External Noise Evaluation Of The XV-15 Tiltrotor Aircraft

A series of tests were conducted to examine the external acoustical characteristics of the XV-15 TiltRotor Research Aircraft for use in civil applications. Data were obtained for several constant glideslope approaches and level flyovers at various airspeeds and nacelle tilt angles using a ground-based microphone array. These data are . presented in terms of Sound Exposure Level and compared to that for several different - helicopter types. The tiltrotor aircraft is shown to be similar in noise level to these helicopters when in helicopter mode, but is significantly quieter in airplane mode. Sample acoustic waveforms of helicopter mode, tilt rotor mode and airplane mode are compared to show the rather dramatic changes possible in tilt rotor aircraft noise characteristics with flight condition. In appendices to this paper, the noise data are also presented in terms of A-weighted sound pressure levels, and handling characteristics of the XV-15 observed during the constant glideslope approaches are discussed