Fibre Optic Load Sensor for Aircraft Landing Gear Axle
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Solution Overview
Problem
Current load measurement systems for aircraft landing gear, particularly during abnormal events, face challenges due to limitations in sensor accuracy, durability, and the inability to differentiate between vertical and drag loads, making them unsuitable for robust in-service use.
Innovation Solution
A fibre optic load sensing system using Bragg Grating sensors embedded in fibre optic cables clamped or bonded inside the landing gear axles, which measure deflection to determine load components by analyzing changes in fibre geometry, allowing for separation of vertical and drag loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional sensors (e.g. strain gauges) are used for load measurement, then measurement capability is provided, but reliability is limited due to mounting requirements and sensor lifespan
Solution Approach 1:
The patent replaces traditional mechanical strain gauge systems with fibre optic Bragg grating sensors. This substitution eliminates the need for complex mechanical mounting arrangements while providing both high reliability and precise measurement capability. The fibre optic sensors are embedded directly in the axle structure, eliminating mounting errors and improving both durability and measurement accuracy simultaneously.
Solution Approach 2:
The patent uses composite material techniques by embedding fibre optic sensors within the metallic axle structure. This integration creates a composite system where the sensor becomes part of the structural element, eliminating the need for separate mounting hardware and improving both reliability and measurement precision through direct structural integration.
2Measurement precision
If traditional sensors are installed inside the axle, then load measurement is possible, but device complexity increases due to mounting requirements for accuracy
Solution Approach 1:
The patent replaces complex mechanical mounting systems with fibre optic embedding techniques. The Bragg grating sensors are written directly into the fibre optic cable which is then embedded in the axle, eliminating the need for precise mechanical positioning, orientation, and surface finish requirements that characterize traditional strain gauge installations.
Solution Approach 2:
The patent segments the sensing function from the structural element by using separate fibre optic cables embedded in the axle, rather than requiring direct mechanical attachment of sensors to specific locations. This segmentation allows the sensing function to be distributed along the axle length without complex mounting requirements at specific points.
3Adaptability or versatility
If traditional sensors are used, then in-service monitoring is attempted, but reliability is insufficient for robust in-service use
Solution Approach 1:
The patent replaces traditional mechanical sensors with fibre optic Bragg grating sensors that are embedded in the axle structure. This substitution provides robustness for in-service use by eliminating the mechanical mounting interfaces that are prone to failure, while maintaining the capability for continuous load monitoring during aircraft operation.
Solution Approach 2:
The patent performs preliminary embedding of the fibre optic sensors during axle manufacturing, rather than installing them later in service. This preliminary action ensures proper positioning and integration before the axle undergoes operational stresses, thereby improving reliability for subsequent in-service monitoring while maintaining adaptability for continuous use.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate and durable load monitoring, enabling determination of individual wheel loads and load directions, improving aircraft weight and balance assessment and aiding in gear design optimization, with the capability to detect overload conditions.
Implementation Method 1
Bragg Grating sensors written into the fibre reflect the signal light in a way that allows the interrogator to determine the change in radius of the fibre
Implementation Method 2
When the axle bends, the fibre also bends in sympathy. Bragg Grating sensors written into the fibre reflect the signal light in a way that allows the interrogator to determine the change in radius of the fibre
Data Source
AI summary
An aircraft landing gear comprising a fibre optic load sensor for monitoring load in a component of the landing gear, such as an axle. The fibre optic cable is mounted on an inner surface of the component of the landing gear. Typically the fibre optic load sensor comprises one or more Bragg Grating sensors.