James E Spencer

US Patent:

40225461, May 10, 1977

Filed:

Nov 6, 1975

Appl. No.:

5/629577

Inventors:

Jan M. Drees - Dallas TX
Arthur D. Gravley - Euless TX
Charles V. Palachek - Smithfield TX
James L. Spencer - Arlington TX

Assignee:

Textron, Inc. - Providence RI

International Classification:

B64C 2746

US Classification:

416226

Abstract:

A helicopter main rotor has blades with an inboard airfoil having a high lift-drag ratio for efficient hovering and a "shock-free" outboard airfoil for high speed cruise. Each rotor blade has a structural section composed of metal spars and metal skins forming torque boxes accompanied by a nonstructural fairing and after body. Secured within the torque boxes and the after body are honeycomb cellular structures of a metallic and nonmetallic material, depending on the area wherein the cellular structure is secured. At a point along the blade radius, between 60% and 75%, the upper metal skin of the aft torque box changes from an outer contour surface of the blade to a flat surface parallel to and above the cord line. A fairing of fiberglass skin is secured over a nonmetallic cellular structure over the flat surface of the upper metal skin to complete the upper outer airfoil contour outboard of the 75% radius dimension. The lower outer airfoil contour is the metal skin of the aft torque box followed by a fiberglass skin joined at a trailing edge with the fiberglass upper surface.