Helicopter Rotor Braking With Gas Generator Ventilation

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Solution Overview

Problem

Existing methods for rapidly stopping a helicopter's main rotor after landing risk engine damage due to sudden power shutdowns, particularly in multi-engine systems, and require lengthy thermal stabilization phases that hinder quick mission execution.

Innovation Solution

A method involving rapid engine shutdown followed by gas generator ventilation using electric machines, coupled to the turbomachine, and optionally auxiliary power units, to maintain rotor rotation and prevent mechanical stress, allowing for quick rotor stoppage without engine damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the engine is shut down suddenly after high power operation, then the rotor can be stopped quickly, but the engine suffers mechanical stress and thermal damage

Engineering Contradiction:

Improverotor stopping speedVSAvoidengine thermal stability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The shutdown process is segmented into distinct phases: maintaining gas generator rotation separately from rotor rotation, ventilating the combustion chamber independently, and applying brake force to the rotor. This segmentation allows each component to be controlled independently, enabling quick rotor stoppage while maintaining engine thermal stability through separate ventilation and rotation maintenance of the gas generator.

Inventive Principle:

Principle #1Segmentation

2Reliability

If the free turbine is kept idling for thermal stabilization, then the engine is protected from mechanical stress, but the rotor cannot be stopped quickly and mission downtime increases

Engineering Contradiction:

Improveengine mechanical protectionVSAvoidmission downtime

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system separates the thermal stabilization function from the rotor drive function. The gas generator continues rotating and ventilating for thermal stabilization while the free turbine and rotor are independently braked to a stop. This segmentation eliminates the need to keep the rotor spinning for thermal reasons, reducing mission downtime while maintaining engine protection.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediary braking system that acts on the rotor independently of the free turbine. This brake serves as a mediator that allows the rotor to be stopped quickly without affecting the gas generator's thermal stabilization process, thus resolving the conflict between quick stoppage and engine protection.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Speed

If a brake is designed to counteract residual free turbine power, then the rotor can be slowed effectively, but the brake size and weight increase significantly in multi-engine systems

Engineering Contradiction:

Improverotor deceleration rateVSAvoidbrake weight

Core Design Contradiction:

SpeedVSWeight of stationary object

Solution Approach 1:

Instead of designing the brake to counteract and overcome the residual free turbine power, the invention inverts the approach: the brake is designed to work with minimized residual power by allowing the gas generator to continue rotating and ventilating. This inversion reduces the brake sizing requirements significantly while maintaining effective rotor deceleration.

Inventive Principle:

Principle #13The other way round (Inversion)

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 rapid rotor shutdown while maintaining thermal stabilization, reducing downtime and preventing mechanical stress on the engine, suitable for single and multi-engine helicopters.

Implementation Method 1

a maintenance of the rotation of the gas generator for each turbomachine whose combustion chamber is shut down using said at least one electric machine mechanically coupled to the gas generator and powered by the electrical network

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

a stop of the helicopter's main rotor using a brake

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentEP4045770B1Method for rapidly stopping a rotor of a helicopter after landing

Publication Date: 2026.04.15 SAFRAN HELICOPTER ENGINES

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AI summary

Disclosed is a method for quickly stopping the propulsion rotor of a helicopter after landing, comprising, following a request (100) by a pilot of the helicopter to quickly stop the engine, the following steps managed by the control unit of the turbomachine: - detecting (110) the absence of a thermal stabilisation phase of the gas generator of at least one turbomachine, - controlling (130) the extinguishing of the combustion chamber of the gas generator of at least one turbomachine, - maintaining the rotation of the gas generator (140) whose combustion chamber has been extinguished by means of the at least one electrical machine in order to ventilate the gas generator, and - stopping (160) the main rotor of the helicopter by means of a mechanical brake.