Turbine Thrust Scheduling with Trim Interpolation

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Solution Overview

Problem

Auto-throttle systems in gas turbine engines cause sudden thrust changes when disengaged, requiring manual adjustments and making it difficult for pilots to achieve precise throttle settings, leading to potential engine wear or performance issues due to the lack of 'flats' in the TLA-thrust relationship at all thrust points.

Innovation Solution

The engine controller determines and applies a combination of 'flat trim' and 'phase trim' settings to transition from auto-throttle to manual operation, maintaining engine thrust by interpolating among dynamic lookup tables and gradually reducing the 'TLA fine trim' to avoid sudden changes, allowing for 'flats' in the TLA-thrust relationship during manual operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the auto-throttle system disengages and immediately sets TLA fine trim to zero, then the system simplifies control logic, but this causes sudden thrust changes (bumps) and requires manual pilot adjustment

Engineering Contradiction:

Improvecontrol logic complexityVSAvoidthrust continuity

Core Design Contradiction:

Device complexityVSEase of operation

Solution Approach 1:

The system performs preliminary action by gradually reducing the TLA fine trim value over multiple throttle lever movements rather than immediately setting it to zero. This phased approach prepares the system for disengagement while maintaining thrust continuity, eliminating the sudden bump that would otherwise occur.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system applies dynamics by making the TLA fine trim reduction adaptive to pilot behavior. The trim value is gradually reduced only when throttle lever movements are detected, making the transition dynamic and responsive to actual operational conditions rather than following a fixed timeline.

Inventive Principle:

Principle #15Dynamics

2Ease of operation

If the TLA-thrust relationship includes flats at various thrust levels, then the pilot can more easily position the throttle lever, but auto-throttle systems cannot accommodate these flats at all thrust points

Engineering Contradiction:

Improvethrottle positioning easeVSAvoidauto-throttle compatibility

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

The system segments the TLA-thrust relationship into two distinct modes: an auto-throttle mode with a linear relationship that accommodates automated control, and a manual mode with flats that facilitates precise pilot positioning. This segmentation allows each mode to have optimized characteristics without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system dynamically switches between different TLA-thrust relationship configurations based on auto-throttle engagement status. When auto-throttle is engaged, the linear relationship is used; when disengaged, the relationship with flats is activated, providing adaptability to different operational requirements.

Inventive Principle:

Principle #15Dynamics

3Ease of operation

If the TLA is consistently positioned above the desired throttle position, then the pilot achieves desired thrust, but this causes unnecessary wear on the engine due to higher exhaust gas temperatures and rotational speeds

Engineering Contradiction:

Improvethrust achievementVSAvoidengine wear

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The system implements feedback by continuously monitoring the relationship between TLA position and actual thrust output. When the pilot positions the throttle above the desired position, the system detects this discrepancy and provides corrective feedback through the TLA fine trim mechanism, guiding the pilot back to the optimal position that achieves the same thrust with reduced engine stress.

Inventive Principle:

Principle #23Feedback

4Object-generated harmful factors

If the TLA is consistently below the desired throttle position, then the engine operates with reduced wear, but aircraft performance is less than expected

Engineering Contradiction:

Improveengine wear reductionVSAvoidaircraft performance

Core Design Contradiction:

Object-generated harmful factorsVSProductivity

Solution Approach 1:

The system provides real-time feedback to the pilot when the TLA position is below the desired position for achieving target thrust. The TLA fine trim mechanism communicates the discrepancy, enabling the pilot to adjust the throttle position upward to restore optimal performance while being aware of the trade-off between wear and performance.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8682562B2Turbine engine thrust scheduling

Publication Date: 2014.03.25 ROLLS ROYCE CORP

AI summary

This invention relates generally to gas turbine engine thrust scheduling, and more particularly to systems and methods for smoothing thrust inputs to gas turbine engines. In one embodiment, a method for operating a gas turbine engine comprises, upon disengagement of an auto-throttle system, determining a first trim setting corresponding to a TLA setting, determining a second trim setting where the second trim setting reduces to zero during successive manual throttle lever movements, determining a third trim setting comprising a combination of the first trim setting and the second trim setting, and applying the third trim setting to the TLA setting to smoothly transition from auto-throttle to manual operation of the engine while maintaining engine thrust.