Aircraft V-tail Joint for Wing Stiffness and Rotor Clearance
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Solution Overview
Problem
Box-wing aircraft designs face challenges with flutter instability due to reduced stiffness in rear wing mounting arrangements, leading to undesirable speed limitations and reduced payload capacity, while existing solutions compromise aerodynamic efficiency or increase weight.
Innovation Solution
Aircraft structure with a V-tail joint supporting a continuous rear wing span using angularly inclined arms, integrated with a tail cone and aerodynamic fairings, enhances stiffness and clearance between forward and rear rotors, optimizing aerodynamic efficiency and flutter performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the rear wings are mounted directly to the fuselage to improve rigidity and raise the flutter point, then the stiffness and flutter performance are improved, but the vertical clearance between forward and rearward wings is reduced, causing rotor overlap and aerodynamic inefficiency
Solution Approach 1:
The patent applies dimensionality change by transitioning from direct horizontal mounting to angularly inclined mounting. The rear wings are mounted at an angle to the fuselage rather than directly perpendicular, which resolves the vertical clearance issue while maintaining structural rigidity. This angular arrangement allows the wings to be positioned higher above the fuselage, eliminating rotor overlap with forward wings while preserving the stiffness needed to raise the flutter point.
Solution Approach 2:
The patent employs asymmetry through the use of angularly inclined mounting arms that are not perpendicular to the fuselage. This asymmetric mounting configuration optimizes both the vertical clearance for rotor operation and the structural stiffness for flutter resistance, creating a non-standard mounting arrangement that satisfies both requirements simultaneously.
2Reliability
If the maximum flight speed is limited to a level significantly below the flutter point to avoid flutter failure, then flutter safety is improved, but the maximum operating speed and commercial viability are reduced
Solution Approach 1:
The patent applies parameter changes by modifying the structural stiffness parameters through optimized mounting arrangements. By changing the mounting geometry of the rear wings to angularly inclined positions, the structural stiffness is enhanced, which raises the flutter speed. This allows the aircraft to operate at higher speeds safely, as the increased stiffness pushes the flutter point to a higher velocity threshold.
3Speed
If the stiffness of the fuselage and wings is increased to raise the maximum operating speed below the flutter point, then the maximum operating speed is improved, but the weight increases, reducing payload capacity
Solution Approach 1:
The patent applies local quality by concentrating stiffness enhancement at specific critical locations rather than uniformly increasing overall structure weight. The angularly inclined mounting arrangement locally optimizes the stiffness at the rear wing attachment points, providing targeted reinforcement where needed to raise the flutter point without requiring widespread heavy construction throughout the entire airframe.
4Ease of operation
If a T-type vertical connection is used to separate the rear wing from the fuselage and increase vertical clearance, then the vertical clearance and aerodynamic efficiency are improved, but the stiffness of the rear wing mounting is reduced, compromising flutter performance
Solution Approach 1:
The patent applies dynamics by using angularly inclined mounting arms that provide both vertical separation for clearance and structural stiffness for flutter resistance. The inclined geometry creates a dynamic arrangement where the mounting arms simultaneously achieve multiple functions: they position the wings vertically clear of forward rotors while maintaining rigid connection points that resist flutter vibrations.
Data Source
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AI summary
An aircraft structure (10) comprising a fuselage (24), first and second forward wings (20, 22) mounted to and/or extending from opposing sides of the fuselage (24), a continuous rear wing span (34) defining first and second rear wings (30, 32) and a central static connecting portion (36), a first wing connecting member (42) extending between the first forward wing (20) and the first rear wing (30), a second wing connecting member (42) extending between the second forward wing (22) and the second rear wing (32), wherein the rear wing span (34) is supported by a centrally located V tail joint defined by first and second angularly inclined arms (100, 110), first and second electric motors each having rotors, are mounted to each wing (20, 22, 30, 32), each rotor is pivotal between a first configuration for vertical flight, and a second configuration for forward flight.