Aircraft Keel Beam Cutback Configuration
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Solution Overview
Problem
Large aircraft keel beams provide structural support but complicate the installation of environmental control systems and cause undesirable force coupling between the fuselage and wings, due to their complex load path and stress concentration.
Innovation Solution
A keel beam assembly with a cutback configuration at its forward end, featuring a keel attach chord, lower chord, and forward web that extends diagonally to create an open area, allowing for improved assembly and installation of systems while maintaining sufficient vertical support during emergency landings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a typical keel beam structure is used to provide structural support, then the aircraft gains fuselage force transfer capability and wheels-up landing protection, but the complicated structure interferes with installation of environmental control systems
Solution Approach 1:
The keel beam structure is segmented into discrete components (keel attach chord, lower chord, forward web, aft web) that can be independently manufactured and assembled. This segmentation allows environmental control systems to be routed through the spaces between components, eliminating installation interference while maintaining structural integrity through the assembled configuration.
Solution Approach 2:
The invention introduces a diagonal dimension to the keel beam structure through the forward and aft webs that extend diagonally between the chords. This diagonal configuration creates three-dimensional space that accommodates environmental control systems without compromising the longitudinal and vertical load-bearing capabilities of the structure.
2Strength
If a typical keel beam structure is used to provide structural support, then the aircraft gains fuselage force transfer capability, but undesirable force coupling between the fuselage and wings occurs
Solution Approach 1:
The keel attach chord is positioned locally between the rear and front spars rather than directly connecting them, creating a localized decoupling zone. This local configuration allows the keel beam to transfer fuselage forces independently without directly coupling wing and fuselage force paths, eliminating the harmful force coupling effect.
Solution Approach 2:
The lower chord acts as an intermediary element between the keel attach chord and the fuselage bulkheads. This intermediary component provides an alternative load path that transfers fuselage forces to the bulkheads without requiring direct connection between the wing attachment point and fuselage, thereby preventing force coupling.
3Ease of manufacture
If the keel beam structure is simplified to improve system installation, then ease of installation improves, but stress concentration in the fuselage cutout increases
Solution Approach 1:
The forward and aft webs are configured with diagonal extensions that create curved, diagonal load paths rather than sharp angular connections. This curvature distributes stresses more evenly across the fuselage cutout region, reducing stress concentration at critical points while maintaining the simplified assembly configuration.
Data Source
AI summary
Embodiments for aircraft keel beam assembly. One embodiment is a keel beam assembly of an aircraft. The keel beam assembly includes a keel attach chord to connect to a wing center section of the aircraft, the keel attach chord extending in a longitudinal direction between a rear spar and front spar of the aircraft. The keel beam assembly also includes a lower chord disposed underneath the keel attach chord and extending in the longitudinal direction between an aft wheel well bulkhead and a forward bulkhead of the aircraft. The keel beam assembly further includes a forward web to couple the keel attach chord and the lower chord, the forward web including a front edge extending in a diagonal direction from the keel attach chord that is downward and aft toward the lower chord to create an open area forward from the front edge.