Sikorsky Aircraft Corporation

Ashish Bagai

Robert C Moffitt

Timothy A Krauss

David A Kovalsky

Michael S Torok

Robert D Beatty

Thomas Alan Egolf

Kevin P Viola

Robert H Blackwell, Jr

Lauren Kreuscher

John K Karpowich

Bruce F Kay

A rotor blade for a rotary wing aircraft includes a root region extending from a rotor head to about 15% to 20% of a blade radius, a main region extending from a radial extent of the root region to about 80% to 95% of the blade radius, and a tip region extending from a radial extent of the main region to a blade tip. At least a portion of one of the root region, the main region and the tip region includes an airfoil profile section defined by a scaled set of coordinates in which a set of y/c coordinates listed in Table I are scaled by a selected factor.

Airfoil for rotor blade with reduced pitching moment

Main rotor blades of the dual, counter-rotating, rigid coaxial rotor system exhibit a unique unconventional combination of positive and negative twist gradients in which the rotor system rotor Figure of Merit (hover efficiency) is improved by providing a dissimilar twist distribution between the lower rotor blade and the upper rotor blades. This improvement is specifically a result of reduced profile drag of the lower rotor system, achieved by driving the effective operating condition of the lower rotor blades to be similar to the upper rotor blade such that the tip drag losses of the lower main rotor have been reduced considerably using a mathematically vigorous approach. While minimal induced power consumption resulted due to the dissimilar lower main rotor twist, a significant profile power benefit is realized, resulting in the improved hover efficiency with essentially no reduction in rotor forward flight performance.

Rotor blade twist distribution for a high speed rotary-wing aircraft

A main rotor blade incorporating a rotor blade tip region having a tip chord and a tip taper such that the ratio of the main rotor blade chord to the tip chord is approximately 0.30. The tip taper ratio preferably providing an approximately 28% area of reduction in said outer 10% of said blade span. The tip region preferably further including a hover optimized high lift airfoil and a tip sweep that reaches a constant value of approximately 30 degrees along the quarter chord line.

Rotor blade tip planform

A main rotor blade exhibiting a unique planform shape in which the blade chord increases from the root end of the blade inboard region to the outer main region of the blade, where the blade chord achieves a maximum chord at a spanwise location within the main region, then decreases toward a distal tip end. The leading edge preferably is generally straight while the trailing edge is contoured to define the chord. Another characteristic feature of the rotor blade design is the location of the blade-feathering axis in which the feathering axis is located at a mid chord position over some inboard length of the rotor blade then transitions to a quarter chord location. Another characteristic feature is an airfoil distribution along the blade span that transitions from a blunt trailing edge to a sharp trailing edge airfoil suited for mid-range Mach number operation. The tip region preferably utilizes a transonic flow airfoil. Another characteristic feature of the rotor blade design is an unconventional combination of positive and negative twist gradients.

Rotor blade for a high speed rotary-wing aircraft

A rotor blade assembly provides a pitch control assembly to pitch the rotor blade about a rotor blade pitch axis. The pitch control assembly includes a trailing edge flap and a trailing edge servo flap that extend from the trailing edge of the rotor blade. The trailing edge flap is offset in the span wise direction relative to the trailing edge flap. The trailing edge servo flap is located upon a trailing edge servo flap arm linked to the trailing edge flap. To pitch the rotor blade, the trailing edge servo flap is pitched in a direction opposite the desired pitch direction of the trailing edge flap.

Rotor blade pitch control assembly

A multi-element rotor blade includes an individually controllable main element and fixed aerodynamic surface in an aerodynamically efficient location relative to the main element. The main element is controlled to locate the fixed aerodynamic surface in a position to increase lift and/or reduce drag upon the main element at various azimuthal positions during rotation.

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Hamden, CT, United States of America

Ashish Bagai