Aircraft Empennage Control Surface Rib Spar Configuration
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Solution Overview
Problem
Existing designs of large aircraft aerodynamic surfaces, such as empennages, face challenges in achieving a balance between manufacturing simplification and weight reduction, particularly in the configuration of inboard and outboard control surfaces like elevators and rudders, which often require complex rib structures that increase weight and cost.
Innovation Solution
The design optimizes inboard and outboard control surfaces by using a torsion box structure with specific arrangements of ribs and spars, including hinge and actuator fittings, and innovative rib configurations that reduce the number of internal parts while maintaining structural integrity, resulting in a more efficient load path and weight distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional multi-rib structures are used for control surfaces, then structural integrity is maintained, but weight and manufacturing complexity increase
Solution Approach 1:
The control surface is divided into multiple spars (front spar, intermediate spars, rear spar) that work together to provide structural support. This segmentation allows the structure to maintain strength while using fewer, more strategically placed elements compared to traditional multi-rib configurations
Solution Approach 2:
The spars serve multiple functions: they provide structural support, act as attachment points for ribs and control surfaces, and form part of the torsion box structure. This multi-functionality reduces the need for separate structural elements, thereby reducing weight
2Strength
If traditional multi-rib structures are used for control surfaces, then structural integrity is maintained, but manufacturing complexity and cost increase
Solution Approach 1:
The control surface assembly is segmented into modular components (spars, ribs, panels) that can be manufactured separately and assembled. This modularity simplifies manufacturing processes and reduces assembly complexity compared to traditional monolithic multi-rib structures
Solution Approach 2:
Multiple structural functions are merged into the spar system, which serves as both the primary load-bearing structure and the attachment framework for ribs and control surfaces. This consolidation reduces the total number of components and simplifies manufacturing
3Strength
If more ribs are added to control surfaces, then structural strength is improved, but weight increases
Solution Approach 1:
Ribs are strategically placed only where structurally necessary to maintain strength and stiffness, rather than uniformly distributing them across the entire control surface. This localized approach maintains structural integrity while minimizing weight
Solution Approach 2:
The spar structure is designed to preemptively carry loads before ribs are added, allowing for fewer ribs to be used. The spars are positioned to intercept and distribute loads, reducing the need for additional rib support
Data Source
AI summary
An aircraft aerodynamic surface (1) including a torsion box (2) having a front spar (21) and rear spar (22), a first control surface (3) including a front spar (31) and a trailing edge (32) and a second control surface (4) having a front spar (41), a trailing edge (42), and a pivot device (5, 6, 7, 8) for pivotally attaching the first control surface (3) and the second control surface (4) to the rear spar (22) of the torsion box (2), the first control surface is an inboard control surface (4) including two lateral ribs (9, 9′), six inner ribs (11, 12, 13, 14, 15, 10) and an inner spar (16), and the second control surface (3) is an outboard control surface which includes two lateral ribs (20, 20′), three internal ribs (17, 18, 19), two internal spars (24, 24′) and one internal spar (23).