A method for controlling a thermal and electrical power plant for setting in motion at least one rotary member of a rotorcraft, the power plant comprising at least one heat engine and an electrical system provided with at least one electric machine. The method comprises: selecting, with a selector, an operating mode chosen from several operating modes; determining a density altitude and comparing, with a controller, the current density altitude and a threshold density altitude; and controlling, with the controller, the at least one electric machine depending on at least the chosen operating mode as well as the comparison and a necessary power to be supplied to the power transmission system.

A drive system comprises a DC-DC converter that is arranged to receive an input voltage from a battery having a nominal battery voltage. The DC-DC converter has a first mode of operation in which the DC-DC converter generates a regulated output voltage from the input voltage and supplies the regulated output voltage to a load, and a second mode of operation in which the DC-DC converter is by-passed such that the input voltage from the battery is supplied to the load. A controller is arranged to compare the input voltage to a threshold voltage that is less than the nominal battery voltage. The controller operates the DC-DC converter in the first mode when the input voltage is less than the threshold voltage, and operates the DC-DC converter otherwise.

A drive system comprises a DC-DC converter that is arranged to receive an input voltage from a battery having a nominal battery voltage. The DC-DC converter has a first mode of operation in which the DC-DC converter generates a regulated output voltage from the input voltage and supplies the regulated output voltage to a load, and a second mode of operation in which the DC-DC converter is by-passed such that the input voltage from the battery is supplied to the load. A controller is arranged to compare the input voltage to a threshold voltage that is less than the nominal battery voltage. The controller operates the DC-DC converter in the first mode when the input voltage is less than the threshold voltage, and operates the DC-DC converter otherwise.

An aircraft having a vertical takeoff and landing fight mode and a forward flight mode. The aircraft includes an airframe and a versatile propulsion system attached to the airframe. The versatile propulsion system includes a plurality of propulsion assemblies. A flight control system is operable to independently control the propulsion assemblies. The propulsion assemblies are interchangeably attachable to the airframe such that the aircraft has a liquid fuel flight mode and an electric flight mode. In the liquid fuel flight mode, energy is provided to each of the propulsion assemblies from a liquid fuel. In the electric flight mode, energy is provided to each of the propulsion assemblies from an electric power source.

A method of designing a turbofan engine according to an exemplary aspect of the present disclosure includes, among other things, providing a fan section including a plurality of fan blades, providing a low pressure turbine driving the plurality of fan blades through a gear train, providing a fan nacelle and a core nacelle, the fan nacelle at least partially surrounding the core nacelle, providing a fan bypass flow path defined between the core nacelle and the fan nacelle, and providing a fan variable area nozzle in communication with the fan bypass flow path and defining a fan nozzle exit area between the fan nacelle and the core nacelle.

A method of designing a turbofan engine according to an exemplary aspect of the present disclosure includes, among other things, providing a fan section including a plurality of fan blades, providing a low pressure turbine driving the plurality of fan blades through a gear train, providing a fan nacelle and a core nacelle, the fan nacelle at least partially surrounding the core nacelle, providing a fan bypass flow path defined between the core nacelle and the fan nacelle, and providing a fan variable area nozzle in communication with the fan bypass flow path and defining a fan nozzle exit area between the fan nacelle and the core nacelle.

One example aspect of the present disclosure is directed to a method for measuring engine performance. The method includes receiving a plurality of parameters related to engine performance. The method includes receiving an indication of an engine wash event. The method includes determining an effectiveness of the engine wash event based on the plurality of parameters. The method includes performing a comparison of the effectiveness of the engine wash event with an expected effectiveness of the engine wash event. The method includes performing a control action based on the comparison.

One example aspect of the present disclosure is directed to a method for measuring engine performance. The method includes receiving a plurality of parameters related to engine performance. The method includes receiving an indication of an engine wash event. The method includes determining an effectiveness of the engine wash event based on the plurality of parameters. The method includes performing a comparison of the effectiveness of the engine wash event with an expected effectiveness of the engine wash event. The method includes performing a control action based on the comparison.

An electric power supply is disclosed having high-voltage, direct-current (HVDC) circuitry comprising one or more DC pre-charge capacitors and one or more power transistor switches, the HVDC circuitry configured to receive high-voltage, direct-current (HVDC) input power of about 320 volts and/or greater and convert the HVDC input power to multi-phase, high-voltage, alternating-current (HVAC) output power of about 320 volts and/or greater; and low-voltage, direct current (LVDC) circuitry adapted and configured to operate on low-voltage, direct-current, wherein the LVDC circuitry is configured to control and monitor the multi-phase HVAC output power. The electric power supply is further configured to operate in reverse and convert received multiphase HVAC input power to HVDC output power.

A method and system for operating a hybrid propulsion system, includes controllably providing a first power to a first bus and a first inverter, electrically coupling a first motor with a second inverter by way of a second bus, operably converting, by the second inverter, the first power received by the first inverter to a starting power adapted for starting the first motor, and increasing, by the second inverter, the starting power to match the first power received.