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 starter-electric generator being in electrical communication with a power distribution bus, 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; 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; determining a maximum amount of electrical power that may be drawn from the starter-electric generator while also producing the desired amount of thrust; 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; providing the determined auxiliary amount of electrical power to the power distribution bus from an auxiliary power system, 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 one or more shafts of the gas turbine engine; and providing power from the auxiliary electric generator, through the power distribution bus, through the main starter-electric generator of the gas turbine engine, and to one or more shafts of the gas turbine engine. 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; 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; determining a maximum amount of electrical power that may be drawn from the starter-electric generator while also producing the desired amount of thrust; 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; providing the determined auxiliary amount of electrical power to the power distribution bus from an auxiliary power system, 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 one or more shafts of the gas turbine engine; and providing power from the auxiliary electric generator, through the power distribution bus, through the main starter-electric generator of the gas turbine engine, and to one or more shafts of the gas turbine engine.