Radially Extendable Tailboom for Tail Sitter Aircraft
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Solution Overview
Problem
Tail sitter aircraft are unstable on the ground due to a high center of gravity and large wing surface exposed to wind, making them difficult to control during landing and takeoff, and attempts to lower the center of gravity with aft wings reduce aerodynamic stability during forward flight.
Innovation Solution
A tail sitter aircraft design featuring a fuselage with a forward main lifting surface and a radially retractable tailboom assembly with rotatably mounted tail arms that extend to form a stable ground contact base during landing, while reducing tail surface geometry for forward flight, using a propulsion system with independently controllable cross-flow fans or rotor assemblies for thrust and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the tail sitter aircraft uses a conventional fixed tailboom configuration, then the aircraft structure is simple, but the aircraft is unstable on the ground due to high center of gravity and large wing surface exposed to wind
Solution Approach 1:
The tailboom assembly employs radially extendable and retractable tail arms that can dynamically change configuration between landing and forward flight modes. During landing, the tail arms extend radially to form a wide stable base; during forward flight, they retract to minimize aerodynamic drag. This dynamic reconfiguration resolves the contradiction by providing ground stability when needed while maintaining flight efficiency.
Solution Approach 2:
The tailboom assembly is segmented into multiple independently controllable tail arms (typically three) that can be individually extended or retracted. This segmentation allows the system to form a stable triangular base during landing while maintaining structural simplicity through modular design, where each tail arm functions as an independent unit with its own actuator and control surface.
2Stability of the object's composition
If the tail sitter aircraft uses aft wings to lower center of gravity, then ground stability improves, but aerodynamic stability during forward flight deteriorates
Solution Approach 1:
Rather than using fixed aft wings, the invention uses dynamically reconfigurable tail arms with control surfaces that adapt their position and orientation based on flight phase. During forward flight, the tail arms retract and their control surfaces orient to provide aerodynamic stability, while during landing they extend to lower the effective center of gravity and provide ground stability, thus resolving the contradiction between the two stability requirements.
Solution Approach 2:
The tail arms serve multiple functions: they provide structural support for landing (forming a stable base), aerodynamic control during forward flight (with control surfaces), and act as landing gear. This multi-functionality eliminates the need for separate aft wings, allowing the same structure to provide both ground stability and aerodynamic stability at different operational phases.
3Stability of the object's composition
If the tailboom assembly has radially extended tail arms during forward flight, then ground stability is improved, but aerodynamic drag increases
Solution Approach 1:
The tailboom assembly dynamically reconfigures the tail arms between extended and retracted positions based on operational phase. During forward flight, the tail arms retract radially to minimize cross-sectional area and aerodynamic drag. During landing operations, they extend to provide ground stability. This dynamic adjustment resolves the contradiction by providing ground stability only when needed while minimizing energy loss during flight.
Data Source
AI summary
A tail sitter aircraft includes a fuselage having a forward portion, an aft portion and a longitudinally extending fuselage axis. At least two wings are supported by the forward portion of the fuselage. A distributed propulsion system includes at least one propulsion assembly operably associated with each fixed wing and is operable to provide forward thrust during forward flight and vertical thrust during vertical takeoff, hover and vertical landing. A tailboom assembly extends from the aft portion of the fuselage and includes a plurality of rotatably mounted tail arms having control surfaces and landing members. In a forward flight configuration, the tail arms are radially retracted to reduce tail surface geometry and provide yaw and pitch control with the control surfaces. In a landing configuration, the tail arms are radially extended relative to the fuselage axis to form a stable ground contact base with the landing members.