Pusher Propeller Autorotation Power Recovery for Main Rotor Support
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Solution Overview
Problem
Rotorcraft face challenges in reducing descent rates during engine malfunctions, as existing autorotation methods rely solely on aerodynamic forces, which may not provide sufficient power for controlled glide and flare recovery maneuvers, especially in high-speed flights.
Innovation Solution
Incorporating a pusher propeller with variable pitch rotor blades that transitions from generating forward thrust in engine-powered mode to providing power to the main rotor system during autorotation by harnessing airflow, using a drivetrain with a freewheeling unit like a sprag clutch to enable torque transfer from the pusher propeller to the main rotor system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If autorotation relies solely on aerodynamic forces through the main rotor system, then the system remains simple, but the power available for controlled glide and flare recovery is insufficient
Solution Approach 1:
The pusher propeller is designed to perform dual functions: generating forward thrust during engine-powered flight and generating power during autorotation by harnessing airflow. This multi-functionality resolves the contradiction by providing additional power during autorotation without requiring a separate dedicated system, thus limiting the increase in overall device complexity.
Solution Approach 2:
The pusher propeller harnesses the existing airflow through the rotorcraft during autorotation to generate power, rather than requiring an external power source. This self-service approach provides additional power during autorotation while avoiding the complexity of adding external power systems, as the system uses the environmental airflow already present during the autorotation condition.
2Power
If the pusher propeller operates at high pitch for forward thrust, then forward propulsion is effective, but the propeller cannot effectively harness airflow for power generation during autorotation
Solution Approach 1:
The pusher propeller employs variable pitch rotor blades that can be dynamically adjusted between high pitch for forward thrust during engine-powered flight and low pitch for power generation during autorotation. This dynamic adaptability resolves the contradiction by allowing the propeller to optimize its pitch angle for the current operational mode, providing both effective forward propulsion and effective power generation as needed.
Solution Approach 2:
The pitch angle of the pusher propeller blades is changed as a key parameter to adapt to different operational requirements. During engine-powered flight, the pitch is set high for forward thrust; during autorotation, the pitch is reduced to effectively harness airflow for power generation. This parameter change resolves the contradiction by allowing the same propeller to perform both functions effectively.
3Reliability
If the drivetrain continuously transfers torque from the engine to the main rotor system, then power transmission is efficient, but the main rotor system cannot autorotate during engine malfunction
Solution Approach 1:
The engine connection to the main rotor system is extracted or disconnected during autorotation through the freewheeling unit, allowing the main rotor system to rotate independently without being driven by the engine. This extraction resolves the contradiction by enabling autorotation capability during engine failure while the drivetrain can still efficiently transmit power during normal engine-powered operation when the connection is engaged.
Solution Approach 2:
The drivetrain incorporates a freewheeling unit that dynamically changes its torque transmission state based on operational conditions. During normal operation, the drivetrain continuously transfers torque efficiently; during autorotation, the freewheeling unit disengages to allow independent rotor rotation. This dynamic behavior resolves the contradiction by providing both efficient power transmission and autorotation capability as needed.
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
Enhances rotorcraft safety and control by providing additional power to the main rotor system during autorotation, reducing speed decay and enabling more controlled landings by converting kinetic energy into lift, thus improving overall autorotation and flare recovery capabilities.
Implementation Method 1
the pusher propeller is aerodynamically driven responsive to airflow therethrough and the drivetrain is configured to receive torque and rotational energy from the pusher propeller
Data Source
AI summary
A rotorcraft having pusher propeller generated power during autorotations. The rotorcraft has an engine powered mode and an autorotation mode. The rotorcraft includes an engine and a drivetrain configured to receive torque and rotational energy from the engine in the engine powered mode. A main rotor system is coupled to the drivetrain and is rotatable to generate lift and forward thrust for the rotorcraft in the engine powered mode. A pusher propeller is coupled to the drivetrain and is rotatable to generate forward thrust for the rotorcraft in the engine powered mode. In the autorotation mode, the pusher propeller is aerodynamically driven responsive to airflow therethrough and the drivetrain is configured to receive torque and rotational energy from the pusher propeller, thereby providing power to the main rotor system.