A Methodology for Assessing the Operational Performance of an Aircraft-based Eddy Dissipation Rate (EDR) Algorithm

Founded in 1935 as the Radio Technical Committee for Aeronautics, RTCA (as it is now simply known) is an independent standards development organization that allows public-private partnership to develop consensus driven recommendations on technical performance standards for government certification of equipment throughout the international flying community. RTCA Special Committee 206 (SC-206), Aeronautical Information [AI] and Meteorological [MET] Data Link Services, works to develop standards for AI and MET data link capabilities, and members include commercial airlines, airframe manufacturers, avionics manufacturers, meteorological forecasters and researchers, and private weather industry providers. SC-206’s activities are joint with those of the European Organisation for Civil Aviation Equipment (EUROCAE) Working Group 76, allowing harmonization of U.S. and European AI and MET data link work. Under SC-206 and WG-76, joint sub-groups 4 and 2 (SG4/SG2) support RTCA and EUROCAE goals through the development of standards recommendations related to data link of MET information, with an emphasis on aviation-related turbulence.

The International Civil Aviation Organization requires automated turbulence reports from aircraft in flight be in the metric of Eddy (or “Energy”) Dissipation Rate (EDR). Thousands of commercial aircraft from almost 2 dozen airlines report EDR worldwide. There are multiple ways of calculating EDR using aircraft-based sensor data, and each method has strengths and weaknesses depending on user needs. Importantly, the airline industry is eager for the development of a way to standardize performance of EDR calculations, so that data from the different methods will result in the same operational decisions by flight crews.

In response, SG4/SG2 developed RTCA document DO-370, Guidelines for In Situ EDR Algorithm Performance to set requirements for EDR algorithm developers to follow and ensure that their algorithm output was “comparable” to that of other algorithms. At the time of DO-370 development in 2017, there were three major algorithms, and the formulation of performance recommendations was conducted by the developers. DO-370 details procedures to assess algorithm performance in a simulation test environment. While the simulation approach allows for a controlled and repeatable test environment, it does not ensure the algorithms perform that way in a real-world situation.

In the 8 years since DO-370 was published, some airlines have begun using emerging, alternative methods of calculating or inferring EDR. Some of these new methods, such as accelerometer-based tablet applications and EDR data calculated using Automated Dependent Surveillance-Broadcast (ADS-B) output, cannot be evaluated under the current DO-370 guidelines. With the help of the National Center for Atmospheric Research and The MITRE Corporation, SG4/SG2 has developed an updated methodology for validating that an EDR algorithm performs within an acceptable range of error tolerances. The expectation is that this methodology will be formalized in regulatory documents by both RTCA and EUROCAE. This presentation will provide a review of the methodology and progress to date.