Aircraft Stringer Coupling with Access Opening for Quality Control
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Solution Overview
Problem
Coupling stiffening profile elements with inaccessible cavities poses challenges for quality control and repair, as riveted joints and chips fall into the cavity, making inspection and removal difficult, leading to potential damage and noise during flight.
Innovation Solution
A coupling method with an access opening in the cavity allows for mechanical operations and quality control, featuring a fixing hole and fastening element that can be easily inspected and repaired, and includes a reinforced wall to maintain mechanical strength and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If stringers with Ω-profile are used to stiffen CFRP fuselage, then weight is reduced and structural efficiency is improved, but quality control becomes difficult because riveted joints project into inaccessible cavities
Solution Approach 1:
The stringer profile is segmented to include a removable cap that separates the cavity into an accessible region and an inaccessible region. This allows quality control operations to be performed on the accessible portion while maintaining the weight benefits of the closed-cell structure.
Solution Approach 2:
A removable cap acts as an intermediary element that provides access to the cavity for quality control operations. The cap can be removed during inspection and repair, then reinstalled to restore the closed-cell structure, enabling quality control without permanently compromising structural integrity.
2Strength
If fixing holes are drilled in stringer flanks to couple with transverse butt strap, then structural coupling is achieved, but chips and damaged joint parts fall into inaccessible cavity causing noise and damage
Solution Approach 1:
The stringer is segmented with a removable cap that creates an accessible opening into the cavity. This allows chips and damaged parts to be removed from the cavity, eliminating the source of noise and potential damage while maintaining the structural coupling function.
Solution Approach 2:
The cap is extracted or removed to provide access to the cavity for removing harmful elements such as chips and loose parts. After cleanup, the cap is reinstalled to restore the closed-cell structure, thereby extracting the harmful factors without compromising structural integrity.
3Strength
If conventional riveted joints are used to couple stringers, then structural coupling is achieved, but inspection of joint quality is impossible from the cavity side
Solution Approach 1:
The removable cap serves as an intermediary that provides a viewing window into the cavity. During quality control, the cap is removed to allow direct visual inspection of the riveted joints from the cavity side, enabling precise measurement and assessment of joint quality.
Solution Approach 2:
The cap is designed to be removable for preliminary quality control inspections before final assembly completion. This preliminary action allows joint quality to be verified while the structure is still accessible, preventing defective joints from being locked in place.
Data Source
AI summary
This invention provides a coupling method for coupling a first and a second stiffening profile element for an outer skin of an aircraft or space craft. In a first step the stiffening profile elements are arranged on the outer skin in such a manner that the stiffening profile elements oppose each other with their respective front sides and enclose within themselves a cavity. Furthermore, a fixing hole is formed through a wall of at least one of the stiffening profile elements in the cavity inside a coupling zone of the stiffening profile element. An access opening is formed through the wall in the cavity along the coupling zone. A coupling strap, which couples the stiffening profile elements together, is fastened to the coupling zone by means of a fastening element guided through the fixing hole.