Rotorcraft Tail-Boom Airflow for Coanda Anti-Torque Control

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Solution Overview

Problem

Existing rotorcraft anti-torque systems require improvement for enhanced efficiency and control, particularly in countering torque generated by the main rotor and providing effective yaw control.

Innovation Solution

A rotorcraft assembly incorporating a tail boom with an air flowpath, tail rotors driven by electric motors, and a Coanda effect anti-torque system, utilizing slots and thrusters to redirect airflow for anti-torque and yaw control, with a flow regulator to divert airflow between different paths for varying flight modes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If a traditional tail rotor system is used for anti-torque control, then the rotorcraft can counter torque from the main rotor, but the system complexity and weight increase

Engineering Contradiction:

Improveanti-torque controlVSAvoidsystem complexity

Core Design Contradiction:

ForceVSDevice complexity

Solution Approach 1:

The patent extracts the anti-torque function from the traditional mechanical tail rotor system and relocates it to the exhaust flow of the powerplant. The exhaust gases, which would otherwise be wasted, are redirected through a nozzle assembly to provide anti-torque control, eliminating the need for a separate tail rotor mechanism.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent merges the anti-torque control function with the existing powerplant exhaust system. The exhaust flowpath and nozzle assembly are integrated into the fuselage structure, combining propulsion waste heat and momentum with anti-torque control to reduce overall system complexity.

Inventive Principle:

Principle #5Merging (Combining)

2Ease of operation

If tail rotors are used for yaw control, then effective yaw control is achieved, but the device complexity and number of moving parts increase

Engineering Contradiction:

Improveyaw controlVSAvoiddevice complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical tail rotor system with a pneumatic/exhaust-based control system. The nozzle assembly directs exhaust flow to generate aerodynamic forces for yaw control, substituting mechanical rotating blades with a stationary nozzle system controlled by flow diversion.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The exhaust system serves multiple functions: primary propulsion thrust, anti-torque control, and yaw control. This multi-functionality eliminates the need for dedicated tail rotors, reducing device complexity while maintaining all necessary control capabilities.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Force

If an air flowpath system is integrated into the tail boom, then anti-torque efficiency is enhanced, but the manufacturing complexity increases

Engineering Contradiction:

Improveanti-torque efficiencyVSAvoidmanufacturing complexity

Core Design Contradiction:

ForceVSEase of manufacture

Solution Approach 1:

The air flowpath system is segmented into distinct functional sections: the exhaust flowpath from the powerplant, the transition section into the tail boom, and the nozzle assembly at the distal end. This segmentation allows each component to be manufactured and tested separately before integration, reducing overall manufacturing complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The air flowpath is nested within the existing tail boom structure. The tail boom serves as both a structural support element and a conduit for the exhaust flowpath, eliminating the need for separate external ducting and reducing manufacturing steps.

Inventive Principle:

Principle #7Nested doll (Nesting)

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 system provides efficient anti-torque and yaw control, enhancing rotorcraft stability and maneuverability, with redundant modes of operation for reliability and adaptability to different flight conditions.

Implementation Method 1

A rotorcraft assembly incorporating a tail boom with an air flowpath, tail rotors driven by electric motors, and a Coanda effect anti-torque system

Methodology Applied

Scientific EffectCoanda effect: Coanda Effect

Data Source

PatentEP4617171A1Rotorcraft with Anti-torque air system and tail rotor(s)

Publication Date: 2025.09.17 PRATT & WHITNEY CANADA CORP

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AI summary

A rotorcraft assembly (20) for a rotorcraft (20) includes a fuselage (32), a tail structure (34), an air system (28) and a plurality of tail rotors (30). The tail structure (34) is configured as or otherwise includes a tail boom (44). The tail boom (44) projects longitudinally along a centerline (52) out from the fuselage (32) to a distal end (54). The air system (28) includes an air flowpath (120). The air flowpath (120) passes from the fuselage (32) into the tail boom (44) and extends longitudinally within the tail boom (44) towards the distal end (54). The tail rotors (30) are connected to the tail structure (34) at the distal end (54).