Aircraft Landing Gear Gravity Deployment Linkage
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Solution Overview
Problem
Aircraft landing gear generates significant aero-acoustic noise during landing approaches due to high-speed airflow around deployed components, which is undesirable due to noise pollution concerns in populated areas.
Innovation Solution
An aircraft landing gear assembly that deploys by gravity, utilizing a retraction linkage and damping device to reduce noise duration, with a locking mechanism allowing independent movement of joints and a retraction actuator for efficient deployment and retraction, even if the actuator jams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the landing gear is deployed early in the landing approach, then the deployment speed is sufficient, but the duration of aero-acoustic noise increases
Solution Approach 1:
The retraction linkage transitions between two operational states: locked and unlocked. In the unlocked state, the linkage permits relative movement between joints independent of the retraction actuator, enabling rapid gravity-driven deployment. In the locked state, the linkage inhibits relative movement, allowing actuator-controlled retraction. This dynamic state change resolves the contradiction by enabling fast deployment (unlocked state) while maintaining reliable retraction (locked state), thereby reducing noise duration without sacrificing deployment speed.
2Reliability
If the retraction linkage is locked during deployment, then the retraction actuator can effectively retract the landing gear, but the deployment speed decreases
Solution Approach 1:
The system dynamically switches the retraction linkage between locked and unlocked states based on operational phase. During deployment, the linkage is unlocked to permit gravity-driven motion independent of the actuator, achieving fast deployment. During retraction, the linkage is locked to ensure the actuator can effectively control the process. This resolves the contradiction by separating deployment and retraction functions through state transitions.
Solution Approach 2:
In the unlocked state, the landing gear utilizes gravity as a self-service force to drive deployment without requiring actuator power, thereby achieving rapid deployment. The system harnesses the natural gravitational force acting on the main strut to accomplish the deployment function, eliminating the need for powered actuation during this phase.
3Device complexity
If the retraction actuator is used for both deployment and retraction, then the system is simpler, but the noise duration increases due to earlier deployment
Solution Approach 1:
The retraction linkage's ability to dynamically switch between locked and unlocked states enables it to serve dual functions: permitting gravity-driven deployment when unlocked and enabling actuator-controlled retraction when locked. This dynamic functionality allows the same mechanical linkage to facilitate rapid deployment (reducing noise duration) while maintaining reliable actuator-assisted retraction, resolving the contradiction without increasing system complexity.
4Speed
If the retraction linkage permits independent joint movement, then gravity deployment is enabled, but the retraction control becomes more complex
Solution Approach 1:
The retraction linkage dynamically changes its kinematic characteristics by transitioning between locked and unlocked states. In the unlocked state, it permits independent joint movement for gravity deployment. In the locked state, it constrains joint movement for actuator-controlled retraction. This dynamic state change allows the same linkage structure to accommodate both deployment modes without requiring fundamentally different mechanical designs, thereby managing complexity while enabling rapid gravity-driven deployment.
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
Enables faster and more reliable deployment of landing gear later in the landing approach, reducing the duration of aero-acoustic noise and ensuring reliable operation by allowing gravity-driven deployment and actuator-assisted retraction.
Implementation Method 1
the main strut can be moved between a deployed condition, for take-off and landing, and a stowed condition for flight
Implementation Method 2
a damping device arranged to oppose movement of the main strut as it approaches the deployed condition
Data Source
AI summary
An aircraft landing gear assembly having a main strut configured to move between a deployed condition and a stowed condition, a damping device to oppose movement of the main strut as it approaches the deployed condition, a retraction actuator and a mechanical retraction linkage coupled between the aircraft and the main strut, and a locking device. The locking device is operable to change the retraction linkage between a locking condition in which the retraction actuator can apply a stowing force to the main strut through the retraction linkage to move the main strut from the deployed condition to the stowed condition, and an extensible condition in which the retraction linkage permits the main strut to be deployed by way of gravity.