An experimental method for the investigation of subsonic stall flutter in gas turbine engine fans and compressors

A facility for the investigation of stall flutter in aircraft engine compressors and fans was designed. Stall flutter was achieved in the test fan and verified through sonic and photographic methods. The frequency components of the sonic output during flutter were determined using a real-time analyzer. This frequency analysis indicated a dominant peak within 7 percent of the theoretical torsional natural frequency of the blades.

Photographs taken during stall flutter indicated the presence of an interblade phase angle.

The effect of blade stagger angle, flow incidence angle and solidity on flutter speed was determined.