Fixed-Wing Rotorcraft With Tiltable Mast for High-Speed Controllability

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Solution Overview

Problem

Fixed wing rotorcraft are limited to autorotation-assisted straight and level forward flight at a bounded airspeed, compromising controllability at higher speeds.

Innovation Solution

The rotorcraft design includes a tiltable mast with variable rotor disc Angle of Attack (AOA) and a real-time Flight Control System (FCS) for controlling rotor systems and propulsion units, enabling autorotation at both positive and negative AOA to maintain controllability at faster airspeeds through collective and cyclic rotor blade pitch adjustments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If autorotation is used for straight and level forward flight, then controllability is maintained at lower airspeeds, but airspeed is bounded and cannot exceed a maximum value

Engineering Contradiction:

ImproveairspeedVSAvoidcontrollability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The rotor disc Angle of Attack (AOA) is made dynamically adjustable through mast tilting mechanisms, allowing transition between positive and negative AOA configurations. This dynamic adjustment enables the rotorcraft to maintain autorotation controllability while operating at extended airspeed ranges beyond traditional bounds

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the rotor disc AOA parameter from fixed positive values to variable values including negative angles. By adjusting the mast tilt angle, the rotor disc AOA can be optimized for different airspeed regimes, enabling controlled flight at higher speeds while maintaining autorotation benefits

Inventive Principle:

Principle #35Parameter changes

2Speed

If rotor disc AOA is increased to maintain autorotation at higher airspeeds, then forward thrust is improved, but fixed wing lift becomes excessive causing loss of vertical balance

Engineering Contradiction:

ImproveairspeedVSAvoidvertical force balance

Core Design Contradiction:

SpeedVSForce

Solution Approach 1:

Instead of always using positive rotor disc AOA to generate upward lift, the invention inverts the approach by using negative rotor disc AOA at high airspeeds. This generates downward lift from the rotor system, which counteracts the excessive upward lift from fixed wings, restoring vertical force balance while maintaining high speed flight

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The rotor disc AOA parameter is changed from positive to negative values based on airspeed conditions. This parameter inversion allows the rotor system to transition from being a primary lift source at low speeds to a drag/downward force source at high speeds, balancing the overall vertical forces

Inventive Principle:

Principle #35Parameter changes

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 vertical takeoff, high-speed straight and level forward flight, and vertical landing without compromising controllability by managing rotor disc AOA transitions and lift forces.

Implementation Method 1

at least one pair of fixed wings for providing upward lift

Methodology Applied

Scientific EffectAerodynamic lift: Aerofoil

Implementation Method 2

their rotor disc(s) are rotated by airflow passing therethrough

Methodology Applied

Scientific EffectAutorotation: Aerofoil

Implementation Method 3

its rotor disc presents a correspondingly variable Angle of Attack (AOA) relative to airflow between a positive AOA and a negative AOA

Methodology Applied

Scientific EffectAngle of Attack: Aerofoil

Data Source

PatentUS12428141B2Fixed wing rotorcraft

Publication Date: 2025.09.30 EFIX AVIATION LTD

AI summary

Fixed wing rotorcraft capable of a flight trajectory from a vertical takeoff via straight and level forward flight at high airspeed to vertical landing without compromising controllability.