Several facets of rotorcraft competitiveness are being pursued through Subsonic Rotary Wing Project research efforts: efficiency, including aerodynamic performance and structural weight; productivity, which includes high speed, large payloads, long range, and good maneuverability; and environmental acceptance, particularly regarding noise and handling qualities.

The goal of project research is to expand rotorcraft capabilities to meet future civil requirements tied to the Next Generation Air Transportation System, such as increasing capacity and reducing congestion at airports. To this end, advanced rotary wing technologies, design, and analysis techniques will be pursued, enabling new configurations and missions to be developed efficiently and confidently.

Research is focused on areas that industry and other government agencies are not pursuing, or cannot pursue alone. Without intending to predict where the design process will lead when truly effective design and analysis tools are available, some very promising (and very challenging) configurations can be identified to drive the required fundamental research. The challenges faced in rotary wing aviation are among the most complex and demanding of any configuration: highly complex, three-dimensional rotor and fuselage structures, unsteady flows in speed regimes from low subsonic to high transonic, dynamically stalled components, harsh operating environments, highly loaded propulsion systems, and a vehicle that is statically unstable. For dramatic breakthroughs in rotorcraft to be achieved, these technical challenges require an approach that integrates aeronautics disciplines. For example:

• The Variable Speed Rotorcraft Concept demonstrates a variable-speed rotor (reducing rotor tip speed at high-speed cruise operating conditions) integrated with a variable-speed transmission (capable of 50-percent speed reduction from hover to cruise). This integration of the Propulsion and Aeromechanics disciplines will enable advanced high-speed rotorcraft concepts and noise reduction concepts.
• Super-Integrated Control Design integrates flight controls, noise reduction, Propulsion, and Aeromechanics to develop a methodology and design for a broadband rotorcraft control system incorporating a flight control system, engine control, airframe/drive train/rotor load control, active rotor control of vibration and noise, vehicle heath management, and guidance for low-noise operation.
• Advanced Structural and Propulsion Concepts for Interior Noise and Vibration Reduction integrate Structures, Propulsion, and Acoustics to develop and demonstrate interior noise and vibration reduction using optimized combinations of new materials acoustics treatment, reductions in transmission gear vibration, and active noise cancellation.
• Interactional Aeroacoustics Investigation integrates Aeromechanics and Acoustics to validate and assess the capability to predict rotorcraft behavior, including performance, air loads, flow fields, structural loads, and acoustics, by comparing predictions with validation data obtained in advanced wind tunnel experiments.
• Unified Experimental Techniques: Integrated Experimental Systems seeks to develop and integrate experimental methods of enabling efficient, multi-parameter, simultaneous measurements for characterizing rotorcraft behavior and providing validation data.

The Subsonic Rotary Wing Project will focus its research efforts in the most persistent technical challenge areas, producing advances in prediction tool capability and technology in order to expand the role of rotorcraft in civil aviation.