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The paper describes how to use simple models and, if needed, sensitivity analyses to determine the wake vortex categories for new aircraft. The methodology provides a tool for the regulators to assess the relative risk of introducing new aircraft into the current fleet. Nomenclature b= wingspan, ft b 0 = separation of the two rolled up vortices, ft C l = roll moment coefficientDepartment of Transportation FAA = Federal Aviation Administration ICAO = International Civil Aviation Organization IFR = Instrument Flight Rules L = lift MLW = Maximum Landing Weight, lb MTOW = Maximum Certificated Gross Takeoff Weight, lb N = number of non-dimensional time units for vortex strength to go to zero NM = nautical miles NTSB = National Transportation Safety Board q = dynamic pressure, kg/(m sec 2 ) r = radius of vortex, ft RECAT = Recategorization RMC = roll moment coefficient s = spanwise loading coefficient S = wing area, ft 2 sec = second(s) T = non-dimensional time or torque 1 2 U = final approach speed, ft/sec U ∞ = aircraft speed, ft/sec US = United States V v= tangential velocity of a vortex, ft/sec W = weight, lb y = distance along a wing from the center of the fuselage, ft α = angle induced on a section of a wing due to a vortex, radians Γ = vortex circulation strength, ft 2 /sec Γ 0 = initial vortex circulation strength, ft 2 /sec ρ = air density, slug/ft 3

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