Main calculation principle of gear wheel geometry with asymmetrical tooth profile is presented. The paper presents calculation of bending stresses by means of YFS coefficient which takes into account the tooth shape and stress concentration. Graphic method of YFS coefficients calculation is described. Graphic method of stiffness calculation of teeth with asymmetrical profile and results of vibration testing are given.

Tooth gearings are used in transmission systems of aviation engines to carry the torque from the engine to the accessories. Various forces occur in the course of loading their teeth. The cogwheels making up a part of the transmission system of the aviation engine consist of elements affected both by the rigid and soft restoring forces. Spasmodic change of rigidity in the case of changing the number of engaged couples of teeth causes parametric vibrations of cogwheels. It follows from this that transmission is not only a nonlinear, but also a parametric oscillatory system. The maximum amplitude is not realized when passing the resonance in the case of quick changes of the rotation frequency. Two different values of fluctuation can be registered in the steady-state regime for identical values of the rotation frequency. This duality is called bifurcation. Bifurcations of vibrations can be quite often observed in aviation transmission gears. The existence of bifurcation of vibrations in aviation transmission gears is theoretically proved and the pilot study confirming theoretical conclusions about the existence of bifurcation of oscillatory processes in tooth gearings is described in the paper. Bifurcation parameters are determined.