Flexible Printed Circuit Harnesses for Aircraft Engine Fire Resistance

Solution Overview

Problem

Conventional electrical harnesses in gas turbine engines are bulky, heavy, and difficult to manipulate due to their substantial size and weight, which is undesirable for applications like aircraft, where reduced size and weight are essential while maintaining operational fire resistance and avoiding excessive cost and complexity.

Innovation Solution

The use of flexible printed circuit boards (FPCBs) with distinct fire-resistant capabilities, where one FPCB carries critical engine control and hazard detection signals and withstands high temperatures and heat flux without exposure, while a secondary FPCB carries less critical signals, optimizing fire-proofing material usage and reducing bulk and weight.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional wiring harnesses are used, then fire resistance can be achieved through fire-proofing materials, but the harness becomes bulky and heavy

Engineering Contradiction:

Improvefire resistanceVSAvoidharness weight

Core Design Contradiction:

ReliabilityVSWeight of stationary object

Solution Approach 1:

The conductive tracks are divided into two separate flexible printed circuit boards: a first FPCB carrying critical engine control and hazard detection signals, and a second FPCB carrying less critical signals. This segmentation allows fire-proofing materials to be applied selectively only to the first FPCB, reducing the overall weight and bulk of the harness assembly while maintaining necessary fire resistance for critical systems.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Fire-proofing materials are applied locally and selectively only to the first flexible printed circuit board that carries critical signals, rather than uniformly to all conductive tracks. This localized application of fire protection achieves adequate operational fire resistance for critical systems while minimizing the addition of fire-proofing material, thereby reducing overall weight and bulk.

Inventive Principle:

Principle #3Local quality

2Reliability

If fire-proofing materials are applied to all conductive tracks, then fire resistance is maximized, but cost and complexity increase

Engineering Contradiction:

Improvefire resistanceVSAvoidharness complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The conductive tracks are divided into two separate flexible printed circuit boards: a first FPCB carrying critical engine control and hazard detection signals, and a second FPCB carrying less critical signals. This segmentation allows fire-proofing materials to be applied selectively only to the first FPCB, reducing the overall weight and bulk of the harness assembly while maintaining necessary fire resistance for critical systems.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Fire-proofing materials are applied locally and selectively only to the first flexible printed circuit board that carries critical signals, rather than uniformly to all conductive tracks. This localized application of fire protection achieves adequate operational fire resistance for critical systems while minimizing the addition of fire-proofing material, thereby reducing overall weight and bulk.

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If conventional wiring harnesses are used, then all signals can be carried, but the harness is difficult to manipulate

Engineering Contradiction:

Improvesignal carrying capacityVSAvoidmanipulability

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The patent replaces the conventional mechanical wiring harness system (individual wires, cables, connectors, and assembly processes) with a flexible printed circuit board system where conductive tracks are formed through printing and laminating processes. This substitution enables complex signal routing to be achieved through material properties and manufacturing processes rather than mechanical assembly, significantly improving ease of manipulation and installation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS9243559B2Electrical harnesses

Publication Date: 2016.01.26 ROLLS ROYCE PLC

AI summary

An aircraft gas turbine engine has first and second electrical harnesses formed from respective first and second flexible printed circuit boards which each provides a plurality of spaced conductive tracks. The conductive tracks carry signal types which either (i) provide engine control and can cause hazardous engine conditions in the event of their failure, (ii) detect or prevent hazardous conditions of the engine, or (iii) are not of type (i) and/or of type (ii). The first flexible printed circuit board provides all the conductive tracks which carry signals of type (i) or the first flexible printed circuit board provides all the conductive tracks which carry signals of type (ii). The second flexible printed circuit board provides all the remaining conductive tracks. The first electrical harness is fire-resistant for a period of five minutes without any exposure of its conductive tracks so that the conductive tracks can carry their signals.