Aircraft Landing Gear with Hydraulic Fluid Balancer
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Solution Overview
Problem
Current aircraft landing gear systems face limitations in shock absorber break-out load, touchdown hardness, dynamic landing loads, weight on wheels detection, and redundancy, particularly in the 'live axle' configuration, which affects flexibility and maintainability.
Innovation Solution
The proposed aircraft landing gear incorporates a two-stage shock absorber with a hydraulic fluid balancer featuring a second separator piston, allowing for different shock absorbing properties at various stages, and a 'live axle' arrangement with a drive mechanism and braking device mounted on the axle, enabling improved redundancy and flexibility. Additionally, composite bracing struts distribute ground loads efficiently and reduce drag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional single-stage shock absorber is used, then the structure is simple, but the shock absorber break-out load is high and touchdown hardness is excessive
Solution Approach 1:
The shock absorber is divided into two distinct stages: a first stage with a first separator piston and a second stage with a second separator piston. Each stage has different fluid volumes and compression characteristics, allowing the system to provide high break-out load in the first stage and controlled softness in the second stage, thereby resolving the contradiction between structural simplicity and force management.
Solution Approach 2:
The patent changes the physical parameters of the hydraulic fluid system by creating two stages with different fluid volumes, viscosities, and compression ratios. The first stage uses a smaller fluid volume for high break-out load, while the second stage uses a larger fluid volume for softer touchdown, allowing the system to optimize both force characteristics without excessive complexity.
2Device complexity
If a conventional single-stage shock absorber is used, then the structure is simple, but the touchdown hardness is excessive
Solution Approach 1:
The shock absorber is segmented into two stages with different hardness characteristics. The first stage handles initial impact with higher stiffness, while the second stage provides softer cushioning for final touchdown, thereby reducing overall touchdown hardness while maintaining structural efficiency.
Solution Approach 2:
The patent changes the stiffness parameter across two stages by varying fluid volume, viscosity, and compression ratio. The first stage has lower fluid volume for initial support, while the second stage has higher fluid volume for softer touchdown, optimizing the hardness characteristic without excessive structural complexity.
3Volume of moving object
If drive and brake mechanisms are mounted inside the wheel hub, then the structure is compact, but flexibility and maintainability are reduced
Solution Approach 1:
The drive and brake mechanisms are extracted from the wheel hub and mounted on the axle instead. This extraction provides greater flexibility in mechanism design and easier maintainability, while the overall volume increase is minimal since the mechanisms are located in the same general wheel assembly area.
4Volume of moving object
If drive and brake mechanisms are mounted inside the wheel hub, then the structure is compact, but thermal risks to the drive mechanism increase
Solution Approach 1:
The drive mechanism is extracted from the wheel hub and mounted on the axle, separating it from the brake mechanism. This spatial separation improves thermal management by allowing better cooling airflow around the drive mechanism, reducing thermal risks while maintaining a compact overall wheel assembly volume.
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 design enhances shock absorber break-out load, reduces dynamic landing loads, improves weight on wheels detection, and provides greater redundancy and maintainability, while minimizing torque during braking and reducing thermal risks to the drive mechanism.
Implementation Method 1
the hydraulic fluid in the sleeve portion of the rear oleo strut is effectively compressed at reduced stiffness, resulting in a low shock absorber break-out load and a softer touchdown for the aircraft
Implementation Method 2
the hydraulic fluid balancer comprises a second separator piston in the balance chamber such that the balance chamber is fluidly separated into three sections
Implementation Method 3
EP 2 896 517 discloses a shock absorber assembly arranged to be coupled to a vehicle, comprising a first shock absorber element of variable length and a second shock absorber element of variable length
Data Source
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AI summary
The invention provides an aircraft landing gear (100) comprising a first oleo strut (10) comprising a sleeve portion (11) and a slider portion (13), the slider portion being slidable within a hydraulic fluid chamber (12) of the sleeve portion, and a second, similar oleo strut (30). The landing gear also comprises a hydraulic fluid balancer (50) comprising a balance chamber separated into first (55) and second (57) end sections, wherein the hydraulic fluid chamber of the sleeve portion of the first oleo strut is fluidly connected to the first section of the balance chamber and the hydraulic fluid chamber of the sleeve portion of the second oleo strut is fluidly connected to the second section of the balance chamber of the hydraulic fluid balancer. The invention also provides a "live axle" landing gear with a drive mechanism or a braking device (22) being mounted on the axle, and various associated methods.