Most pilots can give a fair recital of the lessons they learned long ago in ground school about the hazard of wake turbulence and how to avoid it. Fewer are aware of how that guidance has changed over time.
A wake turbulence encounter can be a harrowing experience. The study of wake turbulence continues with the FAA modifying its aircraft-separation procedures as aircraft designs and capabilities and understanding of aircraft wake vortices’ behavior evolve.
Safety begins with understanding, and a much better place than your cockpit for refreshing your wake turbulence awareness is the Aeronautical Information Manual (Chapter 7, Section 3). Also, in the Pilot/Controller Glossary that will become effective with the Aeronautical Information Manual’s Aug. 15 revision, pilots will notice that the continuing research that has brought about changes to the FAA’s methodology for classifying aircraft for purposes of wake turbulence separation has also produced changes to the very definition of wake turbulence. The new, leaner definition to appear in the Pilot/Controller Glossary describes wake turbulence as “a phenomenon that occurs when an aircraft develops lift and forms a pair of counter-rotating vortices.”
Some pilots may note for the first time that the NextGen program’s modernization of the air traffic system includes a “wake recat” component—recategorizing aircraft for purposes of wake turbulence separation, and in some cases reducing the required separation.
“Experts in wake turbulence, safety and risk analysis determined that the required separation between certain aircraft can be safely decreased. This determination followed a decade of extensive, collaborative research between the FAA, the DOT’s Volpe National Transportation System Center, EUROCONTROL and the aviation industry,” notes an FAA fact sheet on the topic issued in 2015.
The fact sheet notes that recategorization “is the latest example of how NextGen is transforming the air traffic control system. Safely reducing separation standards between aircraft increases capacity and efficiency, which in turn leads to fewer delays, saving time and fuel burn while reducing the size of aviation’s carbon footprint efficiency, which in turn leads to fewer delays, saving time and fuel burn while reducing the size of aviation’s carbon footprint.”
As you recall from the old ground school lessons on wake turbulence avoidance, earlier aircraft-separation standards were based solely on aircraft weight. More recently, the FAA notes, “airline operations and the mix of aircraft types have changed dramatically, with the rise of regional jets at the light end and aircraft such as the Airbus A380 at the upper end.”
Realizing that aircraft weight alone was not a measure of a wake’s menace—speed, shape, and span are also important factors, as are the rate at which a wake descends or decays—prompted the recategorization that is improving efficiency at numerous major airports, the FAA said. AOPA participated in the safety panel that reviewed the new consolidated wake turbulence guidance, said Rune Duke, AOPA senior director of airspace, air traffic, and aviation security.
To find out if an airport you use is subject to wake turbulence recategorization, he urges pilots to check NOTAM Search for that airport and review any Letters to Airmen on file. An example is this October 2018 Letter to Airmen from the Seattle Terminal Radar Approach Control facility that announced the implementation of recategorization procedures at numerous airports within its airspace. There were no changes required to the use of the terms “Super” and “Heavy” when applicable, and there was no change needed in the format pilots use to file a flight plan, it said. A similar letter was issued for the extremely congested Anchorage, Alaska, airspace.
Whether you fly heavy, light, or ultralight aircraft, the focus on updated ATC separation standards does not release pilots from their obligation to use the same vigilance against wake turbulence that you would apply to avoiding a midair collision—and that includes when complying with ATC instructions to follow other traffic or when accepting a visual approach.
Acceptance of such ATC instructions “is an acknowledgment that the pilot will ensure safe takeoff and landing intervals and accepts the responsibility for providing wake turbulence separation,” the Aeronautical Information Manual chapter notes.