A system platform includes a gas turbine engine coupled to a generator. The generator, driven by the gas turbine engine, supplies power to subsystems of the platform.

An engine includes a first power source configured to drive a first power input, a power output, and a transmission engaged with the first power input and the power output. The transmission includes an epicyclic gear train engaged with the first power input and selectively engageable with the power output. A brake is engageable in a drive condition with the epicyclic gear train to transfer power from the first power input to the power output. The brake in a start condition is disengageable to decouple the first power input from the power output. A start assist motor associated with a second power source is engaged with the transmission to rotate the power output.

A system for starting a turbine engine is provided. The system may comprise a gearbox, an electric starter, and an air turbine starter. The gearbox may have a gearbox input shaft. The gearbox may be coupled to the turbine engine. The gearbox input shaft may be coupled to a spool of the turbine engine. The electric starter may have an electric-starter shaft. The electric-starter shaft may be coupled to the gearbox input shaft. The air turbine starter may have an air-turbine-starter shaft. The air-turbine-starter shaft may be coupled to the gearbox input shaft. The electric-starter shaft and the air-turbine-starter shaft may be radially displaced, circumferentially displaced, or both radially and circumferentially displaced, with respective to an axis of the turbine engine, from one another. The electric starter may be a starter-generator connected alternatively between an auxiliary power source and an auxiliary load.

A system for starting a turbine engine is provided. The system may comprise a gearbox, an electric starter, and an air turbine starter. The gearbox may have a gearbox input shaft. The gearbox may be coupled to the turbine engine. The gearbox input shaft may be coupled to a spool of the turbine engine. The electric starter may have an electric-starter shaft. The electric-starter shaft may be coupled to the gearbox input shaft. The air turbine starter may have an air-turbine-starter shaft. The air-turbine-starter shaft may be coupled to the gearbox input shaft. The electric-starter shaft and the air-turbine-starter shaft may be radially displaced, circumferentially displaced, or both radially and circumferentially displaced, with respective to an axis of the turbine engine, from one another. The electric starter may be a starter-generator connected alternatively between an auxiliary power source and an auxiliary load.

Systems and methods for starting a gas turbine engine can comprise a generator to be driven by the gas turbine engine to supply power to a grid system, a first switch to electrically couple and decouple the generator from the grid system, a first static frequency converter having a first capacity, a second static frequency converter having a second capacity, control means for electrically coupling and decoupling the first and second static frequency converters from the grid system, a synchronizer and a controller configured to operate the generator as a starter-motor with power from: the first static frequency converter to turn the gas turbine engine at a first rate sufficient to start the gas turbine engine within a first time period or the first static frequency converter and the second static frequency converter in synchronization to turn the gas turbine engine at a second rate greater than the first rate.

A gas turbine engine (10) includes a compressor section, a turbine section, and an accessory gearbox (100). A turning unit (200) for the gas turbine engine includes an output assembly (204) configured to be mechanically coupled to the gas turbine engine, and an electric motor (202). The electric motor is operable to rotate, through the output assembly, one or more components of the compressor section or the turbine section at a rotational speed less than about fifty revolutions per minute during a shut-down condition of the gas turbine engine.

A gas turbine engine (10) includes a compressor section, a turbine section, and an accessory gearbox (100). A turning unit (200) for the gas turbine engine includes an output assembly (204) configured to be mechanically coupled to the gas turbine engine, and an electric motor (202). The electric motor is operable to rotate, through the output assembly, one or more components of the compressor section or the turbine section at a rotational speed less than about fifty revolutions per minute during a shut-down condition of the gas turbine engine.

A turbomachine, particularly for a rotary-wing aircraft, including a gas generator provided with a rotary shaft, a first reversible electric machine, a power turbine rotationally driven by a stream of gas generated by the gas generator, at least one accessory from among an oil pump and a fuel pump, an accessory gearbox comprising a gear train configured to drive said at least one accessory, and a second electric machine. The second electric machine is reversible, said first electric machine is mechanically coupled to the gas generator, the accessory gearbox and the second electric machine are mechanically coupled to the power turbine, and the turbomachine is devoid of any kinematic coupling between the gear train of the accessory gearbox and the shaft of the gas generator.

A turbomachine, particularly for a rotary-wing aircraft, including a gas generator provided with a rotary shaft, a first reversible electric machine, a power turbine rotationally driven by a stream of gas generated by the gas generator, at least one accessory from among an oil pump and a fuel pump, an accessory gearbox comprising a gear train configured to drive said at least one accessory, and a second electric machine. The second electric machine is reversible, said first electric machine is mechanically coupled to the gas generator, the accessory gearbox and the second electric machine are mechanically coupled to the power turbine, and the turbomachine is devoid of any kinematic coupling between the gear train of the accessory gearbox and the shaft of the gas generator.

An AC electrical system for a vehicle and methods of operating the same are provided. In one aspect, an AC electrical system includes a first electric machine mechanically coupled with a first spool of a gas turbine engine and a second electric machine mechanically coupled with a second spool of the gas turbine engine. The system also includes a first AC bus and a second AC bus. A first electrical channel electrically couples the first electric machine to the first AC bus and a second electrical channel electrically couples the second electric machine to the second AC bus. The system also includes one or more connection links and one or more power converters for selectively electrically coupling the first and second electrical channels so that electrical power generated by one electric machine can be converted and shared with the other electric machine and electrical loads of the other channel.