Asymmetrical Flexbeam Root Reduces Virtual Flapping Hinge Distance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In rotary wing aircraft, bearingless or hinge-and-bearingless rotor systems face challenges with high natural flapping frequency and moments due to large flapping hinge distances, leading to discomfort and poor flying characteristics, and existing flexbeam elements struggle to reduce virtual flapping hinge distance below 7% of the rotor-disc radius while maintaining structural integrity and aerodynamic efficiency.
Innovation Solution
The implementation of asymmetrical flexbeam roots with unbalanced longitudinal extensions and a nested configuration, mounted to the rotor head via primary and secondary bolts, reduces the virtual flapping hinge distance to less than 7% by allowing closer rotor blade transitions and improved aerodynamic performance, while maintaining structural integrity and reducing manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If bearingless or hinge-and-bearingless rotor systems are used with large flapping hinge distances, then control response and maneuverability are improved, but natural flapping frequency increases and high moments are transferred to the rotor mast and fuselage
Solution Approach 1:
The patent employs asymmetrical flexbeam roots with unbalanced longitudinal extensions that are offset from the centerline of the flexbeam element. This asymmetrical configuration allows the virtual flapping hinge to be positioned closer to the rotor mast (reducing flapping hinge distance to less than 7% of rotor disc radius) while maintaining the necessary flapping motion characteristics, thereby reducing the harmful moments and natural flapping frequency transferred to the fuselage.
2Object-generated harmful factors
If virtual flapping hinge distance is reduced to improve flying characteristics, then moments and natural flapping frequency are reduced, but it becomes extremely difficult to place flexbeam attachment to rotor hub close to rotor center
Solution Approach 1:
The flexbeam root is designed with asymmetrical geometry including unbalanced longitudinal extensions that extend beyond the centerline of the flexbeam element. This asymmetrical design enables the attachment point to be positioned offset from the rotor mast centerline, allowing the virtual flapping hinge to be located at a reduced distance (less than 7% of rotor disc radius) while maintaining proper flexbeam attachment to the rotor hub.
Solution Approach 2:
The patent introduces a longitudinal offset dimension for the unbalanced extensions of the flexbeam root, positioning them at a non-zero longitudinal offset from the centerline. This dimensional adjustment allows the virtual flapping hinge to be moved closer to the rotor mast in the radial direction while accommodating the attachment geometry requirements at the rotor hub interface.
3Object-generated harmful factors
If asymmetrical flexbeam roots with unbalanced longitudinal extensions are used, then virtual flapping hinge distance is reduced to less than 7%, but manufacturing complexity may increase
Solution Approach 1:
The flexbeam elements are constructed using composite materials, which allow for the integration of asymmetrical root geometry and unbalanced longitudinal extensions into a single monolithic structure. This composite construction method simplifies manufacturing by eliminating the need for separate attachment components and complex assembly procedures, while achieving the desired asymmetrical configuration for reduced virtual flapping hinge distance.
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 achieves a reduced virtual flapping hinge distance, enhancing aerodynamic performance and reducing discomfort, while also simplifying manufacturing and maintaining structural integrity, thus improving the flying characteristics of rotary wing aircraft.
Implementation Method 1
During operation, i.e. rotation of the multi-blade rotor, the flexbeam elements must withstand and transfer tremendous centrifugal forces that the rotor blades apply thereto
Implementation Method 2
the flexbeam elements usually comprise torsion weak regions which enable low-force torsional motion of the flexbeam elements for inducing pitch angle adjustments of the rotor blades
Implementation Method 3
these flexbeam elements comprise special, in particular fiber reinforced composite materials that are flexible enough in torsion to allow twisting for blade movement
Implementation Method 4
these flexbeam elements realize flapwise-soft regions that enable flapping of the associated rotor blades in the vertical direction
Data Source
AI summary
A multi-blade rotor for a rotary wing aircraft, comprising a plurality of rotor that is connected to an associated rotor head via a plurality of flexbeam elements, wherein at least one flexbeam element of the plurality of flexbeam elements comprises an asymmetrical flexbeam root that is mounted to the associated rotor head.