Aircraft Engine Pylon Stiffness via Segmented Connection Lobes
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Solution Overview
Problem
New generation turbojet engines, being larger and heavier, require more stiffness in engine mounting pylon-to-wing attachment assemblies to meet aeroelastic requirements and flutter certification, which existing solutions fail to provide without increasing structural weight or changing materials.
Innovation Solution
The proposed pylon mounting assemblies include upper and lower connection members with multiple opposed pairs of connection lobes, utilizing pin connections and rods to restrict degrees of freedom along specific axes, ensuring adequate stiffness while maintaining lightweight construction and aerodynamic efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If existing pylon-to-wing attachment assemblies are used, then the structure remains lightweight, but the stiffness is insufficient to meet flutter certification requirements for new generation turbojet engines
Solution Approach 1:
The attachment assembly is segmented into multiple connection lobes (forward, intermediate, rearward pairs) with different connection types. Each lobe pair provides localized stiffness in specific directions, collectively achieving overall structural stiffness without requiring uniform weight increase across the entire wing box structure.
Solution Approach 2:
Different connection types (pin connections vs. rod connections) are applied to different lobe pairs based on local stiffness requirements. Pin connections provide stiffness in both x and z directions at critical locations, while rod connections provide z-direction stiffness elsewhere, creating non-uniform local quality that optimizes overall stiffness-to-weight ratio.
2Strength
If wing box structural weight is increased to provide sufficient stiffness, then flutter certification requirements are met, but manufacturing cost and complexity increase
Solution Approach 1:
Rather than increasing overall wing box weight, the solution segments the stiffness enhancement into discrete connection lobes with specific connection types. This modular approach allows precise stiffness enhancement only where needed, avoiding unnecessary manufacturing complexity across the entire wing structure.
Solution Approach 2:
The connection characteristics are changed by selecting different connection types (pin vs. rod) for different lobe pairs, altering the local stiffness parameters without changing the overall wing box construction or material properties, thereby maintaining ease of manufacture.
3Strength
If traditional metallic alloys are replaced with composite materials to increase stiffness, then aeroelastic requirements are satisfied, but material cost increases
Solution Approach 1:
Instead of changing materials throughout the entire wing box, the solution applies different connection types at specific local locations (lobe pairs) where stiffness is most critical. This localized approach achieves the required stiffness improvement without the high cost of composite materials across the entire structure.
Solution Approach 2:
The solution changes the connection parameters (pin vs. rod connections) rather than changing the bulk material properties. This allows stiffness enhancement through geometric and connection-type modifications rather than expensive material substitution, maintaining cost-effectiveness.
4Use of energy by moving object
If larger aspect ratio wings with smaller cross sections are used, then fuel consumption is reduced, but the wing stiffness decreases making aeroelastic requirements more critical
Solution Approach 1:
The attachment system is segmented into multiple lobe pairs that collectively compensate for the reduced wing stiffness. By distributing the stiffness enhancement across multiple discrete connection points rather than requiring a single massive connection, the system achieves adequate overall stiffness while maintaining the lightweight large aspect ratio wing design for fuel efficiency.
Solution Approach 2:
The connection lobes are strategically positioned and configured with different connection types to provide localized stiffness enhancement at critical points along the wing span. This allows the overall wing to maintain its lightweight, fuel-efficient geometry while specific local regions provide the necessary stiffness support for the heavy engine.
Data Source
AI summary
Pylon mounting assemblies are provided for mounting an engine (e.g., a turbojet engine) to a wing of an aircraft. The pylon mounting assemblies include an upper pylon connection member, and a lower pylon connection box, wherein the upper pylon connection member and the lower pylon connection box respectively include multiple opposed pairs of connection lobes. At least one pair of the connection lobes includes a pin connection to restrict degrees of freedom thereat along an x-axis and a mutually perpendicular z-axis, while at least one other pair of connection lobes includes a connection rod to restrict degrees of freedom thereat along the z-axis.