Instrumented Fastening Bolt for Aircraft Load Detection
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Solution Overview
Problem
Existing flight control actuator systems for aircraft, particularly the secondary load path of THSA actuators, lack reliability and precision in detecting load engagement, leading to potential misinterpretation of primary path failures and increased maintenance complexity.
Innovation Solution
A flight unit control system featuring an instrumented fastening bolt with measurement areas that detect load without stressing the bolt, utilizing strain gauges placed in cavities with thinned walls to measure shear deformation, and a locking mechanism that isolates tensile forces away from measurement areas, allowing for precise load detection without modifying existing systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are placed on the secondary path to detect load, then load detection capability is improved, but the system becomes complicated and integration into the actuator becomes difficult
Solution Approach 1:
The fastening bolt serves multiple functions: it mechanically connects the secondary path components and simultaneously acts as the sensing element through its integrated strain gauges. This multi-functionality eliminates the need for separate detection devices, reducing system complexity while maintaining measurement precision.
Solution Approach 2:
The measurement system is merged with the fastening bolt structure itself. The strain gauges are directly mounted on the bolt, combining the mechanical fastening function and the measurement function into a single integrated component, thereby simplifying the overall system architecture.
2Measurement precision
If the secondary path detection system is modified to include projecting elements and extensometer gauges, then load detection precision is improved, but the intervention time and cost increase
Solution Approach 1:
The fastening bolt is pre-configured with strain gauges and appropriate geometry during manufacturing, so that when installed on the secondary path, load detection is immediately enabled without requiring additional modification steps, projecting elements, or complex assembly procedures on-site.
3Reliability
If the fastening means stresses the instrumented bolt in the measurement area, then the bolt is securely locked in position, but the strain gauges produce erroneous readings
Solution Approach 1:
The fastening system is segmented into distinct functional zones: the measurement area on the bolt shaft where strain gauges are mounted and where no stress should be applied, and the threaded end area where the nut applies clamping force. This spatial segmentation ensures that locking forces are isolated from the measurement zone, maintaining both reliable locking and accurate readings.
Solution Approach 2:
The unthreaded shaft portion of the bolt acts as an intermediary element that transmits the clamping force from the nut to the secondary path components without transmitting stress to the measurement area. This intermediary zone isolates the strain gauges from mechanical stress while maintaining the structural integrity of the connection.
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
Enhances the reliability and precision of load detection on the secondary path, simplifying integration and reducing maintenance costs by providing accurate feedback to flight control computers without altering the flight unit's structure.
Implementation Method 1
a thinned wall capable of being deformed under the action of a shear stress applied to the bolt
Implementation Method 2
at least one strain gauge which is placed in the bottom of a cavity against the thinned wall, each strain gauge being capable of detecting a deformation of the thinned wall
Data Source
AI summary
A flight unit control system having at least one instrumented fastening bolt connecting an aircraft carrier structure and a load path, the instrumented bolt having at least one measurement area for detecting that the load path is under load and including a fastener for locking the instrumented bolt in a position relative to the aircraft carrier structure and load path and wherein the measurement area has two cavities and at least one strain gauge and wherein the fastener includes a plate which is positioned at a threaded end of the instrumented bolt which bears against one of the aircraft carrier structure and the load path and which extends perpendicularly to an axis of the bolt and a nut which is placed at the threaded end of the instrumented bolt to immobilize the instrumented bolt relative to the aircraft structure or the load path.