Experimental investigation of counter-rotating propfan flutter at cruise conditions

This article presents wind-tunnel experimental flutter results, at transonic relative flows, for a 0.62-m-diam composite propfan model. A blade row that fluttered was tested alone and with a stable aft counter-rotating blade row. The major objectives of the experiment were to study the effects of the second blade row on the row in flutter and to investigate the flutter. Results show that the second row had a small stabilizing effect. Two distinct flutter modes were found within the operating regime of the rotor, both apparently single-degree-of-freedom instabilities, associated respectively with the first and second natural blade modes. For both flutter modes, flutter boundary, frequency, nodal diameter, and blade displacement data are given. The blade displacement data, obtained with an oplical method, give an indication of the flutter mode shape at a span near the blade tip. (Author)