Aircraft Gearbox Bracket Fuse Mechanism for Fan Blade Out Protection
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Solution Overview
Problem
Conventional aircraft gearbox designs face challenges in balancing weight reduction with the need for strength, particularly in withstanding fan blade out (FBO) loads, where fuses are prone to triggering due to machining tolerances and icing loads.
Innovation Solution
Incorporating a fuse mechanism with notches in the bracket that are sized based on the minimum cross-sectional area and designed to break at a predetermined percentage of the nominal FBO load, allowing the gearbox to be constructed with lighter materials while ensuring structural integrity against secondary loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional gearbox designs use strong materials to withstand FBO loads, then the gearbox can handle fan blade out loads, but the aircraft weight increases
Solution Approach 1:
The bracket is segmented into two functional zones: a sacrificial portion with reduced cross-sectional area containing notches that will break under FBO loads, and a remaining portion that maintains full structural integrity. This segmentation allows the gearbox to be designed for normal loads while the sacrificial portion handles the FBO event, eliminating the need to strengthen the entire gearbox structure.
Solution Approach 2:
The sacrificial portion of the bracket is designed as a disposable element that will break during an FBO event to protect the more valuable remaining bracket and gearbox components. By allocating a portion of the bracket as sacrificial material, the design protects the primary structure without requiring excessive strengthening of the entire assembly.
2Reliability
If fuses are incorporated with tight tolerance notches to prevent premature triggering, then the fuse can protect against FBO loads, but machining tolerances cause the fuse to trigger during icing loads
Solution Approach 1:
The bracket exhibits local quality variation through its non-uniform cross-sectional area. The sacrificial portion has reduced area with notches specifically designed to fail at a predetermined load threshold, while the remaining portion maintains full structural properties. This local differentiation allows the fuse to trigger only under genuine FBO conditions rather than normal operational variations like icing loads.
Solution Approach 2:
The cross-sectional area parameter is changed in the sacrificial portion to create a predetermined failure point. By controlling the geometry and dimensions of this reduced-area section, the fuse can be calibrated to break at a specific load threshold that distinguishes FBO events from normal operational loads, improving reliability while avoiding premature triggering during icing conditions.
3Strength
If the entire gearbox is designed to withstand FBO loads, then structural integrity is maintained, but material cost and weight increase excessively
Solution Approach 1:
The bracket is divided into a sacrificial portion and a remaining portion, where only the sacrificial portion is designed with reduced material content. The remaining portion maintains full structural integrity and is designed to withstand both normal operational loads and the forces generated when the sacrificial portion fails during an FBO event.
Solution Approach 2:
The sacrificial portion acts as a protective sacrificial element that absorbs the extreme FBO load through controlled failure. This allows the more valuable remaining bracket and gearbox components to be designed for normal operational loads only, significantly reducing overall material usage and weight while maintaining structural integrity where it matters most.
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
Enables the design and manufacture of a gearbox system using lighter materials by allocating a portion of the bracket as sacrificial material, ensuring the remainder can withstand loads less than the fuse-triggering event, thus reducing weight while maintaining safety and operational reliability.
Implementation Method 1
A fuse is incorporated in a bracket (216). The fuse may correspond to a sacrificial material that disengages at a threshold associated with a load.
Data Source
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AI summary
Aspects of the disclosure are directed to a system (200) associated with an aircraft engine (10), comprising a gearbox (204), a link (210) coupled to the gearbox (204), and a bracket (216) coupled to the link (210), where the bracket (216) includes at least one notch (436a) formed in the bracket (216) to provide a pilot for a fuse trigger, and where a portion (446a, 446b) of the bracket (216) contained within the at least one notch (436a, 436b) breaks away from the bracket (216) when the system (200) experiences a load that is less than a nominal load associated with a fan blade out event of the aircraft engine (10).