AU2021105139A4 - A vtol flight system - Google Patents

Abstract

A VTOL FLIGHT SYSTEM ABSTRACT The present invention relates to a system of aircraft involving a fixed-wing aircraft 5 (100) and at least an external agent (199) capable of VTOL that form a momentary short / vertical takeoff and landing (STOL / VTOL) flight system when required. Embodiments of the external agent (199) include rotary-wing aircraft (200). Most Illustrative Diagram: FIG. 3(b) cv)r CL a-L

Description

cv)r

CL a-L

A VTOL FLIGHT SYSTEM FIELD OF INVENTION

The present invention relates generally to aircraft. More specifically, the invention relates to a vertical takeoff and landing (VTOL) flight system involving a fixed-wing aircraft and at least an external agent capable of vertical flight.

BACKGROUND OF INVENTION

Personal aviation and aerial ridesharing such as Uber Air are on the rise globally. In the words of Airborne, "OEMs and startups alike are racing the clock to launch the first electric vertical take-off and landing (eVTOL) aircraft by 2025" [1]. Many of the airframes used to realize eVTOL is largely based the combination of a fixed wing and a multicopter aircraft [2]. Therefore, at present a majority of the VTOL-capable fixed-wing aircraft have VTOL means on board, even though VTOL function is only needed for a relatively short period of time, primarily during takeoff and landing. While onboard VTOL hardware offers operational flexibility e.g., a VTOL-capable fixed-wing aircraft can takeoff and landing virtually anywhere, eVTOL aircraft intended for aerial ridesharing or urban air mobility (UAM), on the other hand, tend to operate in and out ofknown airports and therefore, equipping each and every aircraft with onboard hardware necessary to achieve VTOL may not be an efficient approach especially for large-scale deployment of UAM.

Thus, the present invention proposes the concept of a VTOL flight system wherein a fixed-wing aircraft may be optimized for cruising flight in terms of speed and energy consumption, and the transient need for VTOL is met via external agent(s) capable of vertical flight. This approach is envisaged to be of particularly beneficial for intercity travels involving medium-haul flights.

SUMMARY OF INVENTION

A short / vertical takeoff and landing (STOL / VTOL) system comprises a fixed-wing aircraft and at least a supporting external agent capable of hovering, and VTOL. External means being external with respect to the fixed-wing aircraft. The external agent(s) generate(s) vertical lift to enable itself / themselves to be airborne and to provide STOL / VTOL function for the fixed-wing aircraft (100) when required. In embodiments, the external agent(s) is/are temporarily attached to one fixed-wing aircraft to provide VTOL capabilities to said fixed-wing aircraft thereby forming a momentary integrated VTOL flight system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) is a perspective view of an exemplary fixed-wing aircraft comprising a longitudinal axis (L.A.), a center of gravity (C.G.), four horizontal propulsors and at least an attachment means in accordance with the present invention.

FIG. 1(b) is a perspective view of an exemplary external agent in the form of a rotary wing aircraft in accordance with the present invention.

FIG. 1(c) shows a rotary-wing aircraft in the form of a coaxial rotor helicopter being attached to the fixed-wing aircraft as depicted in FIG. 1(a), momentarily forming an integrated VTOL flight system in accordance with the present invention.

FIG. 2 is an embodiment of the fixed-wing aircraft comprising two turbofan engines.

FIG. 3(a) is a perspective view of an exemplary external agent in the form of a bicopter in accordance with the present invention.

FIG. 3(b) shows a bicopter being attached to a fixed-wing aircraft momentarily forming an integrated VTOL flight system in accordance with the present invention.

FIG. 3(c) is a top view of the embodiment in FIG. 3(b) with the arrows indicating the direction of tilt of the rotor disk thrusts in order to actuate a right yaw via differential cyclic control during VTOL.

FIG. 4(a) is a perspective view showing an embodiment of the fixed-wing aircraft comprising at least two boom-like structures in accordance with the present invention.

FIG. 4(b) shows two rotary-wing aircraft momentarily attached to the fixed-wing aircraft in accordance with the present invention.

FIG. 5(a) is a perspective view showing an embodiment of the rotary-wing aircraft in the form of a tandem rotor helicopter in accordance with the present invention.

FIG. 5(b) is a perspective view showing a plurality of tandem rotor helicopters being attached to the fore wing and rear wing of the fixed-wing aircraft in accordance with the present invention.

FIG. 5(c) is a perspective view with the arrows indicating the direction of tilt of the rotor disk thrusts.

FIG. 5(d) is an embodiment of the fixed-wing aircraft in accordance with the present invention.

FIG. 6 shows an embodiment of the rotary-wing aircraft in the form of a tricopter in accordance with the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention relates to a short / vertical takeoff and landing (STOL/ VTOL) flight system comprising a fixed-wing aircraft and at least a supporting external agent capable of hovering, and VTOL. The external agent(s) generate(s) vertical lift to enable itself / themselves to be airborne and to provide STOL / VTOL function for the fixed-wing aircraft (100).

The fixed-wing aircraft acquires momentary VTOL capability with aid from the external agent(s) thereby forming an integrated VTOL flight system. Examples of viable candidates for the external agent are rotary-wing aircraft and aircraft which rely on jet propulsion for hovering and VTOL. In the present invention, external agent in the form of a rotary-wing aircraft will primarily be used as illustrative example. Afterall, a rotary-wing aircraft is known for its VTOL capabilities and hovering efficiency.

In real life scenario, the present invention may be implemented as follows: In a busy urban airport, there are three fixed-wing aircraft departing and two fixed-wing aircraft approaching the airport for a vertical landing. Multiple departure and landing can take place concurrently using multiple VTOL flight system in accordance with the present invention. One rotary-wing aircraft will be attached to each departing fixed-wing aircraft, forming three VTOL flight systems. All three fixed-wing aircraft can vertical takeoff simultaneously and depart for different destinations. Likewise, two rotary-wing aircraft are used to vertically land two fixed-wing aircraft. In a second scenario involving a rural airport operating with a much tighter budget, there are two fixed-wing aircraft and there is only one rotary-wing aircraft supporting their VTOL flights. At any given one time, only one fixed-wing aircraft will takeoff vertically or land vertically. The fixed-wing aircraft and the rotary-wing aircraft form a momentary VTOL flight system. An advantage of the present invention is that the VTOL-capable fixed-wing aircraft does not need to carry VTOL components on board, and this is expected to result in a lighter airframe and lower manufacturing cost and also the aircraft can be much more optimized for forward flight, achieving greater energy efficiency and range. This supports the concept of green aviation.

FIG. 1(a) is a perspective view of an exemplary fixed-wing aircraft (100) capable of forward flight in accordance with the present invention. The fixed-wing aircraft (100) comprises at least a fuselage (102), a fore wing (104), a rear wing (106), a longitudinal axis (L.A.), a center of gravity (C.G.), at least a horizontal propulsor (108), and at least an attachment means (110). The attachment means (110) enables a rotary-wing aircraft to be attached to the fixed-wing aircraft (100) for VTOL flight. The attachment process can be guided using various methods, such as optical time of flight sensing which have resolution in millimeters. In the exemplary fixed-wing aircraft (100) shown in FIG. 1(a), the attachment means (110) is located substantially along the longitudinal axis (L.A.) of the fixed-wing aircraft (100) and close to the center of gravity (C.G.) of the fixed-wing aircraft (100) when viewed from a top view perspective.

While one horizontal propulsor (108) is sufficient to provide forward thrust during forward flight, it is preferably that the fixed-wing aircraft (100) comprises at least a pair of horizontal propulsors (108) as shown in FIG. 1(a) to enable yaw control via differential thrust during VTOL. This arrangement helps to ensure that the load of VTOL flight control requirements are distributed between the rotary-wing aircraft (200) and the fixed-wing aircraft (100) instead of either one of the aircraft having to fulfill the entire VTOL flight control requirements. This holds true not only for rotary wing aircraft (200) but also for other types of external agents as well. The flight system in the present invention may be descriptively termed as "VTOL flight system".

Additionally, the exemplary fixed-wing aircraft (100) comprises at least a vertical stabilizer (112) and necessary control surfaces (114) to actuate roll, pitch and yaw during flight. Furthermore, each of the horizontal propulsors (108) of the exemplary fixed-wing aircraft (100) comprises at least a propeller (116) and the propeller (116) is of variable-pitch for effective yaw control via differential thrust during VTOL.

FIG. 1(b) is a perspective view of an external agent (199) in the form of a rotary-wing aircraft (200) in accordance with the present invention. The rotary-wing aircraft (200) comprises at least a rotor to generate vertical lift to make itself to be airborne and to provide VTOL function for the fixed-wing aircraft (100) when required. Examples of rotary-wing aircraft that may be used in the present invention are single-rotor helicopters with tail rotors, compound helicopters, tandem rotor helicopters, coaxial rotor helicopters, and multirotors. A coaxial rotor helicopter (201) is one of the types of helicopters having no tail boom and tail rotor and the relatively compact design is well suited for the present invention as an agent to provide VTOL function. Another viable candidate of the external agent (199) is a tandem rotor helicopter because tandem rotor helicopters are generally known for their high payload capabilities. In embodiments of the present invention, the rotary-wing aircraft (200) comprises at least a rotor, a fuselage and at least an attachment means to attach itself to the fixed-wing aircraft (100). As for the exemplary coaxial rotor helicopter (201) as shown in FIG. 1(b), it comprises two sets of rotor (202A, 202B), a fuselage (204) and at least an attachment means (206) to attach itself to the fixed wing aircraft (100). The rotors (202A, 202B) provide vertical lift and each set of rotor (202A, 202B) is counter-rotating to each other. The rotors (202A, 202B) are connected to the fuselage via co-axial main shafts (208). The coaxial rotor helicopter (201) uses cyclic control for pitch and roll. The yaw control is accomplished by increasing the collective pitch of one rotor, e.g. the lower rotor (202A) and decreasing the collective pitch on the other, e.g. the upper rotor (202B).

FIG. 1(c) shows at least one rotary-wing aircraft (200) exemplified by a coaxial rotor helicopter (201) being attached to the fixed-wing aircraft (100) shown in FIG. 1(a) using the attachment means (110, 206), thus forming a momentary integrated VTOL flight system in accordance with the present invention. Various approaches may be used to realize the attachment means (110, 206). For example, they may be mechanical or electro-mechanical in nature. One approach is to use mechanical latching method.

In preferred embodiment, the rotary-wing aircraft (200) should approach the fixed-wing aircraft (100) substantially from the side rather than from the front or back of the fixed-wing aircraft (100) when initiating VTOL. This is to avoid the rotor wash of the rotary-wing aircraft (200) hitting the wings (104, 106) of the fixed-wing aircraft (100) while it is airborne which may cause unpredictable flight characteristics, for example, pushing the fixed-wing aircraft (100) downward or causing undesirable pitching. For such requirement to be fulfilled, the spacing between the fore wing (104) and the rear wing (106) should therefore be larger than the diameters of the rotors (202A, 202B) of the rotary-wing aircraft (200). The spacing is defined as the distance between the trailing edge of the fore wing (104) and the leading edge of the rear wing (106). An external agent (199) that relies on jet engine to achieve VTOL will likely have jet blast in the downward direction. Thus, to generalized, the external agent(s) (199) should approach the fixed-wing aircraft (100) substantially from the side of the fixed-wing aircraft (100) when initiating VTOL.

FIG. 2 is an embodiment of the fixed-wing aircraft (100) wherein the horizontal propulsor (108) is based on turbine engine, for example, turbofan and turbojet. The exemplary fixed-wing aircraft (100) in FIG. 2 comprises two turbofan engines, one on each side, so that yaw may be initiated either by differential thrust or by thrust vectoring. The fixed-wing aircraft (100) also comprises two vertical stabilizers (112), each located towards the tip of the rear wing (106) in order to avoid blade strike by the coaxial rotor helicopter (201) shown in FIG. 1(b).

FIG. 3(a) is an embodiment of the rotary-wing aircraft (200) in the form of a bicopter, which is a variation of a tandem rotor helicopter wherein the rotary-wing aircraft (200) comprises two rotors (202) arranged laterally, one on each side of said aircraft (200); a fuselage (204); and at least an attachment means (206). The front of the rotary-wing aircraft (200) is indicated by an arrow in the illustration. Each rotor (202) is equipped with cyclic pitch control and collective pitch control which are similar to those of a conventional helicopter. The rotary-wing aircraft (200) approaches the fixed-wing aircraft (100) substantially from the side of the fixed-wing aircraft (100) when initiating VTOL in accordance with the present invention. This is to prevent the rotor wash of the rotary-wing aircraft (200) from hitting the fore wing (104) or rear wing (106) of the fixed-wing aircraft (100). FIG. 3(b) is a perspective view showing the rotary-wing aircraft (200) in the form of a bicopter being attached to the fixed-wing aircraft (100). Referring now to FIG 3(c), to actuate a right yaw during vertical takeoff of the fixed-wing aircraft (100), differential cyclic control is used, i.e. the rotor disk thrust of the left rotor is tilted forward via the cyclic pitch control while the rotor disk thrust of the right rotor is tilted backward, thus producing a torque that yaws the rotary-wing aircraft (200) and the fixed-wing aircraft (100) as a single integrated entity. Bicopters that rely on tilt rotors instead of cyclic pitch control may also be used in the present invention and the principle of yaw of the integrated entity based on tilting of rotor disk thrusts remains similar.

FIG. 4(a) is yet another embodiment of the present invention wherein the fixed-wing aircraft (100) comprises at least two boom-like structures (118), one boom-like structure (118) on each side of the fixed-wing aircraft (100), the boom-like structures (118) run longitudinally from the fore wing (104) to the rear wing (106), each of the boom-like structures (118) comprises at least an attachment means (110) on which the rotary-wing aircraft (200) can be attached to. The fixed-wing aircraft (100) has at least one horizontal propulsor (108). In this embodiment, at least two rotary-wing aircraft (200) are momentarily attached to the fixed-wing aircraft (100), each rotary-wing aircraft (200) is attached to the respective boom-like structures (118) as shown in FIG. 4(b). Differential cyclic control between the two rotary-wing aircraft (200) located on left side and right side of the fixed-wing aircraft (100) is used to actuate yaw during VTOL. The rotary-wing aircraft (200) may be attached to the fuselage (102) of the fixed-wing aircraft (100). Thus, in general, a plurality of rotary-wing aircraft may be momentarily attached to the fixed-wing aircraft (100) wherein differential cyclic control among the rotary-wing aircraft (200) is used to actuate yaw during VTOL.

In yet another embodiment of the present invention, the rotary-wing aircraft (200) is a tandem rotor helicopter as shown in a perspective view in FIG. 5(a). Said rotary-wing aircraft (200) comprises a fuselage (204), a front rotor (202), a rear rotor (202), a fore arm (210A), and a rear arm (21OB). The front rotor (202) is connected to the fuselage (204) via the fore arm (210A), and the rear rotor is connected to the fuselage (204) via the rear arm (210B). The rear arm (210B) is longer than the fore arm (210A) so as to avoid the rotor wash of the rear rotor (202) from hitting the wings (104, 106) of the fixed-wing aircraft (100). In general, the rear arm (210B) should be longer than the fore arm (21OA) by 15% to 45% depending on the wing chord towards the wing tips.

A plurality of the rotary-wing aircraft (200) in the form of a tandem rotor helicopter are attached to the fore wing (104) and rear wing (106) of the fixed-wing aircraft (100) whenever VTOL function is required. FIG. 5(b) is a perspective view showing two rotary-wing aircraft (200) in the form of a tandem rotor helicopter being attached to the fore wing (104) and rear wing (106) of the fixed-wing aircraft (100) with one rotary-wing aircraft (200) on each side of the respective wings (104, 106). The rotary-wing aircraft (200) apply synchronized differential cyclic control to actuate yaw control of the fixed wing aircraft (100), and arrows in FIG. 5(c) indicate the direction of tilt of the rotor disk thrusts of the respective rotary-wing aircraft (200) in order to actuate a right yaw during VTOL.

FIG. 5(d) shows the corresponding fixed-wing aircraft (100) that the rotary wing aircraft (200) may be attached to. Said fixed-wing aircraft (100) comprises a fuselage (102), a single horizontal propulsor (108) mounted on the vertical stabilizer (112), at least an attachment means (110) is disposed towards the tips of the fore wing (104) and rear wing (106), and control surfaces (114). Thinner airfoils are used near wingtips so that it is easier for the rotary-wing aircraft (200) to be attached to the fixed-wing aircraft (100) in a sideway manner during the attachment process.

In an alternative embodiment, rotary-wing aircraft (200) in the form of a multirotor may be used. There are various types of multirotors such as, tricopter, quadcopter, hexacopter and octacopter. In particular, a tricopter in 'Y' configuration as shown in FIG. 6 may offer a more authoritative yaw while being relatively compact compared to other types of multirotors. It yaws by tilting the rotors (202) at the rear, similar to that of a conventional tricopter.

The foregoing description of the present invention has been presented for purpose of illustration and description. Furthermore, the description is not intended to limit the invention to the form disclosed herein. Consequently, variations and modifications commensurate with the above teachings, and skill and knowledge of the relevant art, are within the scope of the present invention. The embodiments described hereinabove are further intended to explain best modes known of practicing the invention and to enable other skilled in the art to utilize the invention in such or other embodiments and with various modifications required by the particular application(s) or use(s) of the present invention. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art.

References:

1. M. Francesco (2020) Is the Urban Air Mobility Industry ready for Take-Off? https://www.airborne.com/urban-air-mobility-the-rise-of-evtol-vehicles/ 2. ArduPilot Dev Team (2020) QuadPlane Overview. https://ardupilot.org/plane/docs/quadplane-overview.html

Claims (20)

CLAIMS:

1. A vertical takeoff and landing (VTOL) flight system comprising:

a fixed-wing aircraft (100) capable of forward flight, the fixed-wing aircraft (100) comprises a longitudinal axis, a center of gravity, a left side, and a right side; and

at least an external agent (199) capable of VTOL;

wherein at least one external agent (199) is attached to the fixed-wing aircraft to provide VTOL capabilities to said fixed-wing aircraft (100) when required thereby forming a momentary VTOL flight system.

2. The VTOL flight system in Claim 1, wherein the external agent (199) is a rotary wing aircraft (200), said rotary-wing aircraft (200) comprises at least a rotor (202, 202A, 202B) to generate vertical lift, a fuselage (204), and at least an attachment means (206) to attach itself to the fixed-wing aircraft (100).

3. The VTOL flight system in Claim 2, wherein a plurality of rotary-wing aircraft (200) are attached to the fixed-wing aircraft during VTOL, further wherein differential cyclic control among the rotary-wing aircraft (200) is used to actuate yaw during VTOL.

4. The VTOL flight system in Claim 2, wherein the fixed-wing aircraft (100) further comprises at least a fuselage (102), a fore wing (104), a rear wing (106), at least a horizontal propulsor (108), and at least an attachment means (110) on which the rotary-wing aircraft (200) can be attached to.

5. The VTOL flight system in Claim 4, wherein the fixed-wing aircraft (100) further comprises at least two boom-like structures (118), one boom-like structure (118) on each side of the fixed-wing aircraft (100), the boom-like structures (118) run longitudinally from the fore wing(104) to the rear wing (106), each of the boom-like structures (118) comprises at least an attachment means (110) on which the rotary wing aircraft (200) can be attached to.

6. The VTOL flight system in Claim 5, wherein differential cyclic control between the two rotary-wing aircraft (200) located on the left side and the right side of the fixed-wing aircraft (100) is used to actuate yaw during VTOL.

7. The VTOL flight system in Claim 1, wherein the fixed-wing aircraft (100) further comprises at least a pair of horizontal propulsors (108) to enable yaw control via differential thrust during VTOL.

8. The VTOL flight system in Claim 7, wherein each of the horizontal propulsors comprises at least a propeller (116), the propeller (116) is of variable-pitch for yaw control via differential thrust during VTOL.

9. The VTOL flight system in Claim 4, wherein the fore wing (104) and rear wing (106) are substantially identical in terms of wingspan and wing chord.

10. The VTOL flight system in Claim 4, wherein the attachment means (110) is located substantially along the longitudinal axis of the fixed-wing aircraft (100) and close to the center of gravity of the fixed-wing aircraft (100) when viewed from a top view perspective.

11. The VTOL flight system in Claim 2, wherein the rotary-wing aircraft (200) is a coaxial rotor helicopter (201).

12. The VTOL flight system in Claim 1, wherein the external agent (199) approaches the fixed-wing aircraft (100) substantially from the side of the fixed-wing aircraft (100) when initiating VTOL.

13. The VTOL flight system in Claim 4, wherein the spacing between the fore wing (104) and the rear wing (106) is larger than the diameters of the rotors (202, 202A, 202B) of the rotary-wing aircraft (200).

14. The VTOL flight system in Claim 2, wherein the rotary-wing aircraft is a multirotor.

15. The VTOL flight system in Claim 2, wherein the rotary-wing aircraft is a bicopter.

16. The VTOL flight system in Claim 4, wherein the rotary-wing aircraft (200) is a tandem rotor helicopter, the rotary-wing aircraft (200) comprises a fuselage (204); a front rotor (202); a rear rotor (202); a fore arm (210A), and a rear arm (210B); the front rotor (202) is connected to the fuselage (204) via the fore arm (21OA), and the rear rotor (202) is connected to the fuselage (204) via the rear arm (210B).

17. The VTOL flight system in Claim 16, wherein a plurality of the rotary-wing aircraft (200) are attached to the fore wing (104) and rear wing (106) of the fixed wing aircraft (100) whenever VTOL function is required.

18. The VTOL flight system in Claim 17, wherein the rear arm (210B) of the rotary wing aircraft (200) is longer than its fore arm (210A) by 15% to 45%.

19. The VTOL flight system in Claim 17, wherein the synchronized differential cyclic control of the rotary-wing aircraft (200) is used to actuate yaw control of the fixed wing aircraft (100).

20. A fixed-wing aircraft (100), wherein the fixed-wing aircraft (100) acquires VTOL capability from at least an external agent (199), the external agent (199) generates vertical lift to enable itself to be airborne and to provide VTOL function for the fixed wing aircraft (100) when required.

Page 1/14

112

100 114 114

108

114 110 106 104 114 102 C.G. 106

116 108 108 114

L.A.

108

FIG. 1(a)

Page 2/14

199 / 200 / 201

208 208 204

206

202B

202A

FIG. 1(b)

Page 3/14

200

100

110

206

FIG. 1(c)

Page 4/14

112

108

100 106

108 112

106

FIG. 2

Page 5/14

202

204 202

Front

206

FIG. 3(a)

Page 6/14

100

200

FIG. 3(b)

Page 7/14

100

200

FIG. 3(c)

Page 8/14

100

106 108 118 110

106 104

110

118

104

FIG. 4(a)

Page 9/14

200

118

200 118

FIG. 4(b)

Page 10/14

202

200

210B

202 210A

204

206

212

FIG. 5(a)

Page 11/14

200

106

200 100

200

104

200

FIG. 5(b)

Page 12/14

200

200 100

200

200

FIG. 5(c)

Page 13/14

112 108

106 114 100

110 114

106 104

114

102 110

110 114

104

110

FIG. 5(d)

Page 14/14

200 202

202 202

206 204

202

FIG. 6