Patent Description:
<CIT> in an abstract states that "A distributed propulsion system (<NUM>) is described that includes at least one turbine engine (<NUM>) including an engine shaft (<NUM>) and at least one mechanically driven propulsor (12A), wherein a propulsor shaft (<NUM>) of the at least one mechanically driven propulsor is not co-axial with the engine shaft of the at least one turbine engine and is driven by the engine shaft of the at least one turbine engine. The distributed propulsion system further includes at least one generator (<NUM>) driven by rotation of at least one of the engine shaft of the at least one turbine engine or the propulsor shaft of the at least one mechanically driven propulsor. The distributed propulsion system also includes at least one electrically driven propulsor (12B), wherein a propulsor motor (<NUM>) of the at least one electrically driven propulsor drives a propulsor fan (<NUM>) of the at least one electrically driven propulsor based on electricity produced by the at least one generator.

<CIT> in an abstract states that" Features for a tail-sitter aircraft having efficiently designed propulsive elements are disclosed. The aircraft may have a tail with landing mounts to support the aircraft in a vertical position for takeoff and landing. The aircraft may have a hybrid propulsion system including an electric power source, such as a generator and an electric motor, and a prime power subsystem, such as an internal combustion engine. The electric and prime power subsystems may be used controllably in varying amounts depending on the phase of flight, such as takeoff, horizontal flight, landing, or maneuvers. The aircraft may have blades with piezo elements to provide shape-changing capability to the blade. The shape of the blade, such as the pitch and/or twist, may be controllably changed for optimal efficiency with the blade depending on phase of flight. The blade shape may be changed from a rotor-like shape during takeoff and landing, to a propeller-like shape during horizontal flight.

<CIT> in an abstract states that "A hybrid aircraft propulsion system (<NUM>). The system (<NUM>) comprises a gas turbine engine (<NUM>) having a turbine system (30a, 30b, <NUM>) comprising first and second turbine sections (30a, 30b). The gas turbine engine (<NUM>) further comprises a first combustor (<NUM>) provided upstream in core flow from the turbine system (30a, 30b, <NUM>), and a second combustor (<NUM>) provided between the first and second turbine sections (30a, 30b). The hybrid aircraft propulsion system further comprises an energy storage system (<NUM>) and an electric propulsion system (<NUM>) electrically coupled to the energy storage system (<NUM>).

<CIT> in an abstract states that "An aircraft includes a fuselage, a forward wing assembly, and aft wing assembly, and a propulsion system. The propulsion system includes a first primary thrust propulsor and a first secondary thrust propulsor, the first primary thrust propulsor being different than the first secondary thrust propulsor. Both the first primary thrust propulsor and the first secondary thrust propulsor are mounted to the same one of: a starboard side of the aft wing assembly, a port side of the aft wing assembly, a starboard side of the forward wing assembly, or a port side of the forward wing assembly.

A hybrid-electric powertrain for an aircraft is defined in claim <NUM>, with some optional features set out in the claims dependent thereto.

An example hybrid-electric powertrain for an aircraft disclosed herein includes a gas turbine propulsion engine including a first propulsor and a gas turbine engine to drive the first propulsor to produce thrust, a generator operably coupled to a drive shaft of the gas turbine engine, and an electric propulsion unit including a second propulsor and an electric motor to drive the second propulsor to produce thrust. During a first mode of operation, the gas turbine propulsion engine and the electric propulsion unit are activated to produce thrust. Further, during the first mode of operation, the generator is driven by the gas turbine engine to produce electrical power to power the electric propulsion unit. During a second mode of operation, the gas turbine propulsion engine is activated to produce thrust and the electric propulsion unit is deactivated.

An example aircraft disclosed herein includes a wing and a hybrid-electric powertrain including a gas turbine propulsion engine coupled to the wing, a generator to be driven by the gas turbine propulsion engine, and an electric propulsion unit coupled to the wing. During a first mode of operation, the gas turbine propulsion engine is activated to produce thrust and the gas turbine propulsion engine drives the generator to produce electrical power for activating the electric propulsion unit to produce thrust. During a second mode of operation, the electric propulsion unit is deactivated.

An example method disclosed herein includes operating a hybrid-electric powertrain of an aircraft in a first mode of operation during a first segment of flight. The hybrid-electric powertrain includes a gas turbine propulsion engine, a generator to be driven by the gas turbine propulsion engine, and an electric propulsion unit. During the first mode of operation, the gas turbine propulsion engine is activated to produce thrust and the gas turbine propulsion engine drives the generator to produce electrical power for activating the electric propulsion unit to produce thrust. The method also includes operating the hybrid-electric powertrain during a second segment of flight in a second mode of operation. During the second mode of operation, the gas turbine propulsion engine is activated and the electric propulsion unit is deactivated.

In general, the same reference numbers will be used throughout the drawing(s) and accompanying written description to refer to the same or like parts. The figures are not to scale.

Unless specifically stated otherwise, descriptors such as "first," "second," "third," etc., are used herein without imputing or otherwise indicating any meaning of priority, physical order, arrangement in a list, and/or ordering in any way, but are merely used as labels and/or arbitrary names to distinguish elements for ease of understanding the disclosed examples. " In such instances, it should be understood that such descriptors are used merely for identifying those elements distinctly that might, for example, otherwise share a same name.

Aircraft typically include one or more propulsion engines (e.g., turboprop engines, turbofan engines, etc.) that are powered by hydrocarbon-burning turbine engines, referred to herein as gas turbine engines. These gas turbine engines are typically sized by the maximum power requirements needed for take-off, climb, and emergency situations. In general, gas turbine engines are most fuel efficient at or near their maximum power (e.g., throttle) settings. During cruise, the gas turbine engines operate at reduced a power setting (e.g., around <NUM>% of maximum power). This leads to inefficient operation and additional fuel burn at cruise, because the engines are oversized and operating at sub-optimal power settings for fuel efficiency.

In recent years, environmental pressure has spurred renewed efforts to decrease fuel consumption as well as move away from hydrocarbons to curb emissions. Some concepts focus on using hydrogen as the zero-emissions fuel, and utilize hydrogen fuel cells as the means to convert the fuel into electricity used to power electric motors. Other concepts use batteries and auxiliary powerplants known as 'range extenders' in a series hybrid arrangement. This new breed of distributed hybrid-electric architecture focuses on hydrogen fuel cells as the power generation system or uses batteries and small range-extenders that are scheduled to run near their best operating point. However, the technology readiness level and achievable system-level specific power figures of these architectures is low compared to conventional gas turbine engines, which severely limits the achievable range with these architectures.

Disclosed herein are example hybrid-electric powertrains for aircraft that include one or more gas turbine propulsion engines (used as primary propulsion engines) and one or more electric propulsion units (used as secondary propulsion engines) distributed along the wings of an aircraft. The electric propulsion unit(s) (which can also be referred to as electric propulsion nacelles) include electric motors with propulsors (e.g., propellers, fans) to produce thrust. The example hybrid-electric powertrain can be operated in different modes of operation in which the electric propulsion unit(s) are activated to produce thrust and supplement the thrust provided by the gas turbine propulsion engine(s). This enables the gas turbine propulsion engines to be sized smaller and operate at or near their optimal efficiency ranges during cruise and other segments of flight. This improves fuel efficiency and reduces emissions. Further, the electric propulsion unit(s) can be distributed along the wings of the aircraft and, thus, when activated, can wash the wings with airflow. This arrangement improves lift generation and the increase in the number of propulsors reduces yawing moments in the case of an engine failure. As a result, the wing and the vertical fin areas can be made smaller, with further benefits in terms of cruise efficiency.

To provide electrical power for the electric propulsion unit(s), the example hybrid-electric powertrain includes one or more electric generators that are driven by the gas turbine propulsion engine(s). For example, a gas turbine propulsion engine disclosed herein can be implemented as a turboprop engine that includes a gas turbine engine and a propulsor (e.g., a propellor) that is driven by the gas turbine engine. A drive shaft of the gas turbine engine is mechanically coupled to and drives the generator (during certain modes of operation). Therefore, during periods in which the electric propulsion unit(s) are activated, the generator can generate electrical power to power the electric propulsion unit(s). In some examples, when the electric propulsion unit(s) are not activated, the generator is mechanically and/or electrically decoupled from the gas turbine engine so as not to produce an unnecessary load on the gas turbine engine.

The gas turbine engine(s) of the gas turbine propulsion engine(s) include inter-turbine burners (ITBs). An ITB is an additional combustor placed between the gas generator exit and the power turbine to reheat the engine gas stream before it enters the power turbine. The ITBs can be turned on during periods of high-power demand to increase the power output of the gas turbine engine(s). For example, the ITBs can be turned on during take-off or climb. This enables the gas turbine propulsion engines to generate additional power (which equates to additional thrust) during these flight segments. This also provides additional power to drive the electric generators to produce electrical power for powering the electric propulsion units. Therefore, the ITBs can be used to increase engine power at the maximum power setting during certain segments of flight. This enables the gas turbine engines to be sized smaller. As such, the gas turbine engines can be sized so to operate at their most fuel efficient speeds during cruise. Therefore, the gas turbine engines can be sized for better fuel efficiency and lower emissions at cruise, unlike known engines that are oversized for cruise speeds and have to throttle down. Further, gas turbine engines are a convenient source of compressed air for use in the aircraft cabin, whereas hydrogen fuel-cell architectures need other, less expedient means to generate compressed air.

As disclosed above, the example hybrid-electric powertrain can be operated in different modes, which may be based on the segment of flight and/or power demand. For example, during segments of flight that demand higher power, such as during take-off, climb, and landing, the hybrid-electric powertrain can be operated in a first mode of operation. During the first mode of operation, the gas turbine propulsion engines are activated and the electric propulsion units are activated. As such, all of the engines are activated and produce thrust. During the first mode of operation, the gas turbine engines of the gas turbine propulsion engines drive the generators to produce electrical power for operating the electric motors of the electric propulsion units. The ITB can be activated during the first mode of operation to increase power output of the gas turbine engines, which results in higher thrust and additional power for driving the electrical generators. The electric generators power the electric propulsion units, which produce additional thrust that is beneficial during take-off, climb, and landing.

During other segments of flight where less power is demanded, such as during cruise, the hybrid-electric powertrain can be operated in a second mode of operation. During the second mode of operation, the gas turbine propulsion engines are still activated or running, but the electric propulsion units are deactivated (since less thrust is needed to maintain speed and altitude at cruise). During the second mode of operation, the ITBs are deactivated. Further, in some examples, the generator(s) are mechanically and/or electrically decoupled from the gas turbine propulsion engines to reduce load on the gas turbine propulsion engines. In some examples, the hybrid-electric powertrain can be operated in a third mode of operation in which the ITBs are activated for short periods to increase power and thrust of the gas turbine engine, without activating the electric propulsion units. This can be used during periods where quick bursts of power or speed are desired, such as during a dash. A dash is a shorter flight segment flown at maximum continuous speed.

As disclosed above, the electric generators provide power directly to the electric propulsion units. Therefore, in some examples, the hybrid-electric powertrain does not require batteries onboard the aircraft. Batteries are heavy and require significant space. As such, the example hybrid-electric powertrain results in reduced weight and greater fuel efficiency compared to other architectures that utilize batteries onboard the aircraft. Further, in some examples, the gas turbine engines can be run on hydrogen, thus removing the source of pollution, or on jet fuel (e.g., Jet-A fuel), in which case the better matching of the size of the engine to the cruise condition leads to a reduction in fuel consumption and emissions. Turning now to the figures, <FIG> illustrates an aircraft <NUM> in which the examples disclosed herein can be implemented. In the illustrated example, the aircraft <NUM> includes a fuselage <NUM>, a first wing <NUM> (a left wing) coupled to and extending from the fuselage <NUM>, a second wing <NUM> (a right wing) coupled to and extending from the fuselage <NUM>, and a tail section <NUM> (sometimes referred to as an empennage). The aircraft <NUM> may be a manned or unmanned aircraft.

The aircraft <NUM> includes an example hybrid-electric powertrain <NUM> that includes multiple engines for generating thrust to fly the aircraft <NUM>. In this example, the hybrid-electric powertrain <NUM> of the aircraft <NUM> includes a first gas turbine propulsion engine <NUM> carried by the first wing <NUM> and a second gas turbine propulsion engine <NUM> carried by the second wing <NUM>. In this example, the first and second gas turbine propulsion engines <NUM>, <NUM> are implemented as turboprop engines. However, in other examples, the first and second gas turbine propulsion engines <NUM>, <NUM> can be implemented as other types of engines, such as turbofan engines. Further, in the illustrated example, the hybrid-electric powertrain <NUM> of the aircraft <NUM> includes a plurality of electric propulsion units distributed along the wings <NUM>, <NUM> of the aircraft <NUM>. For example, as shown in <FIG>, the aircraft <NUM> includes a first electric propulsion unit <NUM> and a second electric propulsion unit <NUM> carried by the first wing <NUM> and a third electric propulsion unit <NUM> and a fourth electric propulsion unit <NUM> carried by the second wing <NUM>. The electric propulsion units <NUM>-<NUM> may also be referred to herein electric propulsion modules or nacelles. The gas turbine propulsion engines <NUM>, <NUM> are powered by hydrocarbon fuel, such as jet fuel (e.g., jet A-<NUM> fuel), whereas the electric propulsion units <NUM>-<NUM> are powered by electrical power. In other examples, the aircraft <NUM> can include more or fewer gas turbine propulsion engines and/or electric propulsion units and the engines can be arranged in other configurations. Further, while in this example the engines <NUM>-<NUM> are coupled to the wings <NUM>, <NUM>, in other examples one or more of the engines <NUM>-<NUM> can be disposed in other locations on the aircraft <NUM> (e.g., on the tail section <NUM>).

In some examples, the gas turbine propulsion engines <NUM>, <NUM> are used as the primary thrust engines, and the electric propulsion units <NUM>-<NUM> are used as secondary thrust engines. The electric propulsion units <NUM>-<NUM> can be activated during certain segments or phases of flight to supplement the thrust generated by the gas turbine propulsion engines <NUM>, <NUM>. For example, during certain phases such as take-off, climb, and landing where higher power is typically needed, the electric propulsion units <NUM>-<NUM> can be activated to produce additional thrust. Then, during other phases such as cruise, the electric propulsion units <NUM>-<NUM> can be deactivated, and the gas turbine propulsion units <NUM>, <NUM> can remain activated to propel the aircraft <NUM>. This enables the first and second gas turbine propulsion engines <NUM>, <NUM> to be sized smaller, because the electric propulsion units <NUM>-<NUM> can be used to provide additional power when needed. As such, the gas turbine propulsion engines <NUM>, <NUM> can be sized for optimal fuel efficiency at cruise, which accounts for a majority of the flight time, thereby reducing fuel consumption and emissions.

<FIG> is a schematic diagram of a portion of the example hybrid-electric powertrain <NUM>. In particular, the example hybrid-electric powertrain <NUM> shown in <FIG> shows the first gas turbine propulsion engine <NUM> and the first and second electric propulsion units <NUM>, <NUM>, but does not show the second gas turbine propulsion engine <NUM> and the third and fourth electric propulsion units <NUM>, <NUM>. However, it is understood that the hybrid-electric powertrain <NUM> can also include the second gas turbine propulsion engine <NUM> and the third and fourth electric propulsion units <NUM>, <NUM>, which can operate in a similar manner as the first gas turbine propulsion engine <NUM> and the first and second electric propulsion units <NUM>, <NUM>. Therefore, to avoid redundancy, a description of the second gas turbine propulsion engine <NUM> and the third and fourth electric propulsion units <NUM>, <NUM> is not provided.

As shown in <FIG>, the first gas turbine propulsion engine <NUM> includes a gas turbine engine <NUM> and a propulsor <NUM> (sometimes referred to as a disc actuator) coupled to and driven by the gas turbine engine <NUM> to produce thrust. The gas turbine engine <NUM> includes a drive shaft <NUM>. The propulsor <NUM> is coupled to (directly or indirectly) the drive shaft <NUM>. During operation, the gas turbine engine <NUM> drives (rotates) the propulsor <NUM> to produce forward thrust. In the illustrated example, the first gas turbine propulsion engine <NUM> includes a transmission <NUM> (e.g., a gearbox, a planetary gear system) that couples the drive shaft <NUM> to the propulsor <NUM>. The transmission <NUM> can change the rotational speed between the drive shaft <NUM> and the propulsor <NUM>. In this example, the propulsor <NUM> is implemented as a propeller. Therefore, in this example, the gas turbine engine <NUM> and the propulsor <NUM> form a turboprop engine. In other examples, the propulsor <NUM> can be implemented as fan of a turbofan engine. The propulsor <NUM> can be on the front of the first gas turbine propulsion engine <NUM> (known as a tractor configuration) or on the rear of the first gas turbine propulsion engine <NUM> (known as a pusher configuration). Also, the propulsor <NUM> can include two or more propulsors, such as two counter-rotating propellers.

In the illustrated example, the gas turbine engine <NUM> includes an engine casing <NUM> and turbomachinery within the casing <NUM>. In this example, the turbomachinery of the gas turbine engine <NUM> includes a compressor <NUM>, a combustion chamber <NUM>, a high pressure turbine (HPT) <NUM>, an inter-turbine burner (ITB) <NUM>, and a low pressure turbine (LPT) <NUM>. The compressor <NUM>, the HPT <NUM>, and the LPT <NUM> can include multiple stages. The compressor <NUM> and at least one of the HPT <NUM> or the LPT <NUM> are coupled by the drive shaft <NUM>. In some examples, the compressor <NUM> includes a high pressure compressor (HPC) that is coupled to and driven by the HPT <NUM> by a first drive shaft (sometimes referred to as a high pressure spool) and a low pressure compressor (LPC) that is coupled to a driven by the LPT <NUM> by a second drive shaft (sometimes referred to as low pressure spool). This arrangement is often referred to as a twin-spool configuration.

During operation of the gas turbine engine <NUM>, air enters the gas turbine engine <NUM> via an inlet <NUM> and flows to the compressor <NUM>. The compressor <NUM> increases the pressure of the air and provides the highly pressurized air to the combustion chamber <NUM>. The highly pressurized air is provided to the combustion chamber <NUM>, where fuel is injected and mixed with the highly pressurized air and ignited. The high energy airflow exiting the combustion chamber <NUM> turns the blades of the HPT <NUM> and LPT <NUM>. The HPT <NUM> and/or the LPT <NUM> rotate the drive shaft <NUM>, which rotates the blades of the compressor <NUM> and also drives the propulsor <NUM> (and, thus, produces forward thrust). Further, the heated air exiting the LPT <NUM> can be exhausted via an exhaust nozzle <NUM>, aftward, where it can produce forward thrust that propels the aircraft <NUM> in a forward direction.

In the illustrated example, the gas turbine engine <NUM> is powered by fuel from a fuel tank <NUM>. The fuel is injected into the combustion chamber <NUM> to run the gas turbine engine <NUM>. In some examples the fuel is jet fuel (e.g., Jet A, Jet A-<NUM>, Jet B). In other examples, other types of fuels can be used, such as hydrogen. Fuel flow is controlled by a valve <NUM>. In the illustrated example, the hybrid-electric powertrain <NUM> includes a controller <NUM> (e.g., an electronic engine controller (EEC), a processor, etc.). The controller <NUM> can operate the valve <NUM> to control the flow of fuel from the fuel tank <NUM> to the combustion chamber <NUM> to increase or decrease the speed of the gas turbine engine <NUM> and control the on/off operations of the first gas turbine propulsion engine <NUM>.

In the illustrated example, the first electric propulsion unit <NUM> includes an electric motor <NUM> (e.g., a brushless DC motor) and a propulsor <NUM> coupled to and driven by the electric motor <NUM>. In this example the propulsor <NUM> is implemented as a propeller. In other examples, the propulsor <NUM> can be implemented as a fan or other type of disc actuator. The electric motor <NUM> can be activated to drive the propulsor <NUM> to produce thrust. The first electric propulsion unit <NUM> also includes a controller <NUM> that controls the operation of the electric motor <NUM>, such as turning on or off the electric motor <NUM> and/or the adjusting the speed of the electric motor <NUM>. In the illustrated example, second electric propulsion engine unit similarly includes an electric motor <NUM>, a propulsor <NUM>, and a controller <NUM>, which operate the same as the first electric propulsion unit <NUM>.

To produce electrical power for the electric motors <NUM>, <NUM>, the example hybrid-electric powertrain <NUM> includes an electric generator <NUM>. The generator <NUM> can be driven by the gas turbine engine <NUM> of the first gas turbine propulsion engine <NUM>. The generator <NUM> is operably coupled to the drive shaft <NUM>. In some examples, the generator <NUM> is directly coupled to the drive shaft <NUM>. In other examples, the generator <NUM> can be indirectly coupled to the drive shaft <NUM>, such as through one or more offtake shafts or gear boxes. In the illustrated example, the generator <NUM> is shown as outside of the gas turbine engine <NUM> (e.g., downstream of the gas turbine engine <NUM>). However, in other examples, the generator <NUM> can be disposed within the casing <NUM> of the gas turbine engine <NUM> or in another position relative to the first gas turbine propulsion engine <NUM>.

In some examples, the generator <NUM> is only used to provide electrical power to the electric propulsion units <NUM>, <NUM> during certain phases or segments of flight. In other phases of flight, the generator <NUM> can be mechanically and/or electrically disconnected so as not to create a load on the gas turbine engine <NUM>. In the illustrated example, the hybrid-electric powertrain <NUM> includes a disconnect <NUM> between the generator <NUM> and the gas turbine engine <NUM>. In some examples the disconnect <NUM> is a mechanical device such as a clutch. The clutch can be operated by the controller <NUM> to connect the generator <NUM> to the drive shaft <NUM> or disconnect the generator <NUM> from the drive shaft <NUM>. Additionally or alternatively, the disconnect <NUM> can be an electromechanical device and/or electrical circuit that prevents the generator <NUM> from receiving power and producing current. The disconnect <NUM> can be controlled by the controller <NUM>.

In the illustrated example, the hybrid-electric powertrain <NUM> has a first power line <NUM> (e.g., one or more wires or cables) between the generator <NUM> and the first electric propulsion unit <NUM> and a second power line <NUM> between the generator <NUM> and the second electric propulsion unit <NUM>. The first and second power lines <NUM>, <NUM> supply electrical power from the generator <NUM> to the respective first and second electric propulsion units <NUM>, <NUM>.

As discussed above, in some examples, the gas turbine engine <NUM> includes the ITB <NUM>. The ITB <NUM> is an additional combustion chamber disposed between the HPT <NUM> and the LPT <NUM> to reheat the air exiting the HPT <NUM>. This reheated air has higher pressure for rotating the blades of the LPT <NUM>, thereby increasing the power output of the gas turbine engine <NUM>. The ITB <NUM> can be turned on or off (activated or deactivated) during certain phases of flight where additional powered is desired. The hybrid-electric powertrain <NUM> has a valve <NUM> that controls the flow of fuel from the fuel tank <NUM> to the ITB <NUM>. The controller <NUM> can open or close the valve <NUM> to control fuel flow to the ITB <NUM> to activate or deactivate the ITB <NUM>. In some examples, the controller <NUM> can also partially open or close the valve <NUM> to increase or decrease the fuel flow to the ITB <NUM> to increase or decrease power on demand. The ITB <NUM> does not affect the normal operation of the gas turbine engine <NUM> when the ITB <NUM> is deactivated. Therefore, the ITB <NUM> can be selectively activated during certain periods when higher power is demanded. In some examples, the gas turbine engine <NUM> can include multiple ITBs between the various stages of turbines.

In some examples, the hybrid-electric powertrain <NUM> can be operated in different modes of operation in which the electric propulsion units <NUM>, <NUM> are activated or deactivated. The hybrid-electric powertrain <NUM> may switch between the different modes of operation based on the phase or segment of flight and/or power demands. The controller <NUM> can control one or more devices (e.g., the valves <NUM>, <NUM>, the disconnect <NUM>, etc.) for causing the hybrid-electric powertrain <NUM> to switch between the different modes of operation.

For example, the hybrid-electric powertrain <NUM> can operate in a first mode of operation during periods of high (e.g., peak) power demand, such as during take-off, climb, and/or landing. During the first mode of operation, the first gas turbine propulsion engine <NUM> and the first and second electric propulsion units <NUM>, <NUM> are activated, which produces relatively high thrust. During the first mode of operation, the generator <NUM> is coupled to and driven by the gas turbine engine <NUM> to produce electrical power for powering the first and second electrical propulsion engines <NUM>, <NUM>. Further, during the first mode of operation, the controller <NUM> opens the valve <NUM> to activate the ITB <NUM>, which increases the power output of the gas turbine engine <NUM>. Not only does this increased power help to produce more thrust from the first gas turbine propulsion engine <NUM>, but the increased power is used to drive the generator <NUM> to produce the electrical power for the electric propulsion units <NUM>, <NUM>.

During periods of lower power demand, such as during cruise, the hybrid-electric powertrain <NUM> can operate in a second mode of operation. During the second mode of operation, the first gas turbine propulsion engine <NUM> is activated to produce thrust and the first and second electric propulsion units <NUM>, <NUM> are deactivated. Therefore, only the gas turbine propulsion engines <NUM>, <NUM> are active and produce thrust to propel the aircraft <NUM>. However, during cruise, less power is needed to maintain speed and altitude. When switching to the second mode of operation, the controller <NUM> can close the valve <NUM> to deactivate or turn off the ITB <NUM>, which helps conserve fuel. Further, the controller operates the disconnect <NUM> to disconnect the generator <NUM> from the gas turbine engine <NUM>, such that the generator <NUM> does not produce an unnecessary load on the gas turbine engine <NUM>. The hybrid-electric powertrain <NUM> can also operate in the second mode of operation during a loiter segment. During a loiter segment, the goal is to stay in the air using as little fuel as possible (irrespective of the amount of ground covered). Loiter speed is typically slower than cruise.

In some examples, the hybrid-electric powertrain <NUM> can also operate in a third mode of operation, which may be used during periods where shorter bursts of speed and power are desired, such as during dash. During the third mode of operation, the ITB <NUM> is activated to increase the power output of the gas turbine engine <NUM>, but the electric propulsion units <NUM>, <NUM> are deactivated. The increased power of the gas turbine engine <NUM> produces higher thrust during periods of higher power demand.

As can be appreciated, because the ITB <NUM> can be selectively activated to increase power on demand, the gas turbine engine <NUM> can be sized smaller so that power output without the ITB <NUM> activated matches the requirements for cruise and operates at peak efficiency. This improves fuel efficiency and reduces emissions. When the ITB <NUM> is activated, the power output is such that the sum of the power going to the propulsor <NUM> and the power to the electric propulsion units <NUM>, <NUM> meets the power demand during the highest demand flight segments (e.g., top-of-the-climb, take-off, emergency situations, etc.).

In the illustrated example of <FIG>, the hybrid-electric powertrain <NUM> does not include a battery for storing electrical power for the electric propulsion units <NUM>, <NUM>. Instead, the electric propulsion units <NUM>, <NUM> are only activated when the generator <NUM> is activated and produces electrical power (e.g., during the first mode of operation). This eliminates the need for batteries onboard the aircraft <NUM>. Batteries are typically very heavy and therefore add weight to the aircraft <NUM>. Also, transferring energy to and from a battery has inherent inefficiencies. Therefore, eliminating the need for batteries can reduce the weight of the system and improve efficiencies. However, in other examples, the hybrid-electric powertrain <NUM> can include one or more batteries to temporarily store electrical power for the electric propulsion units <NUM>, <NUM>.

<FIG> is a perspective view of the first wing <NUM> showing the first gas turbine propulsion engine <NUM> and the first and second electric propulsion units <NUM>, <NUM> coupled to the first wing <NUM>. The first wing <NUM> is shown as transparent to expose some internal parts and connections. The gas turbine engine <NUM>, the propulsor <NUM>, and the generator <NUM> are labeled in <FIG>. In the illustrated example, the gas turbine engine <NUM> and the generator <NUM> are disposed within a nacelle <NUM> that is coupled to the first wing <NUM>. Thus, the generator <NUM> can be incorporated into the nacelle <NUM> of the first gas turbine propulsion engine <NUM>. The propulsor <NUM>, the electric motor <NUM>, and the controller <NUM> of the first electric propulsion unit <NUM> are also labeled in <FIG>. The first electric propulsion unit <NUM> is integrated into and/or coupled to a nacelle <NUM> that is coupled by a pylon <NUM> to the first wing <NUM>. The propulsor <NUM>, the electric motor <NUM>, and the controller <NUM> of the second electric propulsion unit <NUM> are also shown in <FIG>. The second electric propulsion unit <NUM> is similarly integrated into and/or coupled a nacelle <NUM> that is coupled by a pylon <NUM> to the first wing <NUM>. In some examples, the first and second electric propulsion units <NUM>, <NUM> are modular and can be removed from or attached to the first wing <NUM>. This enables one or more of the electric propulsion units <NUM>, <NUM> to be removed in certain situations to decrease vehicle weight and drag.

As shown in <FIG>, the first and second electric propulsion units <NUM>, <NUM> are spaced apart along the first wing <NUM> outboard of the first gas turbine propulsion engine <NUM>. In some examples, spacing the electric propulsion units <NUM>, <NUM> along the first wing <NUM> is advantageous because the electric propulsion units <NUM>, <NUM>, when activated, produce a more even or uniform flow of air along the first wing <NUM>, which improves lift and control. While in this example the hybrid-electric powertrain <NUM> includes two electric propulsion units, the hybrid-electric powertrain <NUM> can include any number of electric propulsion units (e.g., three, four, five, etc.). The plurality of electric propulsion units can be spaced apart in various configurations on the first wing <NUM>.

As shown in <FIG>, the first and second power lines <NUM>, <NUM> are disposed in (e.g., routed through) the first wing <NUM> (e.g., in the wing box) between the generator <NUM> and the first and second electric propulsion units <NUM>, <NUM>. When the generator <NUM> is activated (e.g., during the first mode of operation), electrical power is supplied through the power lines <NUM>, <NUM> to the first and second electric propulsion units <NUM>, <NUM>. Also shown in <FIG> is an example cross power line <NUM>, which electrically couples the generator <NUM> to another generator on the second wing <NUM>. Therefore, if one of the gas turbine propulsion engines <NUM>, <NUM> and/or the generators is inoperable (e.g., losses power), the other generator can supply power to the electric propulsion units <NUM>, <NUM> on the other wing. Therefore, power can be easily distributed to the affected side of the aircraft <NUM>. In this example, the propulsor <NUM> of the first electric propulsion unit <NUM> is implemented as a propeller having a plurality of blades <NUM> (one of which is referenced in <FIG>). In some examples, the blades <NUM> are moveable (e.g., foldable) between a deployed position and a folded position to reduce drag. <FIG> shows the blades <NUM> in the deployed position, and <FIG> shows the blades <NUM> the folded position. In the folded position, the blades <NUM> are tilted or folded rearward relative to the deployed position. In other examples the blades <NUM> can be tiled or folded forward. The blades <NUM> can be moved to the deployed position during times when the electric propulsion units <NUM>, <NUM> are activated to produce thrust, such as during the first mode of operation (e.g., during take-off, climb, or landing). The blades <NUM> can be moved to the folded position during times when the electric propulsion units <NUM>, <NUM> are not activated, such as during the second and third modes of operation. This reduces drag caused by the electric propulsion units <NUM>, <NUM>. In some examples, the blades <NUM> are moved by an actuator that is controlled by the controller <NUM>. The other electric propulsion units <NUM>, <NUM>, <NUM> can similarly include foldable propeller blades. In other examples, the electric propulsion units <NUM>-<NUM> can include other means for reducing drag when not activated, such as feathering blades, or fan duct covers in the case of ducted solutions.

As used herein, the phrase "in communication," including variations thereof, encompasses direct communication and/or indirect communication through one or more intermediary components, and does not require direct physical (e.g., wired) communication and/or constant communication, but rather additionally includes selective communication at periodic intervals, scheduled intervals, aperiodic intervals, and/or one-time events.

As used herein, "processor circuitry" is defined to include (i) one or more special purpose electrical circuits structured to perform specific operation(s) and including one or more semiconductor-based logic devices (e.g., electrical hardware implemented by one or more transistors), and/or (ii) one or more general purpose semiconductor-based electrical circuits programmable with instructions to perform specific operations and including one or more semiconductor-based logic devices (e.g., electrical hardware implemented by one or more transistors). Examples of processor circuitry include programmable microprocessors, Field Programmable Gate Arrays (FPGAs) that may instantiate instructions, Central Processor Units (CPUs), Graphics Processor Units (GPUs), Digital Signal Processors (DSPs), XPUs, or microcontrollers and integrated circuits such as Application Specific Integrated Circuits (ASICs). For example, an XPU may be implemented by a heterogeneous computing system including multiple types of processor circuitry (e.g., one or more FPGAs, one or more CPUs, one or more GPUs, one or more DSPs, etc., and/or a combination thereof) and application programming interface(s) (API(s)) that may assign computing task(s) to whichever one(s) of the multiple types of processor circuitry is/are best suited to execute the computing task(s).

While an example manner of implementing the controller <NUM> is illustrated in <FIG>, one or more of the elements, processes, and/or devices illustrated in <FIG> may be combined, divided, re-arranged, omitted, eliminated, and/or implemented in any other way. Further, the example controller <NUM> of <FIG> may be implemented by hardware alone or by hardware in combination with software and/or firmware. Thus, the example controller <NUM> could be implemented by processor circuitry, analog circuit(s), digital circuit(s), logic circuit(s), programmable processor(s), programmable microcontroller(s), graphics processing unit(s) (GPU(s)), digital signal processor(s) (DSP(s)), application specific integrated circuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)), and/or field programmable logic device(s) (FPLD(s)) such as Field Programmable Gate Arrays (FPGAs). Further still, the example controller <NUM> of <FIG> may include one or more elements, processes, and/or devices in addition to, or instead of, those illustrated in <FIG>, and/or may include more than one of any or all of the illustrated elements, processes and devices.

A flowchart representative of example machine readable instructions, which may be executed to configure processor circuitry to implement the controller <NUM> of <FIG>, is shown in <FIG>. The machine readable instructions may be one or more executable programs or portion(s) of an executable program for execution by processor circuitry, such as the processor circuitry <NUM> shown in the example processor platform <NUM> discussed below in connection with <FIG>. The program may be exemplified in software stored on one or more non-transitory computer readable storage media such as a compact disk (CD), a floppy disk, a hard disk drive (HDD), a solid-state drive (SSD), a digital versatile disk (DVD), a Blu-ray disk, a volatile memory (e.g., Random Access Memory (RAM) of any type, etc.), or a non-volatile memory (e.g., electrically erasable programmable read-only memory (EEPROM), FLASH memory, an HDD, an SSD, etc.) associated with processor circuitry located in one or more hardware devices, but the entire program and/or parts thereof could alternatively be executed by one or more hardware devices other than the processor circuitry and/or exemplified in firmware or dedicated hardware. The machine readable instructions may be distributed across multiple hardware devices and/or executed by two or more hardware devices (e.g., a server and a client hardware device). For example, the client hardware device may be implemented by an endpoint client hardware device (e.g., a hardware device associated with a user) or an intermediate client hardware device (e.g., a radio access network (RAN)) gateway that may facilitate communication between a server and an endpoint client hardware device). Similarly, the non-transitory computer readable storage media may include one or more mediums located in one or more hardware devices. Further, although the example program is described with reference to the flowchart illustrated in <FIG>, many other methods of implementing the example controller <NUM> may alternatively be used. For example, the order of execution of the blocks may be changed, and/or some of the blocks described may be changed, eliminated, or combined. Additionally or alternatively, any or all of the blocks may be implemented by one or more hardware circuits (e.g., processor circuitry, discrete and/or integrated analog and/or digital circuitry, an FPGA, an ASIC, a comparator, an operational-amplifier (op-amp), a logic circuit, etc.) structured to perform the corresponding operation without executing software or firmware. The processor circuitry may be distributed in different network locations and/or local to one or more hardware devices (e.g., a single-core processor (e.g., a single core central processor unit (CPU)), a multi-core processor (e.g., a multi-core CPU, an XPU, etc.) in a single machine, multiple processors distributed across multiple servers of a server rack, multiple processors distributed across one or more server racks, a CPU and/or a FPGA located in the same package (e.g., the same integrated circuit (IC) package or in two or more separate housings, etc.).

The machine readable instructions described herein may be stored in one or more of a compressed format, an encrypted format, a fragmented format, a compiled format, an executable format, a packaged format, etc. Machine readable instructions as described herein may be stored as data or a data structure (e.g., as portions of instructions, code, representations of code, etc.) that may be utilized to create, manufacture, and/or produce machine executable instructions. For example, the machine readable instructions may be fragmented and stored on one or more storage devices and/or computing devices (e.g., servers) located at the same or different locations of a network or collection of networks (e.g., in the cloud, in edge devices, etc.). The machine readable instructions may require one or more of installation, modification, adaptation, updating, combining, supplementing, configuring, decryption, decompression, unpacking, distribution, reassignment, compilation, etc., in order to make them directly readable, interpretable, and/or executable by a computing device and/or other machine. For example, the machine readable instructions may be stored in multiple parts, which are individually compressed, encrypted, and/or stored on separate computing devices, wherein the parts when decrypted, decompressed, and/or combined form a set of machine executable instructions that implement one or more operations that may together form a program such as that described herein.

In another example, the machine readable instructions may be stored in a state in which they may be read by processor circuitry, but require addition of a library (e.g., a dynamic link library (DLL)), a software development kit (SDK), an application programming interface (API), etc., in order to execute the machine readable instructions on a particular computing device or other device. In another example, the machine readable instructions may need to be configured (e.g., settings stored, data input, network addresses recorded, etc.) before the machine readable instructions and/or the corresponding program(s) can be executed in whole or in part. Thus, machine readable media, as used herein, may include machine readable instructions and/or program(s) regardless of the particular format or state of the machine readable instructions and/or program(s) when stored or otherwise at rest or in transit.

As mentioned above, the example operations of <FIG> may be implemented using executable instructions (e.g., computer and/or machine readable instructions) stored on one or more non-transitory computer and/or machine readable media such as optical storage devices, magnetic storage devices, an HDD, a flash memory, a read-only memory (ROM), a CD, a DVD, a cache, a RAM of any type, a register, and/or any other storage device or storage disk in which information is stored for any duration (e.g., for extended time periods, permanently, for brief instances, for temporarily buffering, and/or for caching of the information). As used herein, the terms non-transitory computer readable medium, non-transitory computer readable storage medium, non-transitory machine readable medium, and non-transitory machine readable storage medium are expressly defined to include any type of computer readable storage device and/or storage disk and to exclude propagating signals and to exclude transmission media. As used herein, the terms "computer readable storage device" and "machine readable storage device" are defined to include any physical (mechanical and/or electrical) structure to store information, but to exclude propagating signals and to exclude transmission media. Examples of computer readable storage devices and machine readable storage devices include random access memory of any type, read only memory of any type, solid state memory, flash memory, optical discs, magnetic disks, disk drives, and/or redundant array of independent disks (RAID) systems. As used herein, the term "device" refers to physical structure such as mechanical and/or electrical equipment, hardware, and/or circuitry that may or may not be configured by computer readable instructions, machine readable instructions, etc., and/or manufactured to execute computer readable instructions, machine readable instructions, etc..

Thus, whenever a claim employs any form of "include" or "comprise" (e.g., comprises, includes, comprising, including, having, etc.) as a preamble or within a claim recitation of any kind, it is to be understood that additional elements, terms, etc., may be present without falling outside the scope of the corresponding claim or recitation. The term "and/or" when used, for example, in a form such as A, B, and/or C refers to any combination or subset of A, B, C such as (<NUM>) A alone, (<NUM>) B alone, (<NUM>) C alone, (<NUM>) A with B, (<NUM>) A with C, (<NUM>) B with C, or (<NUM>) A with B and with C. As used herein in the context of describing structures, components, items, objects and/or things, the phrase "at least one of A and B" is intended to refer to implementations including any of (<NUM>) at least one A, (<NUM>) at least one B, or (<NUM>) at least one A and at least one B. Similarly, as used herein in the context of describing structures, components, items, objects and/or things, the phrase "at least one of A or B" is intended to refer to implementations including any of (<NUM>) at least one A, (<NUM>) at least one B, or (<NUM>) at least one A and at least one B. As used herein in the context of describing the performance or execution of processes, instructions, actions, activities and/or steps, the phrase "at least one of A and B" is intended to refer to implementations including any of (<NUM>) at least one A, (<NUM>) at least one B, or (<NUM>) at least one A and at least one B. Similarly, as used herein in the context of describing the performance or execution of processes, instructions, actions, activities and/or steps, the phrase "at least one of A or B" is intended to refer to implementations including any of (<NUM>) at least one A, (<NUM>) at least one B, or (<NUM>) at least one A and at least one B.

The term "a" or "an" object, as used herein, refers to one or more of that object. The terms "a" (or "an"), "one or more", and "at least one" are used interchangeably herein. Furthermore, although individually listed, a plurality of means, elements or method actions may be implemented by, e.g., the same entity or object.

<FIG> is a flowchart representative of an example method <NUM> of changing the operating-mode of a hybrid-electric powertrain of an aircraft. The example method <NUM> is disclosed in connection with the hybrid-electric powertrain <NUM>. The example method <NUM> can be performed at least in part by the controller <NUM> of <FIG>, which controls the various devices (e.g., the disconnect <NUM>, the valves <NUM>, <NUM>, etc.) to cause the hybrid-electric powertrain <NUM> to operate in the different modes of operations. Therefore, the example method <NUM> may be representative of machine readable instructions and/or example operations that may be executed and/or instantiated by processor circuitry.

At block <NUM>, the hybrid-electric powertrain <NUM> is operating in the first mode of operation during a first segment of flight. The first segment of flight may correspond to a segment where higher (e.g., peak) power is demanded, such as during take-off, climb, or landing. In the first mode of operation, the gas turbine engine <NUM> is active and drives the propulsor <NUM> to generate thrust. Additionally, the first and second electric propulsion units <NUM>, <NUM> are active to produce additional thrust. During the first mode of operation, the generator <NUM> is mechanically coupled to and driven by the drive shaft <NUM>. For example, the controller <NUM> can control the disconnect <NUM> to connect the generator <NUM> to the drive shaft <NUM>. The generator <NUM> produces electrical power that powers the electric motors <NUM>, <NUM> of the first and second electric propulsion units <NUM>, <NUM>. In some examples, during the first mode of operation, the ITB <NUM> is activated. For example, the controller <NUM> can open the valve <NUM> to enable fuel to flow to the ITB <NUM>. This increases the power output of the gas turbine engine <NUM>, which results in high thrust and additional power for driving the generator <NUM>. At block <NUM>, the hybrid-electric powertrain <NUM> operates in the second mode of operation during a second segment of flight. The second segment of flight may correspond to a segment where lower power is demanded, such as during cruise.

In the second mode of operation, the gas turbine engine <NUM> is active and drives the propulsor <NUM> to generate thrust. However, the first and second electric propulsion units <NUM>, <NUM> are deactivated. The controller <NUM> can activate the disconnect <NUM> to disconnect the generator <NUM> from the gas turbine engine <NUM>, so that the generator <NUM> does not create an unnecessary load on the gas turbine engine <NUM>. During the second mode of operation, the ITB <NUM> is deactivated. The controller <NUM> can close the valve <NUM> to shut off fuel flow to the ITB <NUM>. At block <NUM>, the hybrid-electric powertrain <NUM> operates in the third mode of operation during a third segment of flight. The third segment of flight may correspond to a segment where high power is needed for a relatively short period of time, such as during a dash maneuver. During the third mode of operation, the ITB <NUM> is activated to increase the output power of the first gas turbine propulsion engine <NUM>. This provides increased thrust that may be desired to perform the dahs maneuver. However, during the third mode of operation, the electric propulsion units <NUM>, <NUM> remain deactivated.

In some examples, when the electric propulsion units <NUM>, <NUM> are not activated, such as during the second and third modes of operation, the blades <NUM> of the electric propulsion units <NUM>, <NUM> can be moved to the folded position to reduce drag. The controller <NUM> can activate one or more actuators to move the blades <NUM> to the folded position. Then, when the electric propulsion units <NUM>, <NUM> are to be activated, such as during the first mode of operation, the controller <NUM> can activate the actuator(s) to move the blades <NUM> back to the deployed position.

In some examples, the controller <NUM> can automatically control the hybrid-electric powertrain <NUM> to switch between the different modes of operation. For example, the controller <NUM> can detect (e.g., via one or more sensors and/or input(s)) the segment of flight. Based on the segment of flight, the controller <NUM> can switch the hybrid-electric powertrain <NUM> between the different modes of operation. For example, during take-off, climb, and landing, the hybrid-electric powertrain can be operated in the first mode of operation. Then, during cruise, the hybrid-electric powertrain <NUM> can be operated in the second mode of operation. During a dash maneuver, the hybrid-electric powertrain <NUM> can be operated in the third mode of operation. Additionally or alternatively, the controller <NUM> can switch between the different modes of operation based on pilot input. For example, if the pilot requests additional power, the hybrid-electric powertrain <NUM> can be operated in the first or third modes of operation, and during times of less power demand, the hybrid-electric powertrain <NUM> can be operated in the second mode of operation.

<FIG> is a block diagram of an example processor platform <NUM> structured to execute and/or instantiate the machine readable instructions and/or the operations of <FIG> to implement the controller <NUM> of <FIG>. The processor platform <NUM> can be, for example, a server, a personal computer, a workstation, a self-learning machine (e.g., a neural network), a mobile device (e.g., a cell phone, a smart phone, a tablet such as an iPad™), a personal digital assistant (PDA), an Internet appliance, a DVD player, a CD player, a digital video recorder, a Blu-ray player, a gaming console, a personal video recorder, a set top box, a headset (e.g., an augmented reality (AR) headset, a virtual reality (VR) headset, etc.) or other wearable device, or any other type of computing device.

The processor platform <NUM> of the illustrated example includes processor circuitry <NUM>. The processor circuitry <NUM> of the illustrated example is hardware. For example, the processor circuitry <NUM> can be implemented by one or more integrated circuits, logic circuits, FPGAs, microprocessors, CPUs, GPUs, DSPs, and/or microcontrollers from any desired family or manufacturer. The processor circuitry <NUM> may be implemented by one or more semiconductor based (e.g., silicon based) devices. In this example, the processor circuitry <NUM> implements the controller <NUM>.

The processor circuitry <NUM> of the illustrated example includes a local memory <NUM> (e.g., a cache, registers, etc.). The processor circuitry <NUM> of the illustrated example is in communication with a main memory including a volatile memory <NUM> and a non-volatile memory <NUM> by a bus <NUM>. The volatile memory <NUM> may be implemented by Synchronous Dynamic Random Access Memory (SDRAM), Dynamic Random Access Memory (DRAM), RAMBUS® Dynamic Random Access Memory (RDRAM®), and/or any other type of RAM device. Access to the main memory <NUM>, <NUM> of the illustrated example is controlled by a memory controller <NUM>.

The processor platform <NUM> of the illustrated example also includes interface circuitry <NUM>. The interface circuitry <NUM> may be implemented by hardware in accordance with any type of interface standard, such as an Ethernet interface, a universal serial bus (USB) interface, a Bluetooth® interface, a near field communication (NFC) interface, a Peripheral Component Interconnect (PCI) interface, and/or a Peripheral Component Interconnect Express (PCIe) interface. In the illustrated example, one or more input devices <NUM> are connected to the interface circuitry <NUM>. The input device(s) <NUM> permit(s) a user to enter data and/or commands into the processor circuitry <NUM>. The input device(s) <NUM> can be implemented by, for example, an audio sensor, a microphone, a camera (still or video), a keyboard, a button, a mouse, a touchscreen, a track-pad, a trackball, an isopoint device, and/or a voice recognition system.

One or more output devices <NUM> are also connected to the interface circuitry <NUM> of the illustrated example. The output device(s) <NUM> can be implemented, for example, by display devices (e.g., a light emitting diode (LED), an organic light emitting diode (OLED), a liquid crystal display (LCD), a cathode ray tube (CRT) display, an in-place switching (IPS) display, a touchscreen, etc.), a tactile output device, a printer, and/or speaker. The interface circuitry <NUM> of the illustrated example, thus, typically includes a graphics driver card, a graphics driver chip, and/or graphics processor circuitry such as a GPU.

The interface circuitry <NUM> of the illustrated example also includes a communication device such as a transmitter, a receiver, a transceiver, a modem, a residential gateway, a wireless access point, and/or a network interface to facilitate exchange of data with external machines (e.g., computing devices of any kind) by a network <NUM>. The communication can be by, for example, an Ethernet connection, a digital subscriber line (DSL) connection, a telephone line connection, a coaxial cable system, a satellite system, a line-of-site wireless system, a cellular telephone system, an optical connection, etc..

The processor platform <NUM> of the illustrated example also includes one or more mass storage devices <NUM> to store software and/or data. Examples of such mass storage devices <NUM> include magnetic storage devices, optical storage devices, floppy disk drives, HDDs, CDs, Blu-ray disk drives, redundant array of independent disks (RAID) systems, solid state storage devices such as flash memory devices and/or SSDs, and DVD drives.

The machine readable instructions <NUM>, which may be implemented by the machine readable instructions of <FIG>, may be stored in the mass storage device <NUM>, in the volatile memory <NUM>, in the non-volatile memory <NUM>, and/or on a removable non-transitory computer readable storage medium such as a CD or DVD.

Claim 1:
A hybrid-electric powertrain (<NUM>) for an aircraft (<NUM>), the hybrid-electric powertrain (<NUM>) comprising:
a gas turbine propulsion engine (<NUM>) including a first propulsor (<NUM>) and a gas turbine engine (<NUM>) to drive the first propulsor (<NUM>) to produce thrust;
a generator (<NUM>) operably coupled to a drive shaft (<NUM>) of the gas turbine engine (<NUM>); and
an electric propulsion unit (<NUM>) including a second propulsor (<NUM>) and an electric motor (<NUM>) to drive the second propulsor (<NUM>) to produce thrust, wherein the hybrid-electric powertrain is configured such that,
during a first mode of operation, the gas turbine propulsion engine (<NUM>) and the electric propulsion unit (<NUM>) are activated to produce thrust, and, during the first mode of operation, the generator (<NUM>) is driven by the gas turbine engine (<NUM>) to produce electrical power to power the electric propulsion unit (<NUM>), and
during a second mode of operation, the gas turbine propulsion engine (<NUM>) is activated to produce thrust and the electric propulsion unit (<NUM>) is deactivated;
wherein the gas turbine engine (<NUM>) includes an inter-turbine burner (<NUM>); and
wherein the hybrid-electric powertrain is configured such that, during the first mode of operation, the inter-turbine burner (<NUM>) is activated to increase power output of the gas turbine engine (<NUM>); and, during the second mode of operation, the inter-turbine burner (<NUM>) is deactivated.