STATISTICAL ANALYSIS OF STRUCTURAL FLIGHT TEST DATA

This paper presents an improved method to extract dynamic component loads from a flight test data base for use in helicopter structural substantiations. Current Sikorsky methodology is to use the maximum recorded (high envelope) load for each flight regime from whatever flight test data is available. This load is then assumed to occur every time the particular regime is flown in service. This method is very conservative when a good sample of data is available, but can be unconservative when the data base is small. The improved method is based on a Weibull analysis of the available data and is illustrated with examples from several flight test programs. The method provides a rational means for choosing a "high envelope" load not biased by the size of the test data sample and for "gap filling" and trending a flight test data base. In addition, the Weibull loads distribution obtained can be used in probabilistic approaches to structural substantiation.