Steering Collar Locking Mechanism for Retractable Nose Landing Gear
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Solution Overview
Problem
Retractable nose landing gear with a shrink shock strut experiences issues with wheels/tires freely rotating within the wheel well during flight, potentially leading to jamming when in a shrunk condition, as centering cams disengage and fail to maintain proper orientation.
Innovation Solution
A locking mechanism is introduced, comprising a hydraulically actuated plunger and clevis system that locks the strut piston in place when the landing gear is retracted, along with alternative embodiments like static abutment surfaces and mechanical locks to prevent rotation, ensuring the wheels/tires remain stationary within the wheel well during flight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a shrink shock strut is used to reduce landing gear length for wheel well retraction, then the landing gear can be properly stored during flight, but the wheels/tires become free to rotate and may jam in the wheel well
Solution Approach 1:
The locking mechanism is activated in advance when the landing gear enters the shrunk condition, preventing wheel rotation before it can cause jamming. The plunger engages with the clevis to restrict rotational movement proactively during the retraction process
Solution Approach 2:
A plunger-clevis locking mechanism serves as an intermediary component between the strut piston and the wheel assembly. This intermediary element transfers and controls the rotational constraint, allowing the wheel to rotate when needed while preventing rotation during shrunk retraction
2Ease of operation
If centering cams are used to maintain wheel orientation during landing, then proper wheel alignment is achieved, but the cams disengage during shrunk retraction leaving wheels free to rotate
Solution Approach 1:
The locking mechanism is designed to perform multiple functions: it locks the wheel in position during shrunk retraction, releases to allow rotation when the gear is extended, and works in conjunction with the centering cams during landing. This multi-functional design addresses both the centering requirement and the rotation prevention requirement
3Reliability
If a locking mechanism is added to prevent wheel rotation during shrunk retraction, then wheel jamming is prevented, but device complexity increases
Solution Approach 1:
The locking mechanism is designed to be self-actuating through hydraulic pressure from the existing landing gear system. The plunger automatically engages and disengages based on the gear's extension/retraction state, eliminating the need for separate actuators or complex control systems while maintaining reliability
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 locking mechanism effectively prevents wheels/tires from rotating off-center within the wheel well, preventing jamming and ensuring smooth retraction and deployment of the landing gear, even in case of hydraulic system failures, thereby ensuring safe aircraft operation.
Implementation Method 1
a plunger adapted and configured for hydraulically actuated movement between an unlocked condition when the landing gear is in a fully extended position deployed from the wheel well of the aircraft to permit axial rotation of the strut piston relative to the strut cylinder, and a locked condition when the landing gear is in a shrunk condition retracted within the wheel well of the aircraft to prevent axial rotation of the strut piston relative to the strut cylinder during flight
Data Source
AI summary
A retractable nose landing gear assembly for an aircraft is disclosed, which includes an elongated strut cylinder defining a longitudinal axis, an elongated strut piston mounted for reciprocal movement relative to the strut cylinder between a shrunk condition when the landing gear is retracted into a wheel well of an aircraft and a fully extended condition when the landing gear is deployed from the wheel well for landing the aircraft, and wherein the strut piston is mounted for rotation about the axis of the strut cylinder for steering the aircraft while taxiing on the ground, and a locking mechanism operatively associated with the strut cylinder for preventing rotation of the strut piston about the axis of the strut cylinder when the landing gear is in a shrunk condition retracted within the wheel well of the aircraft during flight.