Lambda Wing Stringer Repair via Through-Fasteners

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Solution Overview

Problem

Current stringer designs for aircraft wings face challenges in repair due to the use of blind fasteners, which are difficult to inspect, and require complex doubler plates, especially for semi-open section designs like Y and hat section stringers, compromising weight efficiency and repair complexity.

Innovation Solution

A lambda section stringer with first and second flanges and planar panels, where doubler plates are attached to conform to exposed faces, using primarily non-blind fasteners, reducing the number of blind fasteners to one-third, allowing for simpler repair and maintaining weight efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If closed or semi-open section stringers (hat section, Y section) are used, then weight efficiency is improved, but repair complexity increases due to requiring complex doubler plates and blind fasteners

Engineering Contradiction:

Improveweight efficiencyVSAvoidrepair complexity

Core Design Contradiction:

Weight of moving objectVSEase of repair

Solution Approach 1:

The stringer is divided into distinct functional components: flanges for attachment to wing cover panels, web for structural strength, and rib attachment surfaces. This segmentation allows each component to be optimized independently and simplifies repair procedures by enabling targeted replacement of damaged sections without requiring complex doubler plates.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of using blind fasteners that require complex doubler plates for inspection, the invention employs through-fasteners that allow direct inspection from both sides. This inversion of the fastening approach simplifies repair and inspection procedures while maintaining the weight efficiency of closed/semi-open section designs.

Inventive Principle:

Principle #13The other way round (Inversion)

2Strength

If blind fasteners are used in closed section stringers, then structural integrity is maintained, but inspection difficulty increases

Engineering Contradiction:

Improvestructural integrityVSAvoidinspection difficulty

Core Design Contradiction:

StrengthVSDifficulty of detecting and measuring

Solution Approach 1:

The invention inverts the fastener type from blind fasteners to through-fasteners. Through-fasteners allow inspection from both sides of the stringer, eliminating the inspection difficulty associated with blind fasteners while maintaining structural integrity through proper fastening of the flanges to the wing cover panels.

Inventive Principle:

Principle #13The other way round (Inversion)

3Ease of repair

If J or I section stringers are used, then repair simplicity is improved, but weight efficiency deteriorates

Engineering Contradiction:

Improverepair simplicityVSAvoidweight efficiency

Core Design Contradiction:

Ease of repairVSWeight of moving object

Solution Approach 1:

The stringer design applies local quality optimization by positioning flanges and web thicknesses to provide maximum structural efficiency. The flanges are designed with appropriate thickness and width to provide necessary attachment surfaces while minimizing overall weight, achieving both repair simplicity and weight efficiency.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS7677496B2Stringer for an aircraft wing and a method of reinforcing thereof

Publication Date: 2010.03.16 AIRBUS OPERATIONS LTD

AI summary

The present invention relates to a stringer for an aircraft wing and a method of reinforcing such a stringer in which the stringer is formed with a substantially lambda shaped section.