Dual Rotor-to-Wing Conversion for Tail Sitter Aircraft

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Solution Overview

Problem

Tail sitter aircraft face inefficiencies in propulsion during forward flight, limiting their endurance due to the inefficiencies of their rotary propulsion systems when transitioning from vertical takeoff and landing to horizontal flight.

Innovation Solution

The aircraft employs a dual rotor configuration that converts into a dual wing configuration during forward flight, utilizing a pusher propeller for thrust and maintaining rotor assemblies in a non-rotatable position to form an x-wing configuration, which provides lift and reduces drag, while also incorporating cyclic and collective control for stability and roll control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a rotary propulsion system is used for vertical takeoff and landing, then VTOL capability is achieved, but propulsion efficiency deteriorates during forward flight

Engineering Contradiction:

ImproveVTOL capabilityVSAvoidpropulsion efficiency

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The rotor assemblies are made dynamically configurable, capable of rotating about the fuselage for VTOL operations and locking into a fixed non-rotatable position for forward flight. This dynamic reconfiguration allows the propulsion system to optimize its efficiency for each flight mode, resolving the contradiction between VTOL capability and propulsion efficiency.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The rotor assemblies serve multiple functions: they provide vertical thrust when rotating for VTOL, and form fixed lifting surfaces (wings) when locked for forward flight. This multi-functionality allows a single component to address both VTOL capability and efficient forward flight propulsion.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Force

If rotor assemblies rotate for vertical thrust, then VTOL operations are enabled, but drag increases during forward flight

Engineering Contradiction:

Improvevertical thrustVSAvoiddrag

Core Design Contradiction:

ForceVSObject-generated harmful factors

Solution Approach 1:

The rotor assemblies transition from a rotating state (generating vertical thrust) to a static locked state (forming fixed wings). This dynamic state change eliminates the drag associated with rotating blades during forward flight while maintaining the ability to generate vertical thrust when needed for VTOL operations.

Inventive Principle:

Principle #15Dynamics

3Force

If a fixed wing configuration is used for forward flight, then lift is generated, but runway requirement increases

Engineering Contradiction:

ImproveliftVSAvoidrunway requirement

Core Design Contradiction:

ForceVSLength of moving object

Solution Approach 1:

The rotor assemblies are positioned and configured in advance to form the wing structure before forward flight begins. This preliminary configuration allows the aircraft to generate lift immediately upon transitioning to forward flight mode, eliminating the need for long runways typically required by fixed-wing aircraft.

Inventive Principle:

Principle #10Preliminary action

4Speed

If tiltrotor configuration is used, then forward airspeed is improved, but downwash inefficiency increases

Engineering Contradiction:

Improveforward airspeedVSAvoiddownwash inefficiency

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

The aircraft extracts the fixed wing structure from the rotating rotor system by locking the rotor assemblies in a fixed position during forward flight. This separation allows the pusher propeller to provide thrust without the interfering downwash effects caused by rotating blades, reducing energy loss while maintaining forward airspeed.

Inventive Principle:

Principle #2Taking out (Extraction)

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

This configuration enhances the aircraft's endurance and efficiency during forward flight by optimizing lift and thrust generation, reducing drag, and improving control capabilities, thereby addressing the propulsion inefficiencies in tail sitter aircraft.

Implementation Method 1

the first and second rotor assemblies rotate about the fuselage to provide vertical thrust

Methodology Applied

Scientific EffectRotational motion:

Implementation Method 2

rotation of the pusher propeller provides forward thrust

Methodology Applied

Scientific EffectRotational motion:

Implementation Method 3

the first and second rotor assemblies are non-rotatable about the fuselage forming a dual wing configuration to provide lift

Methodology Applied

Scientific EffectAerodynamic lift: Aerofoil

Data Source

PatentUS10407169B2Aircraft having dual rotor-to-wing conversion capabilities

Publication Date: 2019.09.10 BELL HELICOPTER TEXTRON INC

AI summary

A tail sitter aircraft includes a fuselage having a forward portion and an aft portion. The forward portion of the fuselage includes first and second rotor stations. A first rotor assembly is positioned proximate the first rotor station. A second rotor assembly is positioned proximate the second rotor station. A tailboom assembly extends from the aft portion of the fuselage and includes a plurality of landing members. A pusher propeller extends from the tailboom assembly. In a vertical takeoff and landing mode, the first and second rotor assemblies rotate about the fuselage to provide vertical thrust. In a forward flight mode, rotation of the pusher propeller provides forward thrust and the first and second rotor assemblies are non-rotatable about the fuselage forming a dual wing configuration to provide lift.