Rotor Blade Attachment Assembly with Hub Extender and Tension Torsion Strap
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Solution Overview
Problem
Existing rotary-wing aircraft main rotor assemblies have large structural envelopes that limit their utility in confined spaces and require cumbersome blade fold systems, which decrease flight efficiency due to drag.
Innovation Solution
A rotor blade attachment assembly with a hub extender, inboard and outboard bearings, and a tension torsion strap that allows for blade folding, reducing the structural envelope and minimizing drag by using a composite material hub extender and elastomeric bearings for efficient pitch control and reduced misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the main rotor blades are designed to fold relative to the main rotor hub to reduce structural envelope, then the aircraft can be stored in confined spaces and deployed rapidly, but the blade fold system becomes cumbersome and increases drag
Solution Approach 1:
The patent employs a flexible blade fold system where the rotor blade can pivot relative to the hub through a controlled mechanism. The blade attachment assembly includes flexible connection elements that allow the blade to transition between extended and folded positions while maintaining aerodynamic efficiency during flight, thus enabling volume reduction without excessive drag penalty.
Solution Approach 2:
The blade fold system is designed as a dynamic mechanism rather than a fixed structure. The blade can change its orientation relative to the hub during operation, allowing it to be extended for flight and folded for storage. This dynamic capability enables the system to adapt between two functional states, resolving the contradiction between maintaining large surface area for flight and reducing volume for storage.
2Adaptability or versatility
If a blade fold system is implemented to reduce structural envelope, then rapid deployment and stowage are enabled, but the system becomes cumbersome
Solution Approach 1:
The blade attachment assembly is segmented into distinct functional components: the hub extender, inboard bearing, outboard bearing, and tension torsion strap. This segmentation allows each component to perform its specific function independently, simplifying the overall fold mechanism while enabling rapid deployment. The modular design reduces complexity by breaking down the fold system into manageable, interchangeable parts.
Solution Approach 2:
The patent introduces intermediary elements such as the tension torsion strap and bearing assemblies that mediate between the blade and hub. These intermediaries facilitate the folding motion while reducing the complexity of direct mechanical connections. The tension torsion strap acts as a flexible connector that enables blade movement without requiring complex locking or actuation mechanisms.
3Ease of operation
If traditional blade fold systems are used, then blade folding is achieved, but misalignment between bearings occurs and flight efficiency decreases
Solution Approach 1:
The patent replaces traditional mechanical bearing support systems with a tension torsion strap mechanism. This substitution eliminates the need for complex mechanical linkages that cause misalignment. The tension torsion strap provides a flexible, tension-based support system that maintains bearing alignment during blade folding and flight operations, improving reliability while maintaining ease of operation.
Solution Approach 2:
The patent changes the operational parameters of the blade attachment system by using elastomeric bearings with specific durometer values (e.g., 60-80 Shore A) and designing the hub extender with optimized dimensions and materials. These parameter changes ensure proper bearing alignment during blade folding while maintaining the necessary stiffness and flexibility for flight operations, thus resolving the misalignment issue.
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
The solution enables rapid deployment, reduced vulnerability to environmental conditions, and improved flight efficiency by minimizing the rotor blade's structural envelope and drag, while maintaining high stiffness and reducing misalignment between bearings.
Implementation Method 1
at least one of the inboard bearing and the outboard bearing is an elastomeric bearing
Implementation Method 2
A tension torsion strap is operably coupled to the inboard bearing and the outboard bearing
Data Source
AI summary
A rotor blade attachment assembly for use with a rotor hub to which a rotor blade assembly is connected includes a hub extender having an inboard end and an outboard end. The inboard end of the hub extender is configured to form a connection with the rotor hub. A blade fold axis about which the rotor blade rotates relative to the rotor hub is defined at the connection. An inboard bearing is mounted within an interior of the hub extender adjacent the inboard end and an outboard hearing is mounted within the interior of the hub extender adjacent the outboard end. A tension torsion strap is operably coupled to the inboard bearing and the outboard bearing.