Landing Gear Shock Strut Heating for Cold-Temperature Damping
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Solution Overview
Problem
Aircraft landing gear shock struts experience performance variations due to temperature changes, leading to potential bottoming and reduced damping efficiency at cold temperatures, affecting safe landing and ground operations.
Innovation Solution
Incorporation of a temperature control unit assembly within the shock strut, comprising a temperature sensor, regulator, and heating element to maintain the nitrogen gas temperature within a predetermined range, ensuring consistent compressibility and viscosity of the fluid, thereby maintaining optimal energy absorption and preventing overload conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the shock strut operates at cold temperatures, then the gas compressibility increases, but the damping efficiency decreases and bottoming occurs
Solution Approach 1:
The patent applies parameter changes by actively controlling the temperature of the nitrogen gas within the shock strut. A heating element is incorporated to raise the gas temperature when it falls below the optimal range (e.g., below -10°C or 14°F), thereby maintaining the compressibility factor within acceptable limits and preventing bottoming while ensuring reliable damping performance across varying ambient temperatures.
Solution Approach 2:
The patent replaces passive mechanical design assumptions with an active thermal control system. Instead of designing the shock strut to accommodate a wide range of temperature variations through mechanical adjustments, the invention uses an electrical heating system controlled by a temperature sensor and regulator to actively maintain optimal gas temperature, substituting thermal management for mechanical adaptation.
2Device complexity
If the nitrogen gas temperature is not controlled, then the device complexity remains low, but the shock strut performance varies with temperature
Solution Approach 1:
The temperature control system operates autonomously using a temperature sensor to monitor gas temperature and a regulator to control the heating element. When the gas temperature drops below the predetermined threshold, the system automatically activates the heating element to raise the temperature, then deactivates it when the optimal range is reached, requiring no external intervention or complex control mechanisms.
Solution Approach 2:
The nitrogen gas serves multiple functions: it provides the spring effect for energy storage and rebound, and simultaneously acts as the medium for temperature sensing and heating control. The same gas chamber that provides mechanical function also serves as the thermal control environment, eliminating the need for separate temperature control chambers or systems.
3Reliability
If heating element is added to control temperature, then the gas compressibility is maintained, but the weight of the shock strut increases
Solution Approach 1:
The heating element is designed to provide just enough heating capacity to raise the gas temperature from the lowest expected ambient temperature to the optimal operating range, not to continuously maintain maximum temperature. The system applies heat only when and to the extent necessary to prevent bottoming, avoiding excessive weight from an oversized heating system.
Solution Approach 2:
The heating element is positioned to heat only the nitrogen gas within the shock strut chamber, not the entire shock strut assembly. This localized heating approach minimizes the required heating capacity and associated weight while effectively maintaining the compressibility factor of the gas where it is needed for shock absorption.
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 ensures predictable and improved shock strut performance by maintaining the compressibility factor of gas and fluid viscosity, reducing the risk of damage from overload events and ensuring reliable operation across varying temperatures, with minimal weight and design modifications.
Implementation Method 1
a heating element configured to heat the nitrogen gas within the mixed fluid chamber
Implementation Method 2
a temperature sensor configured to sense a temperature of the nitrogen gas within the mixed fluid chamber
Implementation Method 3
a trapped volume of gas is compressed as the shock strut is axially compressed, and a volume of oil is metered through a metering orifice. The gas acts as an energy storage device, similar to a spring
Data Source
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AI summary
A landing gear assembly (200) is provided. The landing gear assembly includes a shock strut (202). The shock strut includes a shock strut cylinder (204) and a shock strut piston (206) slidably disposed within the shock strut cylinder. The landing gear assembly further includes a temperature control unit assembly (250) disposed within the shock strut cylinder. The temperature control unit assembly is configured to, responsive to a temperature within the shock strut cylinder falling below a predetermined temperature, heat gas within the shock strut cylinder.