Aircraft Rotor Discrete Flap Hinge Offset Design
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Solution Overview
Problem
Existing main rotor assemblies in rotary-wing aircraft face challenges with discrete, offset flap hinges due to packaging constraints, leading to increased hub moments and aerodynamic drag, which are not effectively managed by prior-art systems.
Innovation Solution
The implementation of a rotor assembly with a discrete, offset flap hinge configuration, utilizing laterally spaced bearings sandwiched between hub/drive plates to create a stiff-in-plane setup, allowing for delta-3 and delta-0 couplings, which provides stability while accommodating pitch links and flap motion, with hinge offsets ranging from approximately 2% to 15% of the rotor radius.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a discrete, offset flap hinge configuration is implemented, then stability and aerodynamic efficiency are improved, but packaging constraints and hub moment management become more difficult
Solution Approach 1:
The patent introduces a lateral offset dimension for the flap hinge axis, positioned at approximately 2% to 15% of the rotor radius from the rotor axis. This dimensional displacement allows the flap hinge to be integrated within the existing hub structure without requiring additional packaging space, while still achieving the stability benefits of a discrete flap hinge configuration.
2Strength
If laterally spaced bearings are used to create a stiff-in-plane setup, then in-plane stiffness and stability are improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent combines the flap hinge function with the existing hub structure by integrating laterally spaced bearings directly into the hub assembly. The bearings are positioned to provide lateral spacing that creates the stiff-in-plane setup, while the flap hinge axis is offset laterally to achieve both structural stiffness and flap motion capability within a single integrated component rather than separate assemblies.
3Productivity
If hinge offsets are increased to accommodate pitch links and flap motion, then aerodynamic performance is improved, but aerodynamic drag and hub moments increase
Solution Approach 1:
The patent optimizes the hinge offset parameter to approximately 2% to 15% of the rotor radius, which provides sufficient lateral displacement to accommodate pitch links and allow free flap motion without excessive offset. This parameter range achieves the necessary aerodynamic efficiency while minimizing the generation of harmful hub moments and aerodynamic drag that would result from larger offsets.
Data Source
AI summary
An aircraft rotor assembly has upper and lower hub plates adapted to be mounted to a central rotor mast for rotation therewith. A plurality of radial arms is connected to at least two flap bearings mounted between the hub plates and forming a discrete flap hinge, each flap hinge defining a flap axis and allowing rotation of the associated arm relative to the hub plates and about the corresponding flap axis. Each of a plurality of blade grips is rotatably connected to one of the arms for rotation about a pitch axis and adapted for mounting of a blade to each blade grip, such that each blade is capable of rotation with the grip about the pitch axis and capable of rotation together with the corresponding arm relative to the hub plates and about the corresponding flap axis.