Aircraft Plug Door Assembly for In-Plane Stress Transfer

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Solution Overview

Problem

Conventional aircraft door conversions from passenger to cargo service require extensive structural reinforcement and modifications, leading to increased weight, cost, and complexity, particularly due to the need to transfer in-plane stresses and accommodate larger door openings, which can interfere with aircraft systems like AOA sensors and affect fuel efficiency and operational safety.

Innovation Solution

The implementation of a plug door assembly that transfers in-plane stresses directly between the door and the fuselage through engagement assemblies, eliminating the need for additional structural framing and allowing the door to operate as both a plug and canopy door, thereby reducing the need for extensive reinforcement and minimizing air turbulence.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional structural reinforcement is added to transfer in-plane stresses for cargo door conversion, then structural integrity is improved, but weight and device complexity increase

Engineering Contradiction:

Improvestructural integrityVSAvoiddoor assembly weight

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The door assembly is divided into multiple discrete stress transfer elements distributed along the door periphery, each independently transferring stress at specific locations rather than requiring a continuous reinforced frame structure

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The stress transfer function is merged with the door assembly itself by integrating stress transfer elements directly into the door structure, eliminating the need for separate external reinforcement structures

Inventive Principle:

Principle #5Merging (Combining)

2Strength

If extensive structural reinforcement is added for in-plane stress transfer, then structural integrity is improved, but manufacturing cost increases

Engineering Contradiction:

Improvestructural integrityVSAvoidmanufacturing cost

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The stress transfer elements are designed as simpler, more economical components that can be manufactured and installed more easily than traditional reinforcement structures, accepting that these elements may require replacement over time

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Area of moving object

If larger door openings are created for cargo service, then cargo loading capability is improved, but interference with aircraft systems increases

Engineering Contradiction:

Improvedoor opening areaVSAvoidinterference with aircraft systems

Core Design Contradiction:

Area of moving objectVSObject-affected harmful factors

Solution Approach 1:

The door assembly incorporates localized stress transfer elements at specific positions around the door periphery, concentrating structural functionality at discrete locations rather than requiring uniform reinforcement across the entire door area

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The stress transfer mechanism transitions from a two-dimensional plane stress distribution to a three-dimensional arrangement with elements positioned at multiple depths and angles, allowing stress transfer without requiring a large planar footprint that would interfere with aircraft systems

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

4Reliability

If conventional plug door design is used, then in-flight safety is improved, but stress transfer capability deteriorates

Engineering Contradiction:

Improvein-flight safetyVSAvoidin-plane stress transfer

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The door assembly is designed to perform multiple functions simultaneously: maintaining in-flight safety through the plug door sealing mechanism while also providing in-plane stress transfer capability through integrated stress transfer elements

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The stress transfer elements are designed with dynamic characteristics that allow them to flex and deform under load, enabling them to transfer in-plane stresses effectively while maintaining the sealing integrity required for in-flight safety

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS11338900B2Aircraft plug door with in-plane load transfer capacity and methods of use

Publication Date: 2022.05.24 CURRY JAMES M

AI summary

A plug door assembly for a pressurized aircraft is provided. The door assembly includes a surround and a door, and connector assemblies along the edges that act to transfer in-plane stresses directly across the fuselage opening via the door, as well as stops that react radial loads generated by cabin pressure. The door assembly obviates the need for a separate frame to transmit stresses around the perimeter of the fuselage opening.