WE CLAIM :
1. A method for operating a multi-shaft aeronautical gas turbine engine
having an electrical machine, the electrical machine including a starter-electric
generator driven by at least one of the shafts of the gas turbine engine, the method
comprising:
determining a desired amount of thrust to be produced from the gas turbine engine;
determining a desired amount of electrical power to be drawn from the starter-electric generator of the gas turbine engine;
producing the desired amount of thrust using the gas turbine engine; and
drawing less than the desired amount of electrical power from the starter-electric generator of the gas turbine engine to allow the gas turbine engine to produce the desired amount of thrust, to produce the desired amount of thrust more quickly, or to maintain a stall margin.
2. The method as claimed in claim 1, wherein determining the desired amount of electrical power to be drawn includes determining an amount of power required to fully operate an environmental controls system, and wherein drawing less than the desired amount of electrical power includes drawing less than the amount of power required to fully operate the environmental controls system.
3. The method as claimed in claim 1, further comprising
determining a maximum amount of electrical power that may be drawn from the starter-electric generator while also producing the desired amount of thrust.
4. The method as claimed in claim 3, further comprising
determining an auxiliary amount of electrical power desired based on the determined desired amount of electrical power to be drawn and the determined

maximum amount of power that that may be drawn from the starter-electric generator while also producing the desired amount of thrust.
5. The method as claimed in claim 4, further comprising
providing the determined auxiliary amount of electrical power to a power distribution bus from an auxiliary power system, wherein the starter-electric generator of the gas turbine engine is also in electrical communication with the power distribution bus.
6. The method as claimed in claim 5, wherein the auxiliary power system includes an energy storage device.
7. The method as claimed in claim 6, wherein providing the determined auxiliary amount of power to the power distribution bus includes providing the determined auxiliary amount of power to the power distribution bus from the battery pack of the auxiliary power system while operating the gas turbine engine under transient engine conditions.
8. The method as claimed in claim 5, wherein the starter-electric generator of the gas turbine engine is a main starter-electric generator, and wherein the auxiliary power system includes an auxiliary electric generator driven by the one or more shafts of the gas turbine engine.
9. An aeronautical gas turbine engine comprising: a compressor section;
a combustion section located downstream of the compressor section;
a turbine section located downstream of the combustion section, the turbine section mechanically coupled to the compressor section by one or more shafts;

an electrical machine in mechanical communication with the one or more shafts, the electrical machine including a starter-electric generator (108) for generating electrical power; and
a controller (122) operably connected to the starter-electric generator (108), the controller (122) configured to reduce an amount of electrical power drawn from the starter-electric generator (108) to an amount below a desired amount to be drawn in order to facilitate a desired amount of thrust production by the gas turbine engine, to facilitate the desired amount of thrust production by the gas turbine engine more quickly, or to maintain a stall margin.
10. The gas turbine engine as claimed in claim, wherein the starter-electric generator (108) is configured for electrical communication with a power distribution bus (110), and wherein the gas turbine engine further includes
an auxiliary power supply (118) also configured for electrical communication with the power distribution bus (110), wherein the controller is further configured to provide electrical power to the power distribution bus (110) from the auxiliary power supply (118) when the amount of power drawn from the starter-electric generator (108) is reduced to facilitate a desired amount of thrust production by the gas turbine engine.