Aircraft Landing Gear Tension Drag Brace for Steering Alignment
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Solution Overview
Problem
Large airplanes face challenges in adding wheels to main landing gear without disrupting the airplane configuration, leading to steering inefficiencies, increased turn radius, tire scrubbing, and loading issues due to fore-aft offset between wing and body landing gear.
Innovation Solution
A body landing gear system with a forward cant angle and retracting trunnion axis, integrated with a folding drag brace, minimizes steering inefficiencies and load issues by aligning the ground contact point with the wing landing gear, preserving the existing load paths and reducing the need for redesign.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If additional wheels are added to main landing gear to increase total brake mass and distribute loads, then pavement loading is improved and wheel/tire/brake load distribution is optimized, but airplane configuration is disrupted and steering efficiency decreases
Solution Approach 1:
The body landing gear is positioned in the fore-aft dimension rather than only laterally, creating longitudinal alignment with the wing landing gear. This dimensional placement resolves the contradiction by achieving both load distribution (through additional gear) and steering efficiency (through longitudinal alignment that minimizes fore-aft offset)
Solution Approach 2:
The body landing gear uses a forward cant angle that is asymmetric relative to the vertical, positioning the ground contact point forward and in-line with the wing landing gear. This asymmetric configuration optimizes both load bearing capability and steering characteristics by eliminating fore-aft offset while maintaining structural integrity
2Reliability
If body landing gear is positioned aft to avoid wing interference, then wing landing gear operation is preserved, but fore-aft offset increases causing steering inefficiency and increased turn radius
Solution Approach 1:
The drag brace is designed as a folding mechanism that dynamically changes configuration between deployment and stowage. During deployment, it provides structural support for the aft-positioned body landing gear; during stowage, it clears the wing landing gear path, thus preserving wing operation while enabling optimal body gear positioning for steering efficiency
3Ease of operation
If body landing gear is positioned forward to improve steering alignment, then steering efficiency increases, but structural load paths are disrupted requiring redesign
Solution Approach 1:
The body landing gear uses a forward cant angle that creates local geometric optimization at the ground contact point, positioning it in-line with the wing landing gear for improved steering. This localized geometric solution achieves steering efficiency without requiring global structural redesign of the entire landing gear system
4Strength
If drag brace is made rigid to provide structural support, then load bearing capacity increases, but volumetric integration becomes difficult
Solution Approach 1:
The drag brace transitions from a rigid load-bearing structure during deployment to a compact folded configuration during stowage. This dynamic transformation allows the structure to provide full structural support when needed while minimizing volumetric occupancy when retracted, resolving the contradiction between strength and volume
Data Source
AI summary
An aircraft includes: a wing landing gear; and a body landing gear which includes a shock absorber strut assembly comprising a wheel, a fixed truss structure and an aircraft structure connection point, a drag brace, and a pivot joint that connects the fixed truss structure to the drag brace; and a body landing gear wheel well configured to store the body landing gear in a stowed position. The drag brace includes an upper drag brace, and a lower drag brace pivotingly attached to the upper drag brace. In a stowed position, the shock absorber strut assembly, the fixed strut structure, the upper drag brace and the lower drag brace may be positioned outside of a swing path of a wing landing gear of the aircraft. In the deployed position, the lower drag brace may be positioned in the swing path of the wing landing gear of the aircraft.