CN113443138A - Vertical take-off and landing capability aircraft with inclined propellers - Google Patents

Abstract

The invention relates to an aircraft capable of ultra-short/vertical takeoff and landing (hyper-STOL/VTOL) and having a positive pitch angle applied to horizontal thrusters (104A, 104B). A positive pitch angle may also be applied to the vertical thrusters (106A, 106B, 106A1, 106A2, 106B1, 106B 2). The present invention seeks to reduce the pitch angle during hover and vertical flight.

Description

Vertical take-off and landing capability aircraft with inclined propellers

Technical Field

The present invention relates to an aircraft capable of ultra-short/vertical takeoff and landing (hyper-STOL/VTOL) with horizontal and vertical thrusters.

Background

Worldwide, personal Air and Air ride sharing, such as Uber Air, is rising. In the case of airborne companies, "OEMs and original companies strive to launch the first electrically powered vertical takeoff and landing (eVTOL) aircraft before 2025 in minutes and seconds" [1 ]. Many fuselages for implementing eVTOL are largely based on a combination of fixed wing and multi-rotor aircraft, also known as "quadroplanes" [2 ]. This type of aircraft is known to have the advantages of vertical take-off and landing, significantly higher cruising speeds and the ability to land vertically at the destination [2 ]. The quadrlane design is built on board but adds at least 4 rotors/propellers [2] for vertical flight. In other words, both horizontal cruise flight and vertical flight have separate propulsion. Thus, typically, when a quadroplane is suspended, its horizontal airplane-like propeller is inactive. Also, when the quadroplane is cruising in the air using wing lift in horizontal flight mode, its powerful helicopter-like vertical propulsion system will be inactive and contribute zero. From our perspective, this is inefficient and not optimized. Other fuselage configurations that enable an aircraft to hover and perform vertical flight are aircraft based on tilting wings and tilting rotors, which include rotatable propulsion units, which are generally more technically complex than quadroplanes [3,4 ].

We propose the concept of a fixed-wing aircraft (airplane) with "tandem rotor stabilizers" as an effective solution to overcome the limitations of the quadrplane design by effectively utilizing horizontal and vertical thrust during hover and vertical flight (malaysia patent application No. PI 2020000674). During hover and vertical flight, the aircraft assumes a type of nose-up attitude known as "ray" with positive pitch angles, so that both horizontal and vertical propellers can contribute to lift through vector decomposition. If both horizontal and vertical propulsion have equal thrust outputs, the aircraft will typically take off or hover at a pitch angle of 45 °. An exemplary embodiment of such an aircraft is shown in fig. 1. However, while such pitch angles are good for drone aircraft applications, they may be somewhat uncomfortable for manned aircraft or aircraft with passengers.

Disclosure of Invention

It is therefore an object of the present invention to attempt to reduce the takeoff and hover pitch angles of an aircraft equipped with "tandem rotor stabilizers".

In malaysia patent application No. PI 2020000674, the thrust vector of the horizontal thruster is substantially parallel to the longitudinal axis of the aircraft, as shown in fig. 1. A significant feature of the present invention is that during levitation and VTOL, the thrust vector of the horizontal thruster is tilted upwards by an angle phi, resulting in a larger vertical thrust component, thereby reducing the pitch angle p. This is achieved by applying the tilt angle phi to the horizontal thruster during hovering and VTOL. The tilt τ may also be applied to the vertical thruster to help further reduce the tilt ρ during hover and VTOL.

Embodiments of the aircraft of the present invention include an aircraft fuselage that may be divided into a forward portion and an aft portion. The aircraft fuselage further comprises at least one pair of wings with ailerons for roll control; at least one pair of horizontal thrusters having a positive inclination phi of 0.5 deg. to 80 deg. with respect to the aircraft longitudinal axis during hovering and VTOL; and at least two vertical thrusters, which can be divided into a forward unit and an aft unit, at least one forward vertical thruster located at the front of the fuselage of the aircraft and at least one aft vertical thruster located at the aft of the fuselage of the aircraft, wherein the forward vertical thrusters and the aft vertical thrusters are in substantially laterally symmetrical positions about the longitudinal axis of the aircraft. The aircraft fuselage in an embodiment may also include at least one fuselage. At least one horizontal thruster may be mounted on each side of the wing, wherein the thrust vector of the horizontal thruster is substantially parallel to the chord line of the respective wing, so that the angle of attack theta of the wing on which the horizontal thruster is mounted is equal to the angle of inclination phi of the thruster. In other words, in the present invention, θ ═ Φ is always correct, and vice versa. It should also be noted that the tilt angle φ of the horizontal thrusters (104A, 104B) may be maintained in the range of 0.5 to 80 during the hyper-STOL.

Furthermore, in accordance with the invention, each wing may have one or more ailerons or elevon wings for roll control, but at least one of the ailerons should be submerged in the strong propeller wash generated by the horizontal thrusters to help ensure effective roll control during vertical flight and hover. Thus, the horizontal thrusters should be mounted in such a way that the ailerons can be exposed to the strong airflow generated by the horizontal thrusters to help ensure adequate roll control in deep wing stall conditions. Thus, the horizontal propeller should be located in front of the aileron.

During hover and vertical flight, both horizontal and vertical thrusters contribute lift through the resolution of the vector. According to the invention, having the horizontal thrusters at the inclination angle φ during vertical flight results in a reduction of the takeoff and hover pitch angles ρ, which is particularly advantageous for manned flight applications.

In a preferred embodiment of the invention, the pitch angle, and hence the angle of attack of the wing on which the horizontal thruster is mounted, is reconfigurable/variable to provide flexibility to meet flight requirements. However, the change in angle of attack may be performed manually or automatically, i.e. the angle of attack of the wing may be set manually and fixed in place using nuts and bolts when the aircraft is parked in a pylon (hanger), or may be changed while airborne. In the present invention, the airplane mainly used for short-distance flight, for example, 10 kilometers, can manually set and lock the attack angle of the wing to +12 degrees. For long range flights (e.g. a flight distance of 500 km), the angle of attack may be manually configured to +5 ° when the aircraft is on the ground. This allows the aircraft to adapt to changing requirements and offers the possibility of prioritizing comfort and vertical flight performance rather than horizontal flight performance and vice versa.

In embodiments of the invention, the aircraft fuselage may also include at least one aerodynamic surface for pitch stability and control during horizontal flight mode, examples of which are a horizontal stabilizer, an inverted V-shaped empennage, and a triangular wing, all of which are exemplified by the various embodiments of the invention described herein. Where a horizontal stabilizer is used, depending on the nature of the application, the entire horizontal stabilizer may be used to actuate pitch control, or the horizontal stabilizer may have a riser for aerodynamic pitch control. The forward thrust of the aircraft in horizontal flight mode (cruise flight) is provided by the horizontal thrusters. In addition, horizontal propellers may be based on various drives, such as electric motors, turbine engines (including turboprop and turbojet engines), internal combustion engines, and solar powered engines.

The aircraft of the present invention is expected to better cope with gusts in VTOL mode than conventional tilt wing aircraft. This is because the vertically inclined wings of a tilted-wing aircraft represent a large surface area for the side wind to push against [5 ]. The invention with poor thrust yaw may also have better authority in VTOL mode in high wind conditions.

All embodiments of the aircraft of the present invention are capable of vertical take-off and landing (VTOL) and ultra-short take-off and landing (hyper-STOL).

Reference will now be made to the drawings, wherein like reference numerals refer to like elements throughout. The foregoing disclosure is provided by way of example and not limitation.

Drawings

FIG. 1 is a side view of an exemplary aircraft including two vertical thrusters (or rotor stabilizers) according to Malaysia patent application No. PI 2020000674;

FIG. 2 is a perspective view of an exemplary aircraft including a pair of horizontal thrusters, each having a fixed inclination of +6, according to the present invention;

FIG. 3 is a side view in hover attitude showing an exemplary aircraft similar to FIG. 2 with pitch angle ρ and with inclination angles φ and t applied to horizontal and vertical thrusters, respectively, and associated forces acting thereon, in accordance with the present invention;

FIG. 4(a) shows an embodiment of the aircraft of the present invention comprising an elliptical fuselage, a pair of upper wings and a pair of lower wings having an angle of attack of 45 during hovering and VTOL;

FIG. 4(b) shows a side view of the embodiment shown in FIG. 4 (a);

FIG. 4(c) is a perspective view of the embodiment shown in FIG. 4(a) and including an inverted V-shaped tail for long distance flights in accordance with the present invention;

FIG. 4(d) is another perspective view of the embodiment of FIG. 4(a) showing the lower wing having a 45 angle of attack and the individual ailerons deflected upward by 45 to affect the resultant thrust vector of the propellers in horizontal flight mode;

FIG. 4(e) is a perspective view of the embodiment shown in FIG. 4(a) including a plurality of lower wings, each lower wing further including an aileron;

FIG. 5(a) shows an embodiment of the invention in which the fuselage comprises four vertical thrusters and a pair of horizontal thrusters and the wing has an angle of attack of 20 °;

FIG. 5(b) is a bottom view of the embodiment shown in FIG. 5 (a);

FIG. 6(a) is a perspective view of an embodiment of the present invention comprising triangular wings and an inverted vertical stabilizer;

FIG. 6(b) is an enlarged view of the vicinity of the front portion of the fuselage of the embodiment shown in FIG. 6 (a);

fig. 6(c) is a side view of the embodiment shown in fig. 6 (a).

Detailed Description

The present invention relates to a fixed wing aircraft (airplane) capable of ultra-short/vertical takeoff and landing (hyper-STOL/VTOL) with reconfigurable trust vectors for horizontal thrusters and vertical thrusters.

FIG. 2 is a perspective view of an exemplary aircraft according to the present invention. The aircraft includes an aircraft fuselage (airframe) (100). The aircraft fuselage 100 may be divided into a forward portion and an aft portion. The aircraft fuselage (100) further comprising at least one fuselage (101), at least one pair of wings (102), the wings (102) having a positive angle of attack during hovering and vertical takeoff and landing, ranging between 0.5 ° and 80 °; at least a horizontal propeller (104A, 104B) is mounted on each wing (102); at least two vertical thrusters (106A, 106B), which can be divided into a forward unit and an aft unit, at least one forward vertical thruster (106A) located forward of the aircraft fuselage and forward of the centre of gravity (C.G.) of the aircraft fuselage, and at least one aft vertical thruster (106B) located aft of the aircraft fuselage (101) and aft of the centre of gravity of the aircraft fuselage, wherein the forward and aft vertical thrusters are in substantially laterally symmetrical positions about the longitudinal axis of the aircraft as shown in fig. 2. In this exemplary aircraft, one horizontal thruster (104A, 104B) is mounted to each side of the wing, with the thrust vector of the horizontal thruster being substantially parallel to the chord line of the respective wing (102), which thus means that phi, the angle of incidence of the horizontal thruster (104A, 104B) is equal to theta, the angle of attack of the wing (102). In this embodiment, the angle of attack is manually fixed at 6 ° when the aircraft is stationary on the ground and to the fuselage (101) by means of nuts and bolts, while in air the angle remains at 6 °. During the level flight mode (cruise flight), forward thrust of the aircraft is provided by the horizontal thrusters (104A, 104B). The horizontal propellers (104A, 104B) may be based on various drives, such as electric motors, turbine engines, internal combustion engines, and solar engines. The two vertical thrusters (106A, 106B) are preferably located at substantially equal distances from C.G for optimum pitch control performance. Further, in this example, the tandem vertical thrusters (106A, 106B) have counter-rotating rotors to counteract the torque effect, and the same principles can be applied to the horizontal thrusters (104A, 104B).

Each wing (102) includes at least an aileron (108) for roll control. The horizontal thrusters (104A, 104B) are mounted in such a way that the ailerons (108) are exposed to the strong airflow generated by the horizontal thrusters (104A, 104B) to help ensure adequate roll control in deep wing stall conditions such as hover, vertical landing and ultra short take-off. Thus, the horizontal thrusters (102A, 102B) should be located in front of the ailerons (108), and in this particular example, the horizontal thrusters (102A) are mounted near the leading edge of the wing (102).

During hover and vertical flight, the horizontal thrusters (104A, 104B) and the vertical thrusters (106A, 106B) contribute to lift via the resolution of vectors. According to the invention, having a wing (102) with a positive angle of attack during vertical flight results in a reduction of takeoff angle and hover pitch angle, which is particularly advantageous for manned flight applications. The angle of attack of the wing (102) is reconfigurable. The change in angle of attack may be performed either manually when the aircraft is on the ground or automatically when the aircraft is airborne.

The aircraft fuselage (100) of the exemplary aircraft includes at least one aerodynamic surface for pitch stability and control during a level flight mode, a level stabilizer (110) in the form of a canard configuration. In this example, as shown in fig. 2, almost the entire horizontal stabilizer (110) is used to initiate pitch control. The use of the horizontal stabilizer (110) for pitch control during cruise flight allows the vertical thrusters (106A, 106B) to be turned off, thereby improving efficiency and extending the range of travel. Optionally, the aircraft fuselage (100) may include at least one vertical stabilizer (112) that is useful for directional stability while gliding or in the event that the horizontal thrusters (104A, 104B) fail and fail to provide a thrust differential for yaw control. There may be more than one vertical stabilizer (112). The vertical stabilizer (112) may further include a rudder (114), although simulations indicate that the aircraft may still turn satisfactorily using only the ailerons and not the rudder (114). Fig. 2 shows at least the rear unit (106B) of the vertical thrusters (106A, 106B) mounted on top of the vertical stabilizer (112). Yaw control during vertical flight mode may be achieved using different thrusts of the horizontal thrusters (104A, 104B).

A set of main landing gears (116) is located aft of the aircraft, behind the center of gravity of the aircraft. Wheeled main (116) and nose (118) landing gears may be used for Hyper-STOL and emergency landing involving runway ground roll. The main landing gear (116) and nose landing gear (118) may be equipped with floats for water operations or skis for snow operations, taking into account the vertical takeoff and landing (VTOL) capability of the aircraft.

The vertical thrusters (106A, 106B) of the present invention may accept variable pitch or fixed pitch rotors (rotors), however, for mechanical simplicity and reduced maintenance costs, the rotors of the vertical thrusters (106A, 106B) are preferably fixed pitch. The same applies to the horizontal thrusters (104A, 104B). This means that each vertical thruster (106A, 106B) can only exert aerodynamic forces in one direction. Vertical thrusters (106A, 106B) with fixed pitch rotors drive the pitch control of the aircraft through differential thrust.

Additionally, tandem vertical thrusters (106A, 106B) may be used to provide partial lift to the aircraft during takeoff and landing, thereby helping to reduce forward airspeed, resulting in ultra-short takeoff/landing distances. Under certain conditions, vertical take-off and landing may be possible without the use of tiltrotors or tiltrotors, as described in malaysia patent application No. PI 2018500050.

Referring now to fig. 3, fig. 3 illustrates an aircraft in the present invention performing hover to gain insight into the forces acting on the aircraft that make hover and VTOL flight possible. The aircraft hovers at a pitch angle ρ (hovering). Each horizontal thruster (104A, 104B) generates thrust T1. Each vertical thruster (106A, 106B) generates a thrust T2. The aircraft has an overall weight (AUW) of W. For ease of explanation, consider the case where T2 is T1. As described above, the wing (102) has an angle of attack θ ═ Φ, and the vertical thrusters (106A, 106B) have an inclination measured with respect to the vertical axis of the aircraft. Note that the vertical axis is parallel to the yaw axis of the aircraft.

Taking into account the horizontal component of the force when the aircraft is suspended, it can be derived

T₁·cos(ρ+φ)＝T₂·sin(ρ+t).

Now, considering the perpendicular component of the force, one can obtain

T₁·sin(ρ+φ)+T₂·cos(ρ+t)＝0.5×W.

In the case where ρ is 16 °, Φ is 40 °, and t is 18 ° as shown in fig. 3

In summary, the vector analysis shows that when the pitch angle ρ is 16 °, and when the horizontal thrusters (104A, 104B) and the vertical thrusters (106A, 106B) generate the same thrust, i.e., T₁＝T₂At 0.30W, a stable hover state is achieved. Thus, all embodiments of the aircraft of the present invention are capable of vertical take-off and landing (VTOL) and ultra-short take-off and landing (hyper-STOL). One way to implement a hyper-STOL is simply by increasing T while maintaining pitch angle ρ and pitch angles φ and T₁/T₂The ratio of (a) to (b). Note that if an embodiment of the present invention is capable of hovering and VTOL flight, it can of course also perform hyper-STOL.

If phi is made 0 deg. and t is 0 as proposed in malaysia patent application No. PI 2020000674, the pitch angle required for hovering will be 45 deg..

The remarkable and interesting results of the vector analysis are as follows:

1.φ＝45° τ＝45° ρ＝0° T₁＝T₂＝0.3536W

2.φ＝45° τ＝45° ρ＝10° T₁＝0.4096W,T₂＝0.2868W

3.φ＝12° τ＝12° ρ＝33° T₁＝T₂＝0.3536W

4.φ＝50° τ＝0° ρ＝20° T₁＝T₂＝0.266W

5.φ＝70° τ＝20° ρ＝5° T₁＝0.3287W,T₂＝0.2013W

6.φ＝80° τ＝0° ρ＝5° T₁＝T₂＝0.251W

results-1 show that when phi and tau are both 45 deg., the aircraft should be able to take off and land vertically with a pitch angle of 0 deg., i.e., the aircraft is in a horizontal position, and both the horizontal thrusters and the vertical thrusters will generate thrust approximately equal to 35% of the total weight W of the aircraft. If the takeoff pitch angle ρ is now increased to 10 ° as shown in result-2, each vertical thruster can only expect to output a thrust of 0.2868W in order to maintain stable hovering. On the other hand, each horizontal thruster should deliver a greater thrust of about 0.4W. This is an efficient design because, in addition to providing thrust for vertical flight, powerful horizontal thrusters can be used for high speed cruising. Result-5 is another interesting result that can be practically achieved.

Result-3 is yet another interesting result, since it shows that an angle of attack of 12 ° can be used for both vertical and horizontal flight involving medium airspeeds, so the wing (102) can simply be locked in position on the fuselage (101). Analysis has shown that for angles of attack of 50 ° and above, the thrust required by each propeller is close to 0.25W. Note that in result-6, 80 ° is about the maximum possible value, since if 90 °, there will be no thrust contribution from the horizontal thrusters (104) and there will be no roll control when there is no propeller wash on the ailerons (108).

Fig. 4(a) is a perspective view of an embodiment of an aircraft according to the invention, wherein the aircraft fuselage (100) comprises a fuselage (101) and the shape of the fuselage (101) is substantially elliptical. An aircraft fuselage (100) includes at least one pair of wings (102). In this exemplary aircraft, each wing (102) also includes an upper wing (102U) and a lower wing (102L), where the upper wing (102U) is a fixed wing with a fixed angle of attack and they are primarily for horizontal flight. According to the invention, the angle of attack θ of the lower wing (102L) and thus the inclination φ of the horizontal thrusters (104A, 104B) during hovering and VTOL is in the range of 0.5 ° to 80 °. According to the present invention, the inclination of the horizontal thrusters (104A, 104B) may be maintained in the range of 0.5 ° to 80 ° during the hyper-STOL. However, in this exemplary aircraft, θ and therefore φ are fixed at 45 during vertical flight and horizontal flight. Each lower wing (102L) includes at least one horizontal thruster (104A, 104B) and at least one aileron (108). Furthermore, the span of each lower wing (102L) is almost the same as the diameter of the rotor of the respective horizontal thruster (104A, 104B). This is because the main function of the lower wing (102L) is for slow or vertical flight. According to the invention, the horizontal thrusters (104A, 104B) should be positioned in front of the ailerons (108) and, in this particular example, they are mounted near the leading edge of the wing (102L). According to the invention, the inclination phi of the horizontal thrusters (104A, 104B) is substantially equal to the angle of attack theta of the lower wing (102L) on which the horizontal thrusters (104A, 104B) are mounted.

Fig. 4(b) is a side view of the exemplary aircraft shown in fig. 4 (a). The elliptical fuselage (101) comprises a horizontal main axis (101 HA). The elliptical body comprises an upper front part, a lower front part, an upper rear part and a lower rear part. The upper front portion is separated from the lower front portion by a horizontal main axis (101 HA). The exemplary aircraft includes at least one forward vertical thruster (106A) disposed on a lower forward portion of the elliptical fuselage (101), and at least one aft vertical thruster (106B) disposed on an upper aft portion of the elliptical fuselage (101). As shown in fig. 4(B), the inclination angle τ of the vertical thrusters (106A, 106B) is 45 °. Thrust vectors T1 and T2 are also shown in fig. 4 (b).

In the case where τ is 45 ° and Φ is 45 °, the takeoff pitch angle ρ is 0 °. This means that in this configuration the aircraft is able to perform VTOL with the fuselage substantially horizontal. The aircraft fuselage (100) further comprises a cockpit windscreen (120). The design of the elliptical fuselage (101) is attractive because at least one front vertical thruster (106A) can be mounted below the cockpit windshield (120), thus helping to keep the pilot's view clear. The embodiment shown in fig. 4(b) is compact and may be suitable for short haul flights. The fuselage (101) also includes at least a portion of an attachment point (122) at the rear to attach the tail assembly as an option for long-haul flight applications.

Fig. 4(c) is a perspective view of the aircraft in a substantially horizontal flight mode, in which both the forward vertical thrusters (106A) and the aft vertical thrusters (106B) are retracted into the fuselage (101) to improve aerodynamic efficiency. The vertical thrusters (106A, 106B) are housed in a compartment having a pair of laterally sliding hatches (119). The tail assembly includes at least one support structure (124), an inverted V-shaped tail (126) that provides combined pitch and yaw functionality during a level flight mode. The inverted V-shaped flight (126) also includes a control surface (128). After the transition to the horizontal flight mode, the angle of attack θ of the lower wing (102L) may be reduced, either manually or automatically, to, for example, 3 °, as shown in fig. 4 (c).

By deflecting the ailerons (108) upwards, the inclination of the thrust vectors of the horizontal thrusters (104A, 104B) can be effectively reduced. To improve the efficiency of this deflection, the rotors of the plurality of horizontal thrusters (104A, 104B) on each lower wing (102L) are smaller than the rotors of the single horizontal thruster (104A, 104B), as shown in fig. 4 (d). Another possible way to increase the efficiency of the process is to have each lower wing (102L) further comprise a plurality of lower wings (102L), each lower wing (102L) comprising at least one aileron (108), as shown in fig. 4 (e). Because θ is 45 ° for this exemplary aircraft, the aileron (108) is deflected 45 ° upwards in fig. 4(d) and 4 (e). The advantage of this approach is that the horizontal thrusters (104A, 104B) do not involve tilting, and only the relatively large deflections of the ailerons (108) are used to control the resultant thrust vector of the horizontal thrusters (104A, 104B). It is desirable that this technique be applicable to θ having a value of 45 ° or less.

Another method of controlling aircraft pitch is to use a weight transfer method. Also, another method of initiating aircraft turning (roll plus yaw combination) during horizontal flight is to use spoilers on the upper wing (102U) instead of the ailerons (108). Due to the ability to influence pitch, roll and yaw during horizontal flight, the optional tail assembly can be eliminated, resulting in a very compact VTOL aircraft suitable for personal aviation that is likely to take off and land in its own backyard.

Fig. 5(a) shows a perspective view of another embodiment of an aircraft according to the invention. The aircraft fuselage (100) of the aircraft comprises a horizontal stabilizer (110) of aft configuration, and the horizontal stabilizer (110) has a riser (111) for aerodynamic pitch control during horizontal flight. The exemplary aircraft includes four vertical thrusters (106a1, 106a2, 106B1, 106B2) arranged such that they exhibit lateral symmetry except that they are located at a distance from the longitudinal axis of the aircraft, as shown in the bottom view of fig. 5 (B).

Referring again to fig. 5(a), the front vertical thrusters (106a1, 106a2) and the rear vertical thrusters (106B1, 106B2) are connected to the respective wings (102) via a support structure (130) such that the angle of attack of the wings 102 affects the inclination of the horizontal thrusters 104A, 104B and the inclination of the vertical thrusters 106a1, 106a2, 106B1, 106B 2. In other words, the change in the inclination angle of the vertical thruster (106a1, 106a2, 106B1, 106B2) is Δ τ ═ Δ Φ ═ Δ θ.

In fig. 5(a), τ ═ Φ ═ θ ═ 20 °, therefore, the aircraft is expected to hover at a pitch angle ρ of 25 °. A particular advantage of this embodiment is that the vertical thrusters (106a1, 106a2, 106B1, 106B2) are inclined together with the horizontal thrusters (104A, 104B) whenever the angle of attack θ of the wing (102) is changed.

At least one set of main landing gear (116) may be placed substantially behind the rear unit of the vertical thrusters (106B1, 106B2) to protect the rotors of the rear unit of the vertical thrusters (106B1, 106B2) from ground impacts. The safety advantage of this arrangement is that as the aircraft pitches upward, the rotors of the rear vertical thrusters (106B1, 106B2) move further away from the ground until a certain pitch angle is reached.

Conventional aircraft typically require the main landing gear to be placed close to the aircraft c.g. in order to rotate at takeoff. However, the main landing gear set (116) may be placed far behind the aircraft's center of gravity. In the present invention, take-off rotation is made possible by the uniqueness provided by the tandem rotor stabilizer in that it provides some lift to the aircraft. This is true for all embodiments of the invention. Another implication is that the main landing gear (116) and nose landing gear (118) are not essential for vertical take-off and landing, and "belly landing" based solutions are possible, especially for light AUW applications (e.g. small unmanned aircraft).

Fig. 6(a) shows a perspective view of yet another embodiment of an aircraft according to the invention, wherein at least one pair of wings has a triangular shape to achieve pitch stability and control. Each wing (102) comprises at least one horizontal thruster (104A, 104B) and at least one elevon (103). This embodiment is also suitable for high speed applications, so the horizontal propellers (104A, 104B) should preferably be of the type that is capable of propelling the aircraft to high airspeeds, such as turbojet engines and turbofan engines. Each horizontal thruster (104A, 104B) comprises a thrust vectoring nozzle (105), the thrust vectoring nozzle (105) having two degrees of freedom to actuate roll and yaw control during hovering and substantially vertical take-off and landing. Among the well-known delta wing design variations are tailor delta wings, compound delta wings, curved arrow delta wings, and oval delta wings [6 ]. In this embodiment, at least the vertical stabilizer (112) is mounted on the rear of the aircraft fuselage (100) and below the aircraft fuselage (100). The aircraft also has two vertical stabilizers (112) at respective wingtips.

Similar to the embodiment shown in fig. 4, the fuselage (101) of the aircraft further comprises a storage compartment (115), as shown in the close-up view of fig. 6 (b). According to the invention, the storage compartment (115) enables the retraction of the vertical pushers (106A, 106B) to increase aerodynamic efficiency. Each storage compartment (115) has at least a hatch (119) that slides in the front-rear direction.

Fig. 6(c) shows a side view of the aircraft shown in fig. 6 (a). It shows that the thrust vectoring nozzle (105) belonging to the horizontal thruster (104A) on the left side of the aircraft is rotated downwards by 45 ° with respect to the longitudinal axis of the aircraft. This in turn causes the effective value of the tilt angle phi of the horizontal thruster (104A) to be approximately 45 deg. as shown in fig. 6 (c).

It is anticipated that if there is a heavy fuel load or payload in the flight such that the aircraft's AUW exceeds the total vertical thrust component of the vertical thrusters (106A, 106B) and the horizontal thrusters (104A, 104B), ultra short take-off is a more appropriate, more efficient option due to the contribution of the wing to generating lift.

The foregoing description of the invention has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit the invention to the form disclosed herein. Variations and modifications commensurate with the above teachings, and skill and knowledge of the relevant art, are therefore 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 others skilled in the art to utilize the invention in such, or other, embodiments and with the various modifications required by the particular applications or uses of the invention. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art.

Reference documents:

1.M.Francesco(2020)Is the Urban Air Mobility Industry ready for Take-Offhttps://www.airborne.com/urban-air-mobility-the-rise-of-evtol-vehicles/

2.ArduPilot Dev Team(2019)QuadPlane Overview.https://ardupilot.org/plane/docs/quadplane-overview.html

3.D.Z.Morris(2017)The V-22Osprey:A Crash Decades in the Making.https://fortune.com/2017/08/05/v22-osprey-crash-australia/

4.DeVry University(2020)Drones:Description&Thesis.https://www.coursehero.com/file/p2mea4o/There-are-4-types-of-drones-majorly-used-namely-Fixed-wing-drone-that-has-long/#/doc/qa

5.Wikipedia(2019)Tiltwing.https://en.wikipedia.org/wiki/Tiltwing

6.Wikipedia(2020)Delta wing.https://en.wikipedia.org/wiki/Delta_wing.

Claims (10)

1. a fixed wing aircraft capable of hover and vertical takeoff and landing (VTOL) while maintaining a positive pitch angle (nose-up attitude) such that both horizontal and vertical thrust contribute to lift via resolution of vectors, comprising:

a longitudinal axis;

a vertical axis;

a center of gravity;

an aircraft fuselage (100) comprising a front portion and a rear portion;

at least one forward vertical thruster (106A) located on a forward portion of the aircraft fuselage (100), the forward vertical thruster (106A) generating a thrust vector;

at least one aft vertical thruster (106B) located on an aft portion of the aircraft fuselage (100), the aft vertical thruster (106B) generating a thrust vector;

at least one pair of wings (102) attached to an aircraft fuselage (100), the wings (102) comprising a chord line; the wing (102) has an angle of attack; the angle of attack is fixed in the air; and

at least one horizontal thruster (104A, 104B) attached to at least one wing (102), the horizontal thruster (104A, 104B) having a positive inclination with respect to the longitudinal axis; each horizontal thruster (104A, 104B) generates a thrust vector, the thrust vector of the horizontal thruster (104A, 104B) being substantially parallel to the chord line of the respective wing (102), such that the inclination of the horizontal thruster (104A, 104B) is equal to the angle of attack of the wing (102), wherein:

the angle of attack of the wing (102) is reconfigurable when the aircraft is on the ground;

the front vertical thruster (106A) and the rear vertical thruster (106B) have a fixed inclination, measured with respect to the vertical axis, ranging from 0 ° to 45 °;

the angle of attack of the airfoil 102 is in the range of 5 ° to 65 °; and

the fixed-wing aircraft has a pitch angle of 33 ° during hover when:

the thrust vectors of the horizontal thrusters (104A, 104B) and the vertical thrusters (106A, 106B) are equal in magnitude;

the angle of attack of the wing (102) is 12 DEG, an

The fixed pitch angle of the vertical propellers (106A, 106B) is 12 deg..

2. The aircraft of claim 1, wherein the aircraft fuselage (100) comprises a fuselage (101); and a fuselage substantially elliptical in shape, wherein the elliptical fuselage comprises an upper front portion, a lower front portion, an upper rear portion, and a lower rear portion; wherein at least one front vertical thruster (106A) is arranged on the lower front portion of the elliptical fuselage (101), and further wherein at least one rear vertical thruster (106B) is arranged on the upper rear portion of the elliptical fuselage (101); wherein each wing (102) further comprises an upper wing (102U) and a lower wing (102L); the upper wing (102U) is a fixed wing having a fixed angle of attack; each of the lower wings (102L) has an angle of attack in the range of 0.5 ° to 80 ° during hover and vertical takeoff and landing; each lower wing (102L) comprising at least one horizontal thruster (104A, 104B) and at least one aileron (108); the horizontal thruster (104A, 104B) is located in front of the aileron (108), the horizontal thruster (104A, 104B) is mounted near the leading edge of the wing (102L); the horizontal thrusters (104A, 104B) have an inclination equal to the angle of attack of the lower wing (102L).

3. The aircraft of claim 2, wherein the span of each lower wing (102L) is approximately the same as the diameter of the rotor of the corresponding horizontal thruster (104A, 104B).

4. The aircraft of claim 1, wherein the aircraft further comprises at least one aerodynamic surface (102, 110, 126) for pitch stability and control during horizontal flight.

5. The aircraft of claim 4, wherein the aerodynamic surface is a horizontal stabilizer (110).

6. The aircraft of claim 4, wherein the aerodynamic surface is a triangular wing (102).

7. The aircraft of claim 1, wherein the aircraft comprises at least two horizontal thrusters (104A, 104B); the horizontal thruster (104A, 104B) is of the turbojet type; each horizontal thruster (104A, 104B) further comprises a thrust vectoring nozzle (105), the thrust vectoring nozzle (105) being capable of having at least one degree of freedom to actuate roll control during hovering and substantially vertical takeoff and landing.

8. The aircraft of claim 1, wherein the aircraft comprises at least two horizontal thrusters (104A, 104B); the horizontal thrusters (104A, 104B) are of the turbofan type; each horizontal thruster (104A, 104B) further comprises a thrust vectoring nozzle (105), the thrust vectoring nozzle (105) being capable of at least one degree of freedom to actuate roll control during hovering and substantially vertical takeoff and landing.

9. The aircraft of claim 1, wherein the aircraft fuselage (100) comprises a fuselage (101); further wherein the fuselage (101) includes a storage compartment (115) to enable retraction of the vertical thrusters (106A, 106B) to improve aerodynamic efficiency.

10. A fixed wing aircraft capable of ultra-short takeoff and landing (hyper-STOL) while maintaining a positive pitch angle (nose-up attitude) such that both horizontal and vertical thrust contribute to lift via resolution of vectors, comprising:

a longitudinal axis;

a vertical axis;

a center of gravity;

an aircraft fuselage (100) comprising a front portion and a rear portion;

at least one forward vertical thruster (106A) located on a forward portion of the aircraft fuselage (100), the forward vertical thruster (106A) generating a thrust vector;

at least one aft vertical thruster (106B) located on an aft portion of the aircraft fuselage (100), the aft vertical thruster (106B) generating a thrust vector;

at least one pair of wings (102) attached to an aircraft fuselage (100), the wings (102) comprising a chord line; the wing (102) has an angle of attack; the angle of attack is fixed in the air; and

at least one horizontal thruster (104A, 104B) attached to at least one wing (102), the horizontal thruster (104A, 104B) having a positive inclination with respect to the longitudinal axis; each horizontal thruster (104A, 104B) generates a thrust vector, the thrust vector of the horizontal thruster (104A, 104B) being substantially parallel to the chord line of the respective wing (102), such that the inclination of the horizontal thruster (104A, 104B) is equal to the angle of attack of the wing (102), wherein:

the angle of attack of the wing (102) is reconfigurable when the aircraft is on the ground;

the front vertical thruster (106A) and the rear vertical thruster (106B) have a fixed inclination, measured with respect to the vertical axis, ranging from 0 ° to 45 °;

the angle of attack of the airfoil 102 is in the range of 5 ° to 65 °.

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