Just as a boat leaves a wake of water, an airplane leaves a wake of air that affects the aerodynamics of trailing aircraft. For four decades, Volpe has supported the Federal Aviation Administration (FAA) in understanding the science of aircraft wake turbulence. Volpe researchers have moved beyond a basic understanding of the physical science of aircraft wake and are now using the information gleaned from their research to improve aviation safety.

"Without Volpe’s contribution to the science of wake turbulence data collection and analysis, RECAT would not have been successful.”

- Jeffrey Tittsworth, Manager of the FAA Wake Turbulence Research Office

Volpe’s recent work on behalf of FAA has focused on wake turbulence recategorization (RECAT), which uses millions of data points on wake turbulence to determine a new set of wake separation standards for various aircraft models. Separation standards define the minimum distance that one aircraft must be behind another during take-offs and landings.

In June, that work—which includes analyzing data, creating risk matrices, and studying new aircraft—helped FAA implement new separation standards at Hartsfield-Jackson in Atlanta, the world’s busiest airport.

Jeffrey Tittsworth, the manager of the FAA Wake Turbulence Research Office, stated, "Without Volpe’s contribution to the science of wake turbulence data collection and analysis, RECAT would not have been successful.”

Improving Efficiency

The amount of wake an aircraft creates, to the first approximation, is proportional to the weight of the aircraft. A typical Boeing 767 can seat around 250 passengers, while a 747 can seat more than 400. A 767 traveling behind a 747 needs 4 nautical miles of separation—but a 747 traveling behind a 767 needs only 2.5 nautical miles of separation.

Even though the 747 seats 60 percent more people, before RECAT, both aircraft were in the “heavy” category and required 4 nautical miles of separation. Bringing that separation down to 2.5 nautical miles goes a long way toward increasing capacity and reducing delays.

Tallying the Results

The RECAT separation standards were first implemented with aircraft operations in Memphis, Tennessee, starting in November 2012. FedEx, the major air carrier at Memphis, reported a 20 percent increase in airport capacity and $1.8 million in fuel savings each month.

Recently, FAA approved Atlanta’s Hartsfield-Jackson to use new separation standards for commercial operations. Fifteen additional major U.S. airports are scheduled to implement these new standards by 2017. Unlike other efforts to improve airport efficiency that may require years of construction, RECAT is a simple rule change that has an immediate impact.

Unlocking the Full Potential of Wake Turbulence Science

Reduced fuel costs and time savings represent the tip of the iceberg of what new separation standards and wake turbulence science can do, said Jonathan Lee, chief of Volpe’s Aircraft Wakes and Weather Division. Environmental, economic, and time savings will increase as Volpe researchers continue to investigate how wake turbulence acts during crosswinds, storms, and other weather events, and under different aircraft configurations and weights.

“The wake research community has a rudimentary capability in model-based wake turbulence approach,” Lee said. “Currently, there are five or six different wake models that will give you five or six different answers with the same set of inputs. Wake models have little maturity close to the ground, which is one of the reasons why the FAA adopted a data driven approach.

As for more futuristic wake solutions, Lee said, “If we can get a better handle on how wakes behave under various weather parameters, including wind, temperature, atmospheric turbulence and other aircraft factors, we might be able to do something even more dynamic.”