AN ALTERNATE METHODOLOGY FOR HARMONIC ANALYSIS OF FLIGHT TEST DATA

Development of a technique for harmonic analysis of flight test data is discussed. The technique is mainly intended for analyzing short segments of data, of the order of a few rotor revolutions. The formulation provides a framework within which the frequencies of the harmonics can be identified along with the harmonic amplitudes. Harmonics from multiple sources such as main and tail rotor are identified simultaneously, under the assumption that the frequencies of the various sources are related to each other through fixed ratios. Variations in mean due to quasi-static variations in the response are also taken into consideration. These improvements lead to accurate estimates where the conventional methods of Fourier analysis provide unacceptable results. The technique developed, however, does not account for contributions from structural modes that may be present in the data.