A gas turbine engine includes a compressor section and a turbine section. A first spool is rotatable with a first turbine of the turbine section and a first compressor of the compressor section. Additionally, a second spool is rotatable with a second turbine of the turbine section and a second compressor of the compressor section. An electric machine is positioned at least partially inward of the core air flowpath of the gas turbine engine along a radial direction of the gas turbine engine. Additionally, the exemplary gas turbine engine includes a gear assembly mechanically coupled to both the first spool and the second spool, such that the first and second spools may each drive the electric machine.

A hybrid engine includes a gas turbine engine having at least one compressor section and at least one turbine section operably coupled to a shaft. The hybrid engine includes an electric motor configured to augment rotational power of the shaft of the gas turbine engine. A controller is operable to monitor for a transient operation request of the hybrid engine, provide the transient operation request to one or more management systems of the hybrid engine to determine whether one or more faults are detected by the one or more management systems, modify one or more stall margin adjustment parameters of the gas turbine engine based on detecting the one or more faults by the one or more management system, and adjust operation of the hybrid engine based on the one or more stall margin adjustment parameters.

An electrical system having a first dual-wound rotary electric machine mechanically coupled with a first gas turbine spool and having 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 having 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.

An electrical system having a first dual-wound rotary electric machine mechanically coupled with a first gas turbine spool and having 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 having 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.

The gas turbine engine for an aircraft includes at least a low pressure spool with a low pressure turbine shaft operatively connected to at least one turbine, the low pressure turbine shaft rotatable about an engine axis, and a low pressure compressor operatively connected to a low pressure compressor shaft that is independently rotatable relative to the low pressure turbine shaft. A differential gearbox has an input operatively connected to the low pressure turbine shaft, a first output and a second output, the first output of the differential gearbox operatively connected to the low pressure compressor shaft and the second output of the differential gearbox operatively connected to an output shaft of the gas turbine engine. The differential gearbox permits the output shaft, the low pressure compressor shaft and the low pressure turbine shaft to rotate at different speeds.

A compressor section is in fluid communication with a fan, which includes a first compressor section and a second compressor section. A turbine section includes a first turbine section driving the fan and the first compressor section and a second turbine section driving the second compressor section and the second compressor rotor. A first performance quantity is defined as a product of the first speed squared and the first area. A second performance quantity is defined as a product of the second speed squared and the second exit area. A performance ratio of the first performance quantity to the second performance quantity is between about 0.2 and about 0.8. A gear reduction is included between the first turbine section and the first compressor section.

A compressor section is in fluid communication with a fan, which includes a first compressor section and a second compressor section. A turbine section includes a first turbine section driving the fan and the first compressor section and a second turbine section driving the second compressor section and the second compressor rotor. A first performance quantity is defined as a product of the first speed squared and the first area. A second performance quantity is defined as a product of the second speed squared and the second exit area. A performance ratio of the first performance quantity to the second performance quantity is between about 0.2 and about 0.8. A gear reduction is included between the first turbine section and the first compressor section.

A gas turbine engine includes a main engine compressor section. A booster compressor changing a pressure of airflow received from the main engine compressor section to a pressure desired for a pneumatic system. The booster compressor operates at airflow conditions greater than a demand by the pneumatic system. A speed change system driving the booster compressor at speeds corresponding to a demand of the pneumatic system. A bleed air system for a gas turbine engine and a method of controlling engine bleed airflow are also disclosed.

Gearboxes for aircraft gas turbine engines, in particular to arrangements for journal bearings such gearboxes, and to related methods of operating such gearboxes and gas turbine engines. Example embodiments include a gearbox for an aircraft gas turbine engine, the gearbox including: a sun gear; a plurality of planet gears surrounding and engaged with the sun gear; and a ring gear surrounding and engaged with the plurality of planet gears, each of the plurality of planet gears being rotatably mounted around a pin of a planet gear carrier with a journal bearing having an internal sliding surface on the planet gear and an external sliding surface on the pin.

Gearboxes for aircraft gas turbine engines, in particular to arrangements for journal bearings such gearboxes, and to related methods of operating such gearboxes and gas turbine engines. Example embodiments include a gearbox for an aircraft gas turbine engine, the gearbox including: a sun gear; a plurality of planet gears surrounding and engaged with the sun gear; and a ring gear surrounding and engaged with the plurality of planet gears, each of the plurality of planet gears being rotatably mounted around a pin of a planet gear carrier with a journal bearing having an internal sliding surface on the planet gear and an external sliding surface on the pin.