PYROTECHNIC WHEEL ACCELERATION SYSTEM

Wheel acceleration systems are disclosed that provide a motive force to at least one wheel of an aircraft, in order to accelerate the aircraft to takeoff speed with the assistance of main engine thrust. The wheel acceleration system includes a pyrotechnic unit configured to generate expanding gases by combusting a propellant, and a rotary propulsion unit pneumatically coupled to the pyrotechnic unit. The rotary propulsion unit includes an impeller configured to be driven by the expanding gases and to deliver torque to the wheel.

BACKGROUND

Most aircraft are equipped with landing gear that enables travel on the ground during takeoff, landing, and taxiing phases. These landing gear comprise a plurality of wheels, which may be arranged according to configurations varying from one aircraft to another. For takeoff, aircraft traditionally rely on main engine thrust in order to reach flying speed.

Aircraft with low engine thrust and relatively high overall mass have lengthy takeoff distances, as it takes a long time for the low thrust to accelerate the aircraft to flying speed. Although this combination is often acceptable, for instance with long-endurance aircraft and self-launching gliders, in many cases the long takeoff distance is not desirable. Indeed, there are times when operation from reduced runway lengths is necessary—such as the operation of aircraft from aircraft ship decks or when operating from improvised airfields of limited length. While catapults and other such mechanisms effectively reduce take distance, such solutions are not always available. Thus, a means of reducing the takeoff length is desired.

Wheel drive systems have been proposed to assist with taxiing, and in some cases to assist aircraft with takeoff. One known wheel drive system is set forth in US Patent Publication No. 2015/0314859, and assigned to Safran Landing Systems. Such a system proposes an undercarriage leg supporting an electric drive actuator, which drives rotation of a landing gear wheel via a reduction gearset. Another known electrical drive system is set forth in US Patent Publication No. 2016/0096619, also assigned to Safran Landing Systems. While these systems are well-suited to taxiing applications, they are not suited to the task of quickly accelerating an aircraft to takeoff speeds, except potentially for very lightweight aircraft. For weight and space reasons, such known systems cannot scale in order to deliver the torque and power output necessary to accelerate even modestly sized aircraft from a ship deck or improvised runway, even with the assistance of main engine thrust.

Accordingly, there is a continuing need in the industry for improved techniques of reducing the takeoff length through an aircraft mounted system.

SUMMARY

The present disclosure provides examples of innovative aircraft-mounted wheel acceleration systems that utilize pyrotechnic cartridge-powered rotary propulsion units, which in turn deliver high torque and power output to one or more aircraft wheels, in order to accelerate the aircraft to flying speed in connection with main engine thrust.

In accordance with an aspect of the present disclosure, a wheel acceleration system is provided. The wheel acceleration system is configured to apply a motive force to at least one wheel mounted to a landing gear of an aircraft. The wheel acceleration system includes a pyrotechnic unit configured to generate expanding gases by combusting a propellant, and a rotary propulsion unit pneumatically coupled to the pyrotechnic unit. The rotary propulsion unit includes an impeller configured to be driven by the expanding gases and to deliver torque to the wheel (e.g., to an output shaft coupled to the wheel).

In any of the embodiments described herein, the rotary propulsion unit and/or the pyrotechnic unit is mounted to the landing gear.

In any of the embodiments described herein, the impeller of the rotary propulsion unit is part of a turbine or an expansion vane motor.

In any of the embodiments described herein, the impeller is coupled to the wheel (e.g., coupled to an output shaft of the wheel) via a reduction gearbox.

In any of the embodiments described herein, the rotary propulsion unit is contained within an outer housing configured to be mounted to the landing gear.

In any of the embodiments described herein, the wheel acceleration system can include a clutch coupling the impeller to the wheel (e.g., coupling the impeller to an output shaft to the wheel, or coupling an output shaft to the wheel).

In any of the embodiments described herein, the wheel acceleration system can include a flywheel coupled with rotary propulsion unit (e.g., to an output shaft of the rotary propulsion unit), the flywheel being configured to selectively engage the aircraft wheel.

In any of the embodiments described herein, the pyrotechnic unit and the rotary propulsion unit are contained in a common outer housing.

In any of the embodiments described herein, the pyrotechnic unit comprises a breech configured to receive a pyrotechnic cartridge containing the propellant.

In any of the embodiments described herein, the pyrotechnic cartridge is a pressure vessel and the pyrotechnic unit is configured to jettison the pyrotechnic cartridge by releasing a gas connector that couples the pyrotechnic cartridge to the pyrotechnic unit.

In any of the embodiments described herein, the wheel acceleration system can include a second rotary propulsion unit comprising a second impeller configured to be driven by the expanding gases of the pyrotechnic unit, the second impeller configured to be driven by the expanding gases and to deliver torque to a second wheel of the aircraft (e.g., to a second output shaft of the second wheel).

In any of the embodiments described herein, the pyrotechnic unit is mounted to a fuselage of the aircraft, the rotary propulsion unit is mounted to the landing gear, and the second rotary propulsion unit is mounted to a second landing gear of the aircraft.

In any of the embodiments described herein, the pyrotechnic unit is configured to deliver the expanding gases to the rotary propulsion unit via a first fluid circuit and to the second rotary propulsion unit via a second fluid circuit.

In any of the embodiments described herein, the pyrotechnic unit and the rotary propulsion unit are mounted to a fuselage of the aircraft or to the aircraft landing gear.

In any of the embodiments described herein, the rotary propulsion unit is configured to rotatably drive the wheel and a second wheel of the aircraft with a plurality of drive shaft assemblies.

In any of the embodiments described herein, the rotary propulsion unit is configured to deliver a torque output of at least 1500 Nm to the wheel (e.g., to an output shaft of the wheel).

In any of the embodiments described herein, the rotary propulsion unit is configured to deliver a power output of at least 800 Kilowatts to the wheel (e.g., to an output shaft of the wheel).

In accordance with another aspect of the present disclosure, a landing gear is provided, equipped with at least one wheel acceleration system as described herein.

In accordance with still another aspect of the present disclosure, an aircraft is provided, equipped with at least one wheel acceleration system of the present disclosure.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appended drawings, where like numerals reference like elements, is intended as a description of various embodiments of the disclosed subject matter and is not intended to represent the only embodiments. Each embodiment described in this disclosure is provided as a representative example or illustration and should not be construed as preferred or advantageous over other embodiments. The representative examples provided herein are not intended to be exhaustive or to limit the claimed subject matter to the precise forms disclosed.

Terms such as, but not limited to, “upper,” “lower,” “inboard,” “outboard,” “top,” “bottom,” “side,” “vertical,” “horizontal,” and “lateral” in the present disclosure is meant to provide orientation for the reader with reference to the drawings and is not intended to be the required orientation of the components or to impart orientation limitations into the claims.

The present disclosure relates to aircraft-mounted wheel acceleration systems, in addition to aircraft landing gear systems and aircraft equipped with such wheel acceleration systems. The wheel acceleration systems of the present disclosure are aircraft-mounted systems configured to assist with the acceleration of the aircraft to flying speeds, for example with the assistance of main engine thrust. Restated, the power delivered by the wheel acceleration systems and main engine thrust together accelerate the aircraft to takeoff speeds. Such systems have wide applicability to commercial and military aircraft. Advantageously, such wheel acceleration systems effectively reduce takeoff distance, which can enable aircraft to operate from aircraft ship decks and/or improvised runways.

As will be described below, the wheel acceleration systems of the present disclosure utilize pyrotechnic charges to generate expanding gases, which in turn drive an impeller that delivers high torque and power to at least one wheel of the aircraft, thereby accelerating the aircraft during the takeoff phase. Following takeoff, the wheel acceleration systems may be stowed on the aircraft or at least partially jettisoned in order to reduce “dead weight.”

Advantageously, the wheel acceleration systems of the present disclosure provide sufficient power density to accelerate military aircraft to takeoff speeds, without overly penalizing flying weight.

FIG. 1Ais a schematic diagram of an aircraft102equipped with a landing gear104and a wheel106. The landing gear104may include one or more struts, legs, or the like. The aircraft102may be any type of aircraft102, for example military “fighter” type aircraft having a takeoff weight of 4,000 kg or greater, which are tasked with operating from improvised runways or ship decks. Accordingly, the landing gear104and wheel106include the landing gear structure and wheels of such aircraft102, including one or more struts, legs, or the like. In the representative embodiment shown, the landing gear104includes a landing gear leg and at least one axle shaft108. The wheel106is mounted upon the axle shaft108or may be coupled to the axle shaft108by a coupler110such that it is configured for rotational movement. As used herein, “aircraft wheel” refers to both the wheel itself and any tire mounted upon the wheel. In one application, the wheels106include the rear wheels of such aircraft (e.g., wheels mounted to the wings or a rearward portion of the fuselage), which generally experience greater friction with the runway surface during takeoff, and thus are well-suited to accelerating the aircraft due to greater traction. However, it is contemplated that the wheel acceleration systems of the present disclosure are suitable for use with the front wheels (i.e., wheels attached to a front portion of the fuselage), rather than the rear wheels. It is further contemplated that wheel acceleration systems of the present disclosure may be utilized on the front and/or rear wheels of a tandem-style landing gear, with wheels on a tail-mounted landing gear, with wheels on landing gear having a plurality of bogies, and with any other type of landing gear.

The aircraft102is equipped with a representative wheel acceleration system120in accordance with an embodiment of the present disclosure, which is configured to apply a motive force to the wheel106. It is contemplated that in some embodiments, the aircraft102is equipped with a plurality of wheel acceleration systems120. For brevity and clarity, a single wheel acceleration system120is described below in connection withFIG. 1A.

The aircraft-mounted wheel acceleration system120may be mounted in a number of configurations relative to the aircraft102. In some embodiments, the wheel acceleration system120is mounted at least partially upon the landing gear104, while in some embodiments, the wheel acceleration system120is mounted at least partially upon a fuselage, wing, or other non-landing gear portion of the aircraft102. Representative mounting configurations are described below with respect toFIGS. 2A-3B.

Referring toFIG. 1A, the wheel acceleration system120includes two primary subsystems: a pyrotechnic unit130and a rotary propulsion unit160. As will be described in detail below, the pyrotechnic unit130is configured to generate expanding gases by combusting a propellant, whereas the rotary propulsion unit160is configured to utilize the expanding gases from the pyrotechnic unit130to create rotary motion, and thus to rotatably drive at least the wheel106. AlthoughFIG. 1Aillustrates certain components as forming part of the pyrotechnic unit130or the rotary propulsion unit160, such demarcations are representative, not limiting. In some embodiments, the rotary propulsion unit160is configured to drive more than one wheel.

In some embodiments, the pyrotechnic unit130is configured to utilize a pyrotechnic cartridge132, which is separate from the pyrotechnic unit130in the illustrated embodiment, but in some embodiments forms part of the pyrotechnic unit130. The pyrotechnic cartridge132includes an outer casing or shell which contains within it a propellant134, e.g., a solid or liquid fuel. Representative solid propellants include ammonium nitrate-based propellants suspended in a combustible binder. Representative liquid propellants include hyrdrazine, red nitric acid and jet fuel, and the like. Representative pyrotechnic cartridges132include MXU-4A and MXU-4A/A starting cartridges, formerly manufactured by Talley Industries, Inc. of Mesa, Ariz. Whether the propellant134is a solid or liquid fuel, its characteristics (e.g., grain composition, size, concentration, chemistry, and/or distribution) can be adjusted to achieve a desired burn rate, gas volume, gas temperature, and other pyrotechnic performance parameters. In some embodiments, the pyrotechnic cartridge132includes an integrated ignitor, e.g., an electro-explosive device (not shown).

A breech136may be provided for forming a pressure vessel configured to receive the pyrotechnic cartridge132, and is selectively sealed by a breech cap138(which itself can form part of the breech136). In the illustrated embodiment, the breech cap138can be selectively opened in order to remove and replace the pyrotechnic cartridge132, e.g., after depletion of the propellant and between flights.

In the illustrated embodiment, the breech136is operatively coupled to an electrical connector140, which is configured to receive an ignition signal, e.g., from a pilot of the aircraft102, a controller on board the aircraft102, or remotely. The ignition signal initiates an ignitor142(e.g., an electro-explosive device, an electrical ignition device, a firing pin, or the like), which in turn ignites the propellant134within the pyrotechnic cartridge132. This ignition of the propellant134causes an exothermic reaction, which generates hot expanding gases144within the pressure vessel formed by the breech136and breech cap138. Some embodiments include a mechanical ignitor, either as an alternative or backup to the ignitor142. Such embodiments include a firing pin or similar mechanical ignition device disposed on or proximal to the breech136.

Fluid circuit146channels the expanding gases from the breech136to the rotary propulsion unit160. Depending on the mounting location of the pyrotechnic unit130, the fluid circuit146can have different forms. For example, in embodiments in which the pyrotechnic unit130and rotary propulsion unit160have a fixed relative location (e.g., both are mounted on the aircraft landing gear as inFIG. 2Aor both located centrally on the fuselage of the aircraft as inFIG. 3B), the fluid circuit146can be a fixed/rigid fluid circuit. In other embodiments in which the relative positions of the pyrotechnic unit130and the rotary propulsion unit160vary during takeoff or flight, the fluid circuit146is a flexible fluid circuit. Such flexible fluid circuit advantageously enables relative movement of the rotary propulsion unit160and the pyrotechnic unit130, e.g., in embodiments in which the pyrotechnic unit130is located centrally on the aircraft fuselage and the rotary propulsion unit160is located on the landing gear104(as inFIG. 3A). Representative fluid circuit146includes high temperature-resistant flexible exhaust ducting, rigid exhaust fluid circuit, articulating exhaust joints, and the like. Although the fluid circuit146is shown as part of the pyrotechnic unit130inFIG. 1A, it may at least partially form part of the rotary propulsion unit160in some embodiments.

A relief valve148is fitted to the fluid circuit146and configured to vent any excess gases produced by the pyrotechnic cartridge132which cannot be consumed by the rotary propulsion unit160(as described below). In the illustrated embodiment, the relief valve148is positioned upstream of an optional gas connector150(e.g., a flanged exhaust fitting) which pneumatically connects the fluid circuit146to the rotary propulsion unit160. However, in some embodiments, the relief valve148and gas connector150have different relative positions. For example, in some embodiments, the relief valve148is located downstream of the gas connector150; in such embodiments, the relief valve148and at least a portion of the fluid circuit146form part of the rotary propulsion unit160. As another example, the gas connector150is disposed at an upstream end of the fluid circuit146(e.g., where the fluid circuit146meets the breech136or breech cap138; accordingly, the relief valve148is also disposed downstream of the fluid circuit146in such embodiments.

The rotary propulsion unit160connects with the pyrotechnic unit130via the fluid circuit146, e.g. at the gas connector150. As noted above, the rotary propulsion unit160is configured to utilize the expanding gases144from the pyrotechnic unit130to create rotary motion, and thus to rotatably drive the wheel106. That is, the rotary propulsion unit160utilizes, for example, an expansion vane motor, a turbine, or similar rotary motor to create torque to drive the wheel106.

Still referring toFIG. 1A, the rotary propulsion unit160is housed within an outer housing162configured for mounting upon the landing gear104or the fuselage, wing, or other part of the aircraft102. In one representative embodiment, the outer housing162includes one or more brackets, fasteners, and the like configured to secure the rotary propulsion unit160to a leg, strut, fuselage, wing, or other part of the aircraft102.

The outer housing162has a gas inlet164in fluid communication with the fluid circuit146and configured to receive the expanding gases144. The outer housing162rotatably supports at least one impeller166therein, the vanes of which are acted upon by the expanding gases144, which causes the impeller166to rotate its impeller shaft168, ultimately delivering torque to the wheel106and accelerating the aircraft102. The spent gases exit the outer housing162through one or more gas outlets170.

In an embodiment, the impeller166is part of an expansion vane motor, i.e., a pneumatic motor wherein the impeller166comprises a rotor and a plurality of expansion vanes housed within an eccentric stator. The expansion vanes expand and contract radially in order to follow the internal eccentricity of the stator. Consequently, the expanding vane surface offsets declining gas pressure within the stator, causing substantially uniform force delivery along an intake arc about the impeller shaft168. One advantageous feature of vane motors is relatively high torque delivery at low speeds. These features make the expansion vane motor well-suited to delivering relatively high starting torque to the impeller shaft168.

One representative expansion vane motor that can be practiced with embodiments of the present disclosure is described in SAE Technical Paper No. 861714, which is hereby incorporated by reference. See Dusenberry, G. and Carlson, D., “Development of a Hot Gas Vane Motor for Aircraft Starting Systems,” SAE Technical Paper 861714, 1986, https://doi.org/10.4271/861714. Other representative pneumatic expansion vane motors that may be employed include the LZL Vane Air Motors manufactured by Atlas Copco Tools and Assembly Systems LLC of Auburn Hills, Mich. Expansion vane motors may be utilized in all embodiments of the wheel acceleration system120, including those having an optional reduction gearbox, flywheel and/or clutch, as described below. In another embodiment, the impeller166is a turbine having fixed vane dimensions. Such turbines are well-suited to high-speed/low-torque applications, and may be utilized in all embodiments of the wheel acceleration system120, including those having an optional reduction gearbox, flywheel and/or clutch, as described below.

The rotary propulsion unit160ofFIG. 1Ais shown with a number of optional features which may be disposed within the outer housing162and utilized alone or in any combination, in any of the embodiments contemplated herein, in order to meet the torque output requirements of the particular application. An optional reduction gearbox172is disposed in the outer housing162and configured to be driven by the impeller shaft168in order to increase the torque delivered to the wheel106(e.g., via at least one output shaft174). Some embodiments of the reduction gearbox172include a plurality of output shafts. An optional flywheel176is disposed on the output shaft174, and an optional clutch178is disposed between the output shaft174and the axle shaft108of the wheel106. The flywheel176and clutch178combination is advantageous because it enables decoupling of the output shaft174from the axle shaft108, and further enables the expanding gases144to accelerate the impeller166and the flywheel176during the initial burn of the propellant134. Once the flywheel176is spinning and the propellant burn is stable, the clutch178can be engaged in order to deliver the combined torque from the impeller166and the flywheel176to the axle shaft108.

In some embodiments, the clutch178is an overdriving clutch that enables the wheel106to spin-up upon landing without spinning the impeller166, reduction gearbox172, flywheel176, or other elements of the rotary propulsion unit160. In some embodiments, the clutch178is a selectable clutch configured to engage the wheel106or the axle shaft108upon receipt of an engagement signal (e.g., from the pilot) and/or automatically (e.g., when the output shaft174reaches a predetermined speed).

To clarify, some embodiments of the rotary propulsion unit160include the clutch178, but not the flywheel176. Other embodiments include neither the flywheel176nor the clutch178, and in such embodiments the output shaft174is directly coupled to the axle shaft108(e.g., a “live axle”), or to a shaft located in the interior of the axle shaft108, which in turn is connected to a hub of the wheel106. Indeed, in any of the embodiments contemplated herein, the output shaft174or flywheel176may deliver torque to the wheel106by acting directly on the wheel106, on the axle shaft108, on a shaft located in the interior of the axle shaft108, or by similar connection schemes.

FIG. 1Bis a schematic diagram of another wheel acceleration system120bin accordance with another representative embodiment of the present disclosure. The wheel acceleration system120ofFIG. 1Bis similar to that ofFIG. 1Aexcept where described below. Accordingly, alike reference numerals and names have alike meanings except where described below. For brevity, certain reference numerals introduced with respect toFIG. 1Aare not reintroduced with respect toFIG. 1B.

The wheel acceleration system120ofFIG. 1Bis configured to minimize flying weight of the aircraft102following takeoff and after depletion of the propellant. This configuration described below avoids the undesirable need for the aircraft102to carry the pyrotechnic cartridge132after depletion of the propellant134, when it is dead weight.

Whereas the pyrotechnic cartridge132ofFIG. 1Ais configured to be manually removed from the breech136between flights, e.g., by a ground crewmember, the pyrotechnic cartridge132ofFIG. 1Bis configured to be jettisoned following depletion of the propellant134. InFIG. 1B, the pyrotechnic unit130does not have a breech or a breech cap; rather, the pyrotechnic cartridge132forms its own pressure vessel which contains the propellant134. Accordingly, the pyrotechnic cartridge132connects directly to the fluid circuit146at a gas connector150, which can be a pyrotechnic fastener, an electromechanical connector, or the like.

Referring still toFIG. 1B, in use, the pyrotechnic cartridge132is ignited prior to or during takeoff, which causes the rotary propulsion unit160to deliver torque to the wheel106. This process depletes the propellant134, after which time the pyrotechnic cartridge132becomes dead weight. Therefore, the gas connector150releases (jettisons) the pyrotechnic cartridge132following takeoff, e.g., upon retraction of the landing gear104or upon receipt of a jettison signal from the pilot. As noted above, the gas connector150can release the pyrotechnic cartridge132by executing a pyrotechnic sequence (in the case of a pyrotechnic fastener), by releasing a latch (in the case of an electromechanical connector), or by a similar release process. Not only does this eliminate dead weight from the aircraft102, but it also reduces the volume occupied by the pyrotechnic unit130, which can enable retraction of the landing gear104into a landing gear bay.

The pyrotechnic wheel acceleration systems described above are unlike and superior to electric taxi (“e-taxi”) systems. First, the pyrotechnic wheel acceleration systems are configured to provide much greater absolute torque and power outputs to the wheel106, which is necessary to accelerate relatively heavy aircraft (e.g., 4,000 kg or greater) to takeoff speeds. For example, any of the wheel acceleration systems120described herein can be configured to provide a torque output of at least 1500 Nm to wheel106through the takeoff roll (either directly to the wheel106, to the axle shaft108, or through a similar connection scheme), resulting in a power output of at least 800 Kilowatts (e.g., 800-1,000 kW) at the end of the runway length or cartridge burn, which lasts from 5-10 seconds. Configurations providing greater torque and power outputs are contemplated. By comparison, known e-taxi systems are incapable of providing such high torque and power outputs.

A second key distinction is that the pyrotechnic wheel acceleration systems are configured to provide much greater power densities than e-taxi systems. The superior power densities of the pyrotechnic wheel acceleration systems described herein stems from reduced power source weight, reduced motor weight, absence or minimization of power controls systems, and/or absence or minimization of cooling systems. For example, pyrotechnic cartridges suitable for the wheel acceleration systems described herein (such as those based on the MXU-4A) could weigh approximately 15 kg, as compared to an approximately 140 kg supercapacitor that would be necessary to deliver a comparable power output. Further, the rotary motors described herein, such as pneumatic expansion vane motors, can weigh approximately 25% of electric motors having comparable power output. Further still, the pyrotechnic wheel acceleration systems of the present disclosure do not require cumbersome electronic control systems that would be necessary for e-taxi systems having comparable power output. Further still, given the low duty cycle and short burn times of the pyrotechnic wheel acceleration systems described herein, liquid cooling systems are not necessary.

As a result of the foregoing advantages, and the unobvious utilization of a pyrotechnic-cartridge in an aircraft system, the pyrotechnic wheel acceleration systems of embodiments of the present disclosure (including the pyrotechnic unit and the rotary propulsion unit) have a power density of at least about 8.0 kW/kg. For example, in some embodiments, the power density of the pyrotechnic wheel acceleration system can be selected from one of the following power densities: at least 9.0 kW/kg; at least 10.0 kW/kg; at least 11.0 kW/kg, at least 12.0 kW/kg; at least 13.0 kW/kg, at least 14.0 kW/kg, at least 15.0 kW/kg, or about any one of these power densities. In some embodiments, the power densities of the pyrotechnic wheel acceleration system is in a range selected from one of the following ranges of power densities: between 8.0-20.0 kW/kg; between about 9.0-18.0 kW/kg; between about 10.0-16.0 kW/kg; between 8.0-12.0 kW/kg; between 10.0-12.0 kW/kg; or between about any one of these ranges. The foregoing power densities are much higher than known assisted taxi systems.

Relatedly, embodiments of the rotary propulsion units of the present disclosure have a power density of, for example, at least 18.0 kW/kg. In some embodiments, the power density of the rotary propulsion unit is in a range between 20.0-30.0 kW/kg. In a representative embodiment, the rotary propulsion unit includes a direct drive vane motor configured to fit inside an 20 cm-diameter aircraft wheel and to generate about 426 kW (570 hp). This rotary propulsion unit weighs between about 19.0 and about 22.0 kg, and weighs about 20.6 kg in some embodiments. Additional components of the pyrotechnic wheel acceleration system (including the cartridge, connections, valves, and the like) weigh in the range of between about 18.0 kg and about 22.0 kg, and about 20.0 kg in some embodiments.

In a certain embodiment, the rotary propulsion unit has a power density of 20.6 kW/kg and the overall pyrotechnic wheel acceleration system has a power density of 10.5 kW/kg.

By comparison, in order for any e-taxi system to provide torque and power outputs as high as 1500 Nm and/or 800 kW, the immense supercapacitors, electric motors, power electronics, and cooling hardware of such an electric system would contribute to a very low power density, rendering it unsuitable for accelerating aircraft weighing at least 4,000 kg to flying or takeoff speeds.

The wheel acceleration systems described herein can be mounted in a number of different configurations to suit particular applications. For example, aircraft having wing-mounted landing gear are well-suited to the representative embodiments shown inFIGS. 2A-2C, whereas aircraft having centralized (e.g., fuselage-mounted) landing gear are well-suited to the representative embodiment shown inFIGS. 3A-3B.

InFIGS. 2A-2B, the wheel acceleration systems are mounted to inboard sides of rear wheels of the aircraft. However, this is not limiting. In variations of any of the embodiments contemplated herein, the wheel acceleration systems can alternatively be mounted to an outboard side of one wheel (such as shown inFIG. 2C). In still other embodiments, the aircraft includes a wheel acceleration system mounted to a front wheel, in addition to or alternatively to the wheel acceleration systems mounted to the rear wheels.

FIG. 2Ashows a front elevation view of a representative military “fighter” type aircraft202having wing-mounted landing gear204and rear wheels206. The aircraft202is equipped with two wheel acceleration systems220, each being mounted to an inboard side of one rear wheel206and together forming part of a common wheel acceleration system.

FIG. 2Bis as breakout view showing details of the starboard wheel acceleration system220, according to one representative mounting configuration which is applicable to all embodiments contemplated herein. As shown, each wheel acceleration system220includes a pyrotechnic unit (“PU”)230and a rotary propulsion unit (“RPU”)260. In some embodiments, each wheel acceleration system220has all of the components of the wheel acceleration system120ofFIG. 1A. In other embodiments, each wheel acceleration system220has all of the components of the wheel acceleration system120ofFIG. 1B. In still other embodiments, each wheel acceleration system220has less than all of the aforementioned components, e.g., an optional flywheel and/or optional clutch are omitted. In still other embodiments, the two wheel acceleration systems220are constructed identically to each other, although this is not necessary.

The PU230is disposed on an inboard side of the RPU260, which is mounted over the axle shaft208of the wheel206in order to facilitate torque delivery. In some embodiments, the PU230and RPU260share a common outer housing. In some embodiments in which the PU230has a jettisonable pyrotechnic cartridge, the entire PU230is configured to be jettisoned following takeoff.

FIG. 2Cis as breakout view showing details of the port-side wheel acceleration system220, according to another representative mounting configuration, which is applicable to all embodiments contemplated herein. Whereas the wheel acceleration system220ofFIG. 2Bis mounted over the axle shaft208of the wheel206, the wheel acceleration system220ofFIG. 2Chas an output shaft274(of the RPU260) coupled directly to a hub or coupler210of the wheel206.

The mounting configurations ofFIGS. 2B-2Care representative, not limiting. For example, any of the embodiments disclosed herein may utilize one or both of the mounting schemes shown inFIGS. 2B-2Con the inboard or outboard sides of one or more wheels, including the rear wheels and/or front wheels.

FIG. 3A—3B show a front elevation view of another representative military “fighter” type aircraft302having centralized, fuselage-mounted landing gear304and rear wheels306, which differs from the wing-mounted landing gear204and wheels206of the aircraft202ofFIG. 2A. Such centralized and narrow landing gear systems are well-suited to wheel acceleration systems having one or more centralized components (i.e., components that serve more than one wheel306). The centralized components can be scaled up in order to provide power and torque to a plurality of wheels306, such as both rear wheels306in the illustrated embodiment. Such systems also provide weight savings as compared to embodiments with a plurality of pyrotechnic units, in which no components serve more than one wheel.

Referring toFIG. 3A, the aircraft302is equipped with a wheel acceleration system320. The embodiment ofFIG. 3Adiffers in that the wheel acceleration system320includes a pyrotechnic unit (“PU”)330centrally mounted to a fuselage312of the aircraft302, and two rotary propulsion units (“RPUs”)360—one mounted to the inboard side of each rear wheel306. Each of the PU330and RPUs360comprise the components of wheel acceleration system120ofFIG. 1A or 1B(some embodiments do not include the optional flywheel and/or clutch). Accordingly, the PU330has at least one gas outlet from the breech or pyrotechnic cartridge (depending on the embodiment), in order to deliver expanding gases via flexible fluid circuit346to each of the RPUs360, which each deliver torque to the respective wheels306. Although the PU330is shown as external to the aircraft fuselage inFIG. 3A, it is contemplated that in some embodiments, the PU330is stowed internally to the fuselage, for improved aerodynamics.

The flexible fluid circuit346enables relative movement of the PU330and RPUs360, for example during articulation, retraction, and extension of the landing gear304. In some embodiments, the flexible fluid circuit346comprises a continuous length of high temperature-resistant flexible exhaust ducting extending from the PU330to each RPU360. In other embodiments, the flexible fluid circuit346comprises one or more sections of rigid exhaust piping, which are coupled together by flexible fluid circuit couplers352(e.g., articulating exhaust joints and the like). In some embodiments, the flexible fluid circuit346is routed along the landing gear struts to improve aerodynamics and to facilitate stowage of the landing gear304during flight. Accordingly, it is contemplated that the fluid circuit346may be at least partially routed internally through the fuselage and/or wing of the aircraft302, rather than fully external to the aircraft302.

Referring now toFIG. 3B, the aircraft302is equipped with a wheel acceleration system320having a different centralized configuration from that ofFIG. 3A. While the wheel acceleration system320ofFIG. 3Bstill comprises the components of wheel acceleration system120ofFIG. 1A or 1B(some embodiments do not include the optional flywheel and/or clutch), it differs in that it includes a centrally-mounted pyrotechnic unit (“PU”)330and a centrally mounted RPU360—both of which are mounted to the fuselage312of the aircraft302. Although the PU330and RPU360are shown as mounted external to the aircraft fuselage inFIG. 3B, it is contemplated that in some embodiments, the PU330and/or RPU360are stowed internally to the fuselage312, for improved aerodynamics.

Because PU330and RPU360are both configured to service both wheels306, power is transferred from the RPU360to the wheels306via a plurality of drive shaft assemblies380. Each drive shaft assembly380includes a plurality of drive shafts382connected by at least one drive shaft coupler384(e.g., universal joints, continuously variable joints, reduction gearboxes, angled gearboxes, or the like). At an upper end, each drive shaft assembly380is operably connected to an output shaft of the RPU360, either directly or via a reduction gearbox. At a lower end, each drive shaft assembly380is operably connected to one of the wheels306, either directly (e.g., to a hub of the wheel), via an axle shaft, via a shaft internal to the axle shaft, via one or more drive shaft couplers384, or via similar connection scheme (as described above). In use, ignition of a pyrotechnic cartridge in the PU330causes the RPU360to deliver torque to both wheels306via the drive shaft assemblies380, thus accelerating the aircraft302.

Thus, the present disclosure provides a number of innovative wheel acceleration systems having an unobvious combination of features that are together configured to accelerate an aircraft to flying speed in connection with main engine thrust, utilizing pyrotechnic cartridge-powered rotary propulsion units, which in turn deliver high torque and power output to one or more aircraft wheels.