Internal Rotor Blade Weight System for Non-Destructive Balancing
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Solution Overview
Problem
Existing systems for balancing rotorcraft blades require components that extend through the outer skins, leading to stress concentrations, premature erosion, and difficult access for adjustment, often necessitating destructive disassembly and heavy, cumbersome weight boxes.
Innovation Solution
A weight system integrated within the rotor blade's spar, using a weight tray bonded and fastened internally, allowing adjustment through the tip end without disturbing the outer surface, featuring a titanium buffer element, static and dynamic weights, and adjustable guide rods for precise balancing without external interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If components extend through outer skins to balance rotorcraft blades, then balancing function is achieved, but stress concentrations and premature erosion occur
Solution Approach 1:
The weight system is extracted from the traditional external mounting configuration and relocated to an internal position within the rotor blade structure. The weights are contained within a weight box that is integrated into the blade's internal volume, eliminating the need for external components that extend through the outer skin. This extraction resolves the technical contradiction by removing the source of stress concentrations and erosion while preserving the balancing function.
Solution Approach 2:
The weight box and weighting components are nested within the existing rotor blade structure. The weight box is positioned inside the blade's internal volume and secured to internal structural elements, creating a nested configuration where the balancing system is contained within the blade rather than extending externally. This nesting approach eliminates external hardware that causes stress concentrations while maintaining effective mass distribution for balancing.
2Ease of operation
If external access doors are created for weight adjustment, then balancing adjustment is enabled, but outer skin integrity is compromised
Solution Approach 1:
The weight box is pre-configured with an access mechanism that is integrated into the blade structure during manufacturing. A access panel or opening is provided in the rotorcraft fuselage or blade housing that allows direct access to the weight box without requiring disassembly of the outer skin. This preliminary provision of access eliminates the need for destructive disassembly while maintaining outer skin integrity.
Solution Approach 2:
An intermediary access panel or opening is provided in the rotorcraft fuselage or blade housing that serves as a mediator between the external environment and the internal weight box. This intermediary structure allows weights to be added or removed without compromising the outer skin of the blade itself, as the access is provided through a separate panel that can be opened and closed without affecting blade structural integrity.
3Reliability
If traditional weight boxes are used, then balancing function is provided, but system weight and complexity increase
Solution Approach 1:
The weight box and weighting system are designed to provide balancing function only at the specific location where mass distribution adjustment is needed. Rather than using a heavy, comprehensive external mounting system, the weight box is sized and positioned to provide precise local mass adjustment within the blade's internal volume. This localized approach minimizes the weight of the balancing system while maintaining effective balancing capability.
Solution Approach 2:
The balancing system utilizes small mass changes through the addition or removal of weights from the internal weight box, rather than requiring large external components. By changing the mass parameter through incremental weight adjustment within the confined internal space, the system achieves effective balancing with minimal added weight compared to traditional external mounting systems.
Data Source
AI summary
A rotorcraft has a rotor blade having a spar comprising an internal space. A weight system is disposed within the spar and the weight system includes a weight tray having an open top, a weight guide rod connected to the weight tray. The weight guide rod extends in a spanwise direction through an interior of the weight tray and a weight is disposed on the weight guide rod and vertically captured by at least one side wall of the weight tray. The weight guide rod is insertable into the weight tray from a location above the weight tray to restrict longitudinal movement of the weight guide rod relative to the weight tray.