Rotorcraft aeromechanics research extends from first-principles modeling through testing and validation for isolated and multi-disciplinary phenomena. These include aerodynamic performance, air loads and wakes, interactional aerodynamics, rotor loads, vibration, and aeroelastic stability.

Many phenomena in rotorcraft aeromechanics are poorly understood and remain unsolved. For example, a lack of fundamental knowledge of fluid flow phenomena limits the ability to accurately model and calculate unsteady, compressible, three-dimensional aerodynamics needed for performance and loads predictions. Particularly difficult are highly nonlinear convective wake and separated-flow phenomena. There are also important deficiencies in rotorcraft structural dynamics phenomena and multidisciplinary interactions between aerodynamics, structures, engine drive trains, and control systems. Finally, there are new concepts under development within the government and industry to improve rotorcraft aerodynamic and dynamic characteristics. These include concepts such as active-flow control on fuselages (and other fixed surfaces) for drag reduction and active on-blade control (including flow control as well as mechanical controls) for performance improvement and noise, vibration, and load alleviation. Current analysis methods are inadequate to capture the complexity of active-rotor response, and must be further validated and improved before adequate design decisions may be made.

Based on current expertise and support from government and industry partners, NASA will focus its aeromechanics research in the areas of aerodynamics, dynamics, and active controls. The primary goal of this program will be to increase the fundamental understanding of the phenomena and to develop and validate appropriate first-principle-based analysis tools. Experimental test data will be essential to help develop and validate the accuracy of the analysis methods. Existing data will be used where appropriate and new experiments will be undertaken to acquire additional test data where needed. It is anticipated that a broad range of experiments will be needed, including small- and large-scale testing. It will be necessary to obtain high-quality, accurate data of sufficient resolution to discriminate important local aerodynamic phenomena.

UH-60 Airloads Program Tutorial
The purpose of the UH-60 Airloads Program was to obtain an extensive set of data on an aircraft in flight with a particular focus on the measurement of blade airloads. The aircraft was tested over a wide range of flight conditions, both in steady flight and in maneuvers. Acoustic measurements were made relative to both ground and airborne microphones.The UH-60 Airloads Program Tutorial was designed to augmentt helicopter graduate education courses based on the extent and richness of the UH-60A flight test database. Beyond this primary purpose, the tutorial can be used to provide an in-depth introduction to helicopter technology for anyone working in the field.

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