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To enable rotor noise tests in anechoic chamber AC-2 of TsAGI, the facility has been modified and a rotor rig has been specifically designed and manufactured. An experimental study of geometrically similar models of APIAN-INF rotor has been performed in smallscale anechoic chamber AC-2 of TsAGI and in large-scale anechoic wind tunnel DNW-LLF, allowing the comparison between the results. The dimension of the rotor model tested in TsAGI was 60% of the model tested in DNW-LLF. Numerical simulations of the aerodynamic and acoustic characteristics of the rotors have also been carried out. The data obtained in DNW-LLF were used for validation of the numerical results, as well as of the experimental data obtained in AC-2.

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An experimental study of a noise-reduction concept for realistic small-scale (1:10) landing gears has been performed. The concept is based on the idea of the 'flat back' of a cylindrical leg and is realized as the truncated-cylinder form of the main leg of a landing gear, as well as a flat plate behind the main leg of a landing gear at several distances. It has been obtained that the concept does reduce overall noise of the realistic small-scale landing gear models by up to 2.4 dB. The effect of noise reduction has been observed for landing gears both with and without wheels. The effect has been found to persist in the presence of a small yaw angle. Thus, it is concluded that this noise-reduction technology is sufficiently robust and mature to be applied to large-scale models.