Distributed Elevons for Tailsitting Biplane Aircraft Control
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Solution Overview
Problem
Current VTOL aircraft lack the efficiency and speed of fixed-wing aircraft, and tiltrotor and tiltwing designs face inefficiencies in vertical takeoff and landing due to downwash and control complexities.
Innovation Solution
A tailsitting biplane aircraft with a counter-rotating coaxial rotor system and a distributed array of elevons that can tilt to generate thrust vectors, allowing transition between thrust-borne lift in VTOL orientation and wing-borne lift in biplane orientation, with a flight control system that manages elevon faults to maintain aircraft stability and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If tiltrotor aircraft use fixed wing for forward flight, then speed and range are improved, but downwash inefficiencies occur during vertical takeoff and landing
Solution Approach 1:
The aircraft separates the lifting function from the propulsion function by using a dedicated coaxial rotor system for vertical lift and a fixed wing for forward flight. The coaxial rotors are positioned to clear the wing during forward flight, eliminating downwash interference while maintaining both VTOL capability and efficient forward flight performance.
Solution Approach 2:
The coaxial rotor system operates in a vertical plane for VTOL while the fixed wing operates in a horizontal plane for forward flight. This dimensional separation allows independent optimization of each system without interference, resolving the downwash efficiency problem while maintaining speed and range benefits.
2Loss of energy
If tiltwing aircraft rotate wing to vertical orientation for VTOL, then vertical thrust efficiency is improved, but control complexity increases during hover
Solution Approach 1:
The control system is segmented into multiple independent control surfaces (elevons at wingtips, stabilizer, and rotor blade pitch controls) that can be independently actuated. This distributed control architecture provides multiple degrees of freedom for hover control without requiring complex mechanical tilting mechanisms, reducing overall system complexity while maintaining vertical thrust efficiency.
Solution Approach 2:
The elevons serve multiple functions: they provide roll control during forward flight, pitch control during hover, and can be used for thrust vectoring. This multi-functionality reduces the need for separate control surfaces and complex control mechanisms, simplifying the overall control system while maintaining effective hover control capability.
3Force
If distributed array of elevons is used for control, then control authority is improved, but system complexity increases
Solution Approach 1:
Multiple elevon control surfaces are merged into a coordinated control system managed by a flight control computer. The flight control computer integrates commands to all elevons, providing centralized control logic that simplifies the operation of the distributed control surfaces while maintaining enhanced control authority through their combined effect.
Solution Approach 2:
The flight control system incorporates feedback from sensors monitoring aircraft attitude, accelerometers, and gyros to continuously adjust elevon positions. This closed-loop control provides enhanced stability and control authority while automating the coordination of multiple control surfaces, reducing the perceived complexity for the pilot and improving overall control precision.
4Reliability
If flight control system performs corrective action for elevon faults, then reliability is improved, but processing complexity increases
Solution Approach 1:
The flight control system continuously monitors the health and position of all elevons before faults occur. Pre-programmed fault tolerance algorithms are ready to execute immediately upon detecting an anomaly, switching to degraded control modes or redistributing control authority to healthy control surfaces. This preliminary preparation ensures rapid response to faults without requiring complex real-time decision-making, maintaining reliability while managing processing complexity.
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 vertical takeoff and landing, high-speed forward flight, and enhanced control authority through omnidirectional thrust vectoring and redundant elevon control, improving the aircraft's versatility and reliability.
Implementation Method 1
A propulsion assembly is coupled to the fuselage and includes a counter-rotating coaxial rotor system that is tiltable relative to the fuselage to generate a thrust vector
Implementation Method 2
An elevon is coupled to each of the tail assemblies such that the elevons form a distributed array of elevons. In the biplane orientation, the distributed array of elevons is configured to collectively provide pitch authority for the aircraft and differentially provide roll authority for the aircraft
Data Source
AI summary
An aircraft includes an airframe with first and second wings having a fuselage extending therebetween. A propulsion assembly is coupled to the fuselage and includes a counter-rotating coaxial rotor system that is tiltable relative to the fuselage to generate a thrust vector. Tail assemblies are coupled to wingtips of the first and second wings each having an elevon that collectively form a distributed array of elevons. A flight control system is configured to direct the thrust vector of the coaxial rotor system and to control movements of the elevons such that the elevons collectively provide pitch authority and differentially provide roll authority for the aircraft in the biplane orientation. In addition, when the flight control system detects an elevon fault, the flight control system is configured to perform corrective action responsive thereto at a distributed elevon level or at a coordinated distributed elevon and propulsion assembly level.