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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, determin

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.

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1. A method for operating a gas turbine engine, comprising: before disengagement of an auto-throttle system, receiving, by an engine controller, a Throttle Lever Angle (TLA) setting and a TLA fine trim setting applied by the auto-throttle system that together provide a desired engine thrust;upon dis

1. A method for operating a gas turbine engine, comprising: before disengagement of an auto-throttle system, receiving, by an engine controller, a Throttle Lever Angle (TLA) setting and a TLA fine trim setting applied by the auto-throttle system that together provide a desired engine thrust;upon disengagement of the auto-throttle system, determining, a first trim setting corresponding to the TLA setting;determining, by the engine controller, a second trim setting defined from the first trim setting and the TLA fine trim setting, wherein the second trim setting gradually reduces to zero during successive manual throttle lever movements;determining, by the engine controller, a third trim setting comprising a combination of the first trim setting and the second trim setting; andapplying the third trim setting to the TLA setting as a substitute for the fine trim setting to smoothly transition from auto-throttle to manual operation of the engine while maintaining engine thrust. 2. The method of claim 1, wherein the first trim setting corresponds to at least one flat in a TLA-thrust relationship defining manual operation of the engine. 3. The method of claim 2, wherein the at least one flat lies between engine idle thrust and maximum takeoff thrust. 4. The method of claim 2, wherein each of the at least one flat corresponds to a thrust level associated with a plurality of TLA settings. 5. The method of claim 4, wherein each of the plurality of TLA settings comprises a range of 2 degrees. 6. The method of claim 1, wherein the second trim setting comprises subtracting, by the engine controller, the first trim setting from the TLA setting. 7. The method of claim 1, wherein the auto-throttle system comprises a TLA-thrust relationship defining engine thrust that increases with increasing TLA between idle thrust and maximum takeoff thrust. 8. The method of claim 1, wherein the engine controller determines the first trim setting by interpolating among a plurality of trim settings in a dynamic lookup table. 9. A method for operating a gas turbine engine, comprising: upon disengagement of an auto-throttle system, determining by an engine controller, a Throttle Lever Angle (TLA) trim setting corresponding to a measured TLA, wherein the TLA trim setting gradually reduces to zero during successive manual throttle lever movements; andapplying the TLA trim setting to the measured TLA to transition from auto-throttle to manual operation of the engine while maintaining engine thrust;a lookup cycle corresponding to a current measured TLA, wherein for each lookup cycle, the engine controller creates a lookup table comprising a plurality of TLA trim settings as a function of TLA, wherein the engine controller determines a current TLA trim setting corresponding to the current measured TLA;wherein the engine controller sets the TLA trim setting in the lookup table equal to zero for TLA's corresponding to engine idle thrust and to maximum takeoff thrust, and to the current TLA trim setting for TLA's between engine idle thrust and maximum takeoff thrust;wherein the engine controller is a computer processor. 10. A method for operating a gas turbine engine, comprising: automatically maintaining engine thrust when transitioning to manual operation of the engine following disengagement of an aircraft auto-throttle system, comprisingsubstituting a first Throttle Lever Angle (TLA) trim setting computed by an engine controller for a last TLA trim setting provided by the auto-throttle system;adding, by the engine controller, the first TLA trim setting to a measured TLA setting to form a new TLA setting; andapplying the new TLA setting to the engine to maintain engine thrust, wherein subsequent manual throttle movements gradually reduces the first trim setting to zero. 11. The method of claim 10, wherein the first trim setting comprises trim corresponding to the introduction of at least one flat in a TLA-thrust relationship defining manual operation of the engine. 12. The method of claim 11, wherein the at least one flat lies between engine idle thrust and maximum takeoff thrust. 13. The method of claim 11, wherein each of the at least one flat corresponds to a thrust level associated with a plurality of TLA settings. 14. The method of claim 13, wherein each of the plurality of TLA settings comprises a range of 2 degrees. 15. The method of claim 11, wherein when the auto-throttle system disengages, the engine controller sets one component of the first trim setting equal to the last trim setting minus a trim corresponding to at least one flat in a TLA-thrust relationship defining manual operation of the engine. 16. The method of claim 10, wherein the auto-throttle system comprises a TLA-thrust relationship defining engine thrust that increases with increasing TLA between idle thrust and maximum takeoff thrust. 17. The method of claim 10, wherein the engine controller determines at least one component of the first trim setting by interpolating among a plurality of trim settings in a dynamic lookup table. 18. The method of claim 10, wherein the auto-throttle system comprises a first TLA-thrust relationship defining engine thrust that increases with increasing TLA between idle thrust and maximum takeoff thrust, and wherein manual operation of the engine corresponds to a second TLA-thrust relationship defining a plurality of constant levels of engine thrust corresponding to a plurality of ranges of TLA settings. 19. The method of claim 10, wherein subsequent manual throttle movements gradually reduces the first trim setting to zero includes (a) measuring the TLA setting corresponding to each manual throttle movement, and(b) for each measured TLA setting and corresponding applied TLA setting between an idle thrust setting and a maximum thrust setting, interpolating by the engine controller between an applied TLA trim setting and zero to obtain a new TLA trim setting that is less in magnitude than the applied TLA trim setting. 20. The method of claim 1, including the steps of (a) measuring the TLA setting corresponding to each manual throttle movement, and(b) for each measured TLA setting and corresponding applied TLA setting between an idle thrust setting and a maximum thrust setting, interpolating by the engine controller between an applied third trim setting and zero to obtain a new TLA trim setting that is less in magnitude than the applied third trim setting. 21. The method of claim 9, including the steps of (a) measuring the TLA setting corresponding to each manual throttle movement, and(b) for each measured TLA setting and corresponding applied TLA setting between an idle thrust setting and a maximum thrust setting, interpolating by the engine controller between the applied TLA trim setting and zero to obtain a new TLA trim setting that is less in magnitude than the applied TLA trim setting.