Sikorsky Aircraft Corporation

United Technologies Corporation

T Alan Egolf

Brian Ernest Wake

Mark Winfield Scott

Fabio Paolo Bertolotti

Duane C Mccormick

Peter F Lorber

Stuart S Ochs

Anton J Landgrebe

Ebru Usta

A rotor hub fairing system includes an upper hub fairing, a lower hub fairing and a shaft fairing therebetween. The rotor hub fairing system reduces the total drag on a dual, counter-rotating, coaxial rotor system. Other aerodynamic structures may be mounted to the shaft fairing, hub fairings and airframe to facilitate flow around the upper and lower hub fairings to reduce flow separation and drag.

Rotor hub fairing system for a counter-rotating, coaxial rotor system

A rotor hub fairing system includes an upper hub fairing, a lower hub fairing and a shaft fairing therebetween. The rotor hub fairing system is sized and configured to reduce the overall drag on a dual, counter-rotating, coaxial rotor system. Preferably, the rotor hub fairing is fully integrated. The shaft fairing preferably includes a minimal thickness at the midsection to reduce drag with an increasing thickness adjacent the upper and lower hub fairings to reduce the flow separation on the hub fairing surfaces without overly excessive drag. Other aerodynamic structures, such as a horizontal splitter and/or a plurality of turning vanes may be mounted to the shaft fairing to facilitate flow around the upper and lower hub fairings to reduce flow separation and drag.

Blade vortex interaction (BVI) noise, associated with the operation of aircraft having rotary-wing blades, is abated by the inclusion of an ovate loop tip (,) at the tip portion (,) of each of the rotary wing blades. The ovate loop tip (,) is substantially ovate in shape transverse to the direction of rotation of the rotary-wing blades (,). The ovate loop tip (,) includes upper and lower halves (,&Prime;) of similar or substantially identical geometry, and is positioned substantially symmetrically with respect to a plane (,) defined substantially by the chord of the rotary-wing blade at or near the tip portion (,). The upper and lower halves (,&Prime;) of the ovate loop tip (,) have a common origin or root at their point of attachment with the blade tip portion (,). This geometry and positioning of the ovate loop tip (,) reduces the intensity of the resulting tip vortex, while also minimizing additional loads and stresses on the blade.

Ovate loop for rotary-wing blades

In one embodiment for a helicopter main rotor assembly, a half-plow vortex generator is mounted in combination with the upper aerodynamic surface of each main rotor blade and is operative to generate a primary corotating vortex of sufficient strength to interact with and accelerate the dissipation of the tip vortex generated by the same main rotor blade, thereby reducing blade-vortex interaction noise radiating from the helicopter main rotor assembly. The half-plow vortex generator has a right triangular planform configuration defined by a length, a width, and an apex angle. The three-dimensional configuration of the vortex generator is further defined by an apex height. The apex height is the primary determinant of the strength of the generated primary corotating vortex and is defined in terms of the thickness of the main rotor blade at the local chord where the vortex generator is mounted. The apex height may be approximately equal to the local thickness, but preferably has a magnitude within the range of about one-eighth to about three-quarters of the local thickness. The length, width, and apex angle are secondary determinants of the strength of the primary corotating vortex generated by the half-plow vortex generator. The length and width of the vortex generator are defined in terms of the tip chord length of the main rotor blade, the length preferably having a magnitude within the range of about one-fourth to one-half of the tip chord length and the width preferably having a value of about one-third of the length of the vortex generator. The apex angle preferably has a value within the range of about twenty to about thirty degrees. The mounting site for the half-plow vortex generator is defined in terms of the length of the local and tip chords, respectively. The vortex generator is mounted inboardly from the tip of the main rotor or blade a spanwise distance having a magnitude preferably within the range of about one-half of to about equal to the tip chord length in substantial alignment with the local chord. The apex of the vortex generator is mounted inwardly from the leading edge of the main rotor blade by a chordal distance having a magnitude of about one-quarter the local chord length.

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Glastonbury, CT, United States of America

T Alan Egolf