Aircraft Propulsion Nacelle Monocoque Load Transfer
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Solution Overview
Problem
Traditional pylon and internal frame structures used in aircraft are structurally inefficient for transferring loads from the propeller-gearbox-engine assembly to the fuselage, especially in demanding VTOL and STOL configurations where weight is a critical factor.
Innovation Solution
A lightweight, structurally efficient hub and gearbox system that directly transfers rotor loads to the nacelle Out Mold Line (OML) monocoque, eliminating the need for concentrated internal structures and enhancing stiffness and strength efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional pylon and internal frame structures are used to transfer loads from the propeller-gearbox-engine assembly to the fuselage, then the structural strength and stiffness requirements can be met, but the overall weight of the aircraft increases significantly
Solution Approach 1:
The patent merges the nacelle structure with the wing structure by making the nacelle an integral part of the wing's load-bearing framework. The gearbox is mounted directly to the wing spar through the nacelle, eliminating separate pylon structures. This integration allows the wing itself to carry the propulsion loads, reducing the need for additional dedicated load-bearing components and thereby reducing overall weight while maintaining structural strength.
Solution Approach 2:
The nacelle structure serves multiple functions: it encloses the gearbox, transfers propulsion loads to the wing, and contributes to the overall wing structural framework. By making the nacelle a multi-functional component that simultaneously provides mechanical enclosure and structural load-bearing capability, the design eliminates the need for separate non-structural cowlings and dedicated pylons, reducing weight while maintaining all necessary functions.
2Ease of repair
If traditional non-structural cowling is used to enclose the gearbox-engine assembly, then maintenance access is easy, but the structure is heavy compared to a single load-bearing monocoque
Solution Approach 1:
The patent combines the enclosure function with the structural load-bearing function into a single integrated nacelle assembly. The nacelle is designed as a load-bearing structure that is part of the wing framework, eliminating the need for separate non-structural cowling. This integration reduces weight while the design maintains maintenance accessibility through strategic placement of access panels and service ports in the nacelle structure.
3Device complexity
If concentrated internal structures are used to support the propeller-gearbox-engine assembly, then the load transfer path is established, but the structural efficiency and stiffness are reduced
Solution Approach 1:
The patent extracts and eliminates concentrated internal support structures such as pylons and internal frames by directly integrating the gearbox mounting to the wing spar through the nacelle. This extraction simplifies the load transfer path by removing unnecessary intermediate structural elements, thereby improving structural efficiency and stiffness while reducing device complexity.
Solution Approach 2:
Instead of using internal structures to bridge the gap between the propulsion assembly and the fuselage, the patent inverts the approach by having the nacelle and wing structure directly bear the loads at the outer mold line. The load path is inverted from an internal concentrated support system to a distributed external monocoque structure, improving structural efficiency by utilizing the wing's inherent stiffness and strength.
Data Source
AI summary
Loads from the propeller-gearbox-engine assembly are transferred to an airframe directly, without concentrated internal structure. In preferred embodiments this is accomplished using a lightweight, structurally efficient hub and gearbox that transfer their rotor loads directly to the nacelle OML (Out Mold Line) monocoque. By keeping the load path direct and at the largest diameter, the structure achieves higher stiffness and strength efficiency than conventional point loaded internal frames.