Blade-tip vortices and their interaction with the helicopter blades play an important role in the generation of noise on rotorcrafts. Full-scale vortex visualization is essential for the understanding of these effects and the validation of sub-scale experiments and numerical simulations. In the present work, the reference-free Background Oriented Schlieren (BOS) method was used to visualize bla...

This paper presents the development of a multibody dynamics model of a VTOL teetering rotor. The developed model includes a teetering hub, containing a flexure and torque tube, rotor blades, pitch links, and swashplate system. A non-teetering rotor configuration, which modified the baseline teetering rotor by removing the teetering hinge, is also developed, and its aeromechanics characteristics...

by Ryan T. Kelly Aero-optical disturbances produced from turbulent compressible flow-fields can seriously degrade the performance of an optical signal. At compressible flight speeds these disturbances stem from the density variations present in turbulent boundary-layers and free-shear layers; however helicopters typically operate at incompressible speeds which nearly eliminates the aberrating e...

The focus of this study is on the attitude estimation of the four-rotor helicopter known as quadrotor. The choice of the algorithm is a complementary filter based on quaternions. For the four-rotor helicopter system has nonlinear, strong coupling, multi-variable features, it is difficult to obtain the accurate attitude values, and in order to solve this problem a quaternion-based complementary ...

All single-rotor helicopters require an antitorque device (usually a tail-rotor system) to counter the fuselage’s reaction to the rotation of the main-rotor system. From 1988 through 1993, there were 74 U.S. civil turbine-engine helicopter accidents involving the helicopter’s tail-rotor system, according to statistics from the U.S. National Transportation Safety Board (NTSB) and the U.S. Federa...

An approximate numerical mthod is presented for analysis and determination of modal characteristics in straight, pretwisted non-unifom helicopter blades. The analysis considers the coupled flapwise bending (out of plane), chordwise bending (in plane), and torsion vibration of both rotating and non-rotating blades. The proposed method is based on the integral expansion of Green functions (struct...

The Short-Haul-Civil-tiltrotor (SHCT) component of the NASA Aviation System Capacity Program is an effort to develop the technologies needed for a potential 40-passenger civil tiltrotor. The variable diameter tiltrotor (VDTR) is a Sikorsky concept aimed at improving tiltrotor hover and cruise performance currently limited by disk loading that is much higher in hover than conventional helicopter...

Current trends in the design of helicopter have shown that in order to be economically viable and competitive it is necessary to investigate new design concept which may give an improvement in performance and operational flexibility goal and expanding the flight envelope of rotorcraft, but must be shown to be costeffective. The helicopter has carved a niche for itself as an efficient vertical t...

The US Army Aeroflightdynamics Directorate (AFDD), the French Office National d’Etudes et de Recherches Aérospatiales (ONERA) and the Georgia Institute of Technology (GIT) are working under the United States/France Memorandum of Agreement on Helicopter Aeromechanics to study rotorcraft aeromechanics issues of interest to both nations. As a task under this agreement, a comparative study of the D...

An Xcell-60 5 ft rotor diameter hobby helicopter was instrumented to perform autonomous aggressive maneuvers. Avionics system, state estimator design, and vibration isolation are presented in detail. Analysis of helicopter dynamics based on flight data is given. 1 Ph. D. candidate, Department of Aeronautics and Astronautics, [email protected] 2 M.S. candidate, Department of Electrical Engineering...