The advent of novel electric-powered propeller aircraft designs brings back increased focus on assessment of aircraft whirl flutter. During operation of propeller-driven aircraft, generation of aerodynamic forces on the propeller blades and their interaction with the inertial and elastic forces of the blades cause this phenomenon. In this study, an analytical model is presented for the solution of whirl flutter of propellerengine system. The engine-propeller configuration is assumed to be rigid, while it is flexibly mounted to undergo angular displacement in the vertical (pitch) plane of the propeller axis and in the horizontal (yaw) plane. The stability characteristics of the presented model is analytically investigated and plotted for varying advance ratio values.