Real-Time, Maneuvering Flight Noise Prediction for Rotorcraft Flight Simulations

This proposal outlines a plan for developing new technology to provide accurate real-time noise prediction for rotorcraft in steady and maneuvering flight. Main rotor and tail rotor thickness and loading noise, including Blade-Vortex Interaction noise and Tail-Rotor Interaction noise, will be predicted with physics-based methods by enhancing a real-time lifting surface/free-vortex-wake blade aerodynamics module and coupling it to maneuvering flight acoustic prediction software modified for operation in a time-marching flight simulation environment. Also included will be methods to account for spherical spreading, atmospheric absorption, and ground effect for flat level terrain. All new software will be designed with the eventual goal of supporting both high fidelity and real-time solutions through a hierarchy of methods. Phase I will provide the development of proof of concept prototype software demonstrated for both steady and maneuvering flight. Phase I will also see an evaluation of real-time potential of the various models. Phase II will provide the development of a fully-functional, noise prediction software module with real-time and high fidelity capability designed for easy coupling with flight simulation software. Phase II will also see additional enhancements in the areas of acoustic propagation, High Speed Impulsive noise, and engine and transmission noise.

The proposed technology has strong potential for facilitating public acceptance of civil V/STOL aircraft and improving the survivability of military rotorcraft. Potential non-NASA applications include; (1) fast evaluation of acoustic impact of new rotary-wing concepts, (2) reduced noise rotary-wing aircraft design using real-time methods within optimization algorithms, (3) improved survivability of military aircraft through improved prediction of long range detection and stealth mission planning, (4) a new capability for pre-mission, stealth training within flight simulators, (5) a key technological step toward real-time cockpit monitoring of ground noise levels during flight, (6) improved land use and flight path planning by the FAA and commercial airports, (7) reduction in acoustic detectability of remotely operated aircraft used in surveillance missions, and (8) improved flight simulator training through realistic audio cues as requested by pilots for certain flight conditions (e.g. the onset of vortex ring state).

The proposed effort directly responds to NASA's SBIR solicitation goal of developing validated physics-based multidisciplinary computational tools applicable for the design, analysis and optimization of rotorcraft in the area of acoustics. The solicitation also directly addresses NASA's goal of reducing noise levels at airports while increasing airport capacity. The computational tools proposed will enhance NASA's ability to conduct detailed assessments of candidate V/STOL concepts, design low noise flight trajectories, perform land use assessment and to evaluate the impact of noise control procedures on crew workload without a need for expensive flight tests. The tool will allow NASA to assess ground noise impact associated with new concepts, such as the current Heavy Lift and High Speed Rotorcraft concepts being studied.

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