Rotor craft are elastic vibration systems with a highly complex dynamic behaviour. Along with the vibration-generating units in the area of the fuselage, such as the engine turbines, the rotating rotor head structure, including the elastic rotor blades, plays a decisive role in the overall dynamic system. This vibrational input can also strongly be felt in the cabin. An exact description of the unsteady aerodynamics and the dynamic interaction between the airframe and the rotor is necessary to enable safe and stable flight operations as well as to take constructive measures for the improvement of flight comfort.
Modern helicopter developments are underlined by innovative solutions in the areas of rotor blades and rotor concepts. Optimised blade shapes can lead to noise reduction and improved performance. The aeroelastic interaction could completely impede the development of new rotor craft configurations, such as the tilt rotor aircraft, because of the critical problem of whirl flutter in these configurations.
As a consequence of these innovations, the accuracy requirements on the aeroelastic models for evaluation of the stability and the accurate prediction of vibrational loads for the entire helicopter have clearly increased.
The work is described in detail in the following sections: