Abstract: A 2 m diameter,soft inplane or stiff inplane,isolated hingeless rotor model in hover has been tested to investigate its aeroelastic stability.The hingeless rotor blade is constructed with flap lag torsion coupling.The investigation aims at effects of structural and dynamic parameters,such as the collective pitch,precone,sweep,blade lag frequency and rotor rotational speed on the aeroelastic stability.A new and simple technique is applied to the tests so that the excitation of cyclic pitch is accomplished at the blade lag regressing frequency in vertical direction.The experiment shows that the aeroelastic stability of the hingeless rotor blade in hover is slightly influenced by the rotor rotational speed and the blade sweep,but strongly influenced by the collective pitch,precone and blade lag frequency.