Mcdonnell Douglas Helicopter Company

Mcdonnell Douglas Corporation

Thu N Vu

Michael C Frengley

Brian Koorosh Hamilton

Stephen Lewis Guymon

Murray J Hines

The present invention relates to an improved helicopter rotor system including a contoured flexure strap having a simplified geometrical configuration. The flexure strap serves to join the rotary hub assembly with the rotor blades and is formed of fiberglass. The primary load carrying fibers of the flexure strap preferably extend in the same direction as the spanwise axis of the flexure strap in order to withstand the centrifugal forces acting on the strap. The inboard end portion of the flexure strap includes two separate ends, with one of the ends extending in a vertically upward direction and the other end in a vertically downward direction. This allows the ends of flexure straps positioned on opposite sides of the rotary hub assembly to overlap one another and be retained in place by a single pin and bolt assembly. A cloth wrap of composite matrix material surrounds portions of the flexure strap to provide redundancy which prevents the fibers in the flexure strap from delamination when subjected to forces arising during operation of the helicopter.

Contoured flexure strap for helicopter rotor system

A method for making helicopter rotor blades includes wrapping a prepreg strap around the conical or cylindrical outboard end of each weight segment. The weight segment is then placed in the rotor blade spar and goes through the spar cure cycle with it. Primary retention is provided by adhesive bonding between the weight and the spar. Secondary retention is by hoop tension in the strap, acting through interlaminar shears at the co-cured interface with the spar.

Method of making a leading edge weight retention assembly for a

Leading edge weights for helicopter rotor blades are required to provide blade chordwise balance and maintain rotor inertia. Provision for retention of the leading edge weights in a high centrifugal force field, after failure of the primary adhesive bond, is necessary. The invention discloses wrapping a prepreg strap around the conical or cylindrical outboard end of each weight segment. The weight segment is then placed in the rotor blade spar and goes through the spar cure cycle with it. Primary retention is provided by adhesive bonding between the weight and the spar. Secondary retention is by hoop tension in the strap, acting through interlaminar shears at the co-cured interface with the spar.

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Tempe, AZ, United States of America

Thu N Vu