Flexible Mounting Assembly for Helicopter Airframe Stress Reduction
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Solution Overview
Problem
In helicopter airframe structures, the interaction between top and bottom structural members and vertical frame members leads to stress loading at connection points, particularly during transient load conditions such as take-off, which complicates the installation of access features like doors and windows.
Innovation Solution
A flexible mounting assembly is used, comprising a vertical frame member, an isolation frame member, and a horizontal shear wall assembly, allowing relative vertical motion between the top and bottom structural members while maintaining load-carrying capabilities, thereby reducing stress loading and facilitating the installation of access features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rigid connection between top and bottom structural members is used, then structural strength is improved, but stress loading at connection points increases during transient loads
Solution Approach 1:
The mounting assembly uses a flexible connection mechanism that allows relative vertical motion between the top and bottom structural members during transient loads. The flexible mounting assembly includes a flexible element that can deform to accommodate movement while maintaining connection, transforming the rigid static connection into a dynamic adaptive connection that reduces stress at connection points during helicopter take-off and landing.
Solution Approach 2:
The flexible mounting assembly changes the mechanical parameters of the connection by introducing flexibility and motion capability. The flexible element can elongate, compress, or deform under load, allowing the connection to adapt its stiffness and strength characteristics based on operational conditions, thereby reducing peak stress loading at the connection points while maintaining overall structural integrity.
2Stress or pressure
If flexible connection between structural members is used, then stress loading at connection points is reduced, but structural stability deteriorates
Solution Approach 1:
The flexible mounting assembly implements a dynamic connection that adapts to operational conditions. During normal operation, the flexible element maintains sufficient rigidity to preserve structural stability and prevent excessive movement. During transient loads, the same flexible element can deform to accommodate motion, reducing stress while maintaining overall structural integrity through controlled flexibility rather than complete rigidity.
Solution Approach 2:
The flexible mounting assembly modifies the mechanical parameters of the connection by introducing controlled flexibility. The flexible element's material properties and geometric configuration allow it to change its stiffness characteristics based on load conditions, maintaining structural stability under normal operation while reducing stress during transient events through parameter adaptation rather than fixed rigidity.
3Strength
If rigid mounting structure is used, then load-carrying capability is improved, but installation of access features becomes more difficult
Solution Approach 1:
The flexible mounting assembly segments the structural connection into distinct components: the top structural member, the flexible mounting assembly (with flexible element), and the bottom structural member. This segmentation allows the flexible element to be installed independently to accommodate access features like doors and windows, while the overall load-carrying path through the top and bottom structural members remains intact and rigid.
Solution Approach 2:
The flexible mounting assembly acts as an intermediary between the rigid top and bottom structural members. This intermediate flexible element allows for the installation of access features by providing movement accommodation and stress reduction, while still transmitting loads between the structural members. The flexible mounting assembly mediates between the need for rigid load transmission and the need for flexible access feature installation.
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 flexible mounting assembly reduces stress loading at connection points and allows for the installation of access features without accounting for relative movement between structural members, minimizing distortion during transient loads.
Implementation Method 1
A flexible mounting assembly is used, comprising a vertical frame member, an isolation frame member, and a horizontal shear wall assembly, allowing relative vertical motion between the top and bottom structural members while maintaining load-carrying capabilities
Data Source
AI summary
A flexible mounting assembly allows relative movement between a top and a bottom structural member of an air frame, for instance, a helicopter. The flexible mounting assembly comprises a vertical frame member and an isolation frame member where one of the vertical frame member and the isolation frame member has a pin and the other of the vertical frame member and the frame isolation member has an aperture adapted to slidingly receive the pin in a way to accommodate relative vertical motion therebetween while substantially restraining lateral movement therebetween. The flexible mounting assembly may also include a horizontal shear wall assembly extending between adjacent vertical frame members that accommodates relative vertical motion between top and bottom structural members while substantially restraining lateral movement therebetween.