Helicopter Trim Tab Retention via Segmented Head and Cavity
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Solution Overview
Problem
Existing trim tab systems in helicopter main rotor blades require frequent replacement and replacement processes are cumbersome, leading to inefficiencies and increased maintenance costs due to the permanent bonding and differing adjustments needed for each blade.
Innovation Solution
A trim tab retention system featuring a cavity with orthogonal dimensions and a tapered head portion that allows secure retention without adhesives, enabling easy removal and replacement by sliding spanwise and moving chordwise, utilizing materials like aluminum and carbon/glass fibers to manage strain and prevent fretting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If trim tabs are permanently bonded to the trailing edge of the blade, then the trim tab is securely retained, but the trim tab cannot be easily replaced or adjusted
Solution Approach 1:
The trim tab is divided into distinct segments: a head portion that fits within a cavity in the blade housing, and a tail portion that extends through an opening. This segmentation allows the trim tab to be securely retained while enabling easy removal and replacement by sliding the trim tab spanwise and moving it chordwise.
Solution Approach 2:
The head portion of the trim tab is nested within a cavity in the blade housing, with the cavity having a first dimension larger than the second dimension. This nesting arrangement provides secure retention while allowing the trim tab to be installed and removed without damaging the blade housing.
2Manufacturing precision
If trim tabs are permanently bent as part of track and balance procedures, then blade to blade differences are minimized, but the trim tabs cannot be adjusted or replaced without complex procedures
Solution Approach 1:
The trim tab design allows for dynamic adjustment and replacement. The head portion can be inserted into and removed from the cavity, and the tail portion can be moved through the opening. This dynamic design enables simple replacement procedures while maintaining the ability to perform track and balance procedures by bending the trim tab.
Solution Approach 2:
The cavity and opening are pre-configured with specific dimensional relationships (first dimension larger than second dimension) to facilitate easy installation and removal. This preliminary design of the retention structure eliminates the need for complex adjustment procedures during maintenance.
3Ease of operation
If the cavity has a first dimension larger than the second dimension, then the trim tab can be easily installed and removed, but the retention mechanism becomes more complex
Solution Approach 1:
The cavity has different dimensional characteristics at different locations: the first dimension (width) is larger than the second dimension (depth). This local variation in dimensions allows the trim tab to be easily installed and removed while maintaining a relatively simple overall cavity structure. The head portion of the trim tab corresponds to the larger first dimension, enabling easy manipulation during installation and removal.
Data Source
AI summary
A trim tab for use in a blade housing includes a cavity connected to an opening extending from the cavity out a trailing edge of the blade housing, the cavity has a first dimension which is greater than a second dimension of the opening at a same spanwise location of the blade housing. The trim tab has a trim portion, a head portion having a head dimension substantially similar to the first dimension, and a tail portion connecting the trim portion and the head portion. The tail portion has a tail dimension substantially similar to the second dimension such that the trim tab is retainable by the blade housing when the head portion is disposed within the cavity and the tail portion is disposed within the opening.