Modal Tailboom Flight Control for Compound Helicopters

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Solution Overview

Problem

Conventional helicopters are limited by retreating blade stall, and compound helicopters with pusher propellers positioned aft of the tail rotor face structural instability and lack multi-modal flight capabilities.

Innovation Solution

A modal tailboom flight control system for compound helicopters, featuring a pusher propeller positioned forward of the anti-torque system, allowing for independent control of rotational speeds and pitch of rotor blades to operate in both forward thrust and anti-torque modes, enhancing stability and flight capabilities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If the pusher propeller is positioned aft of the tail rotor, then the anti-torque thrust lever arm is reduced, but the structural stability deteriorates

Engineering Contradiction:

Improveanti-torque thrust lever armVSAvoidstructural stability

Core Design Contradiction:

ForceVSStability of the object's composition

Solution Approach 1:

The patent inverts the conventional arrangement by positioning the pusher propeller forward of the tail rotor instead of aft. This inversion allows the tail rotor to be placed outboard of the pusher propeller rotor disk, creating a longer lever arm for anti-torque thrust while improving structural stability through optimized force distribution and reduced interference between propulsion systems.

Inventive Principle:

Principle #13The other way round (Inversion)

2Speed

If conventional helicopters use retreating blade stall control, then forward speed is limited, but the compound helicopter configuration with pusher propeller aft provides insufficient anti-torque leverage

Engineering Contradiction:

Improveforward airspeedVSAvoidanti-torque thrust effectiveness

Core Design Contradiction:

SpeedVSForce

Solution Approach 1:

The patent transitions from conventional two-dimensional rotor blade control to a three-dimensional compound configuration with independently controllable pusher propeller and tail rotor. This dimensional change enables simultaneous optimization of forward thrust and anti-torque effectiveness through independent rotational speed and pitch control of both propulsion systems, allowing high forward airspeeds while maintaining effective anti-torque leverage.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Force

If the pusher propeller is positioned forward of the anti-torque system, then the lever arm for anti-torque thrust is optimized, but the pusher propeller becomes vulnerable to debris

Engineering Contradiction:

Improveanti-torque thrust lever armVSAvoiddebris damage to pusher propeller

Core Design Contradiction:

ForceVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an intermediary protective structure positioned between the pusher propeller and potential debris sources. This intermediary element protects the pusher propeller from debris damage while allowing the optimized forward positioning to maintain the long lever arm for anti-torque thrust effectiveness.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 high forward airspeeds while maintaining structural stability and multi-modal flight capabilities, including vertical takeoff and landing, by optimizing the lever arm for anti-torque thrust and protecting the pusher propeller from debris.

Implementation Method 1

a pusher propeller coupled to the drivetrain and rotatable to generate forward thrust for the compound helicopter in the forward thrust mode

Methodology Applied

Scientific EffectThrust generation: Jet

Implementation Method 2

an anti-torque system coupled to the drivetrain and rotatable to generate anti-torque thrust for the compound helicopter in the anti-torque mode

Methodology Applied

Scientific EffectAnti-torque thrust: Jet

Data Source

PatentEP3683143B1Modal tailboom flight control systems for compound helicopters

Publication Date: 2022.03.09 TEXTRON INNOVATIONS INC

Figure 1A~1B
Figure 1C
Figure 2

AI summary

A modal tailboom flight control system (102) for a compound helicopter (104) is operable in a plurality of modes including a forward thrust mode and an anti-torque mode. The modal tailboom flight control system (102) includes a tailboom (116), a drivetrain (100) extending through the tailboom (116), an anti-torque system (108) coupled to the drivetrain (100) and rotatable to generate anti-torque thrust for the compound helicopter (104) in the anti-torque mode and a pusher propeller (106) coupled to the drivetrain (100) and rotatable to generate forward thrust for the compound helicopter (104) in the forward thrust mode. The pusher propeller (106) is positioned forward of the anti-torque system (108).