Tilt Rotor Blade Flapping for Noise Reduction
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Solution Overview
Problem
Tilt rotor aircraft generate excessive noise due to aerodynamic interference between blades and wings, which becomes a concern as their usage increases in urban areas.
Innovation Solution
A control system for tilt rotor aircraft that allows blades to flap during flight, adjusting their pitch and out-of-plane angle using stationary and rotational swashplates coupled with pitch links, and a computing device to manipulate these controls, reducing noise by increasing the distance between blades and wings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If blades are kept rigid and fixed in position during flight, then structural strength and control precision are improved, but aerodynamic interference with wings increases and noise levels rise
Solution Approach 1:
The patent applies the dynamics principle by enabling blades to flap dynamically during flight. The blade assembly includes a flapping hinge that allows blades to move relative to the rotor hub, changing their position and orientation in response to aerodynamic conditions. This dynamic movement reduces aerodynamic interference with wings during forward flight, thereby reducing noise levels while maintaining structural integrity through controlled motion rather than rigid fixation.
Solution Approach 2:
The blade control mechanism is segmented into multiple independent components: the rotor hub, flapping hinge, pitch hinge, stationary swashplate, and rotational swashplate. Each component performs a specific function - the flapping hinge allows vertical movement, the pitch hinge controls blade angle, and the dual swashplates coordinate control inputs. This segmentation enables complex blade motion control while keeping each individual component relatively simple and manageable.
2Object-affected harmful factors
If blades are allowed to flap during flight, then noise reduction is achieved, but control system complexity increases
Solution Approach 1:
The dual swashplate system performs multiple functions simultaneously. The stationary swashplate converts pilot control inputs into collective and cyclic pitch changes, while the rotational swashplate translates these changes to all rotating blades. This multi-functional design allows a single control system to manage both the flapping motion and pitch control, reducing the need for separate mechanisms and simplifying the overall control architecture despite the complex blade motions enabled.
3Object-affected harmful factors
If distance between blades and wings is increased, then aerodynamic interference and noise are reduced, but aircraft performance may be compromised
Solution Approach 1:
The flapping mechanism enables blades to dynamically adjust their vertical position during flight. During forward flight, blades naturally flap upward, increasing the vertical distance between the rotating blades and the wings, thereby reducing aerodynamic interference and noise. During vertical takeoff and landing, blades return to a lower position to maintain optimal performance characteristics. This dynamic adjustment allows the aircraft to optimize blade-wing spacing for different flight regimes without permanently sacrificing performance.
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 noise levels by allowing blades to react to aerodynamic changes, minimizing the rate of force changes and resulting in lower loading noise, thus mitigating the noise pollution issue.
Implementation Method 1
allowing blades to flap during at least a portion of a flight... allowing blades to react to aerodynamic changes... minimizing the rate of force changes and resulting in lower loading noise
Data Source
AI summary
A control system for a multi-rotor aircraft is described that results in lower operating noise. Allowing blades to flap during flight reduces aerodynamic interference as blades pass by other aircraft components, such as wings or the fuselage. Pitch links coupled to a rotational swashplate can be used to allow flapping during flight. The swashplates can allow the canting of the rotors to change a rotational or out-of-plane angle of the blades to decrease noise.