Impact of Atmospheric Boundary Layer Turbulence on Noise from Helicopter and Advanced Air Mobility Aircraft

A major barrier to public acceptance of commercial rotorcraft operations is noise. The emerging advanced air mobility (AAM) market is expected to use well-designed, quieter electric vertical takeoff and landing (eVTOL) aircraft to avoid current limitations on helicopter operations in urban areas caused by their acoustic impact. This paper introduces the conceptual Penn State University Reference Aircraft 3 (PSU-RA3) to understand the potential acoustic impact of tiltrotor eVTOL aircraft, such as the Joby S4. A new quasi-steady implementation of the Penn State Noise Prediction System (PSU-NPS) is presented. PSU-MulTINoise, a novel time-domain broadband noise prediction code was developed and integrated into the system to model broadband noise from atmospheric boundary layer (ABL) turbulence interacting with the rotors. The ABL forms in the near-surface flow as the wind passes over the terrain and as thermal gradients drive convective motion. The system was validated against previously published flight test data for the Airbus AS350 and a Joby preproduction prototype. Variations in arrival and departure maneuver noise were studied around three heliports in New York City (NYC): the Downtown Manhattan Heliport (JRB), LaGuardia Airport (LGA), and John F. Kennedy International Airport (JFK). Predicted noise levels increased when ABL turbulence was included. Significant variation in average day noise level (DL) contours was observed between heliports owing to differences in adjacent urban terrain. The variation was greater for the PSU-RA3 eVTOL than for the AS350 helicopter. The results show that changes in noise levels owing to AAM operations in urban areas should be evaluated using site-specific terrain and atmospheric conditions.