Expandable Strut Assembly for Aircraft Wing

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Solution Overview

Problem

Existing aircraft strut designs face challenges in efficiently managing weight, aerodynamic drag, and structural integrity across various flight conditions, particularly in transitioning between thin cross-sections for cruise and thicker cross-sections for compressive loads.

Innovation Solution

An expandable strut assembly with a shape transition mechanism that transitions between contracted and expanded positions, and between contracted and expanded airfoil shapes, using a drive mechanism with variable length structural members and an actuation mechanism driven by spine members and compression chains.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a full-span strut is used to address the -1 g pushover flight condition, then the strut can carry compressive loads, but the strut becomes thick and heavy due to longer buckling length

Engineering Contradiction:

Improvecompressive load capacityVSAvoidstrut weight

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The strut employs a dynamic cross-sectional area that can expand and contract along its length. During -1 g pushover conditions, the strut expands to increase buckling resistance and carry compressive loads. During cruise conditions, the strut contracts to minimize weight and drag, resolving the contradiction between strength and weight through temporal variation of structural properties.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The strut's cross-sectional area parameter is changed dynamically along its length and over time. The variable cross-sectional area allows the strut to optimize its buckling length and load-bearing capacity when needed, while reducing material usage during normal operation, thereby addressing the weight-strength tradeoff.

Inventive Principle:

Principle #35Parameter changes

2Weight of moving object

If jury struts are added to break up buckling length, then the primary strut can be thinner and lighter, but aerodynamic drag increases

Engineering Contradiction:

Improvestrut weightVSAvoidaerodynamic drag

Core Design Contradiction:

Weight of moving objectVSObject-affected harmful factors

Solution Approach 1:

Instead of permanently adding jury struts that increase drag, the invention dynamically activates additional support structures only when needed for buckling resistance. The variable cross-sectional area mechanism provides temporary reinforcement during compressive load conditions without the permanent drag penalty of fixed auxiliary struts.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention extracts the essential function of jury struts (reducing buckling length) and implements it through a different mechanism - variable cross-sectional area expansion - that eliminates the harmful side effect (aerodynamic drag) associated with permanent auxiliary structures.

Inventive Principle:

Principle #2Taking out (Extraction)

3Object-affected harmful factors

If cable struts are used to reduce aerodynamic drag, then drag is low, but the wing must be sized for cantilever conditions and becomes heavier

Engineering Contradiction:

Improveaerodynamic dragVSAvoidwing weight

Core Design Contradiction:

Object-affected harmful factorsVSWeight of moving object

Solution Approach 1:

The variable cross-sectional area strut provides dynamic structural support that allows the use of lighter cable-like structures during cruise (low drag) while maintaining adequate support during compressive load conditions. This eliminates the need to oversized the wing for cantilever conditions, resolving the drag-weight contradiction.

Inventive Principle:

Principle #15Dynamics

4Strength

If the strut cross section is expanded to carry compressive loads, then buckling resistance increases, but aerodynamic drag increases

Engineering Contradiction:

Improvebuckling resistanceVSAvoidaerodynamic drag

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The strut cross-sectional area is dynamically varied along its length and over time. During cruise, the strut maintains a thin profile to minimize drag. During -1 g pushover conditions, the strut expands to increase buckling resistance. This temporal and spatial variation resolves the contradiction between strength and drag.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The cross-sectional area parameter of the strut is changed dynamically based on loading conditions. The variable geometry allows the strut to optimize aerodynamic efficiency during normal flight while providing adequate structural resistance to buckling when required, eliminating the need to maintain a permanently thick cross-section.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12286222B2Expandable strut assembly for a wing of an aircraft and method of using the same

Publication Date: 2025.04.29 THE BOEING CO

AI summary

There is provided an expandable strut assembly for a wing of an aircraft, having a strut with a strut cross section with an airfoil shape, and the strut having an outboard end coupled to the wing, an inboard end coupled to a fuselage, and an elongate body, and having at least one shape transition assembly connected to the strut. Each shape transition assembly is configured to transition the strut between a contracted position and an expanded position, and is configured to transition the strut cross section between a contracted airfoil shape and an expanded airfoil shape. Each shape transition assembly has a shape transition mechanism attached to an interior of the strut. The shape transition mechanism includes fixed length structural members, and a drive mechanism of variable length structural member(s), includes an actuation mechanism connected to the shape transition mechanism, and an activation mechanism coupled to the actuation mechanism.