Rotary Wing Rotor Blade Pitch Control for High Advance Ratio Flight
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Solution Overview
Problem
Rotating wing aircraft are limited in maximum flight speed due to phenomena such as retreating blade stall, increased drag at rotor tips, and reverse airflow over retreating blades, restricting them to speeds below 200 mph.
Innovation Solution
A rotary wing aircraft design with a rotor having an even number of blades at equal angular intervals, where the rotor is rotated to cause alternating advancing and retreating blade movements, and tip jets powered by the aircraft's propulsive jet engines, with adjustable blade pitch angles and rotor disc angles to optimize lift and reduce drag, allowing for speeds exceeding 200 mph.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the rotor rotates at high speed to achieve high flight speed, then the flight speed increases, but retreating blade stall occurs and drag increases
Solution Approach 1:
The rotor blade pitch angles are dynamically adjusted during flight to optimize performance. The system transitions from fixed pitch to variable pitch control, allowing the blades to adapt their angle of attack in real-time to prevent stall conditions while maintaining high forward speed
Solution Approach 2:
The invention changes the operational parameters of the rotor system by adjusting blade pitch angles and rotor disc angles. This allows the system to operate efficiently at high advance ratios where traditional fixed-pitch rotors would experience blade stall and excessive drag
2Device complexity
If the rotor blade pitch angles are fixed, then the device complexity is reduced, but lift optimization and drag reduction are limited
Solution Approach 1:
The system employs variable pitch control mechanisms that allow blade pitch angles to be adjusted during flight operations. This dynamic capability enables optimal lift generation and drag reduction across different flight conditions without requiring overly complex control systems
Solution Approach 2:
The rotor system is designed to perform multiple functions: generating lift, controlling drag, and maintaining stability across a wide range of forward speeds. The variable pitch mechanism serves all these functions simultaneously, reducing the need for separate specialized systems
3Device complexity
If the rotor disc angle is fixed, then the device complexity is reduced, but the ability to optimize lift at high speeds is limited
Solution Approach 1:
The rotor disc angle is made variable to allow dynamic optimization of lift generation. This enables the system to maintain effective lift production even at high forward speeds where fixed disc angles would result in insufficient lift or increased drag
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 vertical takeoff and landing while achieving flight speeds greater than 200 mph by optimizing lift and reducing drag through controlled blade angles and tip jet assistance, significantly surpassing current rotary wing aircraft speed limitations.
Implementation Method 1
The energy to rotate the rotor results from a windmill-like effect of air passing through the underside of the rotor
Implementation Method 2
The Bernoulli effect of the airflow moving over the rotor surface creates lift
Implementation Method 3
To provide initial rotation of the rotor, jet engines were secured to the tip of each blade of the rotor and powered during takeoff, landing, and hovering
Data Source
AI summary
A method for equalizing rolling moments at high advance ratios is disclosed including impelling an aircraft in a forward direction at an airspeed by means of a thrust source and rotating a rotor of the aircraft at an angular velocity with respect to the airspeed effective to cause a positive total lift on each blade due to air flow over the blades in the retreating direction when the blade is moving in the retreating direction. The rotor includes an even number of blades placed at equal angular intervals around the rotor hub. One or both of cyclic pitch and rotor angle of attack are adjusted such that a rolling moment of the retreating blade due to reverse air flow is between 0.3 and 0.7 times a rolling moment on the advancing blade due to lift.