Catcher Pin Assembly Load Inspection via Compressible Element
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Solution Overview
Problem
Conventional engine mounting systems for aircraft require time-consuming and difficult inspections to determine if a catcher pin is loaded, as they necessitate fully removing or loosening bolts, which are often in hard-to-access locations, leading to potential vibration issues and maintenance challenges.
Innovation Solution
A catcher pin assembly incorporating a compressible element, such as a conical spring washer, and a lockable retaining element that applies a predetermined resistance to movement, allowing for the detection of load without disassembling the pin, using a method that involves determining the unloaded pin torque and applying a test torque to assess if the pin is loaded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the catcher pin is tightly clamped to prevent vibration, then the reliability of the connection is improved, but the ease of inspection deteriorates because the pin cannot be easily removed or loosened for testing
Solution Approach 1:
The connection system is segmented into multiple independent catcher pins, each with its own lockable retaining element. This allows individual inspection of each pin without affecting the others, and the segmentation enables the testing function to be separated from the clamping function through the use of a separate compressible element
Solution Approach 2:
A compressible element (such as a spring washer) is introduced as an intermediary between the head of the pin and the mounting element. This intermediary provides the necessary clamping force to prevent vibration while allowing the pin to be tested for load status without complete disassembly, as the compressible element can be compressed to release the pin temporarily
2Measurement precision
If the lock nut is loosened to inspect the pin, then the measurement precision of load status is improved, but the loss of time increases due to the need to replace or refurbish locking arrangements
Solution Approach 1:
The system enables self-testing through the application of test torque to the head of the pin. The compressible element allows the pin to be tested in its installed position without requiring removal or refurbishment of locking arrangements. The load status is determined by whether the pin rotates under applied torque, providing a simple self-diagnostic function
Solution Approach 2:
The compressible element is pre-compressed during assembly to establish the clamping force. This preliminary action creates a predetermined resistance to movement that can be overcome by applying test torque, allowing the pin to be tested without loosening the lock nut. The system is prepared in advance to allow testing while maintaining the locked state
3Ease of operation
If the pin is fully removed for inspection, then the ease of operation is improved, but the loss of time increases and the risk of vibration issues upon reinstallation increases
Solution Approach 1:
The compressible element serves as an intermediary that allows the pin to be tested while remaining in its installed position. By compressing this element, the pin can be temporarily released for testing without complete removal, and then re-clamped without requiring reinstallation procedures that risk vibration issues
Solution Approach 2:
The testing function is extracted from the installation/removal process. Instead of requiring the pin to be fully removed for inspection, the system allows the testing action to be performed on the installed pin through the application of test torque, separating the inspection function from the disassembly function
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 quick and reliable inspection of the catcher pin's load status without disassembling the locking arrangement, simplifying maintenance and reducing the risk of vibration and corrosion-related issues, while ensuring accurate detection of load changes due to component failures.
Implementation Method 1
a compressible element which when compressed to a predetermined degree by the pin applies a predetermined resistance to rotation of the pin
Implementation Method 2
The compressible element and/or at least a part of the pin and/or the mounting element and/or the retaining element may be provided with an anti-friction coating
Data Source
AI summary
A catcher pin assembly for attachment to a catcher link of an aircraft frame, the catcher pin assembly having an engine mounting element, a catcher pin, a compressible element, and a nut, which is lockable to the catcher pin, the compressible element being compressed between the pin and the mounting element and/or between the mounting element and the nut, in the assembled condition of the assembly, such that the compressible element applies a predetermined resistance to rotation of the catcher pin relative to the mounting element. The invention also relates to a method of testing a catcher pin assembly to determine if the catcher pin is carrying load from the catcher link, the method including applying a predetermined torque to the catcher pin sufficient to overcome the resistance to rotation of the catcher pin when it is unloaded, and determining whether the catcher pin rotates relative to the mounting element.