Summa Corporation

Textron Corporation

Harold E Lemont

Robert C Miller

A helicopter tail rotor (14) is provided with a thrust ring. The thrust ring comprises an annular airfoil (16) having a circular opening which is aligned coaxially with the rotor (14). The plane of the airfoil (16) is essentially parallel to the plane of the rotor (14) but slightly offset downstream from the rotor (14). The cross section of the airfoil (16) can have a wide variety of configurations including flat and cambered. The tip vortices (30) produced by the rotor (14) are captured near the downstream surface of the airfoil (16) to produce a circulating airflow (32) that draws air from the upstream region of the airfoil (16) through the opening therein. The aerodynamic action of the airfoil (16) widens the wake diameter of the wash from rotor (14), increases rotor (14) thrust efficiency, reduces the noise level of rotor (14), enhances transverse stability and lowers the vibration level experienced by helicopter (10). The airfoil (16) further serves as a guard to protect the rotor (14).

Helicopter rotor thrust ring

An all metal, low conductivity, high performance and relatively lightweight, composite structure, in the form of an insulation blanket is operably disposed to be exposed to a high temperature zone, e.g., a high temperature fluid, or on a supporting surface exposed to high temperature. The composite includes two metal skin members spaced from each other by a metallic member functioning as a spacing member. The spacing member is preferably deformed to contact the spaced skin sheets at spaced positions, the space between the skin sheets forming a fluid space which defines a zone of substantially reduced heat transfer by convection. When deformed, the spacing member, or an array of spacers, also provides an elongated path for conduction of heat, and defines a plurality of cavities of limited volume forming stagnant gas pockets. The skin sheets may be perforated to vent the cavities and to provide expansion space for absorbing thermal growth by the metal components of the composite. The spacing member also operates as a shield against the transfer of heat by radiation with the effect that the composite has a heat transfer coefficient substantially dictated by the thermal conductivity of the fluid in the space between the skin members. Use of metal components, principally of commercially available materials, permits fabrication of composites having various shapes and structural strengths, e.g., vibration, compaction, fatigue, etc., good chemical stability and easily repaired. Various different forms and alternate arrangements are described.

Insulation system

A thermal insulation composite includes at least a first metallic skin sheet, and a plurality of non-combustible metallic filaments randomly interlocked to form a wool and affixed to said first skin sheet. A second metallic skin sheet may be affixed to said wool and said first sheet, or the second skin sheet may be a surface of the structure to be insulated. A fluid is present in the interstices of the filaments and in the zone between the skin sheets. Each of the filaments has a significant length to cross-sectional diameter ratio to minimize its thermal conductivity. The filaments also preferably have a circular cross section to minimize the area of contact and hence the heat conducted between adjacent filaments. In this manner, the conductivity of the wool is made primarily dependent upon the thermal conductivity of the fluid in the interstices of the filaments. Heat transmission by radiation is inhibited by providing a plurality of radiation shields interposed between multiple layers of the wool. The skin sheets, wool, and radiation shields are bonded by stitches or staples to form an insulation blanket. The interstices of the filaments are of many different sizes so that the insulation has characteristics for absorbing sound waves over a significant band of frequencies. The composite may be used to insulate ducts, airfoil surfaces, fire walls and to form fireproof garments, and has the unique capability of being fabricated into a variety of structural shapes.

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Arlington, TX, United States of America

Harold E Lemont