An exemplary gas turbine engine assembly includes a fan section including a fan, a first spool having a first turbine operatively mounted to a first turbine shaft, and a second spool having a second turbine operatively mounted to a second turbine shaft. The first and second towershafts are respectively coupled to the first and second turbine shafts. An accessory drive gearbox includes a set of gears. A compressor is driven by the first towershaft. A transmission couples a starter generator assembly to the set of gears. The transmission is transitionable between a first mode where the starter generator assembly is driven at a first speed relative to the second towershaft in response to rotation of the second towershaft, and a second mode where the starter generator assembly is driven at a different, second speed relative to the second towershaft in response to rotation of the second towershaft.

An exemplary gas turbine engine assembly includes a fan section including a fan, a first spool having a first turbine operatively mounted to a first turbine shaft, and a second spool having a second turbine operatively mounted to a second turbine shaft. The first and second towershafts are respectively coupled to the first and second turbine shafts. An accessory drive gearbox includes a set of gears. A compressor is driven by the first towershaft. A transmission couples a starter generator assembly to the set of gears. The transmission is transitionable between a first mode where the starter generator assembly is driven at a first speed relative to the second towershaft in response to rotation of the second towershaft, and a second mode where the starter generator assembly is driven at a different, second speed relative to the second towershaft in response to rotation of the second towershaft.

A system for starting a turbine engine is provided. The system may comprise a gearbox, a first starter, and a second starter. The gearbox may have an gearbox input shaft. The gearbox input shaft may be rotationally coupled to a spool of the turbine engine. The first starter may have a first-starter shaft. The second starter may have a second-starter shaft. The second-starter shaft may be coaxial with the first-starter shaft. The first starter and the second starter may each be coupled to the gearbox input shaft independently of one another.

A system for starting a turbine engine is provided. The system may comprise a gearbox, a first starter, and a second starter. The gearbox may have an gearbox input shaft. The gearbox input shaft may be rotationally coupled to a spool of the turbine engine. The first starter may have a first-starter shaft. The second starter may have a second-starter shaft. The second-starter shaft may be coaxial with the first-starter shaft. The first starter and the second starter may each be coupled to the gearbox input shaft independently of one another.

A system for starting a turbine engine is provided. The system may comprise an gearbox, and electric starter, and an air turbine starter. The gearbox may have a gearbox input shaft. The gearbox input shaft may be coupled to a turbine engine. The gearbox input shaft may be rotationally coupled to a spool of the turbine engine. The electric starter may be coupled to the gearbox input shaft. The air turbine starter may be coupled to the gearbox input shaft. The electric starter and the air turbine starter may be separated by the gearbox. 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 an gearbox, and electric starter, and an air turbine starter. The gearbox may have a gearbox input shaft. The gearbox input shaft may be coupled to a turbine engine. The gearbox input shaft may be rotationally coupled to a spool of the turbine engine. The electric starter may be coupled to the gearbox input shaft. The air turbine starter may be coupled to the gearbox input shaft. The electric starter and the air turbine starter may be separated by the gearbox. The electric starter may be a starter-generator connected alternatively between an auxiliary power source and an auxiliary load.

An engine system includes a gas turbine engine with a first compressor, a first combustor, and first turbine. The engine system also includes a secondary power unit with a second compressor, a second combustor, a second turbine, a third compressor coupled to the second compressor, and an electric motor-generator, where the secondary power unit is coupled to the gas turbine engine and includes a heat exchanger. A controller is operable to determine an operating mode of the engine system, select an input energy source and an output type of the secondary power unit based on the operating mode, control the secondary power unit based on the input energy source and the output type as selected, detect a change in the operating mode of the engine system, and modify the input energy source and/or the output type of the secondary power unit based on the change in the operating mode.

The invention relates to a method for starting a turbine engine in cold weather, including a starting system intended for rotating a drive shaft of the turbine engine, the method comprising the following steps: a pre-starting step in which a first starting signal is generated to control the drive shaft in a first direction of rotation about a longitudinal axis (X) and in a second opposite direction of rotation in an alternating manner; and a starting step in which a second starting signal is transmitted to the starting system in order for the latter to drive the drive shaft of the turbine engine in a normal direction of rotation and in which the drive shaft is rotated until a rotation speed that causes the turbine engine to start.

The invention relates to a method for starting a turbine engine in cold weather, including a starting system intended for rotating a drive shaft of the turbine engine, the method comprising the following steps: a pre-starting step in which a first starting signal is generated to control the drive shaft in a first direction of rotation about a longitudinal axis (X) and in a second opposite direction of rotation in an alternating manner; and a starting step in which a second starting signal is transmitted to the starting system in order for the latter to drive the drive shaft of the turbine engine in a normal direction of rotation and in which the drive shaft is rotated until a rotation speed that causes the turbine engine to start.

Electrical systems for connecting rotary electric machines with gas turbine spools are provided. One such electrical system comprises: a first dual-wound rotary electric machine mechanically coupled with a first gas turbine spool and comprising a first three-phase sub-machine and a second three-phase submachine; a second dual-wound rotary electric machine mechanically coupled with a second gas turbine spool and comprising a third three-phase sub-machine and a fourth three-phase submachine; and a set of N=4 bidirectional converter circuits for conversion of alternating current (ac) to and from direct current (dc), each of which has an associated index n=(1, . . . , N), and for all n, the ac side of the nth bidirectional converter circuit is connected with the nth three-phase sub-machine. The dc side of the first converter circuit is connected with the dc side of the third converter circuit, and the dc side of the second converter circuit is connected with the dc side of the fourth converter circuit.