Composite Pitch Control Spider for Ducted Tail Rotor
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Solution Overview
Problem
Current pitch control devices for ducted tail rotors are heavy, complex, and require frequent replacement due to manufacturing tolerances and wear, leading to vibrations and imperfect controllability.
Innovation Solution
A pitch control device with a composite sandwich control input member and a metallic control transfer member, featuring bushings for isolation and centering, and stud bolts for easy assembly, allowing for reduced weight and simplified maintenance by replacing only worn bushings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional pitch control devices use metal components for the control input member, then strength and stiffness are improved, but weight increases
Solution Approach 1:
The control input member is constructed using composite materials (fiber-reinforced plastic) instead of conventional metal materials. This allows achieving the required strength and stiffness properties while significantly reducing the weight of the pitch control device. The composite structure maintains structural integrity under operational loads.
Solution Approach 2:
The invention changes the material parameters by transitioning from metal to composite materials. This parameter change enables optimization of the strength-to-weight ratio, maintaining necessary mechanical properties while reducing density and overall component weight.
2Ease of manufacture
If the control spider is separated into two parts for accessibility and assembling, then ease of assembly is improved, but device complexity increases
Solution Approach 1:
The control spider is divided into two separate parts: a control spider ring and a center plate. This segmentation allows each component to be manufactured and assembled independently, improving ease of assembly and maintenance while managing device complexity through modular design.
Solution Approach 2:
A connection structure with bushings and fasteners serves as an intermediary between the control spider ring and center plate. This intermediary connection enables easy assembly and disassembly while maintaining structural integrity, resolving the complexity through standardized interface design.
3Ease of operation
If push rods are made as strong and stiff as possible, then controllability is improved, but weight increases
Solution Approach 1:
The push rods are constructed using composite materials that provide high strength-to-weight and stiffness-to-weight ratios. This allows achieving the required controllability and mechanical performance while minimizing the weight contribution of these critical control components.
4Ease of operation
If manufacturing tolerances are tight to ensure controllability, then controllability is improved, but manufacturing precision requirements increase
Solution Approach 1:
Bushings are introduced as intermediary elements in the connection between control components. These bushings compensate for manufacturing tolerances and wear, reducing the stringency of precision requirements while maintaining controllability. The bushings absorb dimensional variations and provide smooth operational interfaces.
Solution Approach 2:
The invention changes the operational parameters by introducing compliant elements (bushings) that accommodate tolerance variations. This allows relaxation of manufacturing precision requirements while maintaining the functional performance and controllability of the system.
5Measurement precision
If the control spider ring is centered using a step on the center plate, then centering accuracy is improved, but wear occurs requiring replacement
Solution Approach 1:
Bushings serve as intermediary elements between the centering step and the control spider ring. These bushings reduce direct metal-to-metal or composite-to-composite contact, minimizing wear while maintaining centering accuracy. The bushings can be replaced independently when worn.
Solution Approach 2:
The bushings are designed as consumable components that can be replaced when worn, while the main control spider structure is preserved. This allows recovery and continued use of the high-value control spider components while replacing only the worn bushings, improving overall system reliability and reducing maintenance costs.
Data Source
AI summary
A pitch control device for a ducted tail rotor of a rotorcraft. The pitch control device comprises a control input member with a disc-shaped central component and at least two connecting arms that extend radially from the disc-shaped central component, wherein the disc-shaped central component is provided for being mounted to an associated pitch control shaft of the ducted tail rotor, and a control transfer member with a ring-shaped connector and at least two push rods that extend axially from the ring-shaped connector, wherein each one of the at least two push rods is provided for being coupled to an associated pitch lever of a rotor blade of the ducted tail rotor.