Helicopter Rotor Blade Attachment Separable Junction Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing blade attachments for bearingless rotors in helicopters face challenges in efficiently transmitting lead-lag oscillations to dampers and require a separable junction to facilitate easy folding and maintenance, while maintaining structural integrity and reducing structural height to improve drag behavior.
Innovation Solution
A blade attachment with a separable junction between the airfoil blade and the flexbeam/control cuff unit, utilizing asymmetric bolts with a main bolt and supporting bolt configuration, optimized for lead-lag pivoting stiffness, allowing for easy folding and improved load transmission to dampers, with a reduced structural height and aerodynamic profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a separable junction is provided between the flexbeam/cuff unit and the airfoil blade to allow separate manufacturing and replacement, then ease of manufacture and maintenance is improved, but the mechanical strength and reliability of the connection is worsened due to the high centrifugal forces and bending moments that must be transmitted
Solution Approach 1:
The rotor blade system is divided into separable components: the airfoil blade can be detached from the flexbeam/cuff unit at the junction. This segmentation allows independent manufacturing, inspection, and replacement of the airfoil blade without replacing the entire assembly, directly improving ease of manufacture and maintenance while the patent addresses the strength challenge through specific connection design
Solution Approach 2:
The control cuff is positioned to enclose the flexbeam, creating a nested structural arrangement. The junction connects the airfoil blade to this nested flexbeam-cuff structure, allowing the connection to utilize the structural support of both components simultaneously, thereby maintaining mechanical strength while enabling separability
2Ease of operation
If the junction is designed to be separable to allow the airfoil blade to be pivoted and folded, then ease of operation for folding is improved, but the device complexity increases due to the additional mechanical components required for the separable connection
Solution Approach 1:
The junction is designed with asymmetric bolts that allow dynamic reconfiguration: during normal operation the bolts provide rigid connection for strength, but when loosened they allow the airfoil blade to be pivoted and folded. This dynamic capability enables easy blade folding while the patent manages complexity through the specific asymmetric bolt configuration rather than more complex mechanical mechanisms
3Object-affected harmful factors
If the structural height at the junction is reduced to improve aerodynamics and drag behavior, then the aerodynamic performance is improved, but the manufacturing precision requirements increase to ensure proper alignment and load transmission
Solution Approach 1:
The junction design concentrates the connection features at a specific location with optimized local geometry. The asymmetric bolts are positioned to create minimal structural height protrusion, and the connection geometry is locally optimized to provide sufficient alignment tolerance, thereby improving aerodynamics while managing manufacturing precision requirements through localized design features
Data Source
Figure 1
Figure 2~4
Figure 5~6
AI summary
The invention relates to a blade attachment (1, 20) for a bearingless main rotor of a helicopter with an airfoil blade (2), a flexbeam (3, 21) including a flexbeam body (16, 17) and a flexbeam head (13) at an end of said flexbeam body (16, 17). A control cuff (4, 22) encloses and extends along at least a predominant portion of said flexbeam (3, 21). A separable junction arrangement between said flexbeam head (13), said control cuff (4, 22) and said root end of said airfoil blade (2) is mechanical with removable fasteners. Said removable fasteners comprise a main bolt (7) and at least one supporting bolt (8)