Researchers Tackle Effects of Wake Turbulence at Nation's Airports

October 2010
Topics: Air Traffic Management, Meteorological Factors, Airports, Improving National Airspace System Performance
Wake turbulence, or powerful rotating forces of air that occur during takeoffs, routinely affect airport operations.
plane contrails

Keeping air traffic moving with minimal delays is an essential part of the global economy. Despite the best-laid plans, however, various factors still interfere with traffic flow. Disruptions caused by stormy weather or clouds of volcanic ash result in rerouting, rescheduling, or even grounding flights. But other aspects of aviation that interfere with air traffic can be mitigated by understanding challenges, then countering them at the source.

One factor, known as wake turbulence, is a byproduct of aircraft movement. For years, aviation engineers and scientists have studied the effect of wake turbulence—basically, the powerful rotating forces of air generated by aircraft during takeoffs and in flight—which can present an invisible hazard for other aircraft. "Wakes are of particular concern to pilots and controllers during takeoffs and landings," explains Clark Lunsford, a principal multidiscipline systems engineer at MITRE. "Wake turbulence can have a significant impact on airport capacity, because planes must be spaced far enough apart that they don't encounter each other's wake."

Researchers, including those at MITRE, are making progress in offsetting their effects. "Separation distances are currently fixed based on the weights of the two aircraft," says Laurence Audenaerd, a senior simulation and modeling engineer. "Heavier aircraft generally generate stronger wakes, and can tolerate encountering stronger wake." Audenaerd and Lunsford are part of a team of about a half-dozen MITRE engineers, including a former airline pilot, who are conducting research for a Wake Turbulence Mitigation for Arrivals (WTMA) project.

For several years, MITRE—which operates a federally funded research and development center for the Federal Aviation Administration—has helped the agency by studying and developing ways to reduce the impact of wake turbulence on daily airport operations. "Our role is to help design aviation procedures and determine system impacts," Lunsford says.

The WTMA project is one of several concurrent wake research programs at MITRE investigating issues surrounding arrivals, departures, and separation standards. For this work, MITRE is part of a collaborative team, including NASA and other organizations such as MIT Lincoln Laboratory and the Volpe National Transportation Systems Center (part of the U.S. Department of Transportation's Research and Innovative Technology Administration).

MITRE is a team member among organizations contributing various pieces of the wake turbulence puzzle, working to make sure solutions are operationally feasible and beneficial. "We aren't wake scientists—we don't predict wake behavior," Audenaerd points out. "We're experts at making the information extracted from the data usable, by putting it into the context of air traffic operations for our sponsor."

Discovery through Simulation

The main goal of wake research is to see if there is a way to protect aircraft from wake encounters, while increasing runway capacity under certain conditions. It's a complex proposition—many factors affect takeoff and landing safety, including runway configuration, time of day, wind, and weather conditions.

MITRE contributed to the research by using two capabilities developed within our Center for Advanced Aviation System Development:

  • State-of-the-art airport capacity simulation tools that take into account weather, airport factors, and intricate air traffic control rules that govern flight operations.
  • An air traffic management human-in-the-loop simulation facility that can evaluate human factors and feasibility aspects of potential procedure improvements.

The knowledge gained from simulations has been invaluable for identifying which new wake procedures should be pursued for implementation at specific airports. "Pilots and controllers can test new procedures in a realistic environment," Audenaerd says. "The controller involvement in the simulations was critical in helping uncover operational issues, validating expected benefits, and underscoring potential mitigation strategies regarding wake turbulence."

Among the Busiest

Seventeen of the nation's busiest airports have parallel runway configurations that make them potential candidates for early wake benefits. "We worked with MIT Lincoln Laboratory using results from their detailed wind forecast model that predicts periods when you can run particular arrival and departure procedures," Audenaerd explains. "We assessed a spectrum of procedures in terms of feasibility, benefits, and safety, which forms the foundation for future solutions to be applied to many more airports."

MITRE is currently working to integrate the results of the wake research with other initiatives within the FAA's Next Generation Air Transportation System, which aims to smooth the arrival and departure process at the nation's major airports. "These programs will benefit from this research as well," Audenaerd says.

The wake research team is also developing options for longer-term wake procedures, using wake monitoring and prediction technologies. "We're using our simulation capabilities and aviation experience to fully explore a variety of future scenarios to help ensure that the wake procedures we help the FAA develop will be beneficial and safe," Lunsford adds.

—by Cheryl B. Scaparrotta

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