Additional thrust control of the aircraft

Abstract

Additional thrust control for an aircraft. A system and method for varying additional thrust for an aircraft includes: a first electrically powered fan rotatable about a first axis to direct a first airflow along a first air flow path; and a second electrically powered fan rotatable about a second axis different from the first axis to direct a second airflow along a second air flow path fluidly isolated from the first air flow path, wherein the first and second electrically powered fans are radially arranged about a roll axis of the aircraft and adjacent to a rear end of the aircraft, and the first and second electrically powered fans are configured to draw boundary layer air to form the first and second airflows.

Description

Technical Field

[0001] The present disclosure relates generally to aircraft, and more particularly to additional thrust control for an aircraft. Background Art

[0002] Aircraft such as conventional fixed-wing aircraft typically include one or more engines, such as turbofan jet engines, to provide thrust. Such engines can be selected based on a variety of factors, such as the thrust requirements of the aircraft, the weight of the engine, and the fuel burn rate of the engine. Summary of the Invention

[0003] According to one aspect, a system for varying additional thrust of an aircraft is provided, comprising: a first electric fan rotatable about a first axis to direct a first air flow along a first air flow path; and a second electric fan rotatable about a second axis different from the first axis to direct a second air flow along a second air flow path fluidly isolated from the first air flow path, wherein the first electric fan and the second electric fan are radially arranged about a roll axis of the aircraft and adjacent to a rear end of the aircraft, and the first electric fan and the second electric fan are configured to draw boundary layer air to form the first air flow and the second air flow.

[0004] In some embodiments, the first fan and the second fan are coplanar in a single plane that is substantially parallel to a transverse plane containing a pitch axis of the aircraft and a yaw axis of the aircraft.

[0005] In some embodiments, the first fan and the second fan are bilaterally symmetric in a symmetry plane containing a roll axis of the aircraft and a yaw axis of the aircraft.

[0006] In some embodiments, the system further includes a cowling duct surrounding the first fan to direct air toward the first air flow path and surrounding the second fan to direct air toward the second air flow path.

[0007] In some embodiments, the first electric fan and the second electric fan are driven by electric motors.

[0008] In some embodiments, the electric motor is driven by electrical energy from a generator of the auxiliary power unit.

[0009] In some embodiments, the system further includes an inlet conduit in fluid communication with the auxiliary power unit to direct air to the auxiliary power unit.

[0010] In some embodiments, the electric motor is driven by electrical energy supplied by a battery.

[0011] In some embodiments, the electric motor may function as a generator to convert mechanical energy into electrical energy to supply the battery.

[0012] In some embodiments, the electric motor is driven by electrical energy from a generator of one or more engines of the aircraft.

[0013] In some embodiments, the system further includes a controller for controlling the electric motor.

[0014] In some embodiments, the first electric fan and the second electric fan are ducted fans.

[0015] In some embodiments, the first axis and the second axis are substantially parallel to a roll axis of the aircraft.

[0016] In some embodiments, the first electric fan and the second electric fan are disposed entirely within a distance from the surface of the aircraft that is less than a thickness of a boundary layer formed by the surface of the aircraft during takeoff and cruise, the boundary layer thickness being the distance from the surface to a point where the velocity of the local flow is ninety-nine percent of the ambient free stream velocity.

[0017] In some embodiments, the first electric fan and the second electric fan are positioned adjacent to a tail cone of the aircraft.

[0018] In some embodiments, the system further includes: a first door actuatable between a closed position and an open position, wherein in the closed position, the forward flow of the first airflow in the first flow path is directed from the front end of the aircraft to the rear end of the aircraft, and in the open position, the reverse flow of the first airflow in the first flow path is directed from the rear end of the aircraft to the front end of the aircraft; and a second door actuatable between a closed position and an open position, wherein in the closed position, the forward flow of the second airflow in the second flow path is directed from the second end of the aircraft to the rear end of the aircraft, and in the open position, the reverse flow of the second airflow in the second flow path is directed from the rear end of the aircraft to the front end of the aircraft.

[0019] In some embodiments, the system further includes: a third electric fan rotatable about a third axis to direct a third air flow along a third air flow path; a fourth electric fan rotatable about a fourth axis to direct a fourth air flow along a fourth air flow path; a fifth electric fan rotatable about a fifth axis to direct a fifth air flow along a fifth air flow path; and a sixth electric fan rotatable about a sixth axis to direct a sixth air flow along a sixth air flow path, wherein the third, fourth, fifth, and sixth electric fans are radially arranged about a roll axis of the aircraft and adjacent to a rear end of the aircraft and are configured to draw boundary layer air to form the third, fourth, fifth, and sixth air flows, each of the first, second, third, fourth, fifth, and sixth axes are different from one another, and each of the first, second, third, fourth, fifth, and sixth air flow paths are fluidly isolated from one another.

[0020] According to another aspect, an aircraft is provided that includes a first engine, a second engine, and the system described herein.

[0021] In some embodiments, the system is configured to generate forward takeoff thrust during takeoff of the aircraft to supplement the thrust generated by the first engine and the second engine.

[0022] In some embodiments, the system is configured to generate forward cruise thrust during cruise of the aircraft to supplement the thrust generated by the first engine and the second engine.

[0023] Other features will become apparent from the following description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In the accompanying drawings showing example embodiments,

[0025] Figure 1 is a side view of an aircraft having a system for varying excess thrust according to an embodiment;

[0026] Figure 2 According to an embodiment, Figure 1 A partial perspective view of the aircraft of the system;

[0027] Figure 3A It is along Figure 2 A cross-sectional view of the system taken along line 3A-3A;

[0028] Figure 3B It is along Figure 2 A cross-sectional view of the system taken along line 3B-3B;

[0029] Figure 4A is a schematic side view of a system for varying excess thrust including a flow directing system in a closed position according to an embodiment;

[0030] Figure 4B is a schematic side view of the system, wherein Figure 4A The flow guidance system is in the open position;

[0031] Figure 4C is a schematic side view of a fan and a motor of a system for varying additional thrust according to an embodiment;

[0032] Figure 5 is a front schematic diagram of a system for varying additional thrust according to an embodiment;

[0033] Figure 6 is a schematic diagram of a system for varying additional thrust according to an embodiment, comprising a centralized controller;

[0034] Figure 7 is a schematic diagram of an operating environment of a system for varying additional thrust according to an embodiment;

[0035] Figure 8 is a schematic diagram of another operating environment of a system for varying additional thrust according to an embodiment;

[0036] Figure 9 is a schematic diagram of a further operating environment of a system for varying additional thrust according to an embodiment;

[0037] Figure 10 is a graph illustrating the relationship between additional thrust and the airspeed generated by an aircraft according to an embodiment;

[0038] Figure 11 is a flow chart of a method for controlling additional thrust in an aircraft according to an embodiment; and

[0039] Figure 12 is a schematic diagram illustrating forces acting on an aircraft in flight, according to an embodiment. DETAILED DESCRIPTION

[0040] The design of a new aircraft or the upgrade of an existing aircraft may involve the selection of an engine for conventional propulsion. The engine may be selected based on the aircraft's operational requirements, optimizing factors such as the aircraft's thrust requirements, the engine's weight, the engine's fuel burn rate, and cost.

[0041] However, in practice, the choice of engine for a given size aircraft is based on the types of engines available or available from the engine manufacturer. Certain factors may not be optimized. For example, the engine selected is often too large for most of the aircraft's needs, but is necessary to meet certain thrust requirements of the aircraft (such as static takeoff thrust). As a result, a non-optimal engine is used, which may have to be throttled down (to limit power) to produce less thrust, while larger engines also weigh more. Larger engines may also require additional structure to support the engine on the aircraft.

[0042] Thus, a conventional design using the smallest available thrust compatible engine would result in an overweight engine, which has a compounding effect on the aircraft design.

[0043] As described herein, systems and methods for varying and thereby controlling excess thrust for an aircraft may provide flexibility in engine selection for an aircraft.

[0044] The extra thrust of an aircraft can be represented as a vector with magnitude and direction and can be defined as the vector difference of the aircraft's thrust vector T minus the drag vector D.

[0045] During aircraft operation, the additional thrust can be varied to modify the aircraft's climb and descent, as well as to control the flight path.

[0046] The systems and methods described herein can generate forward thrust, allowing the selection of smaller and lighter engines for an aircraft, or providing less takeoff thrust but providing optimal weight and fuel burn by supplementing the engine thrust with additional forward thrust. Thus, smaller engines with reduced weight and volume can be used, thereby reducing costs.

[0047] Conveniently, smaller engines can also allow the use of smaller vertical stabilizers or vertical tails, which also reduces cost and weight. Smaller rudders that can be attached at the same attachment point on the vertical tail can further reduce cost and weight.

[0048] As a result, the aircraft may have a lower empty air weight (OEW) and improved mission fuel burn.

[0049] Additionally, the forward thrust generated by the system described herein may also provide a climb capability in the event of an aircraft engine failure.

[0050] The systems and methods described herein can also generate reverse thrust to resist the forward motion of the aircraft, thereby providing deceleration or reverse motion. In one example, at high altitude and when descending, reverse thrust can be applied to descend without using the engines and without employing speed brakes.

[0051] Thrust can be applied forward or reverse along the centerline of the aircraft.

[0052] The systems and methods described herein can also control the drag caused by interactions and contacts when an aircraft moves through a fluid, such as air. In particular, the systems can increase or decrease drag, sometimes referred to as contour drag, which is defined as the sum of pressure drag (form drag) and skin friction (skin drag).

[0053] Pressure drag is caused by the increase in pressure in front of an aircraft moving through the air and the decrease in pressure behind it. Skin friction is caused by the interaction between air molecules and the solid surfaces of the aircraft.

[0054] During aircraft movement, a boundary layer forms in the immediate vicinity of the aircraft's surface, where viscosity plays a significant role. The collisions of molecules near the aircraft's surface create a thin layer of fluid near the surface (the boundary layer), where the velocity changes from zero at the surface to the freestream ("clean" airflow) value away from the surface. The boundary layer can be laminar (stratified) or turbulent (disordered).

[0055] The boundary layer increases the effective thickness of the aircraft body by displacement thickness, thus increasing pressure drag.Secondly, shear forces at the aircraft surface produce skin friction drag.

[0056] The systems and methods described herein may reduce drag by drawing in slower moving boundary layer air and redirecting and accelerating it to, for example, the same speed as the aircraft, and reducing the pressure differential between the front and rear surfaces of the aircraft.

[0057] In one example, drag can be increased at high altitudes and while descending, the descent can be performed without using the engine and employing speed brakes.

[0058] Figure 1 1 is a side view of an aircraft 10, which may include a system 12 for varying the additional thrust of the aircraft 10 as described herein. The aircraft 10 may be a fixed-wing aircraft including one or more engines 14. The aircraft 10 may include wings 16, a fuselage 18, and a tailplane 15 including a tail cone 17 and a vertical stabilizer or vertical tail 19. The aircraft 10 may be any type of aircraft, such as a corporate jet, a private jet, a commercial jet, and a passenger jet suitable for civil aviation. For example, the aircraft 10 may be a (e.g., ultra-long-range) business jet, a twin-engine turboprop airliner, or a regional airliner.

[0059] Aircraft 10 can rotate about three axes: a yaw axis YA extending vertically (up and down), about which aircraft 10 yaws left or right; a pitch axis PA extending from wing to wing (side to side), about which aircraft 10 tilts up or down; and a roll axis RA extending from nose to tail (front to back), about which aircraft 10 rotates.

[0060] Aircraft 10 may include an auxiliary power unit (APU) 11 (sometimes referred to as an “auxiliary power system”) that includes a gas turbine engine to provide electric and pneumatic power to aircraft systems as an auxiliary or secondary power source.

[0061] Figure 2 is a partial perspective view of an aircraft 10 including a system 12 according to an embodiment, arranged in a tail cone 17 in the region of a tailplane 15 of the aircraft 10. The system 12 is operable to draw a forward air flow 402 from the environment (such as a boundary layer) through one or more inlets 21 along a flow path 22 and exit at one or more outlets 25, which may be defined by ducts or conduits 23 formed, for example, by a fairing or housing, to generate thrust.

[0062] The system 12 may include a fan 24, such as an electric fan that may be driven by an electric motor, such as electric motor 40. In some embodiments, the fan 24 is a ducted fan.

[0063] In some embodiments, the fan 24 includes one or more rotors 242, such as impellers, and may include rotor blades or airfoils fixed to a main shaft to propel air. The impeller can be used to increase or decrease the pressure and flow of the fluid. In some embodiments, the impeller can be a radial flow impeller (axial inflow and radial outflow) or an axial flow impeller (axial inflow and axial outflow).

[0064] In some embodiments, fan 24 includes one or more stators 244 having stator blades or circumferentially spaced struts. The rotor blades propel the air, which then passes through the stator blades. The stator blades are secured to, for example, flow passage 22 and act as diffusers, partially converting high-speed air to high pressure. Each rotor 242 and stator 244 pair can form a compressor stage.

[0065] Fan 24 may be powered by an electrical source to add energy to a moving fluid (such as air, particularly boundary layer air of aircraft 10 ) by converting electrical energy into mechanical energy (such as by electric motor 40 ), thereby rotating an impeller or blades of fan 24 to push the air, thereby accelerating the airflow to generate thrust for aircraft 10 .

[0066] In some embodiments, fan 24 is disposed adjacent to roll axis RA. In one example, a single fan 24 can be positioned along roll axis RA.

[0067] In some embodiments, the fan 24 can rotate about an axis that is generally parallel to the centerline, such as the roll axis RA. In some embodiments, the fan 24 rotates about an axis that is tilted or angled with respect to the centerline, such as the roll axis RA.

[0068] In one example, the fan 24 may rotate in a first direction to push air toward the rear of the aircraft 10 and may rotate in a second direction opposite the first direction to push air toward the front of the aircraft 10 .

[0069] The fan 24 may function as a turbine to extract energy from a moving fluid, such as air, particularly boundary layer air of the aircraft 10 .

[0070] The fan 24 may extract energy by converting the mechanical energy of the moving fluid (air) that rotates the blades of the fan 24 into electrical energy, for example, by an electric motor 40 acting as a generator, as described in further detail below, and such electrical energy may be stored, for example, in a battery, or used by the electrical systems of the aircraft 10.

[0071] In some embodiments, system 12 may include multiple fans 24, including a first electric fan and a second electric fan, which may provide flexibility and avoid single points of failure. In some embodiments, system 12 includes six fans 24, namely, a third electric fan, a fourth electric fan, a fifth electric fan, and a sixth electric fan. In other embodiments, system 12 may include other suitable numbers and configurations of fans 24.

[0072] Each fan 24 can rotate about one or more axes, the same or different. In some embodiments, a first powered fan 24 can rotate about a first axis to direct a first airflow along a first airflow path defined by a flow channel 22, described below. A second powered fan 24 can rotate about a second axis, different from the first axis, to direct a second airflow along a second airflow path defined by another flow channel 22, described below, that is fluidly isolated from the first airflow path. The first and second axes can be substantially parallel to the roll axis RA of the aircraft 10.

[0073] One or more fans 24 may be radially arranged about the roll axis RA of the aircraft 10 and adjacent the aft end of the aircraft 10, such as adjacent the tail cone 17. In some embodiments, the one or more fans 24 are configured to draw boundary layer air to form an air flow, as described in further detail below.

[0074] One or more fans 24 may operate as a symmetrical pair, which may balance the thrust applied to or drag variations around the aircraft 10 .

[0075] Figure 3A is a cross-sectional view taken along line 3A-3A of system 12 , illustrating an embodiment having six fans 24 .

[0076] In some embodiments, one or more fans 24 may intersect a generally vertical plane, or may be offset or tilted relative to vertical in alignment with, for example, the rear spar in the tail cone 17 of the aircraft 10 .

[0077] In some embodiments, the one or more fans 24 are co-planar in a single plane that is substantially parallel to a transverse plane containing the pitch axis PA of the aircraft 10 and the yaw axis YA of the aircraft 10 .

[0078] One or more fans 24 may be spaced apart to allow cooling between fans 24 .

[0079] In some embodiments, one or more fans 24 of the system 12 may be positioned in a symmetry plane containing the roll axis RA and the yaw axis YA of the aircraft 10, such as Figure 3A The reflection symmetry or bidirectional symmetry is shown in the plane SP).

[0080] In some embodiments, cowlings 26 (forming cowling channels) or other structural components may surround the fans 24 to direct air to the air flow paths of the individual fans 24, thereby forming separate and independent flow channels 22 that are fluidly isolated, and each fan 24 may be fluidly isolated from each other. Conveniently, if a fan 24 or other component of the flow channel 22 fails, the isolated flow channels 22 may allow for less disruption to the other flow channels 22. Figure 4A and Figure 4B An exemplary flow channel 22 is shown in further detail in .

[0081] In some embodiments, multiple flow channels 22 may direct airflow to a single fan 24 .

[0082] Other suitable fan configurations are contemplated to allow for use in supplementing the thrust of the engines 14 of the aircraft 10 .

[0083] The system 12 , and particularly components of the system, such as the fan 24 , may be covered by a skin surface 52 formed from a suitable material, such as aluminum, an aluminum alloy, or a composite material.

[0084] In some embodiments, the skin surface 52 surrounding the fan 24 may have a larger diameter than the skin of a conventional tail cone 17 .

[0085] The skin surface 52 may be radially outward from the trajectory of the fuselage 18 skin, thereby allowing the inlet 21 to direct (intake or exhaust) air.

[0086] At the distal end of the flow channel 20, opposite the inlet 21, an outlet 25 directs the airflow (intake or exhaust) to the environment. The forward airflow 402 may be directed by one or more exhaust outlets 25 to the exhaust stream to exit at the rear of the aircraft 10. The outlets 25 may be separate and independent for each flow channel 22, such as those separated by fairings. Figure 3B As shown in . Figure 3B is a cross-sectional view taken along line 3B- 3B of the system 12 , illustrating the exhaust outlet 25 of each flow channel 22 .

[0087] In some embodiments, the system 12 includes an actuatable door, such as a reverse flow door 32, as part of a flow direction system 30 for each fan 24, as described below with reference to FIG. Figure 4A and Figure 4B Further details.

[0088] Figure 4A is a schematic side view of forward flow 402 drawn in direction A through flow channel 22 of system 12 with reverse flow door 32 in a closed position, according to an embodiment. Figure 4B is a schematic side view of reverse flow 404 of a flow channel 22 with reverse flow door 32 in an open position, according to an embodiment. Each of the plurality of fans 24 of system 12 may be disposed in a separate flow channel 22 as described herein.

[0089] The forward flow 402 may be accelerated by the fan 24 rotating in a first direction to push the air toward the outlet 25 at the rear of the aircraft 10. The acceleration of the forward flow 402 generates a forward thrust applied to the aircraft 10.

[0090] The reverse flow 404 may be accelerated by the fan 24 rotating in the second direction to push the air toward the inlet 21 and the front of the aircraft 10. The acceleration of the reverse flow 404 creates a reverse thrust applied to the aircraft 10.

[0091] like Figure 4A and Figure 4B As shown in FIG, the fan 24 has a plurality of rotors 242 and stators 244.

[0092] The flow direction system 30 includes a reverse flow gate 32 that is rotatably attached to the conduit 23 and can be moved in a reverse direction using a suitable actuator. Figure 4A The closed position shown in Figure 4B , and is actuated, e.g., rotated, between the open positions shown in FIG.

[0093] In some embodiments, the reverse flow door 32 can operate based on position detection of the rotational direction of the fan 24 (e.g., the rotor 242 of the fan 24). For example, when the fan 24 rotates in one direction to direct air flow in direction A, as shown in FIG. Figure 4AAs shown in FIG, the reverse flow door 32 can be operated in a closed position, e.g. Figure 4A When the fan 24 rotates in the opposite direction to direct the air flow in direction B, as shown in FIG. Figure 4B As shown in FIG, the reverse flow door 32 can be operated in an open position, e.g., as Figure 4B As shown in .

[0094] In some embodiments, the rotational direction of fan 24 is detected by a controller to selectively actuate reverse flow door 32 between open and closed positions.

[0095] In the closed position, as Figure 4A As shown in FIG, reverse flow door 32 covers (and in some embodiments, seals) opening 33 in duct 23, thereby directing forward flow 402 in a flow path from a front end of aircraft 10 (such as inlet 21) to a rear end of aircraft 10 (such as outlet 25).

[0096] In some embodiments, the reverse flow door 32 may be, for example, Figure 4B 10 , such as opening 33 , to an open position, thereby directing reverse flow 404 in a flow path in direction B through flow passage 22 from the rear end of aircraft 10 , such as opening 33 , to the front end of aircraft 10 , such as inlet 21 .

[0097] Instead of drawing air from the exhaust plane formed by outlet 25 , door 32 may provide a path for air flow through opening 33 to enter flow passage 22 , thereby creating reverse flow 404 , thus allowing additional reverse thrust to be generated.

[0098] The reverse flow doors 32 may also prevent reverse flow between the flow channels 22 that could affect flow speed and direction by allowing any overpressure or underpressure to vent to the outside air.

[0099] In some embodiments, the exhaust of the forward flow 402 of each fan 24 may be discharged to a common outlet or exhaust port.

[0100] In some embodiments, the exhaust of the reverse flow 402 of each fan 24 may be discharged to a common outlet or exhaust port.

[0101] Figure 4C is a schematic side view of fan 24 (including rotor 242 and stator 244 ) rotatably coupled and driven by electric motor 40 according to an embodiment.

[0102] like Figure 4C As shown in FIG, the input power can be supplied to the electric motor 40 to drive the electric motor 40, which in turn rotates the fan 24. The generated heat can be discharged, for example, out of the flow channel 22 through the outlet 25.

[0103] Figure 5 FIG is a partial front view of the system 12 according to an embodiment. Figure 5 As shown in , the system 12 may include an arrangement of six electric fans 24 disposed within a cavity within the tail cone 17 within the aircraft 10 , such as around the slanted bulkhead 13 .

[0104] The slanted bulkhead 13 may be a reinforcement structure within the tail cone 17 to which components, such as the fan 24, may be attached. The slanted bulkhead 13 may further serve as a fire barrier, for example, for an auxiliary power unit, such as the APU 11.

[0105] In some embodiments, the system 12 , including components such as the fan 24 , forms a self-contained unit within the tail cone 17 .

[0106] In some embodiments, components of the system 12, such as the fan 24, are positioned adjacent to the rear or aft spar of the aircraft 10. In some embodiments, the fan 24 may be positioned to intersect a plane formed by the aft spar of the vertical tail 19, which may serve as a firewall for the APU 11.

[0107] In some embodiments, the fan 24 may be positioned aft of the rear spar, such as within the cavity.

[0108] Figure 5 Also shown is an APU inlet duct 55 in fluid communication with an auxiliary power unit, such as APU 11, for drawing air in to direct the air to the auxiliary power unit.

[0109] The fan 24 and the APU inlet duct 55 may be separated by a cowl so that each is fluidly isolated.

[0110] In some embodiments, components of the system 12 , particularly the fan 24 , are positioned aft of the pylon of the aircraft 10 .

[0111] In some embodiments, fuel tanks in the tail cone 17 of the aircraft 10 may be displaced or removed to provide space to position the fan 24 closer to the centerline of the aircraft 10, thereby allowing for a smaller diameter of the skin surface 52. In some embodiments, the aircraft 10 does not require additional fuel from such tanks due to the improved fuel efficiency achieved by the system 12.

[0112] The system 12 may also include one or more electric motors 40 . In some embodiments, the one or more fans 24 are electric and may be coupled to and driven by the one or more electric motors 40 .

[0113] In some embodiments, electric motor 40 is an AC electric motor, such as an induction electric motor or an asynchronous electric motor, that is driven by an AC current source, such as a three-phase 400 Hz AC current generated by a generator.

[0114] In some embodiments, the electric motor 40 is a DC electric motor that is driven by a DC current source, such as provided by a generator, or a DC current provided by, for example, a battery, an accumulator or an external power source (such as a ground power unit), or a DC current provided by a suitable rectifier (such as a transformer-rectifier unit) that converts the AC current produced by the generator into DC, for example, a 28V DC current.

[0115] The electric motor 40 may be integrated with the one or more fans 24 and may be connected to the one or more fans 24 via a shaft connection (not shown).

[0116] The fan 24 may include multiple sets of rotors and stators, or multiple rows of fan blades. The fan 24 consumes torque obtained from an energy source, such as an electric motor 40. A fan of a particular shape and size may be designed to operate at maximum torque at a given RPM, while at high RPMs, the fan 24 may stall and lose efficiency. Thus, the number of rows of fan blades may be selected based on a combination of fan blade size, number of fan blades, fan speed RPM, and torque input.

[0117] In some embodiments, electric motor 40 can operate as a generator to generate electricity by converting the power from the rotation of fan 24 into electrical power through electromagnetic induction. In some embodiments, this electrical power can be stored in a battery or other suitable storage device.

[0118] One or more fans 24 may be driven by a single electric motor 40. In some embodiments, each fan 24 may be driven by a separate single electric motor 40. In other embodiments, a pair of fans 24 may be driven by a single electric motor 40.

[0119] Other suitable mechanisms for driving fan 24 are contemplated, such as, for example, a heat engine such as an internal combustion engine.

[0120] The system 12 may also include one or more controllers 50 , which may be implemented in hardware and / or software, to monitor and control the power, RPM, and direction of rotation of the fans 24 .

[0121] In some embodiments, one or more controllers 50 can be used to control the electric motor 40, such as the input power to the electric motor 40, and thus control the output torque from the electric motor 40. Thus, the controller 50 can control the rotation direction and speed of the fan 24, thereby controlling the amount of thrust generated for forward or reverse thrust. Each of the multiple fans 24 can operate independently and be controlled individually. For example, some fans 24 can function as thrust generators, while some fans 24 can function as generators.

[0122] In one example, fans 24 located near the top of the aircraft 10 may have a greater impact on the airflow around the vertical tail and, therefore, may be adjusted based on flight parameters, compared to fans 24 located near the bottom of the aircraft 10 (which may have less impact on the airflow and may be further away from the clean air and serve as a better source of regeneration). Thus, the lower fans 24 may be activated for regeneration, and the upper fans 24 may be activated for flight thrust modification.

[0123] In some embodiments, the one or more controllers may be the same or different and control any one or more of the electric motors 40 .

[0124] The system 12 may also include a centralized controller, such as an additional thrust controller 60, such as Figure 6 . The additional thrust controller 60 may provide logic for the operation of the system 12. In some embodiments, the additional thrust controller 60 and the controller 50 may be implemented as an integrated system. In other embodiments, the additional thrust controller 60 and the controller 50 may be implemented separately and independently and in communication with each other.

[0125] The additional thrust controller 60 may be implemented as a computing device or computer. The computer may include one or more data processors (hereinafter referred to as the singular) and one or more computer-readable memories (hereinafter referred to as the singular) storing machine-readable instructions executable by the data processors and configured to cause the data processors to generate one or more outputs (e.g., signals) to perform the steps of the methods described herein.

[0126] The computer may be part of the avionics suite of the aircraft 10. For example, in some embodiments, the computing device may perform additional functions beyond those described herein. In various embodiments, the computing device may include more than one computer or data processor, wherein the methods disclosed herein (or portions thereof) may be performed using multiple computers or data processors, or alternatively, may be performed entirely using a single computer or data processor.

[0127] The data processor may include any suitable means configured to cause a computer to perform a series of steps in order to implement a computer-implemented process such that when the instructions are executed by a computer or other programmable apparatus, the functions / actions specified in the methods described herein are performed.

[0128] The memory may include any suitable machine-readable storage medium. The memory may include non-transitory computer-readable storage media such as, but not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or apparatuses, or any suitable combination of the foregoing. The memory may include any suitable combination of any type of computer memory located internally or externally to the computer. The memory may include any storage means (e.g., device) suitable for retrievably storing machine-readable instructions that are executable by a data processor.

[0129] Various aspects of the present disclosure may be embodied as systems, devices, methods and / or computer program products. Thus, various aspects of the present disclosure may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. In addition, various aspects of the present disclosure may take the form of a computer program product embodied in one or more non-transitory computer-readable media (e.g., memory), the one or more non-transitory computer-readable media having a computer-readable program code (e.g., instruction) embodied thereon. Computer program code for performing operations for various aspects of the present disclosure according to instructions may be written in any combination of one or more programming languages. Such program code may be executed in whole or in part by a computer or other data processing device. It should be understood that, based on the present disclosure, those skilled in the art may easily write computer program code for implementing the methods disclosed herein.

[0130] like Figure 6 As shown in FIG, in some embodiments, the extra thrust controller 60 can be operably connected and in communication with a pilot input 62, an autopilot input 64, a full authority digital engine controller (FADEC) 66, an air data computer (ADC) 68 that digitizes signals received from sensors 69, and one or more controllers 50 for operating one or more electric motors 40 to drive one or more fans 24. In some embodiments, the extra thrust controller 60 is operably connected and in communication with the reverse flow door 32 for controlling and sensing the reverse flow door 32.

[0131] Pilot inputs 62 include inputs from the pilot to the flight controls, such as spoilers 63 for controlling the drag and lift components of the spoilers on the aircraft 10, speed brake push rods (not shown) for controlling the drag generated by the speed brakes, and throttles 64, such as throttle push rods, including controls such as forward and aft thrust control levers.

[0132] The autopilot inputs 65 may include flight mode, as well as airspeed and altitude information that may be input to the additional thrust controller 60 .

[0133] The FADEC 66 is a computing device configured to control engine performance and is in communication with the additional thrust controller 60 , sending information related to the RPM and fuel flow of the engine 14 to the additional thrust controller 60 .

[0134] One or more suitable sensors 69 measure real-time data associated with the operation of the aircraft 10 and receive as input, for example, flight conditions such as airspeed and altitude, temperature, flight path, and air or ground mode.

[0135] The sensor inputs may be received and processed by the ADC 68 , which communicates with the additional thrust controller 60 to transmit flight status information to the additional thrust controller 60 .

[0136] Based on received data, such as information regarding pilot inputs from pilot input 62 , autopilot inputs from autopilot input 65 , engine control information from FADEC 66 , and flight status information from ADC 68 , the additional thrust controller 60 may determine which combination of forward or reverse thrust / drag will be generated by the system 12 .

[0137] Based on the determined forward or reverse thrust / drag, the additional thrust controller 60 may send appropriate RPM, kW, and direction signals to the controller 50 to control each electric motor 40 , and thus each fan 24 .

[0138] In some embodiments, aircraft 10 is operated under pilot control, and flight path angle and aircraft acceleration may be controlled in part by system 12 .

[0139] In some embodiments, the aircraft 10 is operated in cruise mode with the autopilot on, and the additional thrust controller 60 may determine whether operating the fans 24 may result in a reduction in overall fuel burn and may alter the operation of the system 12, such as the amount of power sent to the system 12, to vary the amount of thrust produced, based on the monitored fuel consumption level.

[0140] In some embodiments, the additional thrust controller 60 monitors fuel burn in real time to modify the operation of the system 12 to optimize fuel burn and minimize energy consumption.

[0141] Thus, the additional thrust controller 60 may determine whether a fuel burn reduction may be achieved by operating the fan 24 of the system 12 using energy from the engine 14 , thereby producing an overall fuel consumption gain.

[0142] In some embodiments, the system 12 may be controlled by actuating a throttle lever, such as throttle 64, of the aircraft 10. The additional thrust controller 60 may determine whether to activate the system 12 and whether to increase or decrease thrust as needed.

[0143] In one example, if an engine 14 fails, the additional thrust controller 60 may increase the forward thrust produced by the system 12 .

[0144] In another example, if the speed brake push rod is activated, the additional thrust controller 60 may operate to reduce the thrust generated by the fan 24 and increase the drag.

[0145] In some embodiments, the extra thrust controller 60 can be configured to select an appropriate power source to drive the fan 24, for example, based on the desired amount of thrust generated. The extra thrust controller 60 can also be configured to operate the system 12 in a regenerative mode to capture energy, in situations where more drag or less thrust is desired.

[0146] The power source for powering system 12 may include a power source for operating one or more controllers 50 and / or one or more electric motors 40 to drive fan 24. The power source may include one or more generators, such as generator 50, driven by a gas turbine engine, such as one or more engines 14 or an APU.

[0147] In some embodiments, it may be possible to switch between multiple power sources for system 12 .

[0148] The power source may be selected, for example, by the additional thrust controller 60 based on the usage or operating mode of the system 12 , as discussed in further detail below.

[0149] In some embodiments, an aircraft 10 having a system 12 may include an APU, such as APU 11 , to power fans 24 of the system 12 , for example, for takeoff and go-around.

[0150] In one example, a larger APU than is typically provided may be employed to provide up to 800 shp (shaft horsepower) to the system 12 , particularly for takeoff and go-around operations.

[0151] While one air intake is generally sufficient for an APU used solely to generate electricity for the pneumatic and electrical systems of the aircraft 10, with larger APUs, it may be necessary to include a second air intake to provide additional air to the APU. As an example, two such intakes may be provided in Figure 5 Shown in the figure is the APU inlet 55.

[0152] Now refer to Figure 7 and Figure 9 , various power sources are used to illustrate various operating environments of the system 12. It should be understood that any one or more of the following power sources may be combined to provide power and control for the system 12 and may be controlled by a centralized controller, such as an additional thrust controller 60 (not shown) in communication with each power source and each controller 50.

[0153] Figure 7 is a schematic diagram of an operating environment for a turbine generator 70 , such as the APU 11 , feeding power to a system 12 , according to an embodiment.

[0154] exist Figure 7 In the embodiment shown in FIG, the power source for system 12 may be a turbine generator 70, for example, an auxiliary power unit such as APU 11, including a gas turbine engine 72 and a generator 74 supplied with fuel energy, or other suitable engine and generator. Thus, electric motor 40 is driven by electrical energy from the generator of an auxiliary power unit such as APU 11.

[0155] In some embodiments, the generator 74 is a generator for generating electricity. The generator 74 may be oil-cooled and include a gearbox for converting power from a shaft of a gas turbine engine, such as an APU, into electrical power.

[0156] In some embodiments, generator 74 is a synchronous AC generator (sometimes called an “alternator”), such as a permanent magnet generator.

[0157] In some embodiments, the generator 74 may have a power rating of 120 kVA. In some embodiments, the generator 74 generates AC current, such as a three-phase, 400 Hz, 115 or 120 phase voltage output.

[0158] like Figure 7 As shown in FIG, electrical energy generated from the turbine generator 70 is supplied to the controller 50, and the controller 50 powers and controls the operation of each electric motor 40. Each electric motor 40 is rotatably coupled to a ducted fan pair of the fan 24. Each controller 50 can control the electric motor 40 and serve as a backup for one or more other electric motors 40, so that if the controller 50 of the electric motor 40 fails, the backup controller 50 operates to control and power that electric motor 40.

[0159] The one or more controllers 50 may be of the same or different configurations and control any one or more of the electric motors 40 .

[0160] In use, fuel energy, in this example 18,550 BTU / lb or 11.98 kWh / kg, is supplied to the turbine generator 70 .

[0161] In an example, the turbine generator 70 can operate at an efficiency of approximately 28-48%, where efficiency is defined as useful energy output divided by energy input. In an example, the gas turbine engine 72 can operate at an efficiency of approximately 30% to 50%. In an example, the generator 74 can operate at an efficiency of approximately 95%.

[0162] In an example, the electric motor 40 can operate at approximately 95% efficiency. In an example, each pair of fans 24 can operate at approximately 80% efficiency.

[0163] In an example, the system 12 may be powered by the turbine generator 70 and draw approximately 500 kW of power from the turbine generator 70 in climb mode or automatic power reserve (APR) mode to provide thrust in the event of engine thrust loss during takeoff and missed approach conditions.

[0164] Figure 8 is a schematic diagram of another operating environment of the system 12 according to an embodiment.

[0165] exist Figure 8 In the embodiment shown in FIG, the power source for the system 12 may be a turbine generator 80 comprising a gas turbine engine 14 supplied with fuel energy and a generator 84, or other suitable engine and generator. Thus, the electric motor 40 is driven by electrical energy from the generator 84 of one or more engines 14 of the aircraft 10.

[0166] In some embodiments, the generator 84 may be similar to the wind turbine 74 , including structure and components.

[0167] like Figure 8 As shown in FIG, electric energy generated from the turbine generator 80 is supplied to the controller 50, and the controller 50 supplies power and controls the operation of each electric motor 40. Each electric motor 40 is rotatably coupled to the ducted fan pair of the fan 24. Each controller 50 can control the electric motor 40 and serve as a backup for the other electric motor 40 so that if the controller 50 of the electric motor 40 fails, the backup controller 50 operates to control and supply power to the electric motor 40.

[0168] The one or more controllers 50 may be the same or different and control any one or more of the electric motors 40 .

[0169] In use, fuel energy, in this example 18,550 BTU / lb or 11.98 kWh / kg, is supplied to each turbine generator 80 .

[0170] In an example, the turbine generator 70 can operate at an efficiency of approximately 28-48%, where efficiency is defined as useful energy output divided by energy input. In an example, the engine 72 can operate at an efficiency of approximately 30% to 50%. In an example, the generator 74 can operate at an efficiency of approximately 95%.

[0171] In an example, the electric motor 40 can operate at approximately 95% efficiency. In an example, each pair of fans 24 can operate at approximately 80% efficiency.

[0172] In an example, the system 12 may be powered by the turbine generator 80 and draw approximately 40 to 50 kW of power in cruise mode.

[0173] Figure 9 is a schematic diagram of a further operating environment of the system 12 according to an embodiment.

[0174] exist Figure 9 In the embodiment shown in FIG, the power source of the system 12 may be a battery 90. Thus, the electric motor 40 may be driven by the electrical energy supplied by the battery 90. In some embodiments, the power source includes a plurality of batteries 90, for example, a plurality of batteries configured as a battery pack.

[0175] In some embodiments, battery 90 can have a specific energy density of up to 0.5 kWh / kg. In other embodiments, battery 90 can have a specific energy density of up to 0.2 kWh / kg, and in another example, 0.25 kWh / kg.

[0176] The battery 90 , a plurality of batteries 90 , or a battery pack formed of batteries 90 may supply DC current to the inverter 92 or a plurality of inverters 92 .

[0177] Inverter 92 may be a suitable device or circuit that changes direct current (DC) to alternating current (AC).

[0178] In use, in one example, the inverter 92 can operate at approximately 98% efficiency, while the electric motor 40 can operate at approximately 95% efficiency. In one example, each pair of fans 24 can operate at approximately 80% efficiency.

[0179] like Figure 9As shown in FIG, electric energy generated by the battery 90 is supplied to the controller 50, and the controller 50 supplies power to each electric motor 40 and controls its operation. Each electric motor 40 is rotatably coupled to the ducted fan pair of the fan 24. Each controller 50 can control the electric motor 40 and serve as a backup for the other electric motor 40, so that if the controller 50 of the electric motor 40 fails, the backup controller 50 operates to control and supply power to the electric motor 40.

[0180] The one or more controllers 50 may be the same or different and control any one or more of the electric motors 40 .

[0181] In some embodiments, the electric motor 40 may be reversed to function as a generator to convert mechanical energy into electrical energy.Regenerative braking may be performed by converting mechanical energy from the propulsion of the aircraft 10 into an electrical load.

[0182] One or more batteries 90 can be used to power the system 12 to generate thrust, and can also operate in a regenerative mode to capture airflow, rotate the electric motor 40, and feed electrical energy back to the controller 50 and inverter 92 and the battery 90. The electric motor 40 can be used as a generator to convert mechanical energy into electrical energy to supply the one or more batteries 90. Thus, in the battery configuration, the system 12 is a fully reversible system.

[0183] In one example, the system 12 may capture energy during descent of the aircraft 10 and may be used to power electrical systems such as electric brakes during landing if an engine-driven generator fails, or if power is needed to power systems of a specialized mission aircraft.

[0184] In some embodiments, when in use, the system 12 may generate approximately 1,500 lbs of additional thrust (thrust minus drag) at 110 KCAS (knots corrected airspeed) near VMCG (minimum control speed on ground).

[0185] Figure 10 is a graph showing the relationship between excess thrust (thrust minus drag) in lbs of the aircraft 10 , including the thrust produced by the system 12 , on the y-axis and airspeed in KTAS (true airspeed in knots) on the x-axis.

[0186] Assuming propulsive efficiency, and based on the power input, the additional thrust can be determined by multiplying the input power by the efficiency and then dividing by the airspeed to produce Figure 10 The additional thrust multiplied by the airspeed yields the propulsive power.

[0187] In one embodiment, the additional thrust produced by the system 12 may approximate the thrust deficit between a larger engine (e.g., rated up to 12,600 lbs of static takeoff thrust) and a smaller and lighter engine (e.g., rated up to 7,700 lbs of static takeoff thrust) at a critical engine failure speed.

[0188] The system 12 may be powered by approximately 650 SHP from a power source such as an APU. The system 12 may be powered by a suitable power source, such as the APU 11 or the engine 114, based at least in part on the amount of additional thrust required.

[0189] The system 12 may be configured for various modes of operation of the aircraft 10, including: gate pushback, e.g., using a thrust reverser (TR) throttle pusher as a pilot input; taxiing, e.g., using a control stick with throttle-type inputs; during takeoff, to provide drag control and replace automatic power reserve (APR) by providing centerline thrust; during climb and cruise, e.g., to improve excess thrust (e.g., using an excess thrust controller 60 to adjust the thrust produced by the system 12 using automatic settings to minimize energy consumption) and, if the APU is not needed, to be provided by the main engines 14; flight path control, e.g., using a speed brake pusher to increase drag and allow for rapid thrust direction changes without using multi-function spoilers (MFS); providing backup power to aircraft systems as an alternative to a ram air turbine (RAT); and regeneration, storing energy as needed in a battery such as the battery 90.

[0190] The system 12 can be configured for a reduced VMCG (Minimum Control Speed ​​on Ground). The VMCG is the minimum speed on the ground at which aerodynamic control can be used to maintain directional control with one engine inoperative. Thus, the VMCG is proportional to the asymmetric thrust (when one engine fails) and the rudder deflection applied to offset the asymmetric thrust.

[0191] Using system 12 by generating thrust to counteract asymmetric thrust may allow for smaller VMCG with smaller airframe mounted engines, such as engine 14. Similarly, system 12 may allow for smaller VMCA (minimum control speed in air).

[0192] During various operating modes of the aircraft 10 , the system 12 may draw power from power sources such as those described herein.

[0193] For example, when aircraft 10 is taxiing, it may be propelled by system 12 , which may draw power from APU 11 .

[0194] The system 12 may be configured to generate forward takeoff thrust to supplement the thrust generated by the engines 14 (eg, the first engine and the second engine) during takeoff of the aircraft 10 .

[0195] To generate additional forward thrust for takeoff or as the aircraft 10 climbs or goes around, the system 12 can draw power from the APU 11, which may be needed to supplement the thrust generated by the engines 14 and reduce drag. For example, using smaller engines 14 may require more thrust generated by the system 12 during takeoff.

[0196] In the climb mode, the system 12 may be powered by the APU 11 and configured to operate from a power source (e.g., Figure 7 The generator 74 , shown and described above, draws approximately 500 kW, resulting in approximately 500 kW of energy being applied to the feed system 12 .

[0197] The system 12 may be configured to generate forward cruise thrust to supplement the thrust generated by the engines 14 (eg, the first engine and the second engine) during cruise of the aircraft 10 .

[0198] In cruise mode, the system 12 may be configured to draw approximately 40 to 50 kW from a power source (eg, a generator 84 powered by the engine 14). Figure 8 Thus, approximately 40-50 kW of energy may be required to accelerate the mass flow from the boundary layer back to the actual airspeed, thereby reducing the fuselage pressure drag.

[0199] At cruise, the main systems 14 may be driven primarily by the main engines 14 to provide control over drag, as the APU 11 may be shut down during cruise, which may improve fuel burn.

[0200] During cruise mode, it may be desirable to minimize fuel burn by reducing drag because the engines 14 can generate sufficient thrust. The system 12 can minimize the aircraft's energy use compared to the distance traveled, whereby energy use is defined as the sum of all fuel burn sources. The thrust increase and drag reduction of the system 12 can be modified to minimize fuel burn.

[0201] In some embodiments, the additional thrust controller 60 may manage the supply of power from the aircraft 10 to the system 12 to minimize fuel burn.

[0202] In some embodiments, the additional thrust controller 60 may monitor fuel burn in real time to optimize it, particularly by minimizing the sum of fuel burn of, for example, the engine 14 and the APU 11 .

[0203] During landing or descent, system 12 may generate reverse thrust and added drag to cause aircraft 10 to descend.

[0204] The system 12 can generate drag and descent without using the engine and without using speed brakes.

[0205] In some embodiments, the battery 90 can capture energy during descent and reduce the overall fuel burn of the aircraft 10, and the battery 90 can also power the electric brakes for landing.

[0206] In regenerative mode, system 12 may be operated to generate electrical energy for storage in battery 90 , for example.

[0207] In some embodiments, fan 24 may be configured to rotate through a flow, such as forward flow 402 or reverse flow 404 , to capture energy.

[0208] The fan 24 may be connected to a generator, such as an electric motor 40 that operates as a generator to generate electrical energy, and the electrical energy may be used in a battery pack configuration, such as Figure 9 The battery 90 shown in FIG, or supplied to a suitable system.

[0209] Thus, the fan 24 may function as a ram air turbine as required by the energy system and may operate as a small wind turbine connected to a hydraulic pump or generator of the aircraft 10 .

[0210] In one example, system 12 may generate electricity in the event of a loss of engine 14 , or may be used to provide all power for a particular mission.

[0211] In another example, when in use, some of the fans 24 of the system 12 can generate thrust, while some other fans 24 can generate electrical energy. For example, the system 12 can include six fans 24. Four of the six fans 24 can generate forward thrust, and two of the fans can function as generators, such as in a fault mode.

[0212] The system 12 can be configured to provide backup power for the aircraft 10. In some embodiments, the system 12 is energized when the brakes are released. Then, if one of the engines 14 fails, the system 12 activates to provide automatic performance reserve (APR) (or boost) to generate additional thrust.

[0213] Figure 11 1 is a flow chart of a method for controlling thrust and drag of aircraft 10 according to an embodiment, which may be performed by fan 24 of system 12 to generate forward thrust or reverse thrust, or to increase or decrease drag. These steps are provided for illustrative purposes. Variations on the steps, omissions or substitutions of various steps, or additional steps are contemplated.

[0214] At block 1102 , an air flow, such as the forward flow 402 or the reverse flow 404 , is extracted from a boundary layer formed during movement of the aircraft 10 .

[0215] At block 1104 , air flow may be directed or re-energized by the flow passage 22 to minimize turbulence.

[0216] At block 1106 , the airflow may be accelerated, for example, by rotating the fan 24 in a first direction to push the airflow toward the rear of the aircraft 10 to generate forward thrust, or rotating the fan 24 in a second direction to push the airflow toward the front of the aircraft 10 to generate reverse thrust.

[0217] It should be understood that one or more blocks may be performed in a different order, or in an interleaved or iterative manner.

[0218] In some embodiments, the fan 24 of the system 12 is positioned on the aircraft 10 so that the fan 24 can draw air from within the boundary layer formed by the movement of the aircraft 10. In some embodiments, the fan 24 is positioned on the aircraft 10 so that the only airflow drawn in by the system 12 is boundary layer air, without extending radially beyond the boundary layer to draw in clean air. Thus, in some embodiments, the system 12 draws in only boundary layer air.

[0219] In some embodiments, one or more fans 24 are positioned entirely within a distance from the aircraft surface that is less than the thickness of a boundary layer formed by the surface of aircraft 10 during takeoff and cruise, which may be defined as the distance from the surface to the point where the velocity of the local flow is ninety-nine percent of the velocity of the surrounding free stream.

[0220] The system 12 may use boundary layer ingestion to reduce the propulsive power consumption of the aircraft by generating thrust from the reduced velocity boundary layer air, thereby reducing fuel consumption.

[0221] Conveniently, the system 12 can reduce fuel burn by approximately 3% to 5% by ingesting boundary layer air rather than a clean air stream.

[0222] A key challenge associated with boundary layer induction systems is the ability of the turbomachinery to operate efficiently in highly distorted flows.

[0223] The fan 24 of the system 12 can be arranged to be completely within the boundary layer under certain operating parameters. Thus, the inlet airflow (turbulent) can be slower and the blades of the fan 24 can be thicker because the fan 24 does not have to deal with a fast (laminar) flow to meet pressure fluctuations, and blade stress can be resolved by using thicker blades.

[0224] Figure 12is a schematic diagram illustrating the forces acting on the aircraft 10 in flight: lift L, weight W, thrust T, and drag D, and the climb angle γ, which is defined as the angle between a horizontal plane representing the surface of the earth and the actual flight path followed by the aircraft 10.

[0225] The forces in flight can be defined as follows:

[0226] W sin (γ)=TD (1)

[0227] Where W is the weight of the aircraft 10, γ is the climb angle, T is the thrust, and D is the drag.

[0228] Equation (1) can be rearranged as:

[0229]

[0230] thus,

[0231]

[0232] Thrust T and drag D are vector quantities and thus have magnitudes and directions associated with them. The net external force on the aircraft 10 can be referred to as "excess thrust" and can be defined as thrust T minus drag D, thus also being a vector quantity. The system 12 can be configured to control and vary the excess thrust, for example, by increasing forward or reverse thrust and increasing or decreasing drag, thereby controlling the flight path of the aircraft 10. By determining a desired flight path angle or acceleration based on inputs such as pilot input, autopilot input, and various sensor feedback, a determined amount of energy can be sent to the system 12.

[0233] Thus, thrust T may be modified by system 12 to provide forward or reverse thrust during takeoff and other situations using the techniques described herein.

[0234] Conveniently, the system 12 may replace thrust reversers on engines such as one or more engines 14 and improve fuel combustion on those engines, providing less leakage, less weight, and less cost.

[0235] System 12 may also be configured to modify (increase or decrease) resistance D using the techniques described herein.

[0236] In some configurations, the system 12 may allow for the use of smaller and lighter engines, which may reduce costs. The specific fuel consumption (SFC) of a smaller engine in conjunction with embodiments of the system 12 may be similar or improved compared to a derated larger engine.

[0237] Use of the system 12 may allow for a lighter aircraft 10 with a lower operational empty weight (OEW), in one example, a 6,000 lb reduction in empty weight, thereby reducing costs.

[0238] Based on simulated sample missions, both the smaller engine in combination with an embodiment of the system 12 and the derated larger engine produced similar fuel consumption, and similar range, and aerodynamics did not necessarily need to be optimized.

[0239] In another configuration, the system 12 can replace the thrust reversers on a conventional engine. Based on simulated sample missions, replacing the system 12 can be weight and cost neutral, with a small range increase (about 1%) at maximum payload and a fuel burn reduction of about 1.5% at 600nm.

[0240] Removing the thrust reversers from a conventional engine and including some configurations of the system 12 may result in weight and cost reductions, for example, approximately a 3.5% basis weight (BOW) reduction.

[0241] The system 12 may also allow for an increase in range at maximum payload (approximately >17%) and a reduction in fuel burn of approximately >12% for 600 nm, an increase in initial climb altitude (ICA) for maximum range, full fuel and full load, negligible impact on takeoff weight (WAT) limitations, minimal impact on takeoff distance (with the same range-payload), and a reduction in VMCG / VMCA (for short field operations (SFO)).

[0242] Thus, system 12 may save fleet costs.

[0243] Structurally, in some embodiments, the system 12 does not provide for wing aerodynamic changes, however, the tail box of the aircraft may be removed, thereby further reducing weight and cost, and also increasing range.

[0244] Advantageously, the system 12 may provide higher range, reduced fuel burn (lower fuel consumption), and improved product perception (in the form of a hybrid aircraft).

[0245] The system 12 may allow the aircraft to taxi with the engines shut down, potentially taxiing out of a terminal gate and reducing climb and cruise drag.

[0246] The system 12 can provide both in-flight thrust reversers (flight path control, including steep approaches without multi-function spoilers (MFS), and improved emergency descents), as well as ground thrust reversers (with improved stopping capabilities).

[0247] Because the system 12 can provide reverse thrust, the main engine thrust reversers can be removed from the main engines. Removing the main engine thrust reversers can reduce weight and cost, and in one example, can improve the engine's SFC (specific fuel consumption) by approximately 0.5%.

[0248] The system 12 may also provide improved VMCA / VMCG, additional thrust management along the aircraft centerline, resulting in a smaller vertical tail and reduced weight and cost.

[0249] The system 12 can improve short-distance performance and wet / dirty performance.

[0250] The system 12 may also be configured to function as a ram air turbine (RAT), and the conventional RAT may be eliminated.

[0251] The system 12 may also provide regenerative capabilities, such as with batteries or electrical systems.

[0252] The system 12 may be sized to produce a force equivalent to the missing takeoff thrust for an OEI takeoff and a go-around with the engine being replaced, and may not be required in other phases of flight from a thrust perspective.

[0253] At typical aircraft missions (500 nm and 1000 nm), the integrated system 12 has the potential to reduce fuel burn by over 10%. For example, at a 1000 nm mission, it is possible to reduce fuel burn by 852 pounds of fuel (over one ton of CO2).

[0254] The systems and methods described herein may be used in additional applications, such as integrating the powerplant into the fuselage and reducing the pitching moment caused by engine thrust variations to increase fuel efficiency and potentially eliminate the horizontal tail, thereby reducing weight and cost.

[0255] Other applications include increasing the initial climb altitude (ICA) to attempt to increase flight altitude, such as to 41,000 feet.

[0256] In other applications, embodiments of the system 12 may be adjusted during cruise, via a power management computer, to minimize fuel burn at certain altitudes, including shutting down the APU.

[0257] Of course, the above embodiments are illustrative only and are by no means restrictive. The embodiments described are susceptible to numerous modifications in form, arrangement of parts, details, and sequence of operations. The present disclosure is intended to encompass all such modifications within the scope of the claims.

Claims

1. A system for varying the additional thrust of an aircraft, comprising: a first electric fan rotatable about a first axis to direct a first air flow along a first air flow path; a second motorized fan rotatable about a second axis different from the first axis to direct a second air flow along a second air flow path, the second air flow path being fluidly isolated from the first air flow path; as well as first and second air inlets in fluid communication with the auxiliary power unit to direct air to the auxiliary power unit, wherein the first electric fan and the second electric fan are arranged radially around the roll axis of the aircraft and adjacent to the rear end of the aircraft; The first electric fan and the second electric fan are arranged in a cavity within a tail cone within the aircraft; The first electric fan and the second electric fan are configured to draw boundary layer air to form the first air flow and the second air flow; and The first and second air intakes for the auxiliary power unit are also disposed within a cavity within a tail cone within the aircraft, wherein the first and second electric fans are radially disposed about a roll axis of the aircraft.

2. The system according to claim 1, wherein: The first electric fan and the second electric fan are coplanar in a single plane parallel to a transverse plane containing a pitch axis of the aircraft and a yaw axis of the aircraft.

3. The system according to claim 1, wherein: The first electric fan and the second electric fan are bilaterally symmetrical in a symmetry plane including the roll axis and the yaw axis of the aircraft. 4 . The system of claim 1 , further comprising a cowling duct surrounding the first electric fan to direct air toward the first air flow path, and the cowling duct surrounding the second electric fan to direct air toward the second air flow path.

5. The system according to claim 1, wherein The first electric fan and the second electric fan are driven by respective electric motors.

6. The system according to claim 5, wherein: The electric motor is driven by electrical energy from a generator of the auxiliary power unit.

7. The system according to claim 5, wherein: The electric motor is driven by electric energy supplied from a battery.

8. The system according to claim 7, wherein: The electric motor can function as a generator to convert mechanical energy into electrical energy to supply the battery.

9. The system according to claim 5, wherein: The electric motor is driven by electrical energy from a generator of one or more engines of the aircraft.

10. The system according to claim 5, wherein: The system further includes one or more controllers that control the electric motors.

11. The system according to claim 1, wherein: The first electric fan and the second electric fan are ducted fans.

12. The system according to claim 1, wherein: The first axis and the second axis are parallel to the roll axis of the aircraft.

13. The system of claim 1, wherein: The first and second electric fans are arranged entirely within a distance from an aircraft surface that is less than a boundary layer thickness formed by the aircraft surface during takeoff and cruise of the aircraft, the boundary layer thickness being the distance from the surface to a point where the velocity of the local flow is ninety-nine percent of the ambient free stream velocity.

14. The system of claim 1, further comprising: a first door actuatable between a closed position in which a forward flow of the first airflow in the first airflow path is directed from a forward end of the aircraft to the aft end of the aircraft, and an open position in which a reverse flow of the first airflow in the first airflow path is directed from the aft end of the aircraft to the forward end of the aircraft; and a second door actuatable between a closed position directing a forward flow of the second airflow in the second air flow path from the second end of the aircraft to the aft end of the aircraft and an open position directing a reverse flow of the second airflow in the second air flow path from the aft end of the aircraft to the forward end of the aircraft.

15. The system of claim 1, further comprising: a third electric fan rotatable about a third axis to direct a third air flow along a third air flow path; a fourth electric fan rotatable about a fourth axis to direct a fourth air flow along a fourth air flow path; a fifth electric fan rotatable about a fifth axis to direct a fifth air flow along a fifth air flow path; and a sixth electric fan rotatable about a sixth axis to direct a sixth air flow along a sixth air flow path, The third electric fan, the fourth electric fan, the fifth electric fan, and the sixth electric fan are radially arranged around the roll axis of the aircraft and adjacent to the rear end of the aircraft, and are configured to draw 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 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 each fluidly isolated from one another.

16. An aircraft comprising a first engine, a second engine, and the system of claim 1.

17. The aircraft according to claim 16, wherein: The system is configured to generate forward takeoff thrust during takeoff of an aircraft to supplement the thrust generated by the first engine and the second engine.

18. The aircraft of claim 16, wherein: The system is configured to generate forward cruise thrust during aircraft cruise to supplement thrust generated by the first engine and the second engine.

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