Rotor Blade Weight System Spar Integration
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Solution Overview
Problem
Existing systems for balancing rotorcraft blades require components that extend into or through the outer skins, leading to stress concentrations, premature erosion, and accessibility issues, often necessitating destructive disassembly for adjustments.
Innovation Solution
A weight system is integrated within the spar of the rotor blade, using a weight box attached by both adhesive bonding and fasteners, allowing for adjustments without disturbing the outer surfaces, and enabling access through the tip end for fine-tuning without full disassembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If components extend into or through outer skins to secure balancing weights, then the balancing system can be installed, but stress concentrations and premature erosion occur
Solution Approach 1:
The balancing weight system is extracted from the outer skin location and relocated to the interior of the blade spar. The weight box is positioned inside the spar structure, eliminating the need for components to extend through or into the outer skins, thereby removing stress concentrations and erosion risks from the blade surface.
Solution Approach 2:
The balancing weight box is nested within the existing spar structure of the blade. The weight box fits into the interior space of the spar, utilizing the existing structural cavity, which allows the balancing system to be integrated without modifying or compromising the outer skin integrity.
2Ease of manufacture
If holes are formed in outer skins to accommodate fasteners, then balancing weights can be secured, but aerodynamic surface is compromised
Solution Approach 1:
The fastening system is extracted from the outer skin location and relocated to the interior spar structure. Fasteners secure the weight box internally within the spar, eliminating the need for holes in the outer skin and preserving the continuous aerodynamic surface.
Solution Approach 2:
The weight box and fastening system are nested within the spar interior, allowing secure attachment of balancing weights without penetrating or disrupting the outer skin surface, thus maintaining aerodynamic integrity.
3Ease of operation
If access doors are created in outer skins, then balancing systems become accessible, but structural integrity is reduced
Solution Approach 1:
The access point is extracted from the outer skin and relocated to the blade tip end. The weight box is positioned such that it can be accessed by removing the tip end cap, eliminating the need for access doors in the outer skin and preserving structural integrity.
Solution Approach 2:
Instead of providing access through the lateral outer skin surface (2D access), the system allows access through the tip end dimension (3D access). This dimensional shift enables serviceability without compromising the lateral structural integrity of the blade.
4Ease of repair
If destructive disassembly is required to access balancing system, then blade can be balanced, but time and complexity increase
Solution Approach 1:
The balancing weight box is extracted and positioned in a location (spar interior near tip end) that is naturally accessible for maintenance. The weight box can be accessed by simply removing the tip end cap, eliminating the need for destructive disassembly and reducing maintenance time.
Solution Approach 2:
The weight box is pre-positioned within the spar structure during manufacturing, with the tip end cap designed for easy removal. This preliminary arrangement ensures that future adjustments require minimal disassembly, saving time and avoiding destructive 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
This solution prevents premature erosion, maintains a smooth aerodynamic surface, and allows for reliable bondline inspection and easy adjustment of rotor blades, enhancing the balance and longevity of the blades.
Implementation Method 1
a weight box attached by both adhesive bonding and fasteners
Data Source
Figure 1
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AI summary
A weight system (200) for a rotor blade (118) includes a weight box (202) open in an outboard direction, a weight guide rod (212) connected to the weight box (202), the weight guide rod (212) extending in a spanwise direction through an interior of the weight box (202), and a span balance weight (206) disposed within the weight box (202), the span balance weight (206) being captured between the weight guide rod (212) and the weight box (202).