Large Variable-Speed Tilt Rotors for Reduced-Rotor eVTOL Aircraft
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Solution Overview
Problem
Existing eVTOL aircraft designs face challenges in efficiently carrying a payload of at least 500 pounds while using a reduced number of rotors, balancing vertical lift and forward propulsion, and overcoming issues of high power requirements, inefficiency, noise, and safety concerns due to rotor failures.
Innovation Solution
An electric vertical takeoff and landing aircraft is engineered with a reduced number (2-4) of variable speed rigid rotors, utilizing individual blade control actuators and a large wing for lift, and a wing-borne configuration that tilts with the rotors to optimize lift and thrust, ensuring redundancy and efficiency in both vertical and forward flight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a reduced number of rotors (2-4) is used, then device complexity is reduced, but reliability deteriorates due to increased risk from single rotor failure
Solution Approach 1:
Each rotor is designed to perform multiple functions: it can provide vertical lift when positioned vertically, and can provide forward propulsion when tilted forward. This multi-functionality allows the aircraft to achieve both VTOL capability and efficient forward flight with fewer rotors, resolving the contradiction between reduced rotor count and maintained reliability.
Solution Approach 2:
The rotors are made dynamically tiltable rather than fixed in position. Each rotor can change its orientation from vertical (for lift) to forward-facing (for propulsion), allowing the same rotor to adapt to different flight phases. This dynamic capability reduces the need for separate lift and propulsion rotors, thereby reducing overall rotor count while maintaining system reliability.
2Device complexity
If rotors are used for both vertical lift and forward propulsion, then device complexity is reduced, but efficiency deteriorates in forward flight due to high disc loading
Solution Approach 1:
The rotors dynamically tilt forward during forward flight to transform from a vertical lift configuration to a horizontal propulsion configuration. This dynamic repositioning allows the rotor disc plane to become more perpendicular to the flight direction, reducing disc loading and improving propulsive efficiency while maintaining the dual-function capability.
Solution Approach 2:
The system changes the operational parameters of the rotors by altering their tilt angle and rotational speed according to flight phase. In forward flight, the rotors operate at different tilt angles and RPM compared to hover, optimizing performance for each flight condition and reducing energy loss.
3Power
If high power is used for hover, then vertical lift capability is improved, but use of energy deteriorates when high-speed efficient cruise is also required
Solution Approach 1:
The rotors dynamically adjust their orientation and rotational speed based on flight phase. During hover, they operate in vertical configuration at high RPM to generate sufficient lift power. During cruise, they tilt forward and operate at optimized RPM for propulsive efficiency, thereby managing energy consumption effectively across different flight modes.
Solution Approach 2:
The same rotor system serves both hover and cruise functions, adapting its configuration to meet different power requirements. This eliminates the need for separate lift and cruise propulsion systems, optimizing overall energy usage while maintaining both high hover power capability and efficient cruise 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 design achieves safe and efficient flight with a payload of at least 500 pounds, providing high disc loading, low noise, and robust safety features, including redundancy in motor power and efficient transition between vertical and forward flight modes.
Implementation Method 1
The rotor blades are configured to provide a significant amount of lift during rotor borne flight and can be tilted to provide forward thrust
Implementation Method 2
Each rotor is powered by its own electric motor or motors
Data Source
AI summary
Apparatus, systems, and methods are contemplated for electric powered vertical takeoff and landing (eVTOL) aircraft. Such are craft are engineered to carry safely carry at least 500 pounds (approx. 227 kg) using a few (e.g., 2-4) rotors, generally variable speed rigid (non-articulated) rotors. It is contemplated that one or more rotors generate a significant amount of lift (e.g., 70%) during rotorborne flight (e.g., vertical takeoff, hover, etc), and tilt to provide forward propulsion during wingborne flight. The rotors preferably employ individual blade control, and are battery powered. The vehicle preferably flies in an autopilot or pilotless mode and has a relatively small (e.g., less than 45′ diameter) footprint.