Fa2004 16.33312-7 Power spectral densities for Von Karman model (see MIL-F-8785C) 2(2)=a2[1+(1.3929-36 there ou is the intensity measure of the disturbance, Q is the spatial frequency variable and ln is a length scale of the disturbance All scale parameters depend on day, altitude and turbulence type Different models available for each direction Scale length parameter L (in feet ) varies with altitude-MIL-F 8785C model valid up to 1000 feet h 0.177+0.00023)12 Turbulence intensity for low altitude flight MIL-F-8785C as 0.1W20 (0.17+0.00823h)04 o where w20 is the wind speed as measured at 20 ft o W20<15 knots is classified as light" turbulence W20 a 30 knots is "moderate W20>45 knots is "heavy� Fall 2004 16.333 12–7 • Power spectral densities for Von Karman model (see MIL­F­8785C) −5/6 Φug (Ω) = σ2 2Lu � 1 + (1.339LuΩ)2 u π where σu is the intensity measure of the disturbance, Ω is the spatial frequency variable, and Lu is a length scale of the disturbance. – All scale parameters depend on day, altitude, and turbulence type. – Different models available for each direction. – Scale length parameter L (in feet) varies with altitude – MIL­F­ 8785C model valid up to 1000 feet h Lu = (0.177 + 0.000823h)1.2 – Turbulence intensity for low altitude flight MIL­F­8785C as 0.1W20 σu = (0.177 + 0.000823h)0.4 3 where W20 is the wind speed as measured at 20 ft 3 W20 < 15 knots is classified as “light” turbulence W20 ≈ 30 knots is “moderate” W20 > 45 knots is “heavy