There are described methods and systems for operating an aircraft having two or more engines. One method comprises operating the two or more engines of the aircraft in an asymmetric operating regime, wherein a first of the engines is in an active mode to provide motive power to the aircraft and a second of the engines is in a standby mode to provide substantially no motive power to the aircraft; governing the first engine in the active mode using a first governing logic; and governing the second engine in the standby mode using a second governing logic, the second governing logic based on a target compressor speed and variable geometry mechanism (VGM) settings that are adjusted using trim values dependent on at least one parameter of the second engine in the standby mode.

There are described a method and system for operating a gas turbine engine. The method comprises governing the engine with a primary governing logic to adjust a fuel flow to the engine and governing the engine with at least one complementary governing logic concurrently to the primary governing logic, the at least one complementary governing logic adjusting a position of at least one variable geometry mechanism (VGM) of the engine to prevent a rotational speed of the engine from operating in one or more restricted speed range.

A method of operating a multi-engine aircraft having two or more gas turbine engines includes operating a first engine in a powered mode to provide motive power to the aircraft, and, in flight, operating a second engine in either a powered mode to provide motive power to the aircraft or in a standby mode to provide substantially no motive power to the aircraft. When operating the second engine in the powered mode, pressurized air is bled from a first bleed location of a compressor of the second engine. When operating the second engine in the standby mode, pressurized air is bled from a second bleed location of the compressor of the second engine and supplying the pressurized air to a bleed air system of the second engine. The second bleed location is downstream of the first bleed location within the compressor of the second engine.

A hybrid propulsion system for an aircraft can include a propulsor assembly having at least one propulsor and a power generation system. The power generation system can include a first power assembly, a second power assembly, a first electric machine, and a second electric machine. The first power assembly can be drivingly coupled to the first electric machine to produce a first amount of electric power. The second power assembly can be drivingly coupled to the second electric machine to produce a second amount of electric power. A controller can be operably coupled to the first power assembly, the first electric machine, or both and to the second power assembly, the second power assembly, or both. The controller can be configured to combine at least a portion of the first and second amount of power for electric transfer to the propulsor assembly.

A system for determining and/or controlling motor thrust and engine thrust in a parallel hybrid aircraft. One or more sensors may be configured to monitor one or more flight parameters to generate sensor information. User input including one or more pilot estimates may be received. The sensor information may be obtained. A performance thrust ratio may be calculated based on the user input, the sensor information, an aerodynamic model, a propeller model, and a battery model. The performance thrust ratio may be used to control the motor thrust and engine thrust to improve utilization of electric energy throughout a flight. A first thrust setting for the motor and/or a second thrust setting for the engine may be determined based on the performance thrust ratio.

Embodiments of the disclosure provide a method for operating a combined cycle power plant (CCPP). The method may include generating a power plant model for operating the CCPP, determining whether at least two gas turbines in the power plant model generate a power output, and modeling a fuel consumption of the CCPP for a baseline split ratio between the at least two gas turbines. The method may also include determining whether the variant split ratio meets a quality threshold for the CCPP, and adjusting the CCPP to use the variant split ratio in response to the variant split ratio meeting the quality threshold.

An aspect includes a system for pre-start motoring control for multiple engines of an aircraft. The system includes a first engine starting system of a first engine and a controller. The controller is operable to control a motoring time of the first engine starting system relative to one or more other engine starting systems of one or more other engines of the aircraft by adjusting the motoring time of the first engine starting system within a tolerance of the motoring time of the one or more other engine starting systems in a pre-start motoring sequence.

An engine system comprises first and second electrical generators coupled to lower and higher pressure (LP, HP) shafts respectively of a gas turbine engine. A controller is arranged to receive a signal corresponding to a total electrical power demand P.sub.1 and to output control signals to the electrical generators in response thereto such that the first and second electrical generators output electrical powers (1−y)P.sub.1 and yP.sub.1 respectively when P.sub.1≤P.sub.m1, where 0.5<y≤1 and P.sub.m1 is the maximum electrical output power of the first electrical generator. By satisfying the demand P.sub.1 mostly by extraction of electrical power from the first electrical generator when possible, the additional mechanical stress on the gas turbine engine resulting from electrical power extraction is reduced compared to the case where 50% or more of the demand P.sub.1 is satisfied by the second electrical generator.

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.

The invention relates to an aircraft propulsion system, comprising a main transmission unit (12) and at least two turbojet engines connected to the main transmission unit (12), respectively a first turbojet engine (14a) and a second turbojet engine (14b), each turbojet engine comprising a free turbine (24a, 24b), characterized in that the first turbojet engine (14a) comprises a heat exchanger (30) configured to recover some of the thermal energy from the exhaust gas at the outlet of the free turbine, and in that the propulsion system comprises at least one computer (28a, 28b) configured to control the two turbojet engines and to limit the acceleration and the deceleration of the first turbojet engine (14a) when neither of the turbojet engines is broken down, in order to limit the reactor power transients at the heat exchanger (30).