Double-Swept Tiltrotor Blades for Transonic Hover-Cruise Balance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current tiltrotor aircraft are limited to speeds below Mach 0.5 due to the need for variable or folding rotors, and face challenges with whirl flutter and high disc loading, which complicates achieving both high hover efficiency and high-speed cruise.
Innovation Solution
Designing a tiltrotor aircraft with large, thin, aggressively double-swept rotors and a drive system that reduces rotor RPM in forward flight, using stiff, hingeless rotors with high sweep angles and supercritical airfoils to operate efficiently at Mach 0.65-0.7 without varying rotor diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If large diameter rotors are used for efficient hover, then hover efficiency is improved, but cruise speed is limited due to disc loading constraints
Solution Approach 1:
The rotor system transitions from a static configuration to a dynamic one by enabling variable rotor diameter. The rotor blades can be reconfigured between a large diameter state for hover (improving hover efficiency) and a smaller effective diameter state for cruise (enabling higher speeds). This dynamic adaptability resolves the contradiction by allowing the system to optimize for different flight phases.
Solution Approach 2:
The invention changes the physical parameter of rotor diameter from fixed to variable. By adjusting the rotor diameter parameter according to flight phase (large for hover, reduced for cruise), the system achieves both high hover efficiency and high cruise speed capability, eliminating the traditional trade-off between these two performance metrics.
2Speed
If variable diameter or folding rotors are used to achieve high speed, then cruise speed is improved, but device complexity increases
Solution Approach 1:
The rotor blade is divided into multiple segments or sections that can be independently positioned. This segmentation allows the blade to be reconfigured between different diameter states without requiring complex folding mechanisms. Each segment can be adjusted to achieve the desired rotor diameter, simplifying the overall mechanism compared to traditional folding rotor designs.
Solution Approach 2:
The invention employs a dynamic rotor diameter mechanism that adjusts the rotor size in flight. By using a controlled system that can expand or contract the rotor diameter on demand, the aircraft achieves high cruise speeds without the mechanical complexity of folding rotors. The dynamic adjustment is managed through a control system that coordinates blade positioning.
3Use of energy by moving object
If high rotor RPM is maintained in forward flight, then lift efficiency is improved, but transonic drag and whirl flutter increase at Mach 0.65-0.7
Solution Approach 1:
The rotor system dynamically adjusts its operational parameters based on flight phase. In forward flight at transonic speeds, the rotor diameter is reduced and RPM is optimized to maintain lift efficiency while staying below the whirl flutter threshold. This dynamic adjustment allows the system to operate efficiently at Mach 0.65-0.7 without experiencing excessive transonic drag or whirl flutter.
Solution Approach 2:
The invention changes multiple rotor parameters simultaneously - reducing rotor diameter and adjusting RPM - to optimize performance at transonic speeds. By coordinating these parameter changes, the system maintains adequate lift efficiency while keeping the rotor operation below the critical Mach number for whirl flutter, enabling stable operation at Mach 0.65-0.7.
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 efficient operation at Mach 0.65-0.7 with reduced rotor complexity, improved lift efficiency, and stability by minimizing whirl flutter and maintaining high-speed cruise performance.
Implementation Method 1
The first and second proprotors are sized to collectively provide at least 80% of the lift required for hover
Implementation Method 2
Lockheed C-130J using 32.4 HP/Ft{circumflex over ( )}2 propellers to cruise at 348 knots
Data Source
AI summary
A rotorcraft aircraft design incorporates double swept forward and aft rotor blades configured to provide efficient hover and efficient cruise at Mach number of 0.65-0.7 without varying a diameter of the rotor. The aircraft design combines the benefits of helicopters and fixed-wing aircraft, enabling vertical takeoff and landing (VTOL) capabilities while also achieving improved forward flight speed and reduced noise emissions.