Articulated Rotor Blade Spar Layout for Weight-Stable Flight

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Solution Overview

Problem

Traditional rotor blades for rotary wing aircraft are designed with a center of gravity forward of the aerodynamic center, requiring heavy weights at the leading edge for stability, which increases weight and manufacturing costs while reducing payload capacity.

Innovation Solution

Designing the rotor blade with a shear center forward of the aerodynamic center by making the spar thicker on the forward end and using a lighter construction without a forward weight, achieving dynamic stability through the spar's design and ply configuration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If heavy weights are placed at the leading edge to position the center of gravity forward of the aerodynamic center, then dynamic stability is improved, but blade weight increases and payload capacity decreases

Engineering Contradiction:

Improvedynamic stabilityVSAvoidblade weight

Core Design Contradiction:

Stability of the object's compositionVSWeight of moving object

Solution Approach 1:

The invention changes the spatial relationship parameters between the shear center, aerodynamic center, and center of gravity. Specifically, it positions the shear center forward of the aerodynamic center while placing the center of gravity aft of the aerodynamic center, creating a new stable configuration that eliminates the need for heavy leading-edge weights

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention inverts the traditional rotor blade design paradigm. Instead of placing the center of gravity forward of the aerodynamic center (traditional design), it positions the center of gravity aft of the aerodynamic center while achieving stability through the inverted relationship where the shear center is forward of the aerodynamic center

Inventive Principle:

Principle #13The other way round (Inversion)

2Stability of the object's composition

If heavy leading-edge weights are used to achieve proper center of gravity positioning, then stability is improved, but manufacturing cost increases

Engineering Contradiction:

ImprovestabilityVSAvoidmanufacturing cost

Core Design Contradiction:

Stability of the object's compositionVSEase of manufacture

Solution Approach 1:

The invention extracts and eliminates the heavy leading-edge weights from the rotor blade design. By repositioning the center of gravity aft and utilizing the shear center-aerodynamic center relationship, the design removes the unnecessary weight component while maintaining stability

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention changes the positional parameters of the center of gravity and shear center to achieve stability without requiring additional heavy components, thereby simplifying manufacturing and reducing costs

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If heavy leading-edge weights are added to position the center of gravity forward, then stability is improved, but payload capacity decreases

Engineering Contradiction:

ImprovestabilityVSAvoidpayload capacity

Core Design Contradiction:

Stability of the object's compositionVSQuantity of substance

Solution Approach 1:

The invention extracts the unnecessary heavy leading-edge weights from the design, directly reducing overall blade weight and increasing the available payload capacity while maintaining stability through the repositioned center of gravity and shear center relationship

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentEP4331982B1Method of stabilizing articulated rotor blade

Publication Date: 2026.01.21 LOCKHEED MARTIN CORP

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AI summary

A rotor blade (200) for a rotary wing aircraft includes a leading edge (204) and a trailing edge (206) defining a chordwise direction. The leading edge defines a forward end of the rotor blade and the trailing edge defines an aft end of the rotor blade. The rotor blade has a center of gravity (224) and an aerodynamic center (226) along the chordwise direction. The center of gravity is aft of the aerodynamic center.