CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to Malaysian Patent Application No. PI2020000674, filed on Feb. 6, 2020, the contents of which are incorporated herein by reference.

FIELD OF INVENTION

The present invention relates to a fixed-wing aircraft capable of hyper-short/vertical takeoff and landing (hyper-STOL/VTOL) with non-rotatable vertical propulsions.

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” [Reference 1]. Many of the airframes used to realize eVTOL is largely based on that of a combined fixed wing and multicopter aircraft, also known as a “QuadPlane” [Reference 2]. This type of aircraft is known to have the benefit of vertical takeoff and landing, significantly higher cruising speed, and the ability to land vertically at the destination [Reference 2]. The design of a QuadPlane is built upon an airplane, but with an addition of at least 4 rotors/propellers for vertical flight [Reference 2]. In other words, there are separate propulsions for horizontal cruising flight and vertical flight. So in general, when a QuadPlane is hovering, its horizontal airplane-like propulsion(s) is/are inactive. Likewise, when said QuadPlane is cruising through the air using wing-borne lift in horizontal flight mode, its powerful helicopter-like vertical propulsions are inactive and having zero contribution. This, from our viewpoint, is inefficient and unoptimized. Other well-known airframe configurations that enable an airplane to hover and perform vertical flight are those based on tilt-wings and tilt-rotors involving rotatable propulsion units which often are technologically more complex than a QuadPlane [References 3,4].

The present invention thus proposes an airplane that has the hovering ability of a QuadPlane but incorporate innovative design that facilitates efficient use of both horizontal and vertical propulsions during a hover and vertical flight.

SUMMARY OF INVENTION

There are additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto. In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of the description and should not be regarded as limiting.

The present invention relates to an airplane capable of hyper-short/vertical takeoff and landing (hyper-STOL/VTOL) and with non-rotatable vertical propulsions. An object of the present invention is to overcome a limitation of QuadPlane design by making efficient use of both horizontal and vertical propulsions during hovering and vertical flight.

In our previous Malaysian Patent Application No. PI 2018500050, we proposed the concept of “roto-stabilizer” as an effective solution to overcome the limitations of conventional horizontal stabilizers in the post-stall regime and its primary function is to generate moment about the pitch axis of an airplane, even in stall/post-stall regime. The roto-stabilizer comprises a plurality of rotary wings (or collectively known as a rotor). Said rotor can be fixed-pitch or variable pitch. The trend in eVTOL is to opt for fixed-pitch approach given its mechanical simplicity. The axis of rotation of the rotor is substantially vertical and said rotor is driven by driving means such as an electric motor to generate aerodynamic thrust in a substantially vertical direction, making it possible to actuate pitch control of an airplane while it is stationary on the ground and having no forward airspeed. The “roto-stabilizer” has three primary configurations namely: tail-aft, “above CG” and canard (Malaysian Patent Application No. PI 2018500050).

The present invention may broadly be viewed as a combination of tail-aft and canard configurations of roto-stabilizer, resulting in ability to provide both vertical propulsion or rotor-borne lift and to generate pitching moment about the pitch axis of an airplane. The present invention may therefore be conveniently termed as “tandem roto-stabilizers” and we believed it will play a significant role in the future of personal aviation and aerial ridesharing.

Embodiments of the airplane in the present invention comprise at least two vertical propulsors which may be divided into fore unit(s) and aft unit(s), and at least a longitudinally oriented horizontal propulsor. Embodiments of the present invention may also comprise at least an aerodynamic surface for pitch stability and control during horizontal flight mode, and examples of which are horizontal stabilizer and V-tail, both of which will be exemplified by the various embodiments of the present invention described herein.

In general, each wing comprises at least an aileron for roll control. The airplane's forward thrust during cruising phase is provided by the horizontal propulsor(s). Furthermore, either the entire horizontal stabilizer may be used to actuate pitch control or the horizontal stabilizer can have elevators for aerodynamic pitch control depending on applications. The vertical propulsors are arranged such that the fore unit(s) is/are located on the front section of said airplane while the aft unit(s) is/are located on the back section of the airplane. During hovering and vertical flight the airplane assumes a nose-up attitude known as ‘harrier’ with positive pitch angle so that the horizontal propulsor(s) and the vertical propulsors both contribute to lift via resolution of vectors. Additionally, the horizontal propulsor(s) may be based on a variety of drives such as electric motor, internal combustion, solar engine, and turbine engine.

The subject invention discloses an aircraft capable of a substantially vertical takeoff and a substantially vertical landing with non-rotatable vertical propulsions, the aircraft comprising: a longitudinal axis; a center of gravity; an airframe comprising a front section and a back section; at least one fore vertical propulsor located on the front section of the airframe; at least one aft vertical propulsor located on the back section of the airframe, wherein the fore and aft vertical propulsors are in substantially lateral symmetrical positions about the longitudinal axis of the aircraft; at least one horizontal propulsor on the airframe; wherein said aircraft assumes a nose-up attitude with a positive pitch angle during hovering such that both the horizontal propulsor and the vertical propulsors are contributing to lift via resolution of thrust vectors.

In further embodiments of the invention, the airframe further comprises a pair of main wings, wherein at least one horizontal propulsor is attached to at least one main wing.

In additional embodiments of the invention, the airframe further comprises at least a pair of main wings, wherein the pair of main wings are in substantially lateral symmetrical positions about the longitudinal axis of the aircraft, further wherein each main wing comprises at least one aileron, wherein each aileron is immersed in strong propeller wash generated by the horizontal propulsor for roll control during hovering and vertical flight.

In other embodiments of the invention, the aircraft further comprises at least one aerodynamic surface for pitch stability and control during horizontal flight.

In embodiments of the invention, the aircraft comprises at least one set of main landing gears located behind the center of gravity of said aircraft, and at least one set of nose gears.

In further embodiments of the invention, the airframe further comprises: at least a pair of main wings, wherein the pair of main wings are in substantially lateral symmetrical positions about the longitudinal axis of the aircraft, further wherein at least one horizontal propulsor is mounted proximate to leading edges of the main wings.

In additional embodiments of the invention, the aircraft further comprises at least one aerodynamic surface for pitch stability and control during horizontal flight, wherein the aerodynamic surface is a horizontal stabilizer.

In other embodiments of the invention, the aircraft further comprises at least one aerodynamic surface for pitch stability and control during horizontal flight, wherein the aerodynamic surface is a V-tail.

In further embodiments of the invention, the aircraft comprises at least one set of main landing gears located behind the center of gravity of said aircraft, wherein the set of main gears is placed substantially in line with the aft unit vertical propulsor.

In embodiments of the invention, the aircraft comprises at least one set of main landing gears located behind the center of gravity of said aircraft, wherein the set of main gears is located behind the aft unit vertical propulsor.

In other embodiments of the invention, the aircraft comprises at least one vertical stabilizer.

In additional embodiments of the invention, the aircraft comprises at least one vertical stabilizer, wherein at least one aft vertical propulsor is attached to the top of the vertical stabilizer.

In further embodiments of the invention, the aircraft comprises at least one vertical stabilizer, wherein the vertical stabilizer further comprises a rudder.

In embodiments of the invention, the airframe of said aircraft comprises at least a fuselage.

The subject invention also discloses a method for achieving substantially vertical takeoff, substantially horizontal flight, and substantially vertical landing for an aircraft with non-rotatable vertical propulsions, comprising: (a) powering up at least one fore vertical propulsor, at least one aft vertical propulsor, and at least one horizontal propulsor located on an airframe of the aircraft; (b) ramping up output thrusts of the fore and aft vertical propulsors; (c) ramping up an output thrust of horizontal propulsor to compensate for the effects of headwind; (d) raising a pitch angle of the aircraft by differential thrust provided by the vertical propulsors while simultaneously adjusting the output thrusts of both the vertical propulsors and the horizontal propulsor, such that a resultant thrust vector is substantially pointing in a vertical direction; (e) increasing the resultant thrust vector to cause the aircraft to lift off the ground and enter a vertical flight mode; (f) lowering the pitch angle of the aircraft to initiate a forward flight mode; (g) increasing the pitch angle of the aircraft and increasing vertical lift provided by the vertical propulsors to transition from forward flight mode to a vertical landing mode, until the pitch angle has reached a value wherein a net horizontal force component is substantially zero and a resultant thrust vector is pointing in a substantially vertical direction; (h) reducing output power to both the vertical propulsors and the horizontal propulsor to initiate vertical descent; and (i) decreasing the pitch angle towards zero degree by using differential thrust of the vertical propulsors until a set of main gears is in contact with the ground and the aircraft has landed.

The subject invention further discloses a method for achieving substantially vertical takeoff, substantially horizontal flight, and substantially vertical landing for an aircraft with non-rotatable vertical propulsions, comprising: (a) powering up at least one fore vertical propulsor, at least one aft vertical propulsor, and at least two horizontal propulsors located on pair of main wings attached to an airframe of the aircraft; (b) ramping up output thrusts of the fore and aft vertical propulsors; (c) ramping up an output thrust of horizontal propulsors to compensate for the effects of headwind; (d) raising a pitch angle of the aircraft by differential thrust provided by the vertical propulsors while simultaneously adjusting the output thrusts of both the vertical propulsors and the horizontal propulsors, such that a resultant thrust vector is substantially pointing in a vertical direction; (e) increasing the resultant thrust vector to cause the aircraft to lift off the ground and enter a vertical flight mode; (f) lowering the pitch angle of the aircraft to initiate a forward flight mode; (g) increasing the pitch angle of the aircraft and increasing vertical lift provided by the vertical propulsors to transition from forward flight mode to a vertical landing mode, until the pitch angle has reached a value wherein a net horizontal force component is substantially zero and a resultant thrust vector is pointing in a substantially vertical direction; (h) reducing output power to both the vertical propulsors and the horizontal propulsors to initiate vertical descent; and (i) decreasing the pitch angle towards zero degree by using differential thrust of the vertical propulsors until a set of main gears is in contact with the ground and the aircraft has landed.

The subject invention additionally discloses an airplane capable of hyper-short vertical takeoff and landing (hyper-STOL/VTOL) with non-rotatable vertical propulsions comprising: a longitudinal axis; a center of gravity (C.G.); a front section, and a back section; at least two vertical propulsors, the vertical propulsors are arranged such that they exhibit more or less lateral symmetry about the longitudinal axis of the airplane, the vertical propulsors are further divided into fore unit(s) and aft unit(s), said vertical propulsors are arranged such that the fore unit(s) is/are located on the front section of said airplane while the aft unit(s) is/are located on the back section of the airplane; and at least a horizontal propulsor, wherein said airplane assumes a nose-up attitude with positive pitch angle during hovering such that both the horizontal propulsor(s) and the vertical propulsors are contributing to lift via resolution of vectors.

In further embodiments of the invention, the airplane comprises: at least a pair of main wings, wherein each main wing comprises at least an aileron, having at least one aileron immersed in strong propeller wash generated by the horizontal propulsors for roll control during hovering and vertical flight; and at least an aerodynamic surface for pitch stability and control during horizontal flight mode.

In additional embodiments of the invention, the airplane comprises: at least a set of main gears located behind the center of gravity of said airplane, and at least a nose gear.

In further embodiments of the invention, the horizontal propulsors are mounted close to the leading edges of the main wings.

In other embodiments of the invention, the aerodynamic surface is a horizontal stabilizer.

In additional embodiments of the invention, the aerodynamic surface is a V-tail.

In embodiments of the invention, at least a set of main gears is placed substantially in line with the aft unit(s) of the vertical propulsors.

In additional embodiments of the invention, at least a set of main gears is located behind the aft unit(s) of the vertical propulsors.

In other embodiments of the invention, the airplane comprises at least a vertical stabilizer.

In further embodiments of the invention, the vertical stabilizers further comprise rudders.

In embodiments of the invention, the airplane comprises at least a fuselage.

The subject invention also discloses a method for achieving vertical takeoff—forward flight—vertical landing sequence for the airplane comprising: (a) ramping up the output thrusts of the vertical propulsors, and ramping up the output thrust(s) of horizontal propulsor(s) to compensate for the effects of headwind; (b) raising the airplane's pitch angle by means of differential thrust provided by the vertical propulsors while simultaneously adjusting the output thrusts of both the vertical propulsors and the horizontal propulsor(s) such that the resultant vector is substantially pointing in a vertical direction; (c) further increasing the total rotor-borne lift to cause the airplane to lift off the ground and entering its vertical flight mode; (d) lowering the pitch angle of the airplane to initiate forward flight mode; (e) transitioning from forward flight mode to vertical landing: gradually increasing the pitch angle of the airplane and increasing rotor-borne lift provided by the vertical propulsors; (f) once the pitch angle has reached a value wherein net horizontal force component is substantially zero and resultant vector is pointing substantially vertical, reducing output power to both the vertical propulsors and the horizontal propulsor(s) to initiate vertical descent; (g) when at least a set of main gears is in contact with the ground, gradually decreasing pitch angle towards 0° by using differential thrust of the vertical propulsors.

In embodiments of the subject invention, the term “substantially” is defined as at least close to (and can include) a given value or state, as understood by a person of ordinary skill in the art. In one embodiment, the term “substantially” refers to ranges within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.1% of the given value or state being specified.

There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto. These together with other objects of the invention, along with the various features of novelty, which characterize the invention, are pointed out with

