GB2617362A

GB2617362A - Hybrid flight aircraft

Info

Publication number: GB2617362A
Application number: GB2205008.2A
Authority: GB
Inventors: Warner Martin; William Dennis Charles; David Tutty Brian; James Howland David; Frederick Giordano Theodore
Original assignee: Autonomous Flight Ltd
Current assignee: Autonomous Flight Ltd
Priority date: 2022-04-05
Filing date: 2022-04-05
Publication date: 2023-10-11
Also published as: GB202205008D0

Abstract

An aircraft comprising a fuselage 9, means for providing thrust 6,7 and lift surfaces or wings 1, 2. The aircraft can sustain flight and manoeuvre at low speeds, when the lift surfaces are incapable of providing sufficient lift, the remaining lift provided by the thrusters. At high speed the lift surfaces may be capable of providing all the required lift. Preferably the aircraft can manoeuvre by means of aerodynamic lift surfaces or by means of thrusters whose thrust direction can be changed. The aircraft may have a control system to adjust desired flight characteristics and a system to determine orientation, thruster and surface settings. The aircraft may have a system to detect the onset of aerodynamic stall. The aircraft may have adjustable undercarriage 10 to alter the aircraft’s angle for take-off and landing. Preferably the aircraft may have means to orient the passengers during flight or on the ground.

Description

Description Title:

Hybrid lift aircraft Long title: This invention relates to a mode of flight that allows an aircraft to fly using both thruster lift and surface lift

Introduction and background:

Aircraft traditionally generate the required lift for flight either by using surfaces (e.g. wings) or thrusts (e.g. jets or rotors). Aircraft have also been developed that transition between these modes of lift, allowing hover, vertical flight (which includes vertical take-off and vertical landing) and lower horizontal velocity flight using thrusters, whilst relying on surface lift once the horizontal velocity is sufficient to do so. The major disadvantage of these aircraft is that the wing must be sufficiently large enough to provide all the lift at the desired transit speed, including during manoeuvres where 'g' is pulled. They typically also include a means of aerodynamic control (e.g. elevators and ailerons). This wing provides no lift during vertical flight or hover and is then purely a source of parasitic mass. For aircraft where the time spent in transit flight is relatively small compared to that in vertical flight or hover, there is no advantage in having such a wing. The innovation is to allow a smaller wing, or the same wing at lower speeds, that provides a portion of the lift, while the thrusters provide the remaining lift, which can be rapidly increased to allow control, and hence manoeuvre, or avoid surface stall. Several key enablers are required to allow the aircraft to fly stably and efficiently for extended periods whilst using both thruster and surface lift, and also for it to be suitable for passenger transportation. Additionally, the optional use of fixed thrusters to provide lift and horizontal thrust significantly reduces the complexity, and hence cost and mass.

Summary of invention:

The basic aircraft appears in Figures land 2, which show one possible design as an example, but many other configurations are possible. Figure 2 is used to denote most of the referenced part numbers in the following text. The aircraft consists of a fuselage 9 (or other connecting structure, if required), thruster(s) (6 and 7, rotors or any other device that creates a jet or jets) and lifting surface(s) land 2. At low speeds (which includes hover) the vehicle uses the thrusters for all the required lift (Figure 3) by having the thrusters' axis near vertical. At high speed the lifting surfaces may be sufficiently large to provide all the required lift, with the thrusters' axis near horizontal (Figure 4), which requires a transition mechanism 8.

This invention principally covers operation at an intermediate speed where the lifting surfaces provide some lift, but can no longer provide all the lift, and must be supplemented by the thrusters, see Figure 5. This is termed 'hybrid flight' and is not purely a transitional phase used to get between hover and higher speed flight, but a sustained flight mode. It may be reached from either the low or high-speed orientations mentioned above, or from a rolling take off, and then, when desired, can return to either low or high-speed operation or a perform a rolling landing. A key advantage is that the lifting surfaces can operate at high angles of attack approaching stall, so providing much higher lift for the same wing area compared to conventional aeroplanes (where such angles are avoided in most flight conditions to avoid stall and to allow the capacity to further increase surface lift to enable manoeuvre), but where the high drag penalty associated with these high angles is more energy efficient than if the lift came directly from thrusters.

The ability to rapidly increase thruster thrust means that the lift loss associated with a fully stalled surface can be safely addressed and manoeuvres can be performed without needing to increase the surface lift, which may in itself cause stalling. The latter use of thruster thrust to manoeuvre may also mean that surface control surfaces may no longer be required. Should a lifting surface stall or extra lift be rapidly required for manoeuvre, then the thrusters thrust can be increased and/or a change in thruster angle used to increase the vertical component.

There are five main variants of this hybrid flight; fixed lifting surfaces (fixed in terms of orientation to the fuselage, shape and flap deployment/angle); adjusting lifting surfaces (for example angle, shape or attached flap deployment/angle); adjustable thruster angle(s) (rotating to give different amounts of upward or horizontal thrust); fixed thrusters; and supplementary near horizontal thrusters (to provide additional horizontal thrust); More than one variant can exist on the same aircraft, for example some fixed surfaces and some adjustable.

The fixed surface variant of hybrid flight is as follows. For level forward flight, as in Figure 5, the thrusters (or some of them) are angled partially forward (19). The pitch orientation of the aircraft is adjusted by varying thruster and surface lift distribution, so that the lifting surfaces' angle of attack to the airflow can be set to provide the required lift. Should the vehicle either climb (Figure 6) or dive (Figure 7) the surface angles of attack to the flow can be optimised to avoid stall or loss of lift via again changing the fuselage orientation in pitch. During hybrid flight the thruster thrust (and angle if available) is adjusted to provide suitable propulsive force (i.e. for forward acceleration and to counter drag) and the required additional lift.

The adjusting surface variant of hybrid flight is as follows. The fuselage orientation is achieved via rotor and surface lift distribution as required by the operator, for example for passenger comfort. The lifting surfaces can then be adjusted (via angles 17 and 18, or by shape change or control surface Sand 5 deflection) independently of the fuselage pitch angle. In this way the lifting surfaces can be adjusted to provide optimal lift via angle of attack to the local airflow. Should the vehicle either climb (Figure 6) or dive (Figure 7) the surface adjustment can be optimised to avoid stall or loss of lift. During hybrid flight the thruster thrust and angle (if available) is adjusted to provide suitable propulsive force (i.e. for forward acceleration and to counter drag) and the required additional lift.

In both variants the actual changes in fuselage and thruster angle, and any surface adjustment, will be commanded by flight control systems that respond to operator or guidance system input, and will make use of sensor information, such as the current orientation and movement of the vehicle and its parts, and local airflow information. The lifting surface angles 17 and 18 should be limited to that which avoids stall, which will depend on the direction of the relative airflow. The thruster angles 19 would be expected to be between 45 and 90 deg, but may exceed this for different arrangements, reverse flight and if higher propulsion thrust is required, for example for initial acceleration. The fuselage angle would need to follow the surface angles for the fixed surface case (noting that the surface may be at an initial incidence) or adjusted as desired for the adjusting surface variant, for example to improve passenger comfort.

In all variants, during flight the roll and pitch control can be obtained via thruster and/or lifting surface adjustment (if available). Yaw control can be obtained by thruster adjustment (e.g. unequal angle between opposing thrusters, sideways angling of thrusts away from the centre of mass or via motor torque) and/or adjustment of vertical stabilising surfaces 4.

The fixed thrusters variant in forward flight appears in Figure 8. This variant negates the need for the transition mechanisms, which reduces both mass and cost. This does, however, limit the maximum horizontal speed (as the rotors can no longer provide sufficient horizontal thrust) and requires the aircraft to land at a high angle of attack (i.e. to allow the thrusters to be vertical) as in Figure 9. The high undercarriage angle in Figure 9 may be decreased to that in Figure 5 in flight to reduce drag and on the ground to change the angle of the fuselage to improve passenger or cargo embarkation or disembarkation. The passenger or cargo angle could also be changed independently to the fuselage by other mechanisms, as in Figure 10.

The horizontal thrust may be increased by the use of supplementary horizontal thrusters, shown in Figure 11, allowing higher speeds and greater acceleration. Their angle may also be variable, see Figure 12.

The flight control system or flight controller will adjust aircraft orientation, thrusters and/or surfaces to allow stable flight, manoeuvre and change flight characteristics, notably to allow forward flight with the relevant surfaces at high angles of attack to optimise their lift capability. It may have a system to determine the required aircraft orientation, thruster and surface settings to change flight characteristics or manoeuvre, which may then be enacted by the control system. It may have a system to detect the onset of aerodynamic stall of a surface to allow the control system to take avoiding action or to react to it, for example by decreasing surface angle or increasing thruster thrust.

To assist in enabling hybrid flight at a stable pitch angle, the control system may physically rotate its orientation sensors to cause the aircraft to fly at different orientations, see Figure 13, rather than relying on a software-based solution.

The thrusters (coaxial or closely positioned) may be fixed at different angles so their thrust axes are not parallel, see Figure 14, and by varying the relative thrusts the direction of the resultant thrust can be varied. Should these thrusters not be colocated, as in Figure 15, then forces and moments from the lifting surfaces or supplementary thrusters would be required for stable flight orientation with one set of thrusters at a lower thrust (i.e. the rear ones in Figure 15).

The above description is also applicable to craft operating in other gases and in, or partially submerged in, a liquid, such as water, and may use liquid and/or gas flow instead or in combination with airflow.

Claims

Claims 1) An aircraft consisting of a fuselage (or other connecting structure if required), thruster(s) (rotors or any other device that creates a jet or jets) and lifting surface(s) that can sustain flight and perform manoeuvres at a speed where the lifting surface(s) can only provide a proportion of the lift, and the remaining lift and forces required for manoeuvre is provided by the thrusters.
2) An aircraft according to claim 1, which at lower speeds (which includes hover) can use the thrusters for all the required lift by having thrusters' axes near vertical.
3) An aircraft according to claim 1, which at higher speed may have lifting surfaces sufficiently large to provide all the required lift.
4) An aircraft according to claim land 2, which can manoeuvre by means of thruster thrust or thruster orientation adjustment (this may include that of surfaces within the thruster flow).
5) An aircraft according to claim land 3, which may be manoeuvred by the use of aerodynamic control surfaces.
6) An aircraft according to any of the preceding claims, which has thruster(s) whose thrust direction can be changed; 7) An aircraft according to claim 6, which rotates the thrusters to provide different levels of horizontal and vertical thrust.8) An aircraft according to any of the preceding claims, which has fixed thrusters; 9) An aircraft according to claim 8, which rotates the aircraft about its relevant axis to provide different levels of horizontal and vertical thrust.10) An aircraft according to any of the preceding claims, which has supplementary thrusters for manoeuvre and motion that are primarily not for producing lift in most flight configurations.11) An aircraft according to any of the preceding claims, which has fixed lifting or stabilising surfaces (fixed in terms of orientation to the fuselage, shape and flap deployment/angle); 12) An aircraft according to claim 11, which adjusts the aircraft's orientation to change lift and/or avoid stall.13) An aircraft according to any of the preceding claims, which has adjusting lifting or stabilising surfaces (for example angle, shape or attached flap deployment/angle).14) An aircraft according to claim 13, which adjusts the lifting surfaces to change lift and/or avoid stall.15) An aircraft according to any of the preceding claims, which has a control system to adjust aircraft orientation, thrusters and/or surfaces to allow stable flight, manoeuvre and change flight characteristics.16) An aircraft according to any of the preceding claims, which has a system to determine the required aircraft orientation, thruster and surface settings to change flight characteristics or manoeuvre, which may then be enacted by the control system.17) An aircraft according to any of the preceding claims, which may have a system to detect the onset of aerodynamic stall of a surface to allow the control system to take avoiding action, for example by increasing thruster thrust.18) An aircraft according to any of the preceding claims, which uses an adjustable undercarriage to change the aircraft's angle between that required for entering or leaving flight and that for ground operations or lowing drag.19) An aircraft according to any of the preceding claims, which uses an adjustable system to orient passengers or other elements to a more suitable orientation during flight or on the ground.20) An aircraft according to any of the preceding claims, which physically rotates the orientation sensors of the control system to cause the aircraft to fly at different orientations, rather than relying on a software-based solution.21) An aircraft according to any of the preceding claims, that has thrusters whose thrust axes are not parallel, so that by varying the relative thrusts the direction of the resultant thrust can be varied.22) An aircraft according to any of the preceding claims, whose lifting surfaces can operate at high angles of attack approaching stall, so providing much higher lift for the same wing area compared to conventional aeroplanes (where such angles are avoided in most flight conditions to avoid stall and to allow the capacity to further increase in surface lift to enable manoeuvre), but where the high drag penalty associated with these high angles is more energy efficient than if the lift came from directly thrusters.23) A craft that operates in the same manner as the aircraft according to any of the preceding claims, but does so in another gas or in, or partially submerged in, a liquid, such as water, and that may use liquid and/or gas flow instead or in combination with airflow.