VTOL Rotor Layout and Control for Wingless Forward Lift

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Solution Overview

Problem

Multi-rotor vertical takeoff and landing aircraft face challenges in generating simultaneous lift and propulsive force, leading to high-speed performance issues and increased aircraft size due to the need for fixed wings during forward flight.

Innovation Solution

A vertical takeoff and landing aircraft design featuring a pair of rod-shaped support members with rotors that rotate in predetermined directions, controlled by a controller to achieve an advance ratio of 0.5 or more, minimizing flow field interference and optimizing lift and propulsion, utilizing a propulsion system and lift distribution, with a propulsion system that includes a propulsion device, and a propulsion system, and a propulsion system.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If fixed wings are added to generate lift during forward flight, then lift capability is improved, but aircraft size increases

Engineering Contradiction:
Improvelift capabilityVSAvoidaircraft size
Core Design Contradiction:
ForceVSVolume of moving object

Solution Approach 1:

The rotors are designed to perform multiple functions: generating lift during vertical takeoff and landing, and generating both lift and propulsive force during forward flight. This eliminates the need for separate fixed wings, reducing aircraft size while maintaining lift capability across all flight phases

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The rotor system transitions dynamically between different operational modes through variable pitch angles and rotational speeds. During forward flight, rotors operate at optimized advance ratios to simultaneously generate lift and propulsive force, replacing the static fixed wing configuration with a dynamic multi-functional system

Inventive Principle:
Principle #15Dynamics

2Speed

If rotors are tilted forward to generate both lift and propulsive force, then high-speed performance is improved, but rotor performance deteriorates due to flow field interference

Engineering Contradiction:
Improvehigh-speed performanceVSAvoid rotor performance
Core Design Contradiction:
SpeedVSReliability

Solution Approach 1:

The patent optimizes the advance ratio parameter (ratio of forward speed to rotor tip speed) to a specific range that minimizes flow field interference. By controlling rotational speed and pitch angle to achieve optimized advance ratios, the system maintains both high-speed performance and rotor efficiency, preventing performance deterioration from slipstream interference

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The rotor configuration and control parameters are pre-configured to anticipate and prevent flow field interference before it significantly impacts performance. The system maintains optimized advance ratios during forward flight to proactively minimize slipstream effects on subsequent rotors, preserving rotor performance while achieving high-speed capability

Inventive Principle:
Principle #10Preliminary action

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

The design enables downsizing and speed-up of the aircraft by ensuring lift generation during forward flight primarily through rotors, reducing reliance on fixed wings and minimizing performance reduction from flow field interference.

Implementation Method 1

two or more rotors for vertical climb and descent... rotate in a predetermined rotation direction to generate lift

Methodology Applied
Scientific EffectAerodynamic lift: Aerofoil

Implementation Method 2

a propulsion propeller... rotates to generate propulsive force

Methodology Applied
Scientific EffectAerodynamic thrust: Aerofoil

Data Source

PatentEP4725839A1Vertical takeoff and landing aircraft
Publication Date: 2026.04.15 JAPAN AEROSPACE EXPLORATION AGENCY
  • EP4725839A1 patent drawingFigure 1
  • EP4725839A1 patent drawingFigure 2
  • EP4725839A1 patent drawingFigure 3

AI summary

A vertical takeoff and landing aircraft according to an embodiment of the present invention includes a pair of right and left rod-shaped support members, a propulsion propeller, two or more rotors for vertical climb and descent, and a controller. The pair of right and left rod-shaped support members extend in a front-rear direction and are provided on both a right side and a left side. The two or more rotors are disposed on each of the rod-shaped support members in the front-rear direction, each include a plurality of blades, and rotate in a predetermined rotation direction to generate lift. The controller rotates the rotor during forward flight and controls a rotational speed of the rotor and a pitch angle of the blade to obtain an advance ratio at which an effective lift-to-drag ratio of the rotor is a threshold or more, the advance ratio representing a ratio between a flight speed and a blade tip speed of the rotor.