Abstract
Several small-scale propeller configurations applicable to a conceptual remotely piloted vehicle (RPV) aircraft were designed, fabricated, and tested to determine their performance, acoustic, and detectability characteristics. The tests were conducted in static and simulated forward flight conditions in a wind tunnel. Propellers tested included tractor, pusher, and ducted configurations. The acoustic data obtained were used to determine the slant range and altitude of no detection of each propeller configuration. The acoustic and detectability characteristics of small-scale RPV propellers were found to be significantly different from those of the large-scale propellers. An increase in forward velocity resulted in a significant drop in the SPL's at higher harmonics of blade passage frequency. As expected, tip speed had a very strong effect on noise and detectability in forward flight. It was found that most of the propellers tested would be detected at one of the first few harmonics (mostly first or second) of their blade passage frequency. Of the propellers tested at the design values of thrust and tip speed, three-bladed propellers were generally less detectable than either twoor four-bladed propellers for most of the forward velocities considered. Pusher and ducted propellers were found to be more detectable than their tractor and open counterparts.
Published Version
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