Aircraft Vibration Isolation Using Intermediate Mass
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Solution Overview
Problem
Conventional aircraft vibration isolation systems allow significant noise into the interior cabin, particularly due to turbulent boundary layer noise transmission through structural paths, and adding weight to mitigate this noise is undesirable.
Innovation Solution
A vibration isolation system comprising two isolators and an intermediate mass between them, where the intermediate mass can be electrical cables or cable management systems, is used to attenuate vibrations and noise, with additional noise suppressors like acoustic blankets and skin damping materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional single isolator systems are used, then the structure is simple and weight is minimized, but significant noise transmits into the interior cabin
Solution Approach 1:
The single isolator system is segmented into two separate isolators with an intermediate mass between them. This segmentation creates multiple isolation stages that progressively attenuate vibration and noise transmission from the fuselage to the interior cabin, significantly reducing the harmful noise transmission identified in the contradiction.
Solution Approach 2:
An intermediate mass is introduced as a mediator between the first and second isolators. This intermediate mass acts as a vibration decoupling element that breaks the direct transmission path, forcing vibrations to pass through multiple compliance interfaces which enhances noise isolation performance while managing the increased system complexity.
2Object-affected harmful factors
If heavier closeout structures are used for vibration isolation, then noise transmission is reduced, but aircraft performance is impaired due to additional weight
Solution Approach 1:
The traditional mechanical approach of using heavier rigid closeout structures is replaced with a compliant isolation system consisting of two flexible isolators and an intermediate mass. This substitution achieves superior noise transmission reduction through vibration decoupling rather than through rigid mass, avoiding the penalty of additional aircraft weight while effectively reducing the harmful noise transmission.
3Weight of moving object
If conventional single isolator systems are used, then weight is minimized, but noise transmission to the interior cabin increases
Solution Approach 1:
The isolation system is segmented into two separate isolators with an intermediate mass, creating a multi-stage vibration isolation architecture. This segmentation achieves superior noise transmission reduction by forcing vibrations through multiple compliance interfaces, accomplishing the noise control goal while keeping each individual isolator component lightweight rather than requiring a single heavy isolator or rigid structure.
Solution Approach 2:
The isolation system employs a composite architecture combining two isolators made of different material properties with an intermediate mass. This composite approach optimizes the weight-performance balance by using materials and configurations that provide effective vibration isolation across different frequency ranges, achieving superior noise transmission reduction without excessive weight compared to conventional single isolator systems.
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 configuration significantly reduces noise and vibration transmission into the aircraft cabin while minimizing weight impact, offering improved acoustic attenuation, especially at high frequencies.
Implementation Method 1
Vibration isolators form a potentially 'easier' path for the TBL noise to transmit to the interior cabin at high frequencies
Implementation Method 2
A vibration isolation system having two isolators and an intermediate mass attached between the two isolators
Implementation Method 3
Additional noise and vibration suppression elements, such as acoustic blankets and fuselage skin damping materials
Data Source
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AI summary
A vibration isolation system for attenuating vibration energy between two aircraft structures, such as between the aircraft's fuselage and interior cabin. The vibration isolation system includes a first isolator attached to the first structure, a second isolator attached to the second structure, and an intermediate mass attached between the first and second isolators. The intermediate mass may be electrical cables, wiring bundles, a cable holder, or other component disposed between the two structures. Cable holder intermediate masses can be fabricated from an electrically conductive material to provide electromagnetic interference shielding for cables disposed therein. Multiple vibration isolation systems can be disposed between the fuselage and interior cabin to provide a less noisy cabin. Additional noise and vibration suppressors, such as skin damping material and acoustic blankets, also can be disposed between the fuselage and interior cabin to further reduce noise in the interior cabin.