Rotorcraft Power Control Under Asymmetric N2 Engine Regulation

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Solution Overview

Problem

Existing rotorcraft control systems face challenges in managing engine failures, particularly when one engine is not regulated by N2 rotational speed, leading to increased workload for the crew and risk of mechanical transmission system damage during maneuvers.

Innovation Solution

A method that identifies N2-regulated and non-N2-regulated engines, determines permissible torque limits, and generates a control setpoint to limit power transmission to prevent exceeding critical torque limits, using a control system to manage fuel flow and collective pitch adjustments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the rotorcraft operates with one N2-regulated engine and one non-N2-regulated engine, then the engine can continue to provide power during partial failure, but the mechanical transmission system is at risk of torque overload and damage

Engineering Contradiction:

Improveengine operation continuityVSAvoidtorque overload risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The control system continuously monitors the torque produced by the non-N2-regulated engine and uses this feedback to dynamically adjust the collective pitch and fuel flow of the N2-regulated engine, ensuring that the combined torque remains within safe transmission limits while maximizing power output

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The N2-regulated engine acts as an intermediary that compensates for the unregulated engine's torque variations. By adjusting the N2 engine's output based on real-time torque measurements from both engines, the system mediates the total torque to prevent transmission overload

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If the pilot manually manages power distribution between engines, then flexibility in handling asymmetric engine operation is improved, but the pilot workload increases significantly

Engineering Contradiction:

Improveasymmetric operation handlingVSAvoidpilot workload

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The control system automatically performs the complex task of power distribution management between the two engines. It self-adjusts fuel flow, monitors torque limits, and modifies collective pitch without pilot intervention, thereby reducing workload while maintaining adaptability to asymmetric engine conditions

Inventive Principle:

Principle #25Self-service

3Speed

If the N2-regulated engine compensates for the non-N2-regulated engine by increasing power output, then the lift rotor speed can be maintained, but the torque on the mechanical transmission system may exceed permissible limits

Engineering Contradiction:

Improvelift rotor speedVSAvoidtransmission torque

Core Design Contradiction:

SpeedVSForce

Solution Approach 1:

The system dynamically adjusts the collective pitch and fuel flow of the N2-regulated engine in real-time based on the actual torque output of both engines. This dynamic control ensures that the lift rotor speed is maintained within acceptable limits while preventing the transmission torque from exceeding safe thresholds

Inventive Principle:

Principle #15Dynamics

Data Source

PatentEP4545406B1Method for controlling a rotorcraft, associated rotorcraft and computer program

Publication Date: 2026.02.25 EUROCOPTER FRANCE SA

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AI summary

The present invention relates to a method for controlling a rotorcraft (1), said rotorcraft (1) comprising at least two combustion engines (2, 3), at least one control system (13) and a transmission system (4), said at least two engines (2, 3) being mechanically connected to said transmission system (4) respectively by at least two couplings (25, 26). Such a control method comprises at least one identification of an engine regulated in N2 (2), one identification of an engine not regulated in N2' (3) and the generation of a control setpoint limit for at least a first control system (12) of the engine regulated in N2 (2) and dependent on the rotational speed N2 of at least a first output shaft (5) of the engine regulated in N2 (2).