Design of Experiments Development for Rotorcraft Acoustic Flight Testing

A cooperative acoustics flight test campaign between the US Army and NASA was performed in which design of experiments (DOE) approaches were used to plan the flight test conditions. Three DOE designs were used, a face centered central composite design, circumscribed central composite design, and a hexagonal design. A traditional one-factor-at-a-time approach was also used, and interpolation points were planned to test for the strength of the DOE approaches. This paper documents the design methodology, discusses how response surface models were fit to the data, evaluates the overall response of the models, and evaluates the individual DOE designs. The response surface models were also used to design new test conditions of interest during the experiment, and that process is also documented. For the first time, DOE was shown to be an exceptionally useful tool for rotorcraft acoustics flight test planning, while the full power of the approach has yet to be reached.