Aircraft Engine Startup Monitor Detecting Freewheel Slip

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Solution Overview

Problem

Conventional rotary wing aircraft power plant systems with freewheels can experience mechanical slip during engine startup, leading to potential mechanical rupture and abnormal wear, requiring pilots to visually verify rotor rotation, which is inefficient and risky.

Innovation Solution

A monitor system that measures torque on the upstream portion of the drive train, speed of the gas generator, and rotor speed, using a processor unit to automatically stop engine startup if torque is below threshold and rotor speed is lower than nominal, indicating freewheel slip, thereby preventing damage and reducing pilot workload.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a freewheel is used in the drive train to enable rotor rotation during engine startup, then the rotor can be driven by the engine, but the freewheel may become degraded and slip, leading to mechanical rupture and engine overspeed

Engineering Contradiction:

Improveautomatic engine startupVSAvoidfreewheel slip detection

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The system uses feedback from torque measurement and rotor speed measurement to detect freewheel slip conditions. The processor continuously monitors these parameters and compares them against expected values, providing real-time feedback about freewheel health and enabling automatic detection of degradation and slip events.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces manual visual verification with an automated electronic monitoring system. Sensors measure torque and rotor speed, and a processor analyzes these measurements to detect freewheel slip, substituting the mechanical/visual check with an electronic detection and control system that can automatically respond to anomalies.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If the pilot visually verifies rotor rotation during engine startup, then the drive train operation can be confirmed, but the pilot workload increases and response time is delayed

Engineering Contradiction:

Improvedrive train operation verificationVSAvoidengine startup time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system performs self-verification by automatically monitoring its own operation. The measurement devices and processor continuously check torque and rotor speed parameters, enabling the system to self-diagnose freewheel slip conditions without requiring external pilot intervention, thus maintaining reliability while reducing workload and time loss.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

Real-time feedback from torque and speed measurements enables continuous verification of drive train operation. The processor analyzes this feedback stream to detect anomalies immediately, providing ongoing confirmation of proper operation without requiring periodic visual checks by the pilot.

Inventive Principle:

Principle #23Feedback

3Device complexity

If the engine is started without monitoring freewheel condition, then the startup process is simpler, but mechanical rupture and abnormal wear can occur

Engineering Contradiction:

Improvemonitoring system complexityVSAvoidmechanical damage from freewheel slip

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces measurement devices as intermediaries between the freewheel and the control system. These sensors indirectly monitor freewheel condition by measuring torque and rotor speed, providing information about freewheel health without requiring direct intervention in the drive train mechanics, thus protecting against damage while adding minimal complexity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system replaces complex mechanical monitoring mechanisms with electronic sensing and processing. Instead of using additional mechanical sensors or switches in the drive train, the patent uses electronic measurement of torque and speed parameters, processed by a computer, to detect freewheel slip conditions and prevent mechanical damage.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS9771167B2Monitor system for monitoring the starting of a rotary wing aircraft, an aircraft, and a method using the system

Publication Date: 2017.09.26 EUROCOPTER FRANCE SA

AI summary

A method of starting a turboshaft engine (5) of an aircraft (1), said aircraft (1) being provided with a rotary wing, said aircraft (1) having a freewheel (15) interposed in a drive train (10) between said engine (5) and a rotor (2) of said rotary wing (1), said engine (5) comprising a gas generator (6) and a free turbine (9), the drive train (10) including an upstream portion (11) connecting said free turbine (9) to said freewheel (15), the method comprising the following steps: measuring the torque (Tq) exerted on said upstream portion (11), and measuring a speed of rotation (Ng) of said gas generator (6); comparing said torque (Tq) with a torque threshold (Stq) and comparing said speed of rotation (Ng) with a gas generator speed threshold (Sng); and stopping said engine (5) when said torque (Tq) is less than the torque threshold (Stq) and when said speed of rotation (Ng) is greater than the gas generator speed threshold (Sng).