MODE TRACKING DURING FLUTTER TESTING USING THE MODAL ASSURANCE CRITERION

Tracking the aeroelastic modes of an aircraft through changing flight conditions is an essential element of flight flutter testing, which is made difficult by corrupted data and high modal density. The modal as surance criterion (MAC), a method of evaluating the consistency of two modal vectors, is shown to simplify the mode tracking procedure by pu tting a numerical value on the correlation between pairs of modes iden tified at consecutive flight conditions. Representation of the resulti ng MAC values as a colour map gives a clear visual indication of modal consistency. An automated approach to mode tracking is introduced and shown to work on aircraft-type systems, over significant changes infl ight condition up to and beyond the flutter speed. Some potential prob lems of a practical implementation are discussed.