Differential Thrust Vectoring for Hover Downwash and Anti-Torque

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Solution Overview

Problem

Compound helicopters face challenges in efficiently integrating ducted fans for thrust due to the adverse effects of main rotor downwash on the duct surfaces during hovering, which affects thrust efficiency and structural integrity.

Innovation Solution

The implementation of a differential thrust vectoring system that allows thrusters to rotate relative to the fuselage, enabling thrust vector orientation changes between hover and forward-flight modes, using spindles, actuators, and planetary gear systems to manage torque and provide anti-torque functionality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If ducted fans are integrated on compound helicopters to provide forward thrust and vertical lift, then thrust efficiency is improved, but the duct surfaces suffer adverse effects from main rotor downwash during hovering

Engineering Contradiction:

Improvethrust efficiencyVSAvoidmain rotor downwash effects

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies dynamics by making the ducted fan assembly rotatable relative to the fuselage. The duct can rotate between a first orientation (providing vertical lift during hovering) and a second orientation (providing forward thrust during forward flight). This dynamic repositioning allows the duct to avoid adverse downwash effects during hovering while maintaining thrust efficiency in both flight regimes.

Inventive Principle:

Principle #15Dynamics

2Productivity

If the duct is made sufficiently long to fully decelerate airflow and maximize additional thrust, then thrust efficiency is improved, but large surfaces are created that suffer ill effects from downwash during hovering

Engineering Contradiction:

Improveadditional thrust from pressure differentialVSAvoidduct surface area

Core Design Contradiction:

ProductivityVSArea of stationary object

Solution Approach 1:

The patent resolves this contradiction by making the duct surface area dynamic rather than static. The duct rotates to a first orientation during hovering where the surface area is effectively reduced relative to the downwash direction, minimizing adverse effects. During forward flight, the duct rotates to a second orientation where the full surface area is utilized to maximize thrust efficiency. This dynamic repositioning allows the system to optimize both parameters at different operational phases.

Inventive Principle:

Principle #15Dynamics

3Force

If thrusters are positioned to provide vertical lift during hovering, then lift capability is improved, but torque counteraction becomes more difficult

Engineering Contradiction:

Improvevertical lift forceVSAvoidtorque counteraction mechanism

Core Design Contradiction:

ForceVSDevice complexity

Solution Approach 1:

The patent applies universality by designing the ducted fan assembly to perform multiple functions through a single mechanism. The same rotatable duct assembly that optimizes thrust efficiency and minimizes downwash effects also provides torque counteraction. By rotating the duct to different orientations, the system can provide both vertical lift during hovering and forward thrust during flight, while the differential rotation capability simultaneously handles torque counteraction, eliminating the need for separate torque counteraction mechanisms.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the functions of thrust generation, orientation control, and torque counteraction into a single integrated system. The ducted fan assembly's rotation mechanism combines what would traditionally be separate systems (thrust vectoring and torque management), simplifying the overall device complexity while maintaining all required functions.

Inventive Principle:

Principle #5Merging (Combining)

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 system enhances thrust control and efficiency by allowing thrusters to adjust orientation for optimal lift and forward thrust, effectively counteracting torque effects and improving maneuverability in both hover and forward-flight modes.

Implementation Method 1

a planetary gear system coupled between the first and second spindles

Methodology Applied

Scientific EffectPlanetary gear mechanism: Epicyclic Gearing

Implementation Method 2

This arrangement accelerates the air across the inlet and decelerates the air at the diffuser, thereby creating a pressure differential on the duct across the fan disk, resulting in additional thrust

Methodology Applied

Scientific EffectPressure differential: Pressure Gradient

Data Source

PatentUS12195177B2Differential thrust vectoring system

Publication Date: 2025.01.14 TEXTRON INNOVATIONS INC

AI summary

A differential thrust vectoring system includes a first thruster, a second thruster, a main actuator, and a trim actuator. The system is configured such that actuation of the main actuator causes rotation of the thrusters together about an axis, whereas actuation of the trim actuator causes relative rotation of the first and second thrusters about the axis.