Shock Strut Energy Absorption for Hard-Landing Pressure Spikes
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Solution Overview
Problem
Aircraft shock struts face structural damage during 'hard-landing events' due to pressure spikes exceeding design thresholds, which existing shock absorbing systems fail to adequately mitigate.
Innovation Solution
A shock strut assembly with a mixed fluid chamber, an orifice, and a spring retainer that compresses in response to pressure exceeding an upper threshold, reducing pressure spikes through the use of coned-disc springs and an orifice plate that floats between retainer housing and spring retainer, allowing for energy absorption and automatic resetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional shock strut with air-over-oil arrangement is used, then normal shock absorption during landing is achieved, but pressure spikes during hard-landing events exceed the upper design pressure threshold causing structural damage
Solution Approach 1:
The patent applies beforehand cushioning by installing a supplemental spring system (coned-disc springs) in parallel with the existing air-over-oil shock absorption mechanism. This supplemental spring is pre-configured to engage and provide additional cushioning when pressure exceeds the upper design threshold during hard-landing events, preventing structural damage before it occurs.
Solution Approach 2:
The patent implements parameter changes by introducing a pressure-activated mechanism that alters the shock strut's pressure threshold parameter. The supplemental spring system remains inactive during normal operation but activates when pressure reaches a predetermined upper threshold, effectively changing the pressure absorption characteristics dynamically based on operating conditions.
2Reliability
If the shock strut is designed to withstand higher pressure spikes, then protection against hard-landing damage is improved, but the weight and complexity of the shock strut increases
Solution Approach 1:
The patent applies segmentation by dividing the shock absorption function into two distinct segments: the original air-over-oil system for normal landing conditions and a supplemental spring system for hard-landing events. This segmentation allows each subsystem to be optimized for its specific function without requiring the entire shock strut to be over-engineered for maximum pressure spikes.
Solution Approach 2:
The patent implements dynamics by creating a dynamic, condition-based shock absorption system. The supplemental spring system dynamically engages or disengages based on the pressure conditions, providing additional protection only when needed during hard-landing events while maintaining the simplicity of the original design during normal operation.
3Strength
If the shock strut structure is reinforced to prevent structural damage, then strength is improved, but the weight of the landing gear assembly increases
Solution Approach 1:
The patent applies beforehand cushioning by incorporating a supplemental spring system that provides additional pressure absorption capacity before damage can occur during hard-landing events. This allows the base shock strut structure to maintain its original design weight while the supplemental spring handles the extreme pressure spikes, avoiding the need to reinforce the entire structure.
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 absorbs pressure spikes during hard landings, preventing structural damage to the aircraft and landing gear, while automatically resetting and maintaining normal operating performance without altering the shock strut's designed performance.
Implementation Method 1
a spring configured to compress in response to a pressure in the liquid chamber exceeding an upper threshold, the compression of the spring lowering the pressure in the liquid chamber
Implementation Method 2
a spring configured to compress in response to a pressure in the liquid chamber exceeding an upper threshold
Implementation Method 3
a volume of oil is metered through an orifice. The gas acts as an energy storage device, such as a spring, so that upon termination of a compressing force the shock strut returns to its original length. 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
Implementation Method 4
One type of shock strut generally utilizes an 'air-over-oil' arrangement wherein a trapped volume of gas is compressed as the shock strut is axially compressed
Implementation Method 5
The gas acts as an energy storage device, such as a spring, so that upon termination of a compressing force the shock strut returns to its original length
Implementation Method 6
the spring includes a plurality of coned-disc springs
Implementation Method 7
allowing for energy absorption and automatic resetting
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A shock strut assembly is disclosed herein. The shock strut assembly includes a shock strut cylinder (204) defining a mixed fluid chamber (214), a shock strut piston (208) defining a liquid chamber (212), the shock strut piston operatively coupled to slide within the shock strut cylinder, an orifice support tube (228) coupled to the shock strut cylinder and defining an orifice between the liquid chamber and the mixed fluid chamber, a retainer housing (226) coupled to the orifice support tube and configured to restrict a flow of liquid from the liquid chamber to the mixed fluid chamber, a spring retainer (254) coupled to the orifice support tube and disposed over the retainer housing, and a spring (252) disposed between the retainer housing and the spring retainer.