Report of the 12A Working Group on Determination of Critical Ice Shapes for the Certification to Aircraft
Abstract
Task 12A of the Federal Aviation Administration (FAA) Aircraft In-Flight Icing Plan states that the "FAA, along with industry and research organizations, shall form a working group to explore categories of ice accretions that represent potential safety problems on aircraft" with the goal of developing guidance material on the determination of critical ice accretion shapes and roughness in aircraft certification. Accordingly, the 12A Working Group, on critical ice shapes used in icing certification, was formed under the joint leadership of the FAA and the National Aeronautics and Space Administration (NASA) in November 1997. This report describes the activities and findings of the 12A Working Group and its recommended actions for progress to meet the goals stated in the FAA Aircraft In-Flight Icing Plan. The working group reviewed existing guidance material pertaining to the determination of critical ice shapes; prepared and distributed a survey to manufacturers to gather information as to current practices followed by manufacturers in the determination of critical ice shapes in certification; and surveyed publicly available data on aerodynamic effects of ice accretions (primarily glaze ice accretions). It was found that nearly all publicly available data is two-dimensional, with aerodynamic measurements mainly at low Reynolds numbers. Based on this finding, the working group recommended that the research community acquire more three-dimensional data, and also obtain additional measurements at Reynolds numbers more representative of actual flight conditions. The working group formulated a more formal definition of critical ice shape and described two approaches, an "airfoil sensitivity approach" and a "comprehensive aerodynamic approach," that could result in improved practices and guidance material. These approaches should be viewed as complementary, not mutually exclusive.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2000
- Accession Number
- ADA384818