Dual-Stage Landing Gear Strut for Abnormal Impact Absorption
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Solution Overview
Problem
Conventional oleo-pneumatic shock-absorbing struts in aircraft landing gear are insufficient in managing abnormal landing forces, leading to potential damage due to excessive force transfer during abnormal landing conditions.
Innovation Solution
A dual-stage shock strut design incorporating an oleo-pneumatic first stage and a spring-based second stage, where the first stage absorbs normal impact forces independently and the second stage engages to absorb excessive forces, providing adjustable energy absorption and damping capabilities through varying configurations of springs and damping mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-stage oleo-pneumatic strut is used, then the device complexity is low, but the ability to manage abnormal landing forces is insufficient
Solution Approach 1:
The shock-absorbing strut is divided into two independent stages: a first stage with an oleo-pneumatic system for normal landing forces, and a second stage with a spring-based system for excessive forces. This segmentation allows each stage to be optimized for its specific function, improving overall reliability without requiring complete redesign of the entire system.
Solution Approach 2:
The strut system transitions from a static single-stage design to a dynamic two-stage design where the second stage is selectively engaged based on the magnitude of applied forces. The system adapts its characteristics automatically: the oleo-pneumatic stage handles routine operations while the spring stage activates during abnormal conditions, providing dynamic responsiveness to varying load conditions.
2Strength
If a dual-stage design with spring-based second stage is implemented, then the energy absorption capability for excessive forces is improved, but the device complexity increases
Solution Approach 1:
The second spring-based stage is pre-configured and positioned to engage only when forces exceed the first stage's absorption capacity. This beforehand preparation ensures that excessive forces are immediately cushioned by the second stage without requiring complex real-time control systems, thereby improving energy absorption capability while limiting the increase in device complexity to mechanical positioning mechanisms.
3Adaptability or versatility
If the second stage is designed to engage only under excessive forces, then the adaptability to different landing conditions is improved, but the device complexity increases
Solution Approach 1:
The two-stage system operates autonomously based on the physical conditions of each landing event. The transition between stages is self-regulated by the force magnitude itself, with no external control or monitoring required. This self-service operation achieves high adaptability to different landing conditions while minimizing the complexity of engagement mechanisms.
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 dual-stage design effectively absorbs and dampens a wide range of landing forces, preventing aircraft damage by distributing and dissipating energy efficiently during both normal and abnormal landing conditions, while maintaining a compact and lightweight configuration suitable for retractable landing gear.
Implementation Method 1
converts kinetic energy into potential energy by the use of a pressurized gas, thereby providing elastic spring characteristics
Implementation Method 2
Damping of this energy conversion and reduction of 'bounce' is accomplished via oil or the like, typically being forced through a damping orifice
Implementation Method 3
a spring-based second stage, where the first stage absorbs normal impact forces independently and the second stage engages to absorb excessive forces
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A shock strut is provided that includes a first energy absorption stage or load limiter and a second energy absorption stage or load limiter. The second energy absorption stage or load limiter includes one or more disc springs (205). The shock strut can be employed on both fixed and retractable landing gear alike, while providing design adjustability for obtaining load-deflection curves that accommodate a range of descent or impact velocities.