Compact Aircraft Rear Engine Attachment Design
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Solution Overview
Problem
Conventional rear engine attachments for aircraft are bulky, leading to significant aerodynamic disturbances and space constraints in the bypass duct of turbomachines, which hampers the performance of the engine.
Innovation Solution
A compact rear engine attachment design featuring a first part with clevises and connecting rods, and a second part with a shoe, main rod, and secondary rod, allowing for reduced transverse space usage and improved force reaction, utilizing a ball joint for flexibility and pivot connections for efficient force distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional rear engine attachment structures are used, then the attachment can react the required moment Mx and provide structural stability, but the attachment becomes relatively large and takes up a lot of space in the bifurcation crossing the secondary duct
Solution Approach 1:
The attachment system is divided into two independent parts: a first part (clevis assembly with connecting rods) and a second part (shoe with main rod and secondary rod). This segmentation allows each part to be optimized independently for its specific function, reducing the overall volume while maintaining structural stability and moment reaction capabilities.
Solution Approach 2:
The invention reorients the attachment geometry to take up space primarily in the longitudinal direction rather than the transverse direction. The first part extends along the longitudinal axis with connecting rods arranged to minimize transverse footprint, while the second part is positioned to react moments through longitudinal positioning, thereby reducing interference with the bifurcation and secondary duct.
2Strength
If larger rear engine attachment structures are used, then the attachment can better react forces and moments, but the aerodynamic blocking of the bypass duct increases and performance deteriorates
Solution Approach 1:
By segmenting the attachment into two parts with distinct functions, the design achieves adequate force and moment reaction capabilities through distributed loading paths. The first part handles primary force transmission while the second part reacts moments, allowing smaller individual components that collectively provide the required strength without creating excessive aerodynamic blocking.
Solution Approach 2:
Each part of the attachment is designed with specific local characteristics optimized for its function: the clevis assembly with articulated connecting rods for flexible force transmission, and the shoe with pivot connections for moment reaction. This localized optimization allows minimal transverse footprint while maintaining adequate strength, reducing aerodynamic interference with the bypass duct.
Data Source
AI summary
A rear engine attachment having first and second parts, wherein the first part has two first clevises fixed to a lower face of a pylon, two second clevises fixed to a structural casing, two connecting rods mounted to be articulated between first and second clevises, and two shafts realizing the connections between the connecting rods and the clevises. The second part has a shoe fixed to the lower face and having a bore, a main rod which bears a vertical peg engaging in the bore and which is fixed to the structural casing by a first pivot connection, and a secondary rod fixed to the main rod by a second pivot connection and to the structural casing by a third pivot connection. Such a rear engine attachment is more compact, taking up space in the longitudinal direction and thus minimizing the space taken up in the transverse direction.