Variable Speed Tilt Rotors for eVTOL Payload and Safety
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Solution Overview
Problem
Current electric vertical take-off and landing (eVTOL) aircraft face challenges in safely carrying a payload of at least 500 pounds using a unitary lift and forward propulsion system with no more than four rotors, due to inefficiencies and safety concerns related to rotor failure, high power requirements, and noise levels, especially when transitioning from vertical lift to forward flight.
Innovation Solution
Designing an eVTOL aircraft with a reduced number (2-4) of variable speed rigid non-articulated rotors, where rotors provide significant lift during vertical takeoff and can tilt for forward thrust, using individual blade control actuators to maintain constant thrust and increase shaft torque, and configuring the wing for efficient hover and cruise flight with a slotted flap for roll control and reduced stall speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a reduced number (2-4) of rotors is used for vertical lift and forward propulsion, then the aircraft complexity is reduced and safety is improved, but the power requirements increase and rotor failure risk increases
Solution Approach 1:
The rotor system is designed with variable speed capability, allowing the rotors to operate at optimal speeds for different flight phases (vertical hover, transition, forward flight). This dynamic operation enables a reduced number of rotors to generate sufficient power across all flight conditions without requiring oversizing the power system for peak hover demands alone
Solution Approach 2:
Each rotor is designed to perform multiple functions: providing vertical lift during hover, transitioning to forward propulsion during cruise, and contributing to aircraft control through individual blade control actuators. This multi-functionality allows a reduced number of rotors to replace what would traditionally require more specialized propulsion elements
2Productivity
If variable speed control is implemented on rotors, then rotor efficiency is maintained over a wide speed range, but the device complexity increases due to additional control systems
Solution Approach 1:
The control system is segmented into individual blade control actuators, each independently controlling the pitch of a single blade. This segmentation allows for simplified individual actuator design compared to a centralized complex control system, while achieving variable speed control and efficiency across the full operational range through coordinated operation of the segmented control elements
Solution Approach 2:
The system changes the operational parameters of the rotors by implementing variable speed control and individual blade pitch control. This allows the rotors to adapt their performance characteristics to match different flight conditions, maintaining high efficiency from vertical hover through transition to forward flight without requiring a fundamentally more complex control architecture
3Reliability
If individual blade control actuators are used to maintain constant thrust, then safety is improved during rotor failure, but the device complexity and weight increase
Solution Approach 1:
Individual blade control actuators provide localized control authority on each blade, enabling independent adjustment of blade pitch to compensate for asymmetric loads or rotor failures. This local quality of control distributes the safety function across multiple simple actuators rather than requiring a single complex control system, improving reliability while keeping individual components simple
4Adaptability or versatility
If tilting rotors are used for transition from vertical lift to forward flight, then adaptability is improved, but the device complexity and transition control difficulty increase
Solution Approach 1:
The tilt mechanism is merged with the rotor hub and blade control system, integrating the transition function into the existing rotor architecture. This consolidation eliminates separate tilt mechanisms, reducing overall device complexity while maintaining full adaptability for vertical hover, transition, and forward flight modes through coordinated rotor tilt and blade pitch control
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 enables safe and efficient carrying of a 500-pound payload with reduced noise, lower autorotation descent rates, and improved safety by maintaining rotor efficiency over a wide range of speeds, while allowing for safe transition between vertical and forward flight modes.
Implementation Method 1
rotor blades configured to provide for a disc loading of less than 10 psf, and to provide for an efficient hover
Implementation Method 2
rotors provide significant lift during vertical takeoff and can tilt for forward thrust
Implementation Method 3
The rotor blades are slotted to reduce stall speed
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 at least four, and more preferably at least six variable speed tilt rotors. In some embodiments one or more rotors cooperate to generate at least 50% of the lift, and more preferably at least 70% of the lift, during rotorborne flight (e.g., vertical takeoff, hover, etc). At least some of the blades of each of the at least four rotors are not feathered, retracted, or folded during forward flight. At least one of the variable speed tilt rotors is engineered to be optionally powered by multiple motors, and by multiple battery packs or other independently operating electric power sources. The vehicle preferably flies in an autopilot or pilotless mode and has a relatively small (e.g., less than 45′ diameter) footprint.