Seminars

Abstract: An extraction method to remove blade vortex interaction sound signatures from helicopter transient maneuvering flight acoustics is developed and implemented. The extraction method allows for the investigation of blade vortex interactions independent of other sound sources. The method is a filter of the time-frequency representation of helicopter acoustic signatures, that identifies blade vortex interactions through their high amplitude, high frequency impulsive content. The filtered wavelet coefficients are then inverse transformed to create a pressure signature solely related to blade vortex interactions.

This extraction technique, along with a prescribed wake model, is applied to experimental data extracted from three separate flight maneuvers performed by a Bell 430 helicopter. The maneuvers investigated include a steady level flight, fast- and medium-speed advancing side roll maneuvers. The extraction method is shown to perform admirably throughout each maneuver. One limitation with the technique is identified, and a proposal to mitigate its effects is made. Through the implementation of this technique it is identified that the blade vortex interaction sound pressure level is directly linked to the roll rate of the vehicle, which influences the miss distance of the rotor vortex during interactions.