The COBRA-2 counter rotating fan model with S-shaped blades and m=20 ultra-high bypass ratio is tested at CIAM C-3A test facility (Russia) with the aim of aerodynamic and acoustic performances investigation. The specific blades geometry assumes an improvement of acoustic characteristics for this fan model. However, along with the advanced aerodynamic and acoustic performances of counter rotating fan model it is required to provide an acceptable rotor blades vibration behavior. Moreover, it is necessary to control and measure rotor blades vibrations during tests in order to prevent blade damage. For this purpose, a non-contact blade vibration measurement system (blade tip-timing) is used. This paper describes results of rotor blades vibration parameters for the counter rotating fan model measured by this system. Among the results, indications for occurrence of self-excited blade vibrations and their comparison with calculated data for this type of vibrations are shown.
