RAT Mounting Frame Resonance Control via Segmented Lugs
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Solution Overview
Problem
Ram air turbines (RATs) in aircraft face resonance modes that can be damaging due to their alignment with dynamic loading frequencies, making it challenging to manufacture a high-stiffness support structure that is both lightweight and cost-effective, and complicates installation without a frame.
Innovation Solution
A mounting system for RATs comprising a frame with specific lugs and rods that resist movement in multiple directions, increasing the natural resonant frequencies of the RAT away from its operating range, thereby reducing the likelihood of resonance damage and facilitating installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the stiffness of the support structure is substantially increased to move resonance frequencies away from operating range, then resonance damage risk is reduced, but weight and manufacturing cost increase
Solution Approach 1:
The support structure is divided into multiple discrete mounting elements (lugs and rods) distributed at strategic locations on the frame, rather than using a single monolithic stiff structure. This segmentation achieves the required stiffness through distributed load paths while minimizing material usage and weight.
Solution Approach 2:
The mounting system employs a composite structure combining rigid frame elements with flexible mounting connections (lugs and rods). This composite approach creates a system with optimized dynamic characteristics that achieves high effective stiffness for resonance control without requiring excessive material in any single component.
2Reliability
If the stiffness of the support structure is substantially increased to move resonance frequencies away from operating range, then resonance damage risk is reduced, but manufacturing complexity and cost increase
Solution Approach 1:
The support structure is divided into multiple discrete, standardized mounting elements (lugs and rods) that can be manufactured independently using conventional processes. This segmentation simplifies manufacturing compared to a single complex high-stiffness structure, as each element can be produced with standard tolerances and assembled into the final mounting system.
Solution Approach 2:
The mounting elements (lugs and rods) are designed as universal components that serve multiple functions: structural support, resonance frequency control, and simplified installation. This multi-functionality reduces the need for specialized manufacturing processes and allows use of standard aerospace fastening techniques.
3Ease of operation
If a frame structure is added to the RAT to facilitate installation and improve mounting stiffness, then ease of installation and resonance control improve, but device complexity increases
Solution Approach 1:
The frame structure is segmented into discrete mounting locations with standardized lugs and rod attachment points. This segmentation allows the frame to be manufactured as a modular unit that simplifies installation by providing pre-positioned mounting interfaces, reducing the complexity of field assembly despite adding structural elements.
Solution Approach 2:
The frame with its mounting elements is pre-configured during RAT manufacturing with lugs and rod attachment points positioned to optimize resonance characteristics. This preliminary action ensures that installation requires only simple attachment operations rather than complex field fabrication or alignment procedures.
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 mounting system effectively moves the harmonic frequency range of resonance modes away from the RAT's operating range, reducing the risk of damage and allowing for easier installation while maintaining a lightweight and cost-effective design.
Implementation Method 1
Both in the stowed position and especially in the deployed operating position of the RAT, the RAT can exhibit multiple resonance modes. These resonant modes can be damaging to the RAT and the support structure connecting the RAT to the aircraft if the resonant modes occur within 15% of the dynamic loading frequencies
Implementation Method 2
The theory is known that substantially increasing the stiffness of the support structure of the RAT can move the harmonic frequency range at which these resonance modes of the RAT occur away from the frequencies of the operating range of the RAT
Data Source
AI summary
A ram air turbine (RAT) mounting system includes a frame with a forward end having a first side, a second side disposed opposite the first side, a third side, and a fourth side disposed opposite the third side. The frame also includes an aft end. A first mounting element is connected to the forward end of the frame proximate the first side and the third side. A second mounting element is connected to the forward end of the frame proximate the first side and the fourth side. A first rod is connected to the forward end of the frame proximate the second side and the third side. A second rod is connected to the aft end of the frame.