Aircraft Engine Pylon Mounting Assembly Sloped Stiffness
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Solution Overview
Problem
The existing pylon-to-wing attachment assemblies for newer generation turbojet engines with larger size and weight, and larger aspect ratio wings, fail to meet stiffness requirements for aeroelastic viability and flutter certification, necessitating increased structural weight or material changes.
Innovation Solution
The proposed pylon mounting assemblies include an upper pylon connection member and a lower pylon connection box with a downwardly and rearwardly sloping mounting plane, connected by frangible connectors to provide necessary stiffness and allow separation under excessive loads, thus avoiding material changes and weight increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If existing pylon-to-wing attachment assemblies are used for newer generation turbojet engines, then the attachment structure can be maintained, but the stiffness requirements for aeroelastic viability and flutter certification cannot be met
Solution Approach 1:
The attachment assembly is divided into multiple connector assemblies, each comprising upper and lower mounting blocks with internal truss structures. This segmentation allows each block to independently contribute to the overall stiffness while distributing the structural requirements across multiple components, resolving the contradiction between meeting stiffness requirements and managing design complexity.
Solution Approach 2:
The mounting blocks utilize composite construction with internal truss structures and frangible connectors, combining rigid elements for stiffness with controlled failure mechanisms. This composite approach enables the assembly to meet both stiffness requirements for aeroelastic viability and the complexity constraints through optimized material and structural integration.
2Strength
If the structural weight of the wing box is increased to meet stiffness requirements, then the stiffness for supporting heavier engines is improved, but the overall weight and cost of the aircraft increases
Solution Approach 1:
The stiffness requirement is extracted from the wing box structure and transferred to the pylon-to-wing attachment assembly. By concentrating the stiffness function in the connector assemblies with their internal truss structures, the wing box can maintain its original weight while the attachment assembly provides the necessary structural rigidity for supporting heavier engines.
3Reliability
If frangible connectors are used to allow separation under excessive loads, then crashworthiness requirements are met, but the connection strength under normal operation must be precisely controlled
Solution Approach 1:
The frangible connectors are designed with predetermined failure points and controlled geometry that enable predictable separation under excessive loads. The internal truss structures and mounting block configurations are pre-engineered to fail in specific patterns, ensuring crashworthiness while maintaining precise control over connection strength during normal operation through careful geometric design rather than relying solely on manufacturing tolerances.
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. The upper pylon connection member and the lower pylon connection box respectively define opposed lower and upper mounting surfaces which establish a mounting plane that slopes downwardly and rearwardly relative to aircraft travel direction. At least one connector assembly connects the upper pylon connection member and a lower pylon connection box to one another at the opposed respective lower and upper mounting surfaces thereof.