Hybrid Helicopter Variable Rotor Speed Control
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Solution Overview
Problem
Conventional rotorcrafts face limitations in achieving long-range, high-speed cruising flight while maintaining efficient vertical flight capabilities, often requiring complex and costly solutions that increase weight and reduce safety due to the need for distinct rotor speed settings and additional propulsion systems.
Innovation Solution
A hybrid helicopter design featuring a mechanical interconnection system with collective and cyclic pitch control for the rotor and propeller, where the rotor speed is progressively reduced from a first speed to a second speed as airspeed increases, maintaining a constant Mach number at the blade tip to optimize lift and drag ratios, and eliminating the need for an antitorque rotor by using differential propeller thrust for steering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the rotor speed is maintained at a constant high value for vertical flight, then vertical flight performance is improved, but high-speed cruising performance deteriorates due to excessive Mach number at blade tips
Solution Approach 1:
The patent implements a variable rotor speed system that dynamically adjusts rotor RPM based on flight phase. During vertical flight and low-speed operation, the rotor operates at high speed (e.g., 400-500 RPM) to generate sufficient lift. During high-speed cruising, the rotor speed is reduced (e.g., to 200-300 RPM) to maintain blade tip Mach number below 0.85, preventing compressibility effects and drag divergence. This dynamic speed adjustment resolves the contradiction between vertical flight performance and forward speed capability.
2Ease of operation
If an antitorque rotor is added to counteract main rotor torque, then directional control is improved, but device complexity and weight increase
Solution Approach 1:
The patent combines the antitorque function with the propulsion function by using the same propellers for both purposes. The propellers generate thrust for forward motion while simultaneously providing torque reaction control to counteract the main rotor's torque. This merging of functions eliminates the need for a separate antitorque rotor system, reducing mechanical complexity and weight while maintaining effective directional control.
Solution Approach 2:
The propellers serve multiple functions: they provide forward propulsion, counteract main rotor torque through differential thrust, and enable directional control. This multi-functionality eliminates the need for dedicated antitorque components, simplifying the overall mechanical assembly while achieving the same control objectives.
3Adaptability or versatility
If distinct rotor speed settings are implemented for different flight phases, then flight performance across phases is improved, but device complexity increases due to additional control systems
Solution Approach 1:
The patent implements an automated control system that uses feedback from flight parameters (airspeed, vertical speed, attitude) to automatically adjust rotor speed and propeller pitch. Sensors monitor flight conditions and feed this information to the flight control system, which then adjusts the rotor RPM and propeller blade angle to optimize performance for the current flight phase. This feedback mechanism enables complex multi-phase operation without requiring manual intervention or overly complicated control systems.
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 high-speed cruising with improved lift and drag ratios, reduced power consumption, and simplified mechanical assemblies, achieving exceptional range and versatility while maintaining efficient vertical flight capabilities.
Implementation Method 1
a rotor (10) with collective and cyclic pitch control of the blades of said rotor
Implementation Method 2
at least one solely-propulsive propeller with collective pitch control of the blades of said propeller
Implementation Method 3
the speed of rotation Ω of the rotor is equal to a first speed of rotation Ω1 up to a first flightpath air speed V1 of said hybrid helicopter, and is then reduced progressively in application of a linear relationship as a function of the flightpath air speed of said hybrid helicopter. The Mach number at the tip of the advancing blade is then kept constant.
Implementation Method 4
eliminating the need for an antitorque rotor by using differential propeller thrust for steering
Data Source
AI summary
A hybrid helicopter (1) includes firstly an airframe provided with a fuselage (2) and a lift-producing surface (3), together with stabilizer surfaces (30, 35, 40), and secondly with a drive system including:a mechanical interconnection system (15) between firstly a rotor (10) of radius (R) with collective pitch and cyclic pitch control of the blades (11) of the rotor (10), and secondly at least one propeller (6) with collective pitch control of the blades of the propeller (6); andat least one turbine engine (5) driving the mechanical interconnection system (15). The speed of rotation (Ω) of the rotor (10) is equal to a first speed of rotation (Ω1) up to a first flightpath air speed (V1) of the hybrid helicopter (1), and is then reduced progressively in application of a linear relationship as a function of the flightpath air speed of the hybrid helicopter.