Aircraft Engine Speed Control for Thrust Symmetry

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Solution Overview

Problem

During takeoff, turbojet engines in multi-engine aircraft often exhibit asymmetry in thrust due to varying mechanical conditions, leading to lateral deviations and increased pilot workload, which can disrupt takeoff if not corrected promptly.

Innovation Solution

A method and device that automatically control engine speed by setting an intermediate setpoint value for all engines before takeoff, ensuring all engines reach this value before increasing to takeoff speed, thereby eliminating thrust asymmetry and reducing pilot intervention.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If pilots manually control engine speed during takeoff, then they can respond to thrust asymmetry, but pilot workload increases and response time is delayed

Engineering Contradiction:

Improvethrust symmetryVSAvoidpilot workload

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The control system automatically detects thrust asymmetry between engines and adjusts fuel supply to each engine independently, enabling the system to self-correct without pilot intervention. The flight control computer monitors driving parameters and autonomously balances thrust by modulating fuel flow to the engine producing less thrust.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The system continuously monitors the driving parameter of each engine and compares it against reference values, automatically adjusting fuel supply based on detected asymmetry. This closed-loop feedback mechanism ensures thrust symmetry is maintained throughout the takeoff phase without requiring manual pilot input.

Inventive Principle:

Principle #23Feedback

2Reliability

If pilots manually correct thrust asymmetry, then directional control can be maintained, but takeoff may be interrupted if correction is inappropriate or too late

Engineering Contradiction:

Improvetakeoff continuityVSAvoidcorrection time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system proactively detects and corrects thrust asymmetry in the early stages of takeoff by automatically adjusting fuel supply, preventing asymmetry from developing into a hazardous condition that would require takeoff interruption. The continuous monitoring and immediate automated response ensure corrections are made before critical thresholds are reached.

Inventive Principle:

Principle #10Preliminary action

3Speed

If engine speed is increased rapidly from idle to takeoff speed, then takeoff performance is improved, but thrust asymmetry between engines worsens

Engineering Contradiction:

Improveengine accelerationVSAvoidthrust symmetry

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The system applies different fuel supply adjustments to each engine based on its individual performance characteristics during acceleration. By independently controlling the fuel flow to each engine according to its specific driving parameter deviations, the system maintains thrust symmetry even as overall engine speed increases rapidly from idle to takeoff power.

Inventive Principle:

Principle #3Local quality

Data Source

PatentEP2508735B1Method and device for controlling the operating speed of the engines of an aircraft during the take-off phase

Publication Date: 2016.01.06 AIRBUS OPERATIONS (SAS)

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AI summary

Device (1) comprising means (2, 3, 4, 5) for automatically controlling the engine speed (M1 to M4) such that, as long as all the aircraft engines (AC) do not have, at least at some instant of a takeoff phase, a value of a driving parameter (N1c1 to N1c4) substantially equal to a predetermined intermediate setpoint value of said parameter (N1x), the engine speed cannot exceed an intermediate speed associated with said intermediate setpoint value.