-mile separation between small aircraft and large jets such as the Boeing 747 and a five-mile gap between the light aircraft and Boeing 757s.

Data collected by APL researchers at BWI and other locations will be used to develop a reliable vortex detection system. Such a system would increase airport safety by providing controllers with observed vortex location and intensity information to help them decide when it is necessary to delay landings and takeoffs.

Experimental radar equipment to measure the location, strength, and duration of the vortices will be temporarily installed near the landing end of runway 33L at BWI next week with data collection scheduled for Sept. 16 - 27. 3This is the first time continuous-wave radar has been used in wake vortex research,2 says Leo McKenzie, a project engineer for the APL study. 3The Laboratory has been involved in advanced radar technology since its inception, more than 50 years ago, and we1re optimistic that this type of radar can detect dangerous air patterns.2

APL will install a small, X-band bistatic radar transmitter about 75 feet inside the airport fence adjacent to Route 176 on the east side of runway 33L, with a corresponding receiver west of the runway. Data will be collected from all types of large aircraft routinely using the runway as they descend.

To enhance radar detection of the vortices, sound waves will be released at the end of the runway as an aircraft approaches. The sound waves are expected to be inaudible to the neighborhood area. Researchers will also use an instrumented Lockheed Martin C-130 airplane to emit smoke from its wing tips as it simulates landings at BWI. This will create a visual pattern of the vortices air flow. Data collection is expected to take place from 5-7 p.m. each day and should not affect normal airport activity.

In October the researchers will travel to John F. Kennedy Airport in New York for further wake vortices research that will include teams from the John A. Volpe National Transportation Systems Center, the Massachusetts Institute of Technology, and the National Aeronautics & Space Administration.

For more information contact Helen Worth at the Applied Physics Laboratory: phone: (410) 792-5113; fax: (410) 792-6123; e-mail:

Johns Hopkins University Applied Physics Laboratory

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