Identification of main helicopters resonances by ground vibration test

Six resonances of the helicopter body standing on the airport apron and at least two resonances of the free helicopters the frequencies of which are within the range of basic loadings by the helicopter rotor is called (8+) model. It was proposed to identify (8+) model with the use of resonance tests. It was indicated that (8+) model allows for detuning the resonances from the frequency of working loads, tracing the process of moving through resonances as well as taking off and landing. The paper presents: example of a helicopter on a test rig and visible vibrations inductors; induction of resonance vibrations, induction of resonance vibrations with the forms of pitching, yawing, rolling; induction of resonance vibrations with the forms of pitching with opposite pylon yawing and tipping with opposite pylon yawing; model of helicopter resonances; the multiplication of the resonance amplitude for various velocities of moving through with visible growth of the resonance frequency and reduction of vibrations amplitude; change of the frequencies at the taking off and landing.