Standardization of Gustiness Values from Aircraft

Abstract

A universal turbulence standardization technique is described which is based quantitatively on the atmospheric turbulence itself rather than on the effects it products on an aircraft. It provides a single turbulence intensity number which may be measured continuously in flight in a variety of ways, and, with knowledge of the aircraft type and speed, can be linearly related to the rms value of vertical accelerations of the aircraft. The universal intensity number concept as applied here is an extension for aircraft use of the inertial subrange concept of atmospheric turbulence. In the inertial subrange all the statistical properties of turbulence of wavelengths less than a few hundred meters (the wavelength range which dominates gust loading for most aircraft) can be simply related to a single number. The intensity measurement also has value as a basic meteorological parameter, and has proven to be particularly useful in diffusion studies. The intensity scale is derived from various turbulence power spectrum studies. A larger background of data on turbulent distributions is also available because existing statistical discrete gust and continuous gust data can be fitted approximately to this standardization procedure, and meteorological studies have also given estimates of the distribution of this intensity number. The intensity number can be found from virtually any device moving through the air, as well as by some indirect meteorological means. A particular version of a universal turbulence indicator is described. The universal turbulence intensity rating provides a standard for communication about turbulence and for the collection of statistical turbulence information. It also provides a quantitative method of relating aircraft response and pilot ?feel? to the turbulence, so that the pilot can select or preselect the appropriate speed for specific missions.