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The Helicopter Rotor at High Mach Numbers

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A joint United States Army‐NASA‐Bell experimental investigation has shown that rotor operation at advancing tip Mach numbers above 1.0 is possible and, with special treatment at the blade tip, practical for certain applications. Tests were conducted in the NASA‐Ames 40‐ × 80‐Foot Wind Tunnel with production UH‐1D (NACA 0012 profile) blades and with experimental blades incorporating reduced thickness at the tips. The production blades were evaluated at advancing tip Mach numbers up to .95 and the thin tip blades to Mach 1.025. The production and thin tip blades are compared. The results show that compressibility effects are delayed and that at the higher tip Mach numbers, significant reductions in both power and loads are obtained with the thin tip blades. Additionally, the state of the art of calculating rotorcraft performance at low advance ratios (μ = .3) and at Mach numbers above 0.8 is reviewed and limited experimental data, from special boundary layer instrumentation, are also presented.
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Document Type: Research Article

Affiliations: Bell Helicopter Company, Ft. Worth, Texas

Publication date: 1968-04-01

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  • The Journal of the American Helicopter Society is the world's only scientific journal dedicated to vertical flight technology. It is a peer-reviewed technical journal published quarterly by AHS International and presents innovative papers covering the state-of-the-art in all disciplines of rotorcraft design, research and development. (Please note that AHS members receive significant discounts on articles and subscriptions.)

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