Dual-Stage Shock Strut Servicing Across Varying Temperatures
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Solution Overview
Problem
Current methods for servicing shock struts in aircraft landing gear do not efficiently maintain optimal internal gas and oil levels across varying temperatures, leading to suboptimal performance and extended servicing times.
Innovation Solution
A method for servicing dual-stage, separated gas/fluid shock struts involves charging secondary and primary gas chambers with compressed gas and pumping oil to match specific pressure and extension curves, ensuring the shock strut is serviced to nominal levels regardless of ambient temperature, with minimal cycling and bleeding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional shock strut servicing methods are used, then servicing can be completed with existing equipment, but servicing time is extended and optimal gas/oil levels cannot be maintained across varying temperatures
Solution Approach 1:
The method performs preliminary actions by pre-determining the target pressure and extension values based on temperature before actual servicing. The servicing chart is prepared in advance with all necessary pressure-extension-temperature relationships, allowing the technician to directly look up target values without complex calculations during the servicing process itself.
Solution Approach 2:
The method implements feedback by continuously monitoring the shock strut extension and gas chamber pressure during servicing, comparing these values against the target values from the servicing chart, and adjusting gas charge accordingly. This closed-loop control ensures the shock strut reaches the precise optimal state for the given temperature.
2Reliability
If shock strut servicing is performed without temperature compensation, then the process is simpler, but gas pressure and oil volume cannot be maintained within the design envelope across different temperatures
Solution Approach 1:
The method applies parameter changes by using temperature as the key variable to determine the appropriate gas charge pressure and extension. The servicing chart contains pre-calculated target values for different temperature ranges, allowing the technician to select the correct parameters based on measured temperature, thereby compensating for thermal effects on gas pressure and oil volume.
Solution Approach 2:
The temperature compensation parameters are pre-calculated and stored in the servicing chart before servicing begins. This preliminary preparation eliminates the need for complex real-time calculations or iterative adjustments during the actual servicing process, maintaining simplicity while ensuring reliability across temperatures.
3Manufacturing precision
If extensive cycling and bleeding are performed during servicing, then gas and oil levels can be adjusted, but servicing time increases significantly
Solution Approach 1:
The method performs preliminary calculation of the exact gas charge quantity needed based on the current state and target state from the servicing chart. This allows the technician to charge the gas chamber directly to the correct pressure in a single step, eliminating the need for repeated cycling and bleeding operations that were necessary in traditional methods.
Solution Approach 2:
The method replaces the traditional mechanical trial-and-error approach of cycling and bleeding with a calculated direct-charging approach. By using the servicing chart to determine precise target values, the process substitutes iterative mechanical adjustment with a single calculated operation, significantly reducing time while maintaining precision.
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
This method allows for more efficient and time-effective servicing of shock struts, maintaining optimal oil and gas levels across a range of temperatures, reducing servicing time and minimizing shock strut cycling.
Implementation Method 1
a trapped volume of gas is compressed as the shock strut is axially compressed, and a volume of oil is metered through an orifice. The gas acts as an energy storage device, similar to a spring
Implementation Method 2
Shock struts also dissipate energy by passing the oil through the orifice so that as the shock absorber is compressed or extended, its rate of motion is limited by the damping action from the interaction of the orifice and the oil
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A method for servicing a dual-stage, separated gas/fluid shock strut (100) may comprise measuring a servicing temperature, charging a secondary gas chamber (140) with compressed gas, wherein a secondary chamber pressure corresponds to the servicing temperature, pumping oil into the shock strut (100), and charging a primary gas chamber (130) with compressed gas.