Landing Gear Shock Strut Heating for Cold-Temperature Energy Absorption
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Solution Overview
Problem
Aircraft landing gear shock struts experience performance variations due to temperature changes, leading to potential overload conditions and reduced energy absorption efficiency at cold temperatures, as the nitrogen gas compressibility factor affects the air spring curves and damping performance.
Innovation Solution
A temperature control unit assembly within the shock strut cylinder, comprising a temperature sensor, regulator, and heating element, which maintains the nitrogen gas temperature within a predetermined range to ensure consistent compressibility and viscosity, thereby regulating the air spring curve and enhancing energy absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the shock strut operates at cold temperatures without temperature control, then the device complexity remains low, but the energy absorption efficiency deteriorates due to nitrogen gas compressibility changes
Solution Approach 1:
The patent applies parameter changes by actively controlling the temperature of the nitrogen gas within the shock strut using a heating element controlled by a temperature control unit. This maintains the compressibility factor of the nitrogen gas above 1, ensuring consistent energy absorption performance across varying ambient temperatures without adding excessive complexity to the overall system.
Solution Approach 2:
The patent replaces passive mechanical shock absorption with an active thermally-controlled system. Instead of relying solely on the mechanical properties of nitrogen gas at varying temperatures, the system uses electrical heating elements and temperature control units to actively maintain optimal gas conditions, substituting thermal/electrical control for purely mechanical design approaches.
2Reliability
If a temperature control unit assembly is added to maintain nitrogen gas temperature, then the energy absorption consistency improves, but the device complexity increases
Solution Approach 1:
The patent implements feedback control through a temperature control unit assembly that includes temperature sensors and heating elements. The system continuously monitors the temperature of the nitrogen gas and adjusts heating accordingly to maintain the compressibility factor above 1, ensuring reliable and consistent performance while managing system complexity through automated control.
Solution Approach 2:
The temperature control unit assembly serves multiple functions: it heats the nitrogen gas, monitors temperature, controls heating based on temperature feedback, and maintains optimal compressibility conditions. This multi-functionality consolidates several control tasks into a single integrated assembly, reducing overall system complexity while improving reliability.
3Strength
If the nitrogen gas compressibility factor is maintained above 1 through heating, then the overload prevention improves, but the energy consumption increases
Solution Approach 1:
The patent employs periodic or conditional heating action rather than continuous heating. The temperature control unit activates heating only when the nitrogen gas temperature drops below the threshold required to maintain compressibility factor above 1, and stops heating when the threshold is reached. This periodic action prevents overload conditions while minimizing unnecessary energy consumption.
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 maintains the shock strut's performance by keeping the nitrogen gas compressibility factor above 1, preventing overload conditions and ensuring predictable energy absorption during landing and ground operations, even at subzero temperatures, while being cost-effective and minimally impactful in terms of weight and design modifications.
Implementation Method 1
a heating element configured to heat the nitrogen gas within the shock strut cylinder in response to the temperature within the shock strut cylinder falling below a predetermined temperature
Implementation Method 2
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
AI summary
A landing gear assembly is provided. The landing gear assembly includes a shock strut. The shock strut includes a shock strut cylinder and a shock strut piston slidably disposed within the shock strut cylinder. The landing gear assembly further includes a temperature control unit assembly 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.