Multi-element rotor blade with centrifugal force support cuff
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Solution Overview
Problem
The high parasitic drag generated by struts connecting slats to the main rotor blade in rotary-winged aircraft reduces the beneficial effects of increased lift coefficient, such as reduced noise signatures and improved payload/range capabilities, due to the need to withstand lifting and centrifugal forces.
Innovation Solution
A rotor assembly design featuring a rotor cuff that acts as a centrifugal force support, with struts connected to a slat via a journal bearing allowing radial motion and an actuator-controlled active strut to manage slat position, decoupling centrifugal forces from the struts and reducing their size and drag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If struts are designed to withstand both lifting forces and centrifugal forces, then the structural strength is sufficient, but the parasitic drag increases significantly
Solution Approach 1:
The patent divides the force support functions into two separate components: the rotor cuff supports centrifugal forces, and the struts support only lifting forces. This segmentation allows the struts to be smaller and generate less parasitic drag while maintaining sufficient structural strength.
Solution Approach 2:
The patent extracts the centrifugal force support function from the struts and transfers it to the rotor cuff. This removal of the centrifugal support function from the struts enables them to be designed as smaller, lower-drag components.
2Force
If slats are extended to increase maximum lift coefficient, then thrust and payload capabilities improve, but the strut size and drag increase
Solution Approach 1:
The patent segments the force support functions by having the rotor cuff handle centrifugal forces and the struts handle only lifting forces. This allows the struts to be smaller and generate less drag, preserving the benefits of slat extension for increased lift without the penalty of large, high-drag struts.
3Reliability
If struts are made larger to withstand centrifugal forces, then structural reliability improves, but aerodynamic performance deteriorates
Solution Approach 1:
The patent segments the force support responsibilities: the rotor cuff provides reliable support for centrifugal forces, while the struts provide reliable support for lifting forces. This segmentation allows the struts to be smaller and more aerodynamically efficient while maintaining overall structural reliability through the rotor cuff's centrifugal support.
Solution Approach 2:
The patent extracts the centrifugal force support function from the struts and places it on the rotor cuff. This extraction allows the struts to be designed for optimal aerodynamic efficiency while the rotor cuff ensures structural reliability under centrifugal loading.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design reduces parasitic drag, maintains improved aerodynamic performance by isolating centrifugal forces, and enhances the rotor's thrust and maneuverability while minimizing noise signatures.
Implementation Method 1
a journal bearing connects the slat to the strut allowing relative motion in a radial direction between the slat and the main element of the multi-element rotor blade to prevent transmission of edgewise bending loads into the strut
Implementation Method 2
The rotor blade and the slat are secured to a common rotor cuff such that the rotor cuff acts as a centrifugal force support
Data Source
AI summary
A main rotor assembly for a rotary wing aircraft includes a blade assembly secured to a rotor hub. The blade assembly includes a rotor blade and a slat positioned to define a slat gap between the rotor blade and the slat. One or more struts extend from the rotor blade to the slat to position the slat and control motion of the slat. The rotor blade and the slat are secured to a common rotor cuff such that the rotor cuff acts as a centrifugal force support.