Aircraft Shock Absorber Stiction Reduction via Moveable Wall
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Solution Overview
Problem
Current aircraft weight and balance measurement systems using shock absorber pressure measurements are inaccurate due to static friction or 'stiction' caused by seals and bearings, which can be exacerbated by existing methods to overcome stiction that compromise shock absorber reliability.
Innovation Solution
An aircraft landing gear shock absorber with a moveable wall portion that increases pressure by decreasing the fluid volume, overcoming stiction without fluid leakage, and featuring a control port isolated from the sealed fluid volume to ensure safety and accuracy in weight and balance measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a bump is provided to the shock absorber by increasing and decreasing internal pressure, then stiction is overcome, but reliability decreases
Solution Approach 1:
The shock absorber is divided into two separate fluid systems: a sealed fluid volume for shock absorption and a control fluid volume for bump generation. This segmentation prevents contamination between systems and maintains reliability while enabling accurate measurements through controlled bump generation.
Solution Approach 2:
A moveable wall portion acts as an intermediary between the control fluid and sealed fluid volume. It transmits pressure changes from the control system to the shock absorber fluid without requiring direct fluid connection, preventing leakage paths while enabling bump generation for overcoming stiction.
2Measurement precision
If conventional bump systems are used to overcome stiction, then measurement accuracy improves, but fluid leakage risk increases
Solution Approach 1:
The control port and control fluid volume are extracted from the sealed fluid volume of the shock absorber. This separation removes the leakage risk from the critical measurement system while preserving the ability to generate bumps for accurate measurements.
Solution Approach 2:
The control fluid system uses a disposable or replaceable fluid supply that can be replenished without affecting the sealed shock absorber fluid. This allows the control system to be maintained independently, preventing contamination of the critical measurement fluid.
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
The solution effectively reduces stiction in shock absorbers, enhancing the accuracy of weight and balance measurements while maintaining system reliability and safety by preventing fluid leakage, even in case of failure.
Implementation Method 1
the moveable wall portion is arranged to be moved by a motive force between a first position and a second position, wherein in the second position the effective volume of the chamber is decreased relative to when the moveable wall portion is in the first position such that the shock absorber fluid pressure increases to extend the shock absorber
Implementation Method 2
the control port is arranged to be coupled to a source of control fluid for providing the motive force to move the moveable wall portion from the first position to the second position, wherein the control port is isolated from the sealed fluid volume by the moveable wall portion
Implementation Method 3
The control port may be a hydraulic or pneumatic control port or any other suitable control port
Implementation Method 4
The moveable wall portion can be moveable from the second position to the first position by shock absorber fluid pressure within the chamber
Data Source
AI summary
An aircraft landing gear shock absorber having an inner housing portion slidably coupled within an outer housing portion, and a chamber which defines a sealed fluid volume for containing shock absorber fluid within the shock absorber. The chamber includes a moveable wall portion arranged to move between a first position and a second position, and in the second position the effective volume of the chamber is decreased such that the shock absorber fluid pressure increases, to provide a bump to the shock absorber.