The U.S. Federal Aviation Administration estimates that revised wake turbulence separation standards applied for the first time at Memphis International Airport last November have produced a 15-percent increase in flight-handling capacity at the airport.

The re-categorization (Recat) of wake turbulence separations, a multi-phase effort, “applies advances in knowledge of wake physics” to establish six separation categories based on aircraft weight, approach speeds and wing characteristics. The FAA categorizes aircraft from “A” for very large machines such as the Airbus A380 to “F” for smaller jets and turboprops such as the Cessna Citation and Embraer Brasilia. It previously used five wake turbulence separation categories based primarily on aircraft maximum takeoff weight.

Common to both arrival and departure operations, the new separation standards provide for closer spacing of aircraft on takeoff from a single runway, thereby increasing capacity. The FAA uses as an example the aircraft flown by FedEx Express, the largest carrier at Memphis. Most FedEx aircraft, including the MD-11, Boeing 767 and Airbus A300, fall into category C, according to the agency. Because they share the same category, controllers can separate them by 2.5 nautical miles instead of the previous 4 nautical miles. Overall, the agency said, controllers can manage nine more flights per hour using the new separations.

The FAA plans to apply the “Recat I” separation standards at other airports this year and next, yielding an estimated 7-percent average capacity increase. The Recat II phase will produce “a separation matrix for static pair-wise spacing, with each combination of leader and follower (aircraft) optimized for wake separation,” according to a paper delivered at the Air Traffic Control Association conference last October. Recat III aims to deliver a “weather-based, pair-wise separation” standard.

The Recat initiative is a joint effort of the FAA and Eurocontrol. However, the FAA apparently proceeded ahead of other countries in implementing the new standards. Within the International Civil Aviation Organization (ICAO), “there is an effort to tie Recat Phase I to the international effort of modifying the separation standards for the Airbus A380,” an FAA air traffic procedures advisory committee reported last February. [I]t has become evident that the Airbus agenda is affecting the agenda of the ICAO Wake Turbulence Study Group. As a result, the FAA was forced to withdraw the Recat proposal to ICAO and is currently working to implement the Recat proposal in the U.S.”