Skid Landing Gear Tension Cable Resists Outward Deflection
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Solution Overview
Problem
Conventional skid landing gear systems for rotorcraft experience fatigue failure and cracking due to excessive tensile stresses in the rear cross tube during repeated landings, primarily caused by outward deflection and vertical loads.
Innovation Solution
A skid landing gear assembly that incorporates a tension cable member disposed between the skid tubes, which resists outward deflection by distributing tensile stress and reducing bending loads on the cross tube, utilizing a composite cable with adjustable tension to maintain optimal stiffness and prevent ground resonance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional cross tube with uniform wall thickness is used, then the structure is simple and easy to manufacture, but excessive tensile stress occurs in the lower wall region during landing causing fatigue failure
Solution Approach 1:
The cross tube is designed with non-uniform wall thickness, specifically thicker walls in the lower region that experience higher tensile stresses during landing. This local variation in thickness distributes the stress more effectively and prevents fatigue failure in the critical lower wall area, while maintaining simpler construction elsewhere.
Solution Approach 2:
The cross tube incorporates composite material construction with strategically placed reinforcement elements or layered structures that provide enhanced tensile strength in the lower wall region. This allows the structure to resist fatigue failure from repeated landing loads while maintaining overall structural efficiency.
2Stability of the object's composition
If the cross tube stiffness is increased to avoid ground resonance, then ground resonance is prevented, but the tensile stress in the cross tube during landing increases
Solution Approach 1:
The cross tube employs local thickness variation with increased wall thickness in the lower region where tensile stresses concentrate during landing. This localized reinforcement increases stiffness precisely where needed to prevent ground resonance while managing stress distribution to avoid excessive tensile loads in critical areas.
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 reduces tensile stress on the skid landing gear assembly, enhances the fatigue life of the cross tube, and prevents ground resonance during landings by distributing loads through the tension cable, thereby improving the overall durability and performance of the landing gear.
Implementation Method 1
the tension cable member resists outward deflection of at least a portion of the skid landing gear assembly when a downward load is applied to the skid landing gear assembly
Implementation Method 2
the tension cable member resists outward deflection... when a downward load is applied
Implementation Method 3
the tension cable member comprises a composite cable
Data Source
AI summary
An aspect provides a skid landing gear assembly including a cross member disposed between a first skid tube and a second skid tube, and a tension cable member configured to be disposed in the cross member; wherein the tension cable member resists outward deflection of at least a portion of the skid landing gear assembly when a downward load is applied to the skid landing gear assembly. In other aspects, there are methods of avoiding ground resonance in a skid landing gear assembly, methods of assembling a skid landing gear assembly, methods of operating a helicopter with a skid landing gear assembly, and methods of improving the service life of a skid landing gear assembly.