An engine system for an aircraft includes a first gas turbine engine, a second gas turbine engine, and a control system. The control system is configured to operate the first gas turbine engine with an idle fuel burn schedule in a taxi mode of the aircraft and operate the second gas turbine engine with a sub-idle fuel burn schedule in the taxi mode of the aircraft. The sub-idle fuel burn schedule includes a reduction of the idle fuel burn schedule. A fuel flow of the first gas turbine engine and the second gas turbine engine is increased above the idle fuel burn schedule prior to takeoff of the aircraft.

An engine system for an aircraft includes a first gas turbine engine, a second gas turbine engine, and a control system. The control system is configured to operate the first gas turbine engine with an idle fuel burn schedule in a taxi mode of the aircraft and dry crank the second gas turbine engine in a first pre-takeoff portion of the taxi mode to cool the second gas turbine engine absent fuel burn by the second gas turbine engine. The control system operates the second gas turbine engine with a sub-idle fuel burn schedule in a second pre-takeoff portion of the taxi mode of the aircraft. The sub-idle fuel burn schedule includes a reduction of the idle fuel burn schedule. A fuel flow of the first gas turbine engine and the second gas turbine engine is increased above the idle fuel burn schedule prior to takeoff of the aircraft.

A hybrid-electric propulsion system includes a turbomachine, a propulsor coupled to the turbomachine, and an electrical system, the electrical system including an electric machine coupled to the turbomachine. A method for operating a hybrid-electric propulsion system includes operating, by one or more computing devices, the turbomachine in an idle operating condition; receiving, by the one or more computing devices, a command to accelerate the turbomachine while operating the turbomachine in the idle operating condition; and providing, by the one or more computing devices, electrical power to the electric machine to add power to the turbomachine and increase an acceleration of the turbomachine in response to the received command to accelerate the turbomachine.

An engine system for an aircraft includes a first gas turbine engine, a second gas turbine engine, and a control system. The control system is configured to operate the first gas turbine engine with a sub-idle fuel burn schedule based on detecting landing of the aircraft, where the sub-idle fuel burn schedule includes a reduction of an idle fuel burn schedule. The control system is configured to operate the second gas turbine engine with the idle fuel burn schedule based on detecting landing of the aircraft.

Electrical power systems, including generating capacity of a gas turbine, where additional electrical power is generated utilizing a separately fueled system during periods of peak electrical power demand.

A hybrid-electric propulsion system includes a turbomachine, a propulsor coupled to the turbomachine, and an electrical system, the electrical system including an electric machine coupled to the turbomachine. A method for operating a hybrid-electric propulsion system includes operating, by one or more computing devices, the turbomachine in an idle operating condition; receiving, by the one or more computing devices, a command to accelerate the turbomachine while operating the turbomachine in the idle operating condition; and providing, by the one or more computing devices, electrical power to the electric machine to add power to the turbomachine and increase an acceleration of the turbomachine in response to the received command to accelerate the turbomachine.

Electrical power systems, including generating capacity of a gas turbine, where additional electrical power is generated utilizing a separately fueled system during periods of peak electrical power demand.

A method for controlling an aircraft having at least two engines burning fuel and a transmission system connected to a rotary wing, each engine having a power shaft connected to the transmission system. An energy-saving phase comprises at least one energy-saving period comprising controlling, at an active rating, with a control system, one active engine from the at least two engines, and using the control system to stop or control, at an inactive rating, each inactive engine from the at least two engines that is not the active engine.

Electrical power systems, including generating capacity of a gas turbine, where additional electrical power is generated utilizing a separately fueled system during periods of peak electrical power demand.

A propulsion system is disclosed comprising a gas turbine engine and an acceleration schedule which determines the rate of acceleration of the gas turbine engine from an idle condition in response to a demand for increased thrust off-idle. The acceleration schedule determines the rate of acceleration in dependence upon the value of an engine parameter of the engine the value of which is substantially unaltered by variation in the magnitude of an electrical load drawn from the engine while it is operating in the idle condition.