Converting turbulence eddy dissipation rate (EDR) into aircraft response metric, RMS-g

Under the sponsorship of the Federal Aviation Administration, work was begun in the early 1990's at the National Center for Atmospheric Research to develop and deploy an in situ turbulence measurement and reporting system for commercial aircraft. The concept was to use existing sensors, avionics and communication networks to produce and disseminate a state-of-the-atmosphere turbulence metric – the eddy dissipation rate (EDR). There are approximately 170 aircraft that are flying this system, with another 270 to come on line in the near future. These data are currently used in the Graphical Turbulence Guidance (GTG) operational product, and will be more heavily used in the GTG Nowcast (GTGN) product, which will be operational for the NexGen IOC. Ths EDR data is also used for the development and verification of future NexGen turbulence products. While EDR is a state-of-the-atmosphere quantity, and is the appropriate parameter for aircraft down- and cross-link, as well as for nowcasting and forecasting products, a pilot may prefer to see a metric that is specific to their aircraft and flight condition. This latter metric is the expected standard deviation of the vertical acceleration (aka RMS-g). In this paper, we will present methodologies that can be used to convert EDR into RMS-g. Statistical and case-study analyses will be presented to show that the conversion is an accurate method that can provide valuable tactical and strategic turbulence information to pilots.