Patent Description:
An aircraft such as a conventional fixed-wing aircraft typically includes one or more engines, such as turbofan jet engines to provide thrust. Such engines can be selected based on factors such as thrust requirements of the aircraft, weight of the engine and fuel burn rate of the engine. Prior art documents include <CIT>, which describes an aircraft with an electric propulsor which includes an electric motor, a fan unit, and a thrust control system positioned downstream of and coupled to the fan unit. The electric motor converts electrical power to mechanical rotation to rotationally drive the fan unit and create an air stream directed towards the thrust control system. <CIT> describes an aircraft with an electric propulsion arrangement which includes a fuselage, a wing system attached to the fuselage, and a tail unit attached to a rear part of the fuselage. The electric propulsion arrangement is arranged on each side of the fuselage, an electrical energy generator and electricity storage and supply devices are arranged substantially along a longitudinal axis of symmetry of the fuselage. The aircraft thus incorporates a hybrid motorization. <CIT> describes apparatus for controlling power distribution in an electrical aircraft propulsion unit having a plurality of rotatable adjustable pitch blades provided with a pitch adjusting mechanism. An electrical machine is connected to the electrical propulsion unit so as to provide electrical power when in use and a control system determines the required propulsion and adjusts the pitch angle of the blades so as to increase or decrease the propulsion provided. <CIT> describes an aircraft having a distributed electric propulsion system. The system includes a turbo shaft engine that drives one or more generators. The generator provides power to a plurality of ducted fans driven by an electric motor integrated with the aircraft's wings. The wings can be pivotally attached to the fuselage, thereby allowing for vertical take-off and landing.

According to an aspect, there is provided an aircraft comprising a system for varying excess thrust of said aircraft in accordance with appended claim <NUM>.

In some embodiments, the first fan and the second fan are coplanar in a single plane that is generally parallel to a transverse plane containing a pitch axis of the aircraft and a yaw axis of the aircraft.

In some embodiments, the first fan and the second fan are bilaterally symmetrical in a plane of symmetry containing the roll axis of the aircraft and a yaw axis of the aircraft.

In some embodiments, the system further comprises fairing channels surrounding the first fan to direct air towards the first air flow path and surrounding the second fan to direct air towards the second air flow path.

In some embodiments, the first electric fan and the second electric fan are driven by an electric motor.

In some embodiments, the electric motor is driven by electric energy from an electric generator of an auxiliary power unit.

In some embodiments, the system further comprises an inlet conduit in fluid communication with the auxiliary power unit to direct air to the auxiliary power unit.

In some embodiments, the electric motor is driven by electric energy supplied by a battery.

In some embodiments, the electric motor is operable as a generator to convert mechanical energy into electric energy to supply to the battery.

In some embodiments, the electric motor is driven by electric energy from an electric generator of one or more engines of the aircraft.

In some embodiments, the system further comprises a controller to control the electric motor.

In some embodiments, the first electric fan and the second electric fan are ducted fans.

In some embodiments, the first axis and the second axis are generally parallel to the roll axis of the aircraft.

In some embodiments, the first electric fan and the second electric fan are fully disposed within a distance from the surface of the aircraft that is less than a boundary layer thickness formed from the surface of the aircraft during take-off and cruising of the aircraft, the boundary layer thickness a distance from the surface to a point at which a velocity of a local flow is ninety-nine percent of a velocity of a surrounding freestream flow.

In some embodiments, the first electric fan and the second electric fan are disposed adjacent a tail cone of the aircraft.

In some embodiments, the system further comprises: a first gate actuable between a closed position, to direct a forward flow of the first air flow in the first flow path from a forward end of the aircraft to the aft end of the aircraft, and an open position, to direct a reverse flow of the first air flow in the first flow path from the aft end of the aircraft to the forward end of the aircraft; and a second gate actuable between a closed position, to direct a forward flow of the second air flow in the second flow path from a second end of the aircraft to the aft end of the aircraft, and an open position, to direct a reverse flow of the second air flow in the second flow path from the aft end of the aircraft to the forward end of the aircraft.

In some embodiments, the system further comprises: a third electric fan rotatable about a third axis for directing a third air flow along a third air flow path; a fourth electric fan rotatable about a fourth axis for directing a fourth air flow along a fourth air flow path; a fifth electric fan rotatable about a fifth axis for directing a fifth air flow along a fifth air flow path; and a sixth electric fan rotatable about a sixth axis for directing a sixth air flow along a sixth air flow path, wherein the third electric fan, the fourth electric fan, the fifth electric fan, and the sixth electric fan are disposed radially about the roll axis of the aircraft and adjacent the aft end of the aircraft and configured to intake boundary layer air to form the third air flow, the fourth air flow, the fifth air flow and the sixth air flow, each of the first axis, the second axis, the third axis, the fourth axis, the fifth axis, and the sixth axis are different from each other, and each of the first air flow path, the second air flow path, the third air flow path, the fourth air flow path, the fifth air flow path, and the sixth air flow path are fluidly isolated from each other.

According to another aspect, there is provided an aircraft comprising a first engine, a second engine and a system as described herein.

In some embodiments, the system is configured to generate forward takeoff thrust to supplement thrust generated by the first engine and the second engine during takeoff of the aircraft.

In some embodiments, system is configured to generate forward cruise thrust to supplement thrust generated by the first engine and the second engine during cruise of the aircraft.

Other features will become apparent from the drawings in conjunction with the following description.

In the figures which illustrate example embodiments,.

The design of a new aircraft, or upgrade of an existing aircraft, can involve the selection of engines for traditional propulsion. Engines can be selected based on the operating requirements of the aircraft and to optimize the factors such as thrust requirements of the aircraft, weight of the engine, fuel burn rate of the engine, and cost.

However, in practice, engines are selected on the basis of the types of engines that exist or are available from engine manufacturers for a particular size of aircraft. Certain factors may not be optimized. For example, often the engine selected is too big for most needs of the aircraft, but necessary to meet certain thrust requirements of the aircraft, such as static takeoff thrust. Thus, a non-optimal engine is used, which may have to be de-rated (to limit power) to produce less thrust, and as a larger engine, weighs more. A larger engine can further require additional structure to support the engine on an aircraft.

Thus, traditional design using existing minimum thrust-compliant engines can result in an engine that is overweight, which has a compounding effect on the design of the aircraft.

Systems and methods for varying excess thrust of an aircraft and thereby controlling excess thrust, as described herein, can provide flexibility in engine selection for an aircraft.

Excess thrust of an aircraft can be represented as a vector quantity having magnitude and direction, and can be defined as the vector difference between the thrust vector T minus drag vector D of the aircraft.

During operation of an aircraft, excess thrust can be varied to modify climb and descent of the aircraft, and control of the flight path.

Systems and methods described herein can generate forward thrust, allowing for selection of engines for an aircraft that are smaller and lighter, or provide less takeoff thrust, but offer optimum weight and fuel burn by supplementing engine thrust with additional forward thrust. Thus, smaller engines that have reduced weight and volume can be used, reducing cost.

Conveniently, a smaller engine can also allow for the use of a smaller vertical stabilizer or vertical tail, also reducing cost and weight. A reduced rudder height, which can be attach at the same attachment points on a vertical tail, can further reduce cost and weight.

Thus, an aircraft can have a reduced operating empty weight (OEW) and improved mission fuel burn.

In addition, forward thrust generated by systems described herein can also provide climb capability if an aircraft engine fails.

Systems and methods described herein can also generate reverse thrust to act against the forward travel of the aircraft, providing deceleration or reverse travel. In an example, at high altitude and descent, reverse thrust can be applied to descend without using engines and deploying speed brakes.

Forward or reverse thrust can be applied along a centerline of an aircraft.

Systems and methods described herein can also control drag caused by the interaction and contact of an aircraft as it moves through fluid such as air. In particular, a system can increase or decrease drag, sometimes referred to as profile drag, defined as the sum of pressure drag (form drag) and skin friction (skin drag).

Pressure drag is caused by increased pressure on the front and decreased pressure on the rear of an aircraft moving through air. Skin friction is caused by the interaction between molecules of the air and the solid surface of the aircraft.

During movement of an aircraft, a boundary layer is formed in the immediate vicinity of the aircraft surface where the effects of viscosity are significant. The collision of molecules near the surface of the aircraft creates a thin layer (boundary layer) of fluid near the surface in which the velocity changes from zero at the surface to the free stream ("clean" air flow) value away from the surface. Boundary layers can include laminar flow (layered) or turbulent flow (disordered).

The boundary layer adds to the effective thickness of the aircraft body, through the displacement thickness, hence increasing the pressure drag. Secondly, the shear forces at the surface of the aircraft create skin friction drag.

Systems and methods described herein can reduce drag by ingesting boundary layer air that is slower moving, and redirecting and accelerating it, for example, to the same speed as the aircraft, as well as reducing pressure differential between front and rear surfaces of the aircraft.

In an example, drag can be increased at high altitude and descent, to descend without using engines and deploying speed brakes.

<FIG> is a side view of an aircraft <NUM> which can include a system <NUM> for varying excess thrust of aircraft <NUM>, as described herein. Aircraft <NUM> can be a fixed-wing aircraft comprising one or more engines <NUM>. Aircraft <NUM> can comprise wings <NUM>, fuselage <NUM> and empennage <NUM> including a tail cone <NUM> and a vertical stabilizer or vertical tail <NUM>. Aircraft <NUM> can be any type of aircraft such as corporate, private, commercial and passenger aircraft suitable for civil aviation. For example, aircraft <NUM> can be a (e.g., ultra-long range) business jet, a twin-engine turboprop airliner or a regional jet airliner.

Aircraft <NUM> is rotatable about three axes: a yaw axis YA extending vertically (up and down) about which aircraft <NUM> noses left or right; a pitch axis PA extending from wing to wing (side-to-side) about which aircraft <NUM> noses up or down; and a roll axis RA extending from nose to tail (front-to-rear) about which aircraft <NUM> rotates.

Aircraft <NUM> can include an auxiliary power unit (APU) <NUM> (sometimes called "auxiliary power system"), including a gas turbine engine to supply electric and pneumatic power to aircraft systems as an auxiliary or secondary source of power.

<FIG> is a partial perspective view of aircraft <NUM>, including system <NUM>, in accordance with an embodiment, disposed in tail cone <NUM> of the empennage <NUM> region of aircraft <NUM>. System <NUM> is operable, among other things, to draw a forward flow <NUM> of air from an environment, such as a boundary layer, through one or more inlets <NUM> along a flow channel <NUM> and exit at one or more outlets <NUM>, which can be defined by a duct or conduit <NUM> formed, for example, of fairings or casings, for generating thrust.

System <NUM> can include a fan <NUM>, such as an electric fan which can be driven by a motor such as an electric motor <NUM>. In some embodiments, fan <NUM> is a ducted fan.

In some embodiments, fan <NUM> includes one or more rotors <NUM> such as an impeller and can include rotor blades or airfoils fixed on a spindle to impel air. The impeller can be used to increase or decrease pressure and flow of a fluid. In some embodiments, an impeller can be a radial flow impeller (flow enters axially and leaves radially) or an axial flow impeller (flow enters axially and leaves axially).

In some embodiments, fan <NUM> includes one or more stators <NUM> having stator blades or circumferentially spaced apart struts. Once air is impelled by the rotor blades, it can pass through stator blades. The stator blades are fixed, for example, to flow channel <NUM>, and act as diffusers to partially convert high velocity air into high pressure. Each rotor <NUM> and stator <NUM> pair can form a compressor stage.

Fan <NUM> can be powered by a power source to add energy to a moving fluid (such as air, and in particular, boundary layer air of aircraft <NUM>) by converting electrical energy to mechanical energy (such as by way of electric motor <NUM>) to rotate an impeller or blades of fan <NUM> to impel air, accelerating the airflow to generate thrust for aircraft <NUM>.

In some embodiments, fan <NUM> is disposed adjacent roll axis RA. In an example, a single fan <NUM> can be located along roll axis RA.

In some embodiments, fan <NUM> is rotatable about an axis that is generally parallel to a centerline (such as roll axis RA). In some embodiments, fan <NUM> rotates about an axis that is canted or at an angle to a centerline (such as roll axis RA).

In an example, fan <NUM> is rotatable in a first direction to impel air towards the rear of aircraft <NUM>, and rotatable in a second direction, opposite the first direction, to impel air towards the front of aircraft <NUM>.

Fan <NUM> can also operate as a turbine to extract energy from a moving fluid (such as air, in particular, in a boundary layer of aircraft <NUM>).

Fan <NUM> can extract energy by converting mechanical energy of the moving fluid (air) rotating blades of fan <NUM> to electrical energy, for example, by way of electric motor <NUM> operating as a generator, as described in further detail below, and such electrical energy can be stored, for example, in a battery or for use by an electrical system of aircraft <NUM>.

In some embodiments, system <NUM> can include multiple fans <NUM>, including a first electric fan and a second electric fan, which can to provide flexibility and avoid a single point of failure. In some embodiments, system <NUM> includes six fans <NUM>, namely, a further third electric fan, fourth electric fan, fifth electric fan, and sixth electric fan. In other embodiments, system <NUM> can include other suitable numbers and configurations of fans <NUM>.

Each fan <NUM> can rotate about one or more same or different axes. In some embodiments, a first electric fan <NUM> is rotatable about a first axis for directing a first air flow along a first air flow path, defined by a flow channel <NUM> as described below, and a second electric fan <NUM> is rotatable about a second axis different from the first axis for directing a second air flow along a second air flow path, defined by another flow channel <NUM> as described below, fluidly isolated from the first air flow path. The first axis and the second axis can be generally parallel to roll axis RA of aircraft <NUM>.

One or more fans <NUM> can be disposed radially about roll axis RA of aircraft <NUM> and adjacent an aft end of the aircraft <NUM>, such as adjacent tail cone <NUM>. In some embodiments, one or more fans <NUM> fan are configured to intake boundary layer air to form the air flow, as described in further detail below.

One or more fans <NUM> can be operated as symmetrical pairs, which can balance the application of thrust or modification of drag about aircraft <NUM>.

<FIG> is a cross-sectional view taken along lines 3A-3A of system <NUM>, illustrating an embodiment having six fans <NUM>.

In some embodiments, one or more fans <NUM> can intersect a generally vertical plane, or be offset or canted from vertical, for example, in alignment with an aft spar in tail cone <NUM> of aircraft <NUM>.

In some embodiments, one or more fans <NUM> are coplanar in a single plane that is generally parallel to a transverse plane containing pitch axis PA of aircraft <NUM> and yaw axis YA of aircraft <NUM>.

One or more fans <NUM> can be spaced to accommodate cooling between fans <NUM>.

In some embodiments, one or more fans <NUM> of system <NUM> can be reflectionally symmetrical or bilaterally symmetrical in a plane of symmetry, such as plane SP shown in <FIG>, containing roll axis RA and yaw axis YA of aircraft <NUM>.

In some embodiments, fairing <NUM> (forming fairing channels) or other structural features can surround fans <NUM>, to direct air towards an air flow path for each fan <NUM>, forming separate and independent flow channels <NUM> that are fluidly isolated and each fan <NUM> can be fluidly isolated from each other. Conveniently, isolating flow channels <NUM> can allow for less interference with other flow channels <NUM> if a fan <NUM> or other component of flow channel <NUM> fails. An example flow channel <NUM> is shown in further detail in <FIG> and <FIG>.

In some embodiments, multiple flow channels <NUM> can direct flow to a single fan <NUM>.

Other suitable fan configurations are contemplated to accommodate thrust for supplementing engines <NUM> of aircraft <NUM>.

System <NUM>, in particular, components of said system such as fans <NUM>, can be covered by a skin surface <NUM> formed of a suitable material such as aluminum, aluminum alloy, or composite materials.

In some embodiments, skin surface <NUM> surrounding fans <NUM> can have a diameter larger than the skin of a traditional tail cone <NUM>.

Skin surface <NUM> can be radially outward of the trajectory of fuselage <NUM> skin to allow inlets <NUM> to conduit (intake or outtake) air.

At a distal end of flow channel <NUM>, opposite inlets <NUM>, outlets <NUM> conduit (intake or outtake) flow to the environment. Forward flow <NUM> can be directed to an exhaust stream to exit at a rear of aircraft <NUM> by way of one or more exhaust outlets <NUM>. Outlets <NUM> can be separate and independent for each flow channel <NUM>, for example, separated by fairings, as shown in <FIG> is a cross-sectional view taken along lines 3B-3B of system <NUM>, illustrating exhaust outlets <NUM> for each flow channel <NUM>.

In some embodiments, system <NUM> includes an actuable gate such as a reverse flow door <NUM> as part of a flow direction system <NUM> for each fan <NUM>, as described in further detail with reference to <FIG> and <FIG>, below.

<FIG> is a schematic side view of forward flow <NUM> drawn in direction A through a flow channel <NUM> of system <NUM>, with reverse flow door <NUM> in a closed position, in accordance with an embodiment. <FIG> is a schematic side view of reverse flow <NUM> of flow channel <NUM> with reverse flow door <NUM> in an open position, in accordance with an embodiment. Each of multiple fans <NUM> of system <NUM> can be disposed in a separate flow channel <NUM> as described herein.

Forward flow <NUM> can be accelerated by fan <NUM> rotating in the first direction to impel air towards outlet <NUM> the rear of aircraft <NUM>. The acceleration of forward flow <NUM> generates forward thrust applied to aircraft <NUM>.

Reverse flow <NUM> can be accelerated by fan <NUM> rotating in the second direction to impel air towards inlet <NUM> and the front of aircraft <NUM>. The acceleration of reverse flow <NUM> generates reverse thrust applied to aircraft <NUM>.

As shown in <FIG> and <FIG>, a fan <NUM> can have multiple rotors <NUM> and stators <NUM>.

Flow direction system <NUM> includes a reverse flow door <NUM> that is rotatably attached to conduit <NUM> and actuable, for example, rotatable using a suitable actuator, between a closed position as shown in <FIG> and an open position as shown in <FIG>.

In some embodiments, reverse flow door <NUM> can operate in a position-based detection of direction of rotation of fan <NUM>, for example, a rotor <NUM> of fan <NUM>. For example, reverse flow door <NUM> can operate in a closed position, for example, as shown in <FIG>, when fan <NUM> rotates in a direction to direct air flow in direction A, as shown in <FIG>. Reverse flow door <NUM> can operate in an open position, for example, as shown in <FIG>, when fan <NUM> rotates in an opposite direction to direct air flow in direction B, as shown in <FIG>.

In some embodiments, the direction of rotation of fan <NUM> is detected by a controller to selectively actuate reverse flow door <NUM> between an open and closed position.

In a closed position, as shown in <FIG>, reverse flow door <NUM> covers, and in some embodiments, seals, opening <NUM> in conduit <NUM> to direct forward flow <NUM> in a flow path from a forward end of aircraft <NUM>, such as inlet <NUM> to an aft end of aircraft <NUM>, such as outlet <NUM>.

In some embodiments, reverse flow door <NUM> is rotatable, for example, in direction C shown in <FIG>, to an open position to direct reverse flow <NUM> in a flow path in direction <NUM> through flow channel <NUM> from an aft end of aircraft <NUM>, such as opening <NUM> to a forward end of aircraft <NUM>, such as inlet <NUM>.

Instead of drawing air from an exhaust plane formed by outlets <NUM>, door <NUM> can provide a pathway through opening <NUM> for air flow to enter flow channel <NUM> to generate a reverse flow <NUM>, and therefore can allow for generation of further reverse thrust.

Reverse flow doors <NUM> can also prevent backflow between flow channels <NUM>, that could affect flow speed and direction, by allowing any overpressure or underpressure to be vented to outside air.

In some embodiments, exhaust of forward flow <NUM> for each fan <NUM> can exhaust to a common outlet or exit.

In some embodiments, exhaust of reverse flow <NUM> for each fan <NUM> can exhaust to a common outlet or exit.

<FIG> is a schematic side view of fan <NUM>, including a rotor <NUM> and a stator <NUM>, rotatably coupled and drive by an electric motor <NUM>, in accordance with an embodiment.

As shown in <FIG>, a power input can be supplied to electric motor <NUM> to drive electric motor <NUM> and in turn rotate fan <NUM>. Generated heat can be exhausted to exit flow channel <NUM>, for example, by way of outlet <NUM>.

<FIG> is a partial front schematic view of system <NUM>, in accordance with an embodiment. As shown in <FIG>, system <NUM> includes an arrangement of six electrically-powered fans <NUM> disposed in a cavity in a tail cone <NUM> within aircraft <NUM>, for example, around a canted bulkhead <NUM>.

Canted bulkhead <NUM> can be a reinforced structure within tail cone <NUM>, to which components (such as fans <NUM>) can be affixed. Canted bulkhead <NUM> can further act as a fire barrier, for example, for an auxiliary power unit such as APU <NUM>.

In some embodiments, system <NUM>, including components such as fans <NUM>, forms a self-contained unit within tail cone <NUM>.

In some embodiments, components of system <NUM> such as fans <NUM> are disposed adjacent a rear or aft spar of aircraft <NUM>. In some embodiments, fans <NUM> can be arranged to intersect with a plane formed by an aft spar of vertical tail <NUM> that can serve as a fire wall for APU <NUM>.

In some embodiments, fans <NUM> can be disposed rearward of aft spar, for example, in a cavity.

<FIG> also illustrates APU inlet conduits <NUM> in fluid communication with an auxiliary power unit such as APU <NUM> that intake air to direct air to the auxiliary power unit.

Fans <NUM> and APU inlet conduits <NUM> can be separated by fairing, such that each is fluidly isolated.

In some embodiments, components of system <NUM>, in particular, fans <NUM> are disposed rear of pylons of aircraft <NUM>.

In some embodiments, a fuel tank in tail cone <NUM> of aircraft <NUM> can be displaced or removed to provide space to dispose fans <NUM> closer to a centerline of aircraft <NUM>, thus resulting in a smaller diameter of skin surface <NUM>. In some embodiments, aircraft <NUM> does not require excess fuel from such a fuel tank due to better fuel efficiency achieved by system <NUM>.

System <NUM> can also include one or more electric motors <NUM>. In some embodiments, one or more fans <NUM> are electrically powered and can be rotatably coupled and driven by one or more electric motors <NUM>.

In some embodiments, electric motor <NUM> is an AC motor, for example, an induction motor or an asynchronous motor, driven from an AC current source, such as three-phase, <NUM> AC current produced by an electric generator.

In some embodiments, electric motor <NUM> is a DC motor, driven by a DC current source, such as DC current supplied by a generator, or supplied by, for example, a battery, accumulator, or external power source, such as a ground power unit, or DC current supplied by a suitable rectifier, such as a transformer rectifier unit, to convert AC current generated by a generator to DC, for example, <NUM> V DC current.

Electric motor <NUM> can be integral with one or more fans <NUM>, and can be connected to one or more fans <NUM> by a shaft connection (not shown).

A fan <NUM> can include multiple sets of rotors and stators, or multiple rows of fan blades. Torque available from an energy source (such as motor <NUM>) is consumed by fan <NUM>. A particular fan shape and size can be designed to operate at a maximum torque at a given RPM, and at a high RPM, fan <NUM> can stall and loses efficiency. Thus, a number of rows of fan blades can be selected dependent on a mix of fan blade size, number of fan blades, RPM of fan rotation, and torque input.

In some embodiments, electric motor <NUM> can be operated as an electric generator to generate electricity by transferring power from the rotation of fan <NUM> to electric power by electromagnetic induction. Such electric power can be stored, in some embodiments, in a battery or other suitable storage device.

One or more fans <NUM> can be driven by a single electric motor <NUM>. In some embodiments, each fan <NUM> can be driven by a separate individual electric motor <NUM>. In other embodiments, a pair of fans <NUM> can be driven by a single electric motor <NUM>.

Other suitable mechanism for powering fans <NUM> are contemplated, for example, a heat engine such as an internal combustion engine.

System <NUM> can also include one or more controllers <NUM>, which can be implemented in hardware and/or software, to monitor and control power, RPM, direction of rotation of fan <NUM>.

In some embodiments, one or more controllers <NUM> can be used to control electric motor <NUM>, such as input power to electric motor <NUM>, and thus output torque from electric motor <NUM>. A controller <NUM> can thus control the direction and speed of rotation of fans <NUM> and thus the amount of thrust generated for forward or reverse thrust. Each of multiple fans <NUM> can be operated independently and individually controlled. For example, certain fans <NUM> can act to generate thrust, and certain fans <NUM> can operate as generators.

In an example, fan(s) <NUM> adjacent a top portion of aircraft <NUM> can have more influence on the flow of air around the vertical tail, and thus can be adjusted based on flight parameters, as compared to fan(s) <NUM> adjacent a lower portion of aircraft <NUM> that can have less impact on the flow of air and can be further disposed in clean air and be a better source for regeneration. Thus, for the purposes of regeneration, lower fan(s) <NUM> can be activated and for the purposes of modifying flight thrust, upper fan(s) <NUM> can be activated.

In some embodiments, one or more controllers <NUM> can be the same or different and control any one or more of electric motors <NUM>.

System <NUM> can also include a centralized controller such as excess thrust controller <NUM>, as shown in <FIG>. Excess thrust controller <NUM> can provide logic for operation of system <NUM>. In some embodiments, excess thrust controller <NUM> and controller(s) <NUM> can be implemented as an integrated system. In other embodiments, excess thrust controller <NUM> and controller(s) <NUM> can be implemented separately and independently, and in communication with each other.

Excess thrust controller <NUM> can be implemented as a computing device or a computer. The computer can comprise one or more data processors (referred hereinafter in the singular) and one or more computer-readable memories (referred hereinafter in the singular) storing machine-readable instructions executable by data processor and configured to cause data processor to generate one or more outputs (e.g., signals) for causing the execution of steps of the methods described herein.

The computer can be part of an avionics suite of aircraft <NUM>. For example, in some embodiments, the computing device can carry out additional functions than those described herein. In various embodiments, the computer can comprise more than one computer or data processor where the methods disclosed herein (or part(s) thereof) could be performed using a plurality of computers or data processors, or, alternatively, be performed entirely using a single computer or data processor.

The data processor can comprise any suitable device(s) configured to cause a series of steps to be performed by the computer so as to implement a computer-implemented process such that instructions, when executed by the computer or other programmable apparatus, can cause the functions/acts specified in the methods described herein to be executed.

Memory can comprise any suitable machine-readable storage medium. Memory can comprise non-transitory computer readable storage medium such as, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. Memory can include a suitable combination of any type of computer memory that is located either internally or externally to the computer. Memory can comprise any storage means (e.g. devices) suitable for retrievably storing machine-readable instructions executable by data processor.

Various aspects of the present disclosure can be embodied as systems, devices, methods and/or computer program products. Accordingly, aspects of the present disclosure can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, aspects of the present disclosure can take the form of a computer program product embodied in one or more non-transitory computer readable medium(ia) (e.g., memory) having computer readable program code (e.g., instructions) embodied thereon. Computer program code for carrying out operations for aspects of the present disclosure in accordance with instructions can be written in any combination of one or more programming languages. Such program code can be executed entirely or in part by the computer or other data processing device(s). It is understood that, based on the present disclosure, one skilled in the relevant arts could readily write computer program code for implementing the methods disclosed herein.

As illustrated in <FIG>, in some embodiments, excess thrust controller <NUM> can be operatively connected and in communication with pilot input <NUM>, autopilot input <NUM>, full authority digital engine control (FADEC) <NUM>, an air data computer (ADC) <NUM> that digitizes signals received from sensor(s) <NUM>, and one or more controllers <NUM> for operating one or more motors <NUM> for driving one or more fans <NUM>. In some embodiments, excess thrust controller <NUM> is operative connected and in communication with reverse flow door(s) <NUM> (not shown) for control and sensing of reverse flow door(s) <NUM>.

Pilot input <NUM> includes input from a pilot to flight controls, for example, spoilers <NUM> for controlling drag and lift component of spoilers on aircraft <NUM>, speed brake levels (not shown) for controlling drag produced by speed brakes, and throttles <NUM> such as a throttle quadrant including control such as levers for forward and reverse thrust.

Autopilot input <NUM> can include flight mode, and airspeed and altitude information which can be input to excess thrust controller <NUM>.

FADEC <NUM> is a computing device configured to control engine performance and is in communication with excess thrust controller <NUM> send information relating to RPM and fuel flow of engines <NUM> to excess thrust controller <NUM>.

One or more suitable sensor(s) <NUM> measure real-time data associated with the operation of aircraft <NUM> and received as input, for example, flight conditions such as airspeed and altitude, temperature, flight path, and air or ground mode.

Sensor input can be received and processed by ADC <NUM> that is in communication with excess thrust controller <NUM> to transmit flight condition information to excess thrust controller <NUM>.

Based on received data, such as information related to pilot input from pilot input <NUM>, autopilot input from autopilot input <NUM>, engine control information from FADEC <NUM> and flight condition information from ADC <NUM>, excess thrust controller <NUM> can determine what mix of forward or reverse thrust/drag to be generated by system <NUM>.

Based on determined forward or reverse thrust/drag, excess thrust controller <NUM> can sends controller(s) <NUM> suitable RPM, kW and direction signals to control each electric motor(s) <NUM>, and thus each fan(s) <NUM>, accordingly.

In some embodiments, aircraft <NUM> operates under pilot control, and flight path angle and airplane acceleration can be controlled, in part, by system <NUM>.

In some embodiments, aircraft <NUM> operates in a cruise mode with autopilot on, and excess thrust controller <NUM> can determine whether operating fans <NUM> can result in an overall fuel burn reduction, and can vary operation of system <NUM> such as the amount of power sent to system <NUM> to vary the amount of thrust generated based on monitored fuel consumption levels.

In some embodiments, excess thrust controller <NUM> monitors fuel burn in real time to vary operation of system <NUM> to optimize fuel burn and minimize energy consumption.

Excess thrust controller <NUM> can thus determine if fuel burn reduction can be achieved by running fans <NUM> of system <NUM> using energy from engines <NUM> to result in an overall gain of fuel consumption.

In some embodiments, system <NUM> can be controlled by actuation of a throttle lever, such as throttle <NUM>, of aircraft <NUM>. Excess thrust controller <NUM> can determine whether to activate system <NUM>, and whether to increase or decrease thrust as required.

In an example, should an engine <NUM> fail, excess thrust controller <NUM> can increase the forward thrust generated by system <NUM>.

In another example, if a speed brake lever is activated, excess thrust controller <NUM> can operate to reduce the thrust generated by fans <NUM> and increase drag.

In some embodiments, excess thrust controller <NUM> can be configured to select an appropriate power source to drive fans <NUM>, for example, based on the amount of thrust desired to be generated. Excess thrust controller <NUM> can also be configured to operate system <NUM> in a regeneration mode to capture power, in the event that increased drag or less thrust is desired.

Power source for supply to system <NUM> can include power to operate one or more controllers <NUM> and/or one or more electric motors <NUM> to drive fans <NUM>. A power source can include one or more of an electric generator, such as generator <NUM>, powered by a gas turbine engine such as one or more of engines <NUM> or an APU.

In some embodiments, it is possible to switch between power sources for system <NUM>.

A power source can be selected, for example, by excess thrust controller <NUM>, based on the use or operational mode of system <NUM>, as discussed in further detail below.

In some embodiments, an aircraft <NUM> with system <NUM> can include an APU such as APU <NUM> to provide power fans <NUM> of system <NUM>, for example, for takeoff and go-around.

In an example, a larger APU than would be typically provided can be utilized to provide up to <NUM> shp (shaft horsepower) to system <NUM>, in particular, for takeoff and go-around.

While typically one air intake can be sufficient for an APU that solely generates electricity for pneumatics and electrical systems for aircraft <NUM>, with a larger APU, it can be necessary to include a second intake to provide additional air to the APU. Two such inlets are illustrated by way of example as APU inlets <NUM> in <FIG>.

Turning now to <FIG>, various operating environments of system <NUM> are illustrated with various power sources. It will be appreciated that any one or more of the following power sources can be combined to provide power and control for system <NUM>, and can be controlled by a centralized controller such as excess thrust controller <NUM> (not shown), for example, in communication with at least the power source and each controller <NUM>.

<FIG> is a schematic diagram of an operating environment of a turbo generator <NUM>, such as APU <NUM>, feeding power to system <NUM>, in accordance with an embodiment.

In the embodiment illustrated in <FIG>, a power source for system <NUM> can be a turbo generator <NUM>, for example, an auxiliary power unit such as APU <NUM>, including a gas turbine engine <NUM> supplied with fuel energy and an electric generator <NUM>, or other suitable engine and electric generator. Thus, electric motor <NUM> is driven by electric energy from an electric generator of an auxiliary power unit such as APU <NUM>.

In some embodiments, generator <NUM> is an electric generator used to generate electricity. Generator <NUM> can be oil-cooled and include a gearbox for transferring power from a shaft of a gas turbine engine such as an APU to electric power.

In some embodiments, generator <NUM> is a synchronous AC generator (sometimes referred to as an "alternator"), such as a permanent magnet generator.

In some embodiments, generator <NUM> can have a power rating of <NUM> kVA. In some embodiments, generator <NUM> generates AC current, for example, a three-phase, <NUM>, <NUM> or <NUM> phase voltage output.

As shown in <FIG>, electrical energy generated from turbo generator <NUM> is supplied to controllers <NUM>, and controllers <NUM> supply power and control operation for each electric motor <NUM>. Each electric motor <NUM> is rotatably coupled to a ducted fan pair of fans <NUM>. Each controller <NUM> can control an electric motor <NUM>, and serve as a backup to one or more other electric motors <NUM> such that if a controller <NUM> to an electric motor <NUM> fails, a backup controller <NUM> operates to control and supply power to that electric motor <NUM>.

One or more controllers <NUM> in a configuration can be the same or different and control any one or more of electric motors <NUM>.

In use, fuel energy, in an example <NUM>,<NUM> BTU/lb or <NUM> kWh/kg of fuel energy, is supplied to turbo generator <NUM>.

Turbo generator <NUM> can operate, in an example, at approximately <NUM>-<NUM>% efficiency, whereby efficiency is defined as useful energy output divided by energy input. Gas turbine engine <NUM> can operate, in an example, at approximately <NUM>-<NUM>% efficiency. Generator <NUM> can operate, in an example, at approximately <NUM>% efficiency.

Electric motors <NUM> can operate, in an example, at approximately <NUM>% efficiency. Each pair of fans <NUM> can operate, in an example, at approximately <NUM>% efficiency.

In an example, system <NUM> can be powered by turbo generator <NUM> and draw approximately <NUM> kW from turbo generator <NUM> in a climb mode or an Automatic Power Reserve (APR) mode to provide thrust in the event of an engine thrust loss during takeoff and missed approach conditions.

<FIG> is a schematic diagram of another operating environment of system <NUM>, in accordance with an embodiment.

In the embodiment illustrated in <FIG>, a power source for system <NUM> can be turbo generators <NUM>, including gas turbine engines <NUM> supplied with fuel energy and electric generators <NUM>, or other suitable engine and electric generator. Electric motor <NUM> is thus driven by electric energy from an electric generator <NUM> of one or more engines <NUM> of aircraft <NUM>.

In some embodiments, generator <NUM> can be similar to generator <NUM>, including structure and components.

As shown in <FIG>, electrical energy generated from turbo generators <NUM> is supplied to controllers <NUM>, and controllers <NUM> supply power and control operation of each electric motor <NUM>. Each electric motor <NUM> is rotatably coupled to a ducted fan pair of fans <NUM>. Each controller <NUM> can control an electric motor <NUM>, and serve as a backup to another electric motor <NUM> such that if a controller <NUM> to an electric motor <NUM> fails, a backup controller <NUM> operates to control and supply power to that electric motor <NUM>.

One or more controllers <NUM> can be the same or different and control any one or more of electric motors <NUM>.

In use, fuel energy, in an example <NUM>,<NUM> BTU/lb or <NUM> kWh/kg of fuel energy, is supplied to each turbo generator <NUM>.

Turbo generator <NUM> can operate, in an example, at approximately <NUM>-<NUM>% efficiency, defined as useful energy output divided by energy input. Engine <NUM> can operate, in an example, at approximately <NUM>-<NUM>% efficiency. Generator <NUM> can operate, in an example, at approximately <NUM>% efficiency.

In an example, system <NUM> can be powered by turbo generator <NUM> and draw approximately <NUM> to <NUM> kW in a cruise mode.

<FIG> is a schematic diagram of a further operating environment of a system <NUM>, in accordance with an embodiment.

In the embodiment illustrated in <FIG>, a power source for system <NUM> can be a battery <NUM>. Thus, electric motor <NUM> can be driven by electric energy supplied by battery <NUM>. In some embodiments, the power source includes multiple batteries <NUM>, for example, configured as a battery pack.

In some embodiments, battery <NUM> can have a specific energy density of as high as <NUM> kWh/kg. In other embodiments, battery <NUM> can have a specific energy density of approximately <NUM> kWh/kg, in another example <NUM> kWh/kg.

Battery <NUM>, a plurality of batteries <NUM>, or a battery pack formed from batteries <NUM> can supply DC current to an inverter <NUM> or multiple inverters <NUM>.

Inverter <NUM> can be a suitable device or circuitry to change direct current (DC) to alternating current (AC).

In use, inverters <NUM> can operate at approximately <NUM>% efficiency, and electric motors <NUM> can operate, in an example, at approximately <NUM>% efficiency. Each pair of fans <NUM> can operate, in an example, at approximately <NUM>% efficiency.

As shown in <FIG>, electrical energy generated from battery <NUM> is supplied to controllers <NUM>, and controllers <NUM> supply power and control operation of each electric motor <NUM>. Each electric motor <NUM> is rotatably coupled to a ducted fan pair of fans <NUM>. Each controller <NUM> can control an electric motor <NUM>, and serve as a backup to another electric motor <NUM> such that if a controller <NUM> to an electric motor <NUM> fails, a backup controller <NUM> operates to control and supply power to that electric motor <NUM>.

In some embodiments, electric motors <NUM> can be used in reverse function as generators to convert mechanical energy into electrical energy. Regenerative braking can be performed by transferring mechanical energy from the propulsion of aircraft <NUM> to an electrical load.

One or more batteries <NUM> can be used to power system <NUM> to generate thrust, and can also operate in a regeneration mode to capture airflow, rotate electric motor <NUM> and feed electrical energy back to controllers <NUM> and inverters <NUM> and to batteries <NUM>. Electric motor <NUM> can be operable as a generator to convert mechanical energy into electric energy to supply to one or more batteries <NUM>. Thus, in a battery configuration, system <NUM> is a fully reversible system.

In an example, system <NUM> can capture energy during descent of aircraft <NUM>, which can be used to power electric systems, such as electric brakes on landing, should engine driven generators fail, or if power is needed to feed systems in specialized mission airplanes.

In some embodiments, in use, system <NUM> can produce approximately <NUM>,<NUM> lbs excess thrust (thrust minus drag) at <NUM> KCAS (knots calibrated airspeed), near VMCG (velocity of minimum control on ground) speed.

<FIG> is a graph illustrating a relationship between, on the y-axis, excess thrust (thrust minus drag) in lbs (pounds) of aircraft <NUM>, including thrust generated by system <NUM>, and on the x-axis airspeed in KTAS (knots true airspeed).

Assuming a propulsion efficiency, and based on a power input, excess thrust can be determined by multiplying input power by efficiency, and dividing by airspeed, to generate the graph of <FIG>. Excess thrust multiplied by airspeed results in propulsive power.

Excess thrust generated by system <NUM>, in an embodiment, can approximate the thrust deficit between a larger engine (for example, rated for up to <NUM>,<NUM> lbs static takeoff thrust) and a smaller and lighter engine (for example, rated for up to <NUM>,<NUM> lbs static takeoff thrust) at the critical engine failure speed.

System <NUM> can be driven by approximately <NUM> SHP from a power source such as an APU. System <NUM> can be powered by an appropriate power source, such as APU <NUM> or engines <NUM>, at least in part based on the amount of excess thrust needed.

System <NUM> can be configured for use in a variety of modes of operation of aircraft <NUM>, including pushback at gate, for example, using a thrust reverser (TR) throttle lever as pilot input; taxiing, for example, using a tiller with throttle-type input; during takeoff, to provide drag control and replace an Automatic Power Reserve (APR) by providing centerline thrust; during climb and cruise, for example, improving excess thrust (for example, using an auto setting by way of excess thrust controller <NUM> to adjust thrust generated by system <NUM> to minimize energy consumption) and can be fed by main engines <NUM> if an APU is not required; flight path control, for example, using a speedbrake level to increase drag without multi-function spoilers (MFS) and can allow for rapid thrust direction change; as a ram air turbine (RAT) replacement that can provide backup electrical to aircraft systems; and regeneration, storing energy in batteries such as batteries <NUM>, if needed.

System <NUM> can be configured for reduced VMCG (Velocity, Minimum Control (ground)). VMCG is the minimum speed, while on the ground, that directional control can be maintained using aerodynamic controls, with one engine inoperative. Thus, VMCG is proportional to asymmetric thrust (when one engine fails), and rudder deflection applied to counter the asymmetric thrust.

Use of system <NUM>, by generating thrust to counter the asymmetric thrust, can allow for a reduced VMCG with smaller fuselage mounted engines, such as engines <NUM>. Similarly, system <NUM> can allow for a reduced VMCA (Velocity, Minimum Control (air)).

In various operating modes of aircraft <NUM>, system <NUM> can source power from power sources such as those described herein.

For example, when aircraft <NUM> is taxiing, which can be propelled by system <NUM>, system <NUM> can draw power from APU <NUM>.

System <NUM> can be configured to generate forward takeoff thrust to supplement thrust generated by engines <NUM> (for example, a first engine and a second engine) during takeoff of aircraft <NUM>.

To generate additional forward thrust for takeoff or as aircraft <NUM> climbs or a go around, system <NUM> can draw power from APU <NUM>, which can be required to supplement thrust generated by engines <NUM> and reduce drag. For example, use of a smaller engine <NUM> can require thrust generated by system <NUM> at takeoff.

In a climb mode, system <NUM> can be powered by APU <NUM> and configured to draw approximately <NUM> kW from a power source, for example, generator <NUM> as shown in <FIG> and described above, resulting in an energy drag of approximately <NUM> kW to feed system <NUM>.

System <NUM> can be configured to configured to generate forward cruise thrust to supplement thrust generated by engines <NUM> (for example, a first engine and a second engine) during cruise of aircraft <NUM>.

In a cruise mode, system <NUM> can be configured to draw approximately <NUM> to <NUM> kW from a power source, for example, electrical generators <NUM> powered by engines <NUM>, as shown in <FIG> and described above. Thus, approximately <NUM>-<NUM> kW of energy can be required to accelerate mass flow from the boundary layer back to true airspeed, thus reducing fuselage pressure drag.

In cruise, system <NUM> can be fed by main engines <NUM> primarily to provide control of drag, as APU <NUM> can be shut down during cruise which can improve fuel burn.

During cruise mode, it can be desirable to minimize fuel burn by reducing drag, as sufficient thrust can be generated by engines <NUM>. System <NUM> can minimize energy use by aircraft as compared to distance travelled, whereby energy use is defined as the sum of all sources of fuel burn. An increase in thrust and reduction of drag by system <NUM> can be modified to minimize fuel burn.

In some embodiments, excess thrust controller <NUM> can manage the sources of power from aircraft <NUM> to system <NUM> to minimize fuel burn.

In some embodiments, excess thrust controller <NUM> can monitor fuel burn in real-time to optimize it, in particular, by minimizing the sum of fuel burn, for example, to engines <NUM> and APU <NUM>.

During a landing or descent, system <NUM> can generate reverse thrust and additional drag to descend aircraft <NUM>.

System <NUM> can create drag and descend without using engines and deploying speed brakes.

In some embodiments, batteries <NUM> can capture energy in descent and reduce overall fuel burn in aircraft <NUM>, and batteries <NUM> can also power electrical brakes for landing.

In a regeneration mode, system <NUM> can be operated to generate electrical energy, for example, stored in batteries <NUM>.

In some embodiments, fans <NUM> can be configured to be rotated by a flow such as forward flow <NUM> or reverse flow <NUM>, to capture energy.

Fans <NUM> can be connected to a generator, for example, electric motors <NUM> operating as generators, to generate electrical energy, and the electrical energy can be used in a battery pack configuration such as batteries <NUM> as shown in <FIG>, or supplied to a suitable system.

Thus, fans <NUM> can be used as ram air turbines as required by an energy system and operate as a small wind turbine connected to a hydraulic pump, or electrical generator, of aircraft <NUM>.

In an example, system <NUM> could generate electricity in an instance of a lost engine <NUM>, or could be used to provide all electricity for a special mission.

In another example, in use, certain fans <NUM> of system <NUM> can generate thrust while certain other fans <NUM> can generate electrical energy. For example, system <NUM> can include six fans <NUM>. Four of the six fans <NUM> can produce forward thrust, and two of the fans act as generators, such as in a failure mode.

System <NUM> can be configured to provide standby power for aircraft <NUM>. In some embodiments, system <NUM> is powered on at brake release. Then, if there is a failure of one of engines <NUM>, system <NUM> activates to provide automatic performance reserve (APR) (or boost) to generate additional thrust.

<FIG> is a flowchart of a method for controlling thrust and drag of aircraft <NUM>, according to an embodiment, which can be performed by fans <NUM> of system <NUM> to generate forward or reverse thrust, or to increase or decrease drag. The steps are provided for illustrative purposes. Variations of the steps, omission or substitution of various steps, or additional steps can be considered.

At block <NUM>, a flow of air, for example, forward flow <NUM> or reverse flow <NUM>, is drawn, for example, from a boundary layer formed during movement of aircraft <NUM>.

At block <NUM>, the flow of air can be directed or re-energized by flow channel <NUM> to minimize turbulence.

At block <NUM>, the flow of air can be accelerated, for example, by rotating fan <NUM> in a first direction to impel the flow of air towards the rear of aircraft <NUM> to generate forward thrust, or rotating fan <NUM> in a second direction to impel the flow of air towards the front of aircraft <NUM> to generate reverse thrust.

It should be understood that one or more of the blocks can be performed in a different sequence or in an interleaved or iterative manner.

In some embodiments, fans <NUM> of system <NUM> are disposed on aircraft <NUM> such that fans <NUM> can intake air from within a boundary layer formed by the movement of aircraft <NUM>. In some embodiments, fans <NUM> are disposed on aircraft <NUM> such that the only air flow that is intaken by system <NUM> is boundary layer air, and do not extend radially out past the boundary layer to intake clean air. Thus, in some embodiments, system <NUM> only ingests boundary layer air.

In some embodiments, one or more fans <NUM> are fully disposed within a distance from the surface of the aircraft that is less than a boundary layer thickness formed from the surface of aircraft <NUM> during take-off and cruising of the aircraft, the boundary layer thickness can be defined as a distance from the surface to a point at which a velocity of a local flow is ninety-nine percent of a velocity of a surrounding freestream flow.

Boundary layer ingestion can be used by system <NUM> to decrease the propulsive power consumption of an aircraft, and therefore the fuel consumption, by producing thrust from the reduced velocity boundary layer air.

Conveniently, system <NUM> can provide approximately <NUM> to <NUM>% fuel burn reduction by ingesting boundary layer air instead of clear air flow.

A key challenge associated with boundary layer ingesting systems is the ability of the turbomachinery to operate efficiently in highly distorted flow.

Fans <NUM> of system <NUM> can be disposed being completely in boundary layer at particular operating parameters. Thus, intake flow (turbulent flow) can be slower, and can blades of fans <NUM> can be thicker, because fans <NUM> do not have to deal with fast flow (of laminar flow), to cater to pressure fluctuation, and blade stresses can be addressed by having thicker blades.

<FIG> is a schematic diagram illustrating forces acting on aircraft <NUM> in flight: lift L, weight W, thrust T, and drag D, and a climb angle γ defined as the angle between a Horizontal Plane representing the earth's surface and the actual flight path followed by the aircraft <NUM>.

The forces of flight can be defined as follows: <MAT>
where W is weight of aircraft <NUM>, y is climb angle, T is thrust and D is drag.

Equation (<NUM>) can be rearranged as: <MAT>.

Thrust T and drag D are vector quantities, thus having a magnitude and direction associated with them. The net external force on aircraft <NUM> can be referred to as "excess thrust" and can be defined as thrust T minus drag D, and is thus also a vector quantity. System <NUM> can be configured to control and vary excess thrust, for example, by adding forward thrust or reverse thrust and increasing or decreasing drag, and thus control flight path of aircraft <NUM>. By determining a desired flight path angle or acceleration, based on input such as pilot input, autopilot input and various sensor feedback, a determined amount of energy can be sent to system <NUM>.

Thrust T can thus be modified by system <NUM> to provide forward or reverse thrust during takeoff and other situations using techniques as described herein.

Conveniently, system <NUM> can replace thrust reversers on an engine such as one or more of engines <NUM> and improve fuel burn on those engines, provide less leakage, less weight, and less cost.

System <NUM> can also be configured to modify (increase or decrease) drag D using techniques as described herein.

In some configurations, system <NUM> can allow for use of a smaller and lighter engine, which can be less costly. Specific fuel consumption (SFC) of a smaller engine in combination with an embodiment of system <NUM> can be similar or improved as compared to a de-rated larger engine.

Use of system <NUM> can allow for a lighter aircraft <NUM> with a lower operating empty weight (OEW), in an example, reduced by <NUM> (<NUM> lbs) and thus reduced cost.

Based on simulated sample missions, similar fuel consumption results from both a smaller engine in combination with an embodiment of system <NUM> and a de-rated larger engine, as well as similar range, and aerodynamics was not necessarily optimized.

In another configuration, system <NUM> can replace a thrust reverser on a traditional engine. Based on simulated sample missions, replacement with system <NUM> can be weight and cost neutral, with a small range increase (approximately <NUM>%) at max payload, and approximately <NUM>% fuel burn reduction on <NUM>.

Some configurations of removal of thrust reversers from a traditional engine and inclusion of system <NUM> can result in a weight and cost reduction, for example, a reduction in basic weight (BOW) of approximately <NUM>%.

System <NUM> can also provide a range increase (approximately > <NUM>%) at max payload, and approximately > <NUM>% fuel burn reduction for <NUM>, an initial climb altitude (ICA) increase for max range, a full payload at full fuel, negligible impact on weight at takeoff (WAT) limit, small impact on takeoff distance (with the same range-payload), and VMCG/VMCA reduction (for short field operation (SFO)).

Thus, there is a possibility of fleet cost savings with system <NUM>.

Structurally, in some embodiments, system <NUM> does not provide wing aerodynamics changes, however, an aircraft's tail tank could be removed, providing further weight and cost savings, and still have increased range.

Conveniently, system <NUM> can provide improved range, reduced fuel burn (reduced fuel consumption), as well as improved product perception (in the form of a hybrid-electric airplane).

System <NUM> can allow for the possibility of an aircraft taxiing with engines off, backing out of terminal gates, and climb and cruise drag reduction.

System <NUM> can provide inflight thrust-reversers (flight path control, including steep approach without multi-function spoiler (MFS), and improved emergency descent), as well as on-ground thrust-reversers (with improved stopping capability).

Due to system <NUM> being able to provide reverse thrust, main engine thrust reverse can be removed from the main engines. The removal of main engine thrust reversers can provide a weight and cost savings, and in an example, about <NUM>% SFC (specific fuel consumption) improvement for the engine.

System <NUM> can also provide improved VMCA/VMCG. The management of excess thrust along an aircraft centerline, resulting in a smaller vertical tail and reduced weight and cost.

System <NUM> can improve short field performance and wet/contaminated field performance.

System <NUM> can also be configured to act as a Ram Air Turbine (RAT), and a conventional RAT can be removed.

System <NUM> can also provide regenerative capability, for example, to batteries or electrical systems.

A system <NUM> can be sized to produce the equivalent of the missing takeoff thrust of under one engine inoperative (OEI) takeoff and go-around of the engine being replaced, and can officially not be required from a thrust point of view for other phases of flight.

On typical missions (<NUM> and <NUM>) for an aircraft, integrating system <NUM> has the potential to reduce fuel burn by over <NUM>%. In an example, on a <NUM> mission, there is the potential to reduce fuel burn by <NUM> lbs of fuel (over one ton of CO<NUM>).

Systems and methods described herein can be utilized in additional applications, such as integrating a powerplant into an airframe and reducing pitching moment from engine thrust change to increase fuel efficiency and possibly remove the horizontal tail, resulting in a weight and cost reduction.

Other applications include boosting initial climb altitude (ICA) to try to increase flight altitude, for example, to achieve <NUM> (<NUM> ft).

In other applications, through a power management computer, an embodiment of system <NUM> can be adjusted in cruise to minimize fuel burn when at altitude, including shutting down an APU.

Claim 1:
An aircraft (<NUM>) comprising a system for varying excess thrust of said aircraft (<NUM>), comprising:
a first electric fan (<NUM>) rotatable about a first axis for directing a first air flow along a first air flow path;
a second electric fan (<NUM>) rotatable about a second axis different from the first axis for directing a second air flow along a second air flow path fluidly isolated from the first air flow path,
a third electric fan (<NUM>) rotatable about a third axis for directing a third air flow along a third air flow path;
a fourth electric fan (<NUM>) rotatable about a fourth axis for directing a fourth air flow along a fourth air flow path;
a fifth electric fan (<NUM>) rotatable about a fifth axis for directing a fifth air flow along a fifth air flow path; and
a sixth electric fan (<NUM>) rotatable about a sixth axis for directing a sixth air flow along a sixth air flow path,
wherein the first second, third, fourth, fifth and sixth electric fans (<NUM>) are disposed radially about and around a roll axis (RA) of the aircraft (<NUM>) and adjacent an aft end of the aircraft (<NUM>), and the first, second, third, fourth, fifth and sixth electric fans (<NUM>) are configured to intake boundary layer air to form the first, second, third, fourth, fifth and sixth air flows;
characterized in that the first, second, third, fourth, fifth and sixth electric fans (<NUM>) are disposed in a cavity in a tail cone (<NUM>) within aircraft (<NUM>).