Forward sweep, low noise rotor blade

Details Forward sweep, low noise rotor blade Forward sweep, low noise rotor blade

1995-07-06

1996-12-17

Larson, James

Fluid reaction surfaces (i.e., impellers)

Specific blade structure

Cantilever blade

416242, B64C 27467

Patent

active

055846610

ABSTRACT:
A forward-swept, low-noise rotor blade includes an inboard section, an aft-swept section and a forward-swept outboard section. The rotor blade reduces the noise of rotorcraft, including both standard helicopters and advanced systems such as tiltrotors. The primary noise reduction feature is the forward sweep of the planform over a large portion of the outer blade radius. The rotor blade also includes an aft-swept section. The purpose of the aft-swept region is to provide a partial balance to pitching moments produced by the outboard forward-swept portion of the blade. The rotor blade has a constant chord width; or has a chord width which decreases linearly along the entire blade span; or combines constant and decreasing chord widths, wherein the blade is of constant chord width from the blade root to a certain location on the rotor blade, then decreases linearly to the blade tip thereafter. The noise source showing maximum noise reduction is blade-vortex interaction (BVI) noise. Also reduced are thickness, noise, high speed impulsive noise, cabin vibration and loading noise.

REFERENCES:
patent: 1146121 (1915-07-01), Amnelius
patent: 1692081 (1928-11-01), De La Cierva
patent: 2128780 (1938-08-01), Leff
patent: 3972646 (1976-08-01), Brown et al.
patent: 4168939 (1979-09-01), Schmitz et al.
patent: 4684324 (1987-08-01), Perosino

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