Retractable Helicopter Landing Gear Mechanism
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Solution Overview
Problem
The landing gear on helicopters protrudes into the wind stream, causing drag that reduces top speed and range.
Innovation Solution
A retractable landing gear system comprising a trailing arm, shock strut, link, rotatable latch, and actuator, which allows the gear to move between extended and stowed positions by rotating about pivot points, disengaging and engaging roller pins, and utilizing an actuator to apply moments for rotational movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the landing gear is fixed in an extended position, then the structural simplicity and ease of operation are improved, but the aerodynamic drag increases reducing top speed and range
Solution Approach 1:
The landing gear is designed to be dynamically reconfigurable between extended and retracted positions. The trailing arm assembly with shock strut can rotate about a pivot point on the fuselage, allowing the gear to transition from a fixed extended state to a retracted state that reduces aerodynamic drag during flight, thereby improving top speed and range
Solution Approach 2:
The landing gear components are nested within the fuselage when retracted. The trailing arm rotates to position the wheel assembly inside the fuselage cavity, with the shock strut collapsing inward, effectively nesting the entire landing gear mechanism within the aircraft body to minimize aerodynamic interference
2Productivity
If the landing gear is made retractable, then the aerodynamic drag is reduced improving speed and range, but the device complexity and mechanical reliability requirements increase
Solution Approach 1:
The patent employs simple, robust mechanical components that can be manufactured cost-effectively. The latch mechanism uses basic cam and follower geometry rather than complex electronic systems, and the roller pins are simple cylindrical elements that can be easily replaced if needed, reducing overall system complexity while maintaining reliability
Solution Approach 2:
The latch mechanism is designed to automatically engage and disengage based on the mechanical position of the trailing arm. As the trailing arm rotates during retraction or extension, the cam surface automatically actuates the latch to lock or unlock the gear position, eliminating the need for separate actuators or complex control systems for each movement phase
3Shape
If the landing gear uses a simple fixed structure, then the manufacturing cost and device complexity are reduced, but the aerodynamic performance deteriorates
Solution Approach 1:
The landing gear transitions from a static fixed structure to a dynamic reconfigurable system. During flight, the gear retracts to present a streamlined aerodynamic profile with minimal protrusion into the wind stream. During landing operations, the gear extends to provide the necessary structural support and ground contact capability
Solution Approach 2:
The landing gear is divided into separable functional segments: the trailing arm assembly, the shock strut, the wheel assembly, and the latch mechanism. This segmentation allows each component to be optimized independently for its specific function while enabling the overall system to achieve both aerodynamic efficiency in retracted state and structural simplicity in design
Data Source
AI summary
A method for actuating a landing gear arrangement may include supplying a first pressure to an actuator, applying, by the actuator, a moment on a latch to rotate the latch in a first rotational direction, disengaging a first roller pin, engaging a stopper on a link, rotating the link in the first rotational direction about a pivot, the link coupled between a trailing arm and a shock strut, rotating the shock strut about a second end of the shock strut, rotating the trailing arm about a first end, and engaging a second roller pin.