Vertical take-off and landing aircraft

A vertical take-off and landing (VTOL) aircraft is provided comprising a fuselage (12) defining a forward end and an aft end, the fuselage accommodating at least one engine (56), a left wing (18) and a right wing (20) extending from either side of the fuselage, a lift fan drive system (22) accommodated within each wing, a forward thrust fan drive system (24) fitted proximate the aft end of the fuselage, and a stabiliser arrangement (26) proximate the forward thrust fan drive system. In an embodiment, each wing comprises a rotor housing portion (18.1, 20.1) extending away from the fuselage and a wing tip portion (18.2, 20.2) extending away from the rotor housing portion, the wing tip portion being angled towards the rear and side of the aircraft. In an embodiment, the rotor housing portion comprises two rotor housings, one forward of the aircraft's centre of gravity and one aft of the aircraft's centre of gravity.

RELATED APPLICATIONS

This application is a 35 U.S.C. § 371 national stage filing of International Application No. PCT/IB2015/055376, filed on Jul. 16, 2015, which claims priority to South African Patent Application No. 2014/05312, filed on Jul. 18, 2014. The entire contents of each of the foregoing applications are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to aircraft, and more specifically to a vertical take-off and landing aircraft having the take-off and hover capabilities similar to a helicopter and the performance and range capabilities similar to a regional business jet.

BACKGROUND TO THE INVENTION

Vertical take-off and landing (VTOL) aircraft, as such, are not new. Two of the more successful VTOL aircraft are briefly described below:1. The first VTOL aircraft uses a tilt-rotor design, wherein a tilt-rotor is fitted to the end of each wing. The tilt-rotor is movable between a vertical position, for providing lift for vertical takeoff, and a horizontal position, for providing forward thrust for normal flight. A successful example of the above is the US military's “Osprey” aircraft.2. The second VTOL aircraft uses thrust augmentation and engine compressor bleed aft, in which thrust produced by turbofan/jet engines and engine compressor bleed air is redirected (i.e. augmented) downwardly to achieve vertical take-off. The most successful example of such a design is the British military's AV8 Harrier fighter jet.

Yet a further example of a VTOL aircraft, which the VTOL of the present invention is more closely aligned to, is the Vanguard Omniplane, which was an experimental aircraft program which ran from 1959 to 1962. Vertical lift was achieved through two in-wing three bladed fans, and forward flight was achieved using a shrouded rear propeller. The aircraft also featured covers and closing louvers on the top and bottom of the wings, respectively, to close off the fans and thereby improve aerodynamics during forward flight. This aircraft had inherent stability and control problems, and during testing the aircraft was damaged and the project abandoned.

There remains a need for a VTOL aircraft that is inherently stable, and which has the hover, landing and vertical take-off performance of a helicopter and has the performance and range of a regional business jet.

SUMMARY OF THE INVENTION

According to the invention there is provided a vertical take-off and landing (VTOL) aircraft comprising:a fuselage defining a forward end and an aft end, the fuselage accommodating at least one engine;a left wing and a right wing extending from either side of the fuselage:a lift fan drive system accommodated within each wing;a forward thrust fan drive system fitted proximate the aft end of the fuselage; anda stabiliser arrangement proximate the forward thrust fan drive system.

In an embodiment, each wing comprises a rotor housing portion extending away from the fuselage and a wing tip portion extending away from the rotor housing portion, the wing tip portion being angled towards the rear and side of the aircraft.

In an embodiment, the rotor housing portion comprises two rotor housings, one forward of the aircraft's centre of gravity and one aft of the aircraft's centre of gravity.

In an embodiment, each rotor housing accommodates a lift fan with variable pitch blades, the lift fan forming part of the lift fan drive system.

In an embodiment, the aircraft comprises a stability system having a plurality of inputs, including that of a pilot, and a plurality of actuating outputs. One of the actuating outputs is to control the angular pitch of the blades of the lift fans, with the change in pitch of the fan blades varying the vertical thrust provided by each fan.

For the purposes of this invention, ‘pilot’ is meant to include a remote pilot and an autopilot.

In an embodiment, a lower opening of each rotor housing is fitted with a series of louvers, the louvers being orientated and angled during flight to redirect the thrust generated by the lift fans. The louvers are controlled by the stability system, based on the pilot's inputs and stability sensor inputs into the stability system.

In an embodiment, an upper opening of each rotor housing is fitted with a sealing arrangement to seal off the upper opening, which is under the control of the pilot and flight management system.

In an embodiment, the forward thrust fan drive system comprises two forward thrust ducted fans, the fans being accommodated within a cowling that is fitted on either side of the fuselage tail.

In an embodiment, the length of the fuselage and the wingspan of the aircraft are similar.

In an embodiment, the stabiliser arrangement comprises a horizontal stabiliser extending from each cowling that accommodates one of the forward thrust ducted fans, and a vertical stabiliser that extends from each cowling.

In an embodiment, the stabiliser arrangement may include canards.

In an embodiment, the fuselage comprises multiple turbine engines, with power being transferred from each of the engines to each of the lift fans of the lift fan drive systems through a single planetary gearbox, the multiple turbine engines also being used to power the forward thrust fan drive system through a secondary gearbox.

DETAILED DESCRIPTION OF THE INVENTION

With reference now to the drawings, there is provided a vertical take-off and landing (VTOL) aircraft10comprising a blended body, pressurised fuselage12defining a forward end14and an aft end16.

The aircraft10further comprises a left wing18and a right wing20extending from either side of the fuselage12.

A lift fan drive system22is accommodated within each wing18,20, and a forward thrust fan drive system24is fitted proximate the aft end16of the fuselage12.

A stabiliser arrangement26is fitted proximate the forward thrust fan drive system24at the aft end16of the aircraft10.

In an embodiment, each wing18,20comprises a rotor housing portion18.1,20.1extending away from the fuselage12and a wing tip portion18.2,20.2extending away from the rotor housing portion18.1,20.1, respectively, the wing tip portion18.2,20.2being angled towards the rear and side of the aircraft10(as best shown inFIG. 2).

In an embodiment, the rotor housing portion18.1,20.1comprises two rotor housings18.3,18.4and20.3,20.4, respectively, with rotor housings18.3and20.3being forward of the aircraft's centre of gravity (indicated by line G-G inFIG. 2) and rotor housings18.4,20.4being aft of the aircraft's centre of gravity.

As best shown inFIG. 4, each rotor housing18.3,18.4,20.3,20.4accommodates a lift fan28.1,28,2,28.3and28.4, respectively, with variable pitch blades, the lift fans28.1,28.2,28.3and28.4forming part of the lift fan drive system22.

In an embodiment, the altitude and movement of the aircraft10is controlled and managed using a computer controlled stability system. The system has a plurality of inputs, including at least one gyroscopic sensing system and flight control inputs from a pilot, and a processor to generate a plurality of actuating outputs to make the necessary adjustments to the engine throttle, variable pitch blades, power distribution mechanisms, and aerodynamic control surfaces to ensure the aircraft10moves in the desired direction.

One of the actuating outputs is to control the angular pitch of the blades of the lift fans28.1,28.2,28.3and28.4, with the change in pitch of the fan blades varying the vertical thrust provided by each fan28.1,28.2,28,3and28.4. The ability to change the angular orientation of the blades of each lift fan28.1,28.2,28.3and28.4allows the aircraft10to adjust the thrust output at a constant angular velocity of each fan28.1,28.2,28.3and28.4and affords control of the aircraft10. Variable pitch fan blades are well known in the art and need not be explained in further detail.

The stability system operates in an automated manner, thereby eliminating any danger and reducing pilot workload during vertical take-off and transition to forward flight. The aircraft10is capable of vertical take-off and landing, hover, transition to forward flight and obtaining high speed flight at Regional Aircraft operating altitudes. At least one gyroscope measures pitch, yaw or roll and provides this information, as an input, to the computer controlled stability system. This information along with pilot inputs to the system allows it to compute and make the necessary adjustments to all the control and power mechanisms mentioned above and provide for safe and controlled motion of the aircraft10.

In an embodiment, a lower opening of each rotor housing18.3,18.4,20.3,20.4, as best shown inFIG. 2, is fitted with a series of movable louvers30, the louvers30being orientated and angled during flight to redirect the thrust generated by the lift fans28.1,28.2,28.3and28.4.

The louvers30are controlled by the computer controlled stability system, based on the pilot's inputs and stability sensor inputs into the stability system, as described above.

In an embodiment, as best shown inFIGS. 1 and 3, an upper opening of each rotor housing18.3,18.4,20.3,20.4is fitted with a sealing arrangement32to seal off the upper opening, which is under the control of the pilot and flight management system. InFIG. 4, the sealing arrangement32have been removed, so as to better show the lift fans28.1,28.2,28,3and28.4. During forward flight, for example, the louvers30and the sealing arrangement32(i.e. both below and above the lift fans28.1,28.2,28.3and28.4) may be closed, so as to improve aerodynamics over the wings18,20. Conversely, the louvers30and the sealing arrangement32may be opened to allow airflow through the lift fans28,1,28.2,28,3and28.4during vertical take-off, vertical landing and transition.

As best shown inFIGS. 4 and 5, the forward thrust fan drive system24comprises two forward thrust ducted, multi stage compression fans34,36. The fans34,36are each accommodated within a cowling38,40that is fitted on either side of the tail of the fuselage12, behind the wings18,20. The fans34,36are optimised for high speed flight at Regional Aircraft operating altitudes.

Turning now toFIG. 3, the thrust vectors generated by the lift fans28.1,28.2,28.3and28.4of the lift fan drive system22and the forward thrust ducted fans34,36of the forward thrust fan drive system24are shown. In particular, a forward thrust vector42of each forward thrust ducted fan34,36points horizontal and to the rear of the fuselage12. A front left thrust vector44of the front left lift fan28.1points downward relative to the fuselage12and a front right thrust vector46of the front right lift fan28.3points downward relative to the fuselage12. A rear left thrust vector48of the rear left lift tan28.2points downward relative to the fuselage12and a rear right thrust vector50of the rear right lift fan28.4points downward relative to the fuselage12. The angulations of the thrust of all four lift fans28.1,28.2,28.3and28.4are independently variable, based on the orientation of the thrust directing louvers30beneath the four rotor housings contained in each wing18,20, as illustrated inFIG. 2. This coupled with the variable thrust due to the variable pitch fan blades allows for full control of the aircraft10in the vertical take-off, hover, transition and vertical landing phases of flight. The combinations of the pitch of each blade of the lift fans28.1,28.2,28.3and28.4and the direction of each fan thrust allows for control of pitch, roll, yaw and forward, aft and lateral movement.

The length of the fuselage and the wingspan of the aircraft are similar, and within the size limits of standard helicopter landing pads.

Due to the shorter than usual fuselage, a larger than conventional horizontal stabilising force may be required to control pitch. To address this, in one version, the stabiliser arrangement26comprises a horizontal stabiliser52extending rearwardly and sidewardly from the rear of each cowling38,40, and a V-tail vertical stabiliser54that extends vertically and sidewardly (i.e. at an outward angle) from the rear of each cowling38,40. In another version, the stabiliser arrangement26may include canards (not shown), but which may in turn require the horizontal and vertical stabilisers to be re-designed in order to account for a variable mass in the passenger/cargo area of the aircraft and its effect on centre of gravity movement.

The aircraft10includes a combined power plant for powering the lift fan drive system22and the forward thrust fan drive system24. As best shown inFIGS. 4 and 5, the fuselage12accommodates multiple turbine engines56behind the passenger cabin58, towards the tail section of the fuselage12. The power is transferred from the engines56to each of the lift fans28.1,28.2,28,3and28,4of the lift fan drive system22through a single primary planetary gearbox60, which is positioned in front of the engines56, typically via a clutch (not shown) and drive shafts62.

This arrangement allows redundancy should one engine56fail. Thus, if any one of the engines56fail, the engine56may be disengaged through a clutch (not shown), with the remaining engines56being capable of providing enough power to the aircraft10to perform a vertical landing, thereby providing redundancy to the system.

The multiple turbine engines56are also used to power the forward thrust fan drive system24through the primary planetary gearbox60, a driveshaft64, a secondary splitter gearbox66, and secondary drive shafts68. In one version, power to the forward thrust ducted fans34,36can be engaged and disengaged through a clutch (not shown) during the transition between forward and vertical flight. Again, the computer controlled stability system is used to control the gradual power transfer between the lift fan drive system22and the forward thrust fan drive system24. Alternatively, this may be addressed through the use of variable pitch blades for forward thrust, in which the blades are pitched fine during vertical take-off and then increase during transition.

The engines56have an air-inlet70(FIG. 1) positioned above the fuselage12. Exhausted gases are expelled through the exhaust outlet72(FIGS. 2 and 6) positioned at the rear of the fuselage12, in between the forward thrust ducted fans34and36.