Automated Noise Mitigation for Hybrid-Electric Multirotor Aircraft Using Sound Redirection, Atmospheric Modeling, and Intelligent Flight Planning

Hybrid gasoline-electric propulsion (HGEP) is increasingly being used to power multirotor aircraft due to the superior energy-density of gasoline versus that of batteries. HGEP also maintains significant advantages over alternative hybrid power sources like hydrogen fuel cells because of its significantly lower cost and ability to operate in extreme temperatures, as well as the wide availability of gasoline. One major disadvantage of HGEP is the noise signature of its internal combustion engine (ICE).  In this proposal, new methods of flight planning and multirotor-specific flight control are developed to minimize the detection distance of hybrid ICE powered aircraft. The magnitude of the noise signature is strongly dependent both on the orientation of the aircraft’s exhaust and on environmental conditions such as vertical temperature gradients, wind direction, cloud cover, and altitude. Real time, in situ atmospheric measurements taken onboard the aircraft update sound propagation models that in turn predict detection distance as a function of the orientation of the aircraft with respect to the surrounding areas. Methods of redirecting exhaust noise and piloting the aircraft such that the noise is directed away areas of interest are also developed.  The proposed technologies would allow aircraft operators to plan and fly missions that minimize the chances of detection and minimize the distance between the aircraft and areas of interest, and to better recognize mission risk in real time when detection is imminent. In Phase II, the proposed technologies would be seamlessly integrated into the existing flight planning software.