In Situ Performance Standard for Eddy Dissipation Rate

The FAA, based on industry recommendations, has embarked on a research project that will lead to an Eddy Dissipation Rate (EDR) standard. With this standard, FAA certification officials can determine whether a technique that calculates and reports in situ EDR produces reliable data. EDR is an aircraft-independent, universal measure of turbulence based on the rate at which energy dissipates in the atmosphere. Therefore, a single engine Cessna and a Boeing 747 should produce the same EDR value when flying in the same airspace. However, EDR is not directly measured, but calculated using a variety of parametric data from aircraft avionics and computational algorithms. It is recognized that aircraft will be equipped with diverse avionics and may employ alternative techniques with dissimilar inputs and assumptions to calculate EDR. A standard against which to measure EDR reports is therefore necessary so that the differences in algorithmic approaches and operational inputs do not lead to unacceptable deviations in the resulting EDR values.

The primary benefit of reliable EDR data is to increase the fidelity, accuracy, and confidence in a variety of meteorological applications including: wake vortex predictions, Graphical Turbulence Guidance (GTG), Significant Meteorological Information (SIGMET), and Pilot Reports (PIREP). These applications will facilitate greater real time turbulence situational awareness and enhance both aviation safety and efficiency.

The FAA has assembled a team of subject matter experts from relevant domains and is reaching out to both domestic and international stakeholders to bring together a diverse and comprehensive community of interest to participate in the research project. The specific work elements of the project include: establishing the process by which the EDR performance standard will be defined, identifying the associated performance artifacts, and specifying EDR standard value and label definitions.

To initiate this project, a comprehensive literature search has been conducted to draw EDR information from scores of articles, briefings and reports. This documentation includes: what in situ calculation methods are available, how they are implemented, what data is being reported, where it is available, what implementation problems have been encountered, how the data is used, what performance is required, and how data values and label are defined. This paper introduces the project's approach, and summarizes the analysis of the literature search executed to baseline the project's assumptions.