Shaped rotor blade for reduced loads and vibration

Details Shaped rotor blade for reduced loads and vibration Shaped rotor blade for reduced loads and vibration

2006-08-15

2010-12-07

Look, Edward (Department: 3745)

Fluid reaction surfaces (i.e., impellers)

Specific blade structure

Irregular, flanged or channel forming blade surface

C416S238000, C416S240000

Reexamination Certificate

active

07845911

ABSTRACT:
Rotor blades are pre-bent in at least one of a flap direction and a lag direction, wherein the pre-bent portion comprises at least 20-60% of the length of the blade. Preferred methods include analyzing the rotor dynamic behavior using computational methods, deciding on the operational case (rotor lift load, forward speed, etc.) in which the loads and vibration reductions are desired, and using the computed results to decide on an amount of pre-bending of the unloaded blade so that it comes closer to the feather axis under load. Another class of preferred methods models the bending of a first blade in flight loading conditions, and then designs a second blade having a pre-bend in approximately an equal in magnitude and opposite in direction to the bending. It is contemplated that such “pre-bent” blades can significantly reduce rotor loads and vibration levels of rotorcraft equipped with semi-rigid or rigid rotors.

REFERENCES:
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patent: 3135334 (1964-06-01), Culver
patent: 3999886 (1976-12-01), Ormiston et al.
patent: 4099892 (1978-07-01), Martin
patent: 5111676 (1992-05-01), Ruzicka, Jr. et al.
patent: 6116857 (2000-09-01), Splettstoesser et al.
patent: 6190132 (2001-02-01), Yamakawa et al.
patent: 6582196 (2003-06-01), Andersen et al.
patent: 06056093 (1994-03-01), None

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