A hybrid-electric propulsion system includes a propulsor, a turbomachine, and an electrical system having an electric machine coupled to the turbomachine. A method for operating the propulsion system includes operating, by one or more computing devices, the turbomachine to rotate the propulsor and generate thrust for the aircraft; receiving, by the one or more computing devices, data indicative of an un-commanded loss of the thrust generated from the turbomachine rotating the propulsor; and providing, by the one or more computing devices, electrical power to the electric machine to add power to the turbomachine, the propulsor, or both in response to receiving the data indicative of the un-commanded loss of thrust.

An aircraft propulsion system is disclosed and includes a first gas turbine engine including a first input shaft driving a first gear system, a first fan driven by the first gear system, a first generator supported on the first input shaft and a fan drive electric motor providing a drive input to the first fan, a second gas turbine engine including a second input shaft driving a second gear system, a second fan driven by the second gear system, a second generator supported on the second input shaft and a second fan drive electric motor providing a drive input to the second fan and a controller controlling power output from each of the first and second generators and directing the power output between each of the first and second fan drive electric motors.

Aircraft power and propulsion systems and methods of operating the systems, one method includes: operating electric machines of gas turbine engines as generators to extract mechanical power from spools and generating electrical power therefrom; meeting an electrical power demand of a plurality of electrical loads connected with an electrical system by supplying the plurality of electrical loads with electrical power generated by the electric machines; determining when there is an electrical system and/or the gas turbine engine fault and an amount of electrical power generated by the power and propulsion system is reduced to a lower level; and responsive to the determination: during a time period ΔT, controlling the plurality of electrical loads reducing the electrical power demand; and during the time period ΔT, meeting at least part of the electrical power demand of the plurality of electrical loads by discharging the electrical energy storage system.

Multi-engine aircraft power and propulsion systems and methods of starting the engines of multi-engine aircraft disclosed, including supplying electrical power from an electrical power source to electric machines of the a first gas turbine engine and operating electric machines as motors to drive rotation of spools of the first gas turbine engine; starting the first gas turbine engine by lighting combustion equipment of the first gas turbine engine; operating the electric machines of the first gas turbine engine as generators to extract mechanical power and generate electrical power from spools of the first gas turbine engine; transferring the electrical power to electric machines of a second gas turbine engine and operating the electric machines as motors to drive rotation of spools of the second gas turbine engine; and starting the second gas turbine engine by lighting combustion equipment of the second gas turbine engine.

Multi-engine aircraft power and propulsion systems and methods of restarting an engine of a multi-engine aircraft during fight are provided. One such method comprises: determining a condition to the effect that a flame in the combustion equipment of the second gas turbine engine has been extinguished; responsive to the determination, supplying electrical power from the electrical energy storage system to one or more of the electric machines of the second gas turbine engine and operating said one or more electric machines as motors to limit a reduction in a speed of the one or more spools of the second gas turbine engine following extinguishment of the flame in its combustion equipment; and restarting the second gas turbine engine by relighting the combustion equipment of the second gas turbine engine.

Aircraft power and propulsion systems, aircraft comprising such power and propulsion systems, and methods of restarting a gas turbine engine of such power and propulsion systems during flight are provided. One such aircraft power and propulsion system comprises: a propulsive gas turbine engine comprising a plurality of spools, combustion equipment, one or more electric machines mechanically coupled with one or more of the spools and an electrically-powered fuel pump for delivering fuel to the combustion equipment; an electrical system connected with the one or more electric machines and the electrically-powered fuel pump, the electrical system comprising an energy storage system; and a control system configured to: responsive to a determination to the effect that a flame in the combustion equipment has been extinguished, control the electrical system to supply electrical power from the energy storage system to the fuel pump during an engine restart attempt.

A twin-engine aircraft power and propulsion system including first and second propulsive gas turbine engines, each having combustion equipment and a first and second spool; first, second, third, and fourth electrical power generation sub-systems including electric machines respectively mechanically coupled with the first spool of the first propulsive gas turbine engine, the second spool of the first propulsive gas turbine engine, the first spool of the second propulsive gas turbine engine, and the second spool of the second propulsive gas turbine engine; and first, second, third, and fourth power channels respectively connected with distribution sides of the first electric machine, second electric machine, third electric machine, and fourth electric machine.

A gas turbine engine for an aircraft comprises, in axial flow sequence, a compressor module, a combustor module, and a turbine module. The gas turbine engine further comprises a first electric machine that is rotationally connected to the turbine module, and an electrical energy storage unit. The gas turbine engine is configured to generate a maximum dry thrust T (N). The first electric machine is configured to generate a maximum electrical power P.sub.EM1 (W). The electrical energy storage unit has an energy storage capacity E (Wh), a maximum charge rate C (h.sup.−1), and a maximum discharge rate D (h.sup.−1). The electrical energy storage unit is configured to store electrical energy that may be generated by the first electric machine.

A gas turbine engine for an aircraft comprises, in axial flow sequence, a compressor module, a combustor module, and a turbine module, with a first electric machine being rotationally connected to the turbine module. The first electrical machine is configured to generate a maximum electrical power P.sub.EM1 (W), and the gas turbine engine is configured to generate a maximum shaft power P.sub.SHAFT (W); and a ratio R of:

[00001]$R=\frac{\left(\mathrm{Maximum}\mathrm{Electrical}\mathrm{Power}\mathrm{Generated}=P_{EM1}\right)}{\left(\mathrm{Maximum}\mathrm{Shaft}\mathrm{Power}=P_{SHAFT}\right)}$

is in a range of between 0.005 and 0.020.

The gas turbine engine can have an air mover configured for generating a flow of air around a rotation axis; a surface extending around the rotation axis delimiting a passage for the flow of air downstream of the air mover; an electric machine disposed within the passage and coupled to the air mover; a coolant circuit having: an evaporator circumferentially disposed around at least part of the electric machine and in thermal communication therewith; a condenser having a surface cooler circumferentially disposed at least partially around the surface and in thermal communication therewith; a first conduit fluidly connecting an upper region of the evaporator to an upper region of the condenser; and a second conduit fluidly connecting a lower region of the condenser to a lower region of the evaporator; and a coolant fluid in the coolant circuit.