Filters an velocities ngular Rates Hg→ Hos Figure 2-4: Block diagram for the 6 DOF Dryden Turbulence model. The velocity perturbations ug, Ug, wg are independent outputs of the filtered values of the turbulence scale lengths, L, intensity values g and the white noise input sources. The principle axis coupling of the aircraft is taken into account through the inputs to the angle rate perturbation filters. the turbulence seen for a given airspeed, while larger o values increase the deviation about zero. L and o typically vary with altitude in the lower atmosphere as ground effects become more prominent, but for HWIL simulations they are usually fixed The frequency response of the Dryden filters are shown for the same three cases in Figure 2-6. The filter cutoff frequency is determined by the ratio of the scale length to airspeed, and this effectively produces lower bandwidth filters for larger scale lengths The scale length parameter is chosen according to one of several specifications, all of which take into account the variation of L with altitude. The military reference MIL-F-8785C provides one such model of the scale length at low altitudes, h, whichFigure 2­4: Block diagram for the 6 DOF Dryden Turbulence model. The velocity perturbations ug, vg, wg are independent outputs of the filtered values of the turbulence scale lengths, L, intensity values, σ and the white noise input sources. The principle axis coupling of the aircraft is taken into account through the inputs to the angle rate perturbation filters. the turbulence seen for a given airspeed, while larger σ values increase the deviation about zero. L and σ typically vary with altitude in the lower atmosphere as ground effects become more prominent, but for HWIL simulations they are usually fixed. The frequency response of the Dryden filters are shown for the same three cases in Figure 2­6. The filter cutoff frequency is determined by the ratio of the scale length to airspeed, and this effectively produces lower bandwidth filters for larger scale lengths. The scale length parameter is chosen according to one of several specifications, all of which take into account the variation of L with altitude. The military reference MIL­F­8785C provides one such model of the scale length at low altitudes, h, which 39