F100 fan stall flutter problem review and solution

Abstract

An experimental investigation was conducted to examine an airfoil durability problem in the first fan rotor of the F100 engine. This study incorporated laboratory and simulated engine flight tests, an empirical correlation of aeroelastic stability parameters from engine test data, and substantiation testing of the redesign. The results of this investigation's initial testing showed that rotor failure at high-flight Mach numbers and low altitudes was caused by torsional stall flutter instability. The results of the empirical correlation indicated that a design free of flutter required a decrease in both normalized incidence and reduced velocity. Further, the correlation indicated that the flutter was affected by inlet pressure, a heretofore undocumented phenomenon. The results of the substantiation testing confirmed that the redesign made the rotor flutter-free throughout the entire aircraft flight envelope. It was concluded that an improved stall flutter analysis was required to ensure stable fan and compressor rotor designs. It was further concluded that the effect of changes in inlet pressure level on rotor stability was, in part, the result of the accompanying changes in air density and steady-state aerodynamic loading.