Patent
Advanced airfoils for helicopter rotor application
TLDR
In this article, a family of airfoils for use in rotary wing aircraft, particularly helicopters, is described, characterized by having a maximum c 1.sbsb.max at M = 0.4 and maximum delay in drag divergence while maintaining zero lift pitching moment levels c m.sb.o correctable within the range of -0.01 to +0.Abstract:
A family of airfoils for use in rotary wing aircraft, particularly helicopters, is disclosed. The family is characterized by having a maximum c 1 .sbsb.max at M=0.4 and maximum delay in drag divergence while maintaining zero lift pitching moment levels c m .sbsb.o correctable within the range of -0.01 to +0.01. The present family of airfoils provide high lift at maximum angle of attack when the blade is retreating and maximum delay in drag rise or drag divergence when the blade is advancing. The airfoil section of the family enable a helicopter rotor to counteract, more efficiently, the rolling moment which would otherwise be induced by a rotorcraft's forward flight; this is achieved by the present family of airfoils while maintaining the airfoil sectional pitching moment coefficient at or about zero thereby enabling the blade in which the airfoil sections are incorporated to impose minimum structural loads on the rotorcraft's control system.read more
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Patent
Divergent trailing-edge airfoil
Preston A. Henne,Robert Gregg +1 more
TL;DR: In this article, a special contour near the trailing edge of an airfoil is proposed, which improves the effectiveness of the airfoils by combining a blunt base with a local region of high surface curvature, typically on the lower surface, and upper surface and lower surface slopes that diverge from each other.
Patent
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Patent
Blade profile for aircraft rotor and rotor comprising same
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Patent
Blade section for rotating wings of an aircraft
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Patent
Blade for high speed helicopter
TL;DR: In this paper, the blade tip is thinned between its inboard end and its outboard end so that the outboard part is approximately one half the thickness of the inboard part, while the tip chord remains substantially constant.