First-Ever Re-Categorization of Wake Turbulence Separation Standards a Tremendous Success
Thursday, January 31, 2013

On Wednesday, Jan. 30, NATCA's representative on the re-categorization (RECAT) program and Birmingham Tower/TRACON (BHM) Facility Representative Scott Pressley met with Air Traffic Organization (ATO) Chief Operating Officer David Grizzle and FedEx Express CEO David Bronczek at the Memphis Airport Construction Center. They celebrated the success of the implementation of RECAT wake turbulence separation standards at Memphis Tower/TRACON (MEM).

Capacity at MEM has increased significantly since the revised standards were applied on Nov. 1, 2012.

Wake turbulence forms behind an aircraft as it passes through the air. In certain cases, the wake turbulence generated by large aircraft can be hazardous for aircraft passing behind. This turbulence has been known to cause smaller planes to roll or flip over without warning. Air traffic controllers must follow two different separation standards; one is minimum RADAR separation (2.5 miles, three miles or five miles depending on what type of airspace the aircraft is in) and the other is wake turbulence separation. Wake turbulence separation standards are always the same distance or a greater distance than minimum RADAR separation. Controllers have to use the greater distance in all situations.

The RECAT of wake turbulence separation standards resulted from a decade of collaboration between the FAA, NATCA, DOT/Volpe National Transportation System Center, EUROCONTROL and the aviation industry. Pressley was the NATCA lead in the collaborative process of developing and implementing the RECAT. He explained that this new standard is the first time since 1994 that these categories have been reviewed and changed. The only criterion used in 1994 was the maximum certified gross takeoff weight of each aircraft.

“The tremendous amount of scientific research since 1994 tells us that there are several other factors that should be considered when determining the wake turbulence signature that each aircraft produces,” said Pressley. “These factors include aircraft weight, wing length, wing structure, engine placement and many other factors.”

Experts in wake turbulence, and safety and risk analysis determined that decreasing separation between similar type aircraft is as safe, or safer, than current standards and increases efficiency and capacity.

“While developing this science it was determined that the wake turbulence separation was overly conservative with a large number of aircraft types that are most commonly used throughout our National Airspace System,” said Pressley. “In developing the new categories it was determined that you could split the heavier aircraft into two categories and the next large size group of aircraft into two categories and realize huge results in reduced separation while remaining as safe as we are today.”

The FAA previously used five wake turbulence separation categories based primarily on aircraft weight. The RECAT initiative resulted in six categories, based on weight, approach speeds, and wing characteristics. The categories are labeled A to F, with Category A including very large aircraft such as the Airbus A380 and Category F including smaller planes such as the Cessna Citation and Embraer 120.

FedEx is the largest carrier at Memphis, with about 500 operations each day. Most FedEx aircraft fall under the FAA Category C, including the MD-11, B767, and A300 series aircraft. Because they are in the same category, these aircraft can now be separated by 2.5 to three nautical miles instead of the previously required four nautical miles.

Closer spacing enables FedEx aircraft to be cleared for takeoff with less separation from the previous departure off the same runway. Previously, controllers were required to wait until a departure was several miles from the end of the runway before clearing a second aircraft for takeoff. This reduces by five minutes, under certain runway configurations, the time FedEx aircraft spend in airspace controlled by Memphis TRACON. As a result of the change, FedEx aircraft may now proceed directly from the gate to the runway, cutting average taxi time by three minutes. The FAA estimates a more than 15 percent increase in capacity at MEM as a result of RECAT, an increase of nine additional flights per hour using the new separation standards, lower fuel consumption and fewer emissions.

"This is by far the single-biggest way we can add capacity to the system without pouring an inch of concrete," Southern Regional Vice President Victor Santore said. "It's a big deal."

The FAA plans to expand the new standards to other airports in 2013 and 2014, and estimates an average capacity increase of seven percent. Capacity increases at each airport will depend on the mix of aircraft categories operating at that airport.

“The most important thing to remember is that in the development of RECAT the criteria used was that the process must remain at least as safe as it is today,” said Pressley.