GB2578174A - A ground handling concept for a tail-sitting VTOL aircraft - Google Patents

Abstract

The present invention provides a tail-sitting, tandem wing vertical take-off and landing aircraft 103 (VTOL), the aircraft comprising; a fuselage 200’ pivoted between lateral arms of a yoke (220, figure 2c); the arms of the yoke extending fore and aft and, at or towards the extremities of the arms: the respective fore portions 230' are linked laterally together by an aerofoil (240, figure 1a); and the respective aft portions 230 are linked laterally together by an aerofoil (250, figure 1a). The aircraft further comprises landing skids (400, figures 1c, 1d), 410, 420 and a wheel assembly 450. Additionally, a method for reconfiguring the aircraft between vertical and horizontal configuration is provided.

Description

A ground handling concept for a tail-sitting VTOL aircraft Scope The present invention relates to a vertical take-off and landing aircraft (VTOL), and preferably a tail sitting VTOL aircraft, and even more preferably tandem wing aircraft including apparatus and method for improved ground handling of such aircraft.

Background

Aircraft, and in particular passenger aircraft, typically have to be moved, under their own power or external power, from an embarkation/dis-embarkation zone to a take-off and landing zone. This is often referred to as taxiing and often takes place on what is referred to as a taxiway.

The embarkation/dis-embarkation zone may take the form of an airport terminal gate and the take-off and landing zone may take the form of a runway/landing strip for an aeroplane or a helipad for a helicopter. The embarkation zone and the take-off zone may be connected via a runway.

Aircraft, such as aeroplanes or helicopter, may taxi under their own engine power, using their propeller(s) or rotor(s) which can be noisy, a source of local pollution, but also dangerous to nearby buildings (hangars), parked aircraft and ground personnel. This is particularly true of helicopters that have large rotating wings known as rotors and aircraft having propellers.

Alternatively, aircraft may also be pushed or towed using ground support equipment such as tow-trucks or self-powered towing carts. In the particular case of helicopters equipped with landing skids rather than landing gear and wheels, removable wheels or a wheeled platform may be used to allow the aircraft to be pushed or towed, equivalent features are available for fixed wing aircraft also.

In cases where it may not be possible, practical or safe to perform a self-powered taxi, or in cases where the aircraft may have to be towed, ground support equipment (e.g. tow trucks) may not be available or the equipment available may not be suitable for a given size or type of aircraft.

In addition, reversing of an aircraft, e.g. away from a terminal gate, using its main engines may not be permitted or may not be technically possible if the thrust of the aircraft propellers or rotors cannot be vectored in the correct direction. Hence where reversing is necessary, tow trucks may be required and if their availability is limited this can reduce the efficient use of the aircraft.

There is therefore a need for a drive system to power the wheels of an aircraft and there is also a desire to use such a drive system.

It is therefore desirable to perform what may be referred to as an engine-off autonomous taxi, using for example an on-board electric taxi system, capable of powering one of more wheels of the aircraft, such as landing gear drive systems that are disclosed in US20170305536A1 and US2018037315A1. Such systems are known means to power aircraft wheels landing gear during ground taxi operations, but also to pre-spin the wheels prior to landing, and/or for applying braking torque to the rotating wheel(s) by converting kinetic energy to electrical energy using the drive system motor as a generator.

However, such known systems are not directly suitable for VTOL aircraft and the introduction of new aircraft concepts, such as modern variations on the tail-sitting aircraft concept and in particular when applied to a tandem wing aircraft configuration means that new an alternative ground handling apparatus and methods are required. This includes effective means for support of the aircraft on the ground and also variants to provide improved transportation of the aircraft on the ground.

The present invention The present invention in its various aspects is as set out in the appended claims.

The proposed invention relates in particular to a tail-sitting, tandem wing vertical take-off and landing aircraft such as the aircraft described in invention GB 1721837.1 and depicted in figure la to ld, in various configurations (vertical ground and flight la, horizontal ground and flight lb). In this particular embodiment of a tail-sitting tandem wing aircraft, the cabin is actuated and can be positioned in various configurations by means of a control unit.

Tandem wing aircraft A tandem wing aircraft has two wings. The wings are staggered that is one wing, the first aerofoil, is located fore of the other, second, aerofoil which is aft of the first aerofoil, when viewing the aircraft in its horizontal flight configuration. For the present invention this means that the trailing edge of the fore aerofoil is ahead of and does not overlap the leading edge of the aft aerofoil. The wings of the present invention may be described as significant stagger, that is they do not overlap horizontally in the horizontal flight configuration.

Fore and aft refer to the front and rear potions of the aircraft in its horizontal flight configuration.

The wings are preferably positioned fore and aft of the fuselage when viewing the aircraft in its horizontal flight configuration. By being positioned fore and aft of the fuselage the leading edge of the fore, or leading wing (the first aerofoil), is ahead of the nose of the fuselage and the trailing edge of the aft or trailing wing (the second aerofoil) is behind the tail of the fuselage Preferably by being positioned fore and aft of the fuselage the trailing edge of the leading wing is ahead of the nose of the fuselage and the leading edge of the aft or trailing wing is behind the tail of the fuselage. The benefit of the greater separation is to ensure that the fuselage can be rotated throughout its range of motion, between a vertical flight configuration and a horizontal flight configuration without interfering with the wings, in particular without any interference between the nose of the fuselage and the trailing edge of the leading wing.

If the horizontal separation (when viewing the aircraft in horizontal configuration) between the wings was insufficient for the fuselage to rotate without interference, then the vertical separation (when viewing the aircraft in horizontal configuration) would have to be significantly greater to allow for the fuselage rotation. This would mean that the foot-print of the aircraft (when viewing the aircraft in vertical configuration) would be significantly larger and would require larger take-off and landing infrastructures and larger storage facilities to accommodate aircraft during down-time such as night time or in the event of adverse weather conditions that would prevent flights.

The staggered and offset wing configuration of the present invention, confer the aircraft with a significantly reduced foot-print (<50%) than a similar aircraft with a co-planar wing arrangement.

Another benefit of the greater wing separation is to limit the airflow interactions between the staggered and offset wings and improve the aerodynamic efficiency of the aircraft.

A horizontal flight configuration is when the cords of the wings are parallel or substantially parallel to the ground in flight. If the cords of the wings are no parallel the fore wing is the wing by which horizontal flight configuration is to be judged.

As stated, tandem wing aircraft has two wings. The wings may be offset. That is one wing, the first aerofoil, is located above or below of the other, second, aerofoil which is correspondingly below or above the first aerofoil, when viewing the aircraft in its horizontal flight configuration. For the present invention this means that the top of the fore aerofoil at its maximum thickness and its highest point is below the bottom of the aft aerofoil at its maximum thickness and its lowest point (so located below) or that the top of the aft aerofoil at its maximum thickness and its highest point is below the bottom of the bottom of the fore aerofoil at its maximum thickness and its lowest point (so located above).

The preferred offset of a four passenger version of the present invention is of the order of 4 to 5 metres to be compared to a wing span of the order of 8 to 10 metres.

The fore (first) aerofoil is preferably below the aft (second) aerofoil in the horizontal flight configuration. This provides a clearer view for the pilot. Similarly, by raising the first (fore) wing significantly above the ground and therefore significantly above the pod, the present invention confers to the pilot improved visibility during vertical flight phase, visibility that is crucial in this phase of the flight to the safety of aircraft and its occupants. In prior inventions US 2014/0097290, US 2011/0042509 or US 2018/0093765, pilot visibility is impaired by the presence of the co-planar first wing, in front of the fuselage cockpit. However, as the present invention is VTOL the presence of an aerofoil in the line of sight between a pilot and a runway is less of an issue as the vertical landing places the fore aerofoil above the pilot's head and gives a large unobstructed view for landing.

When using co-planar or quasi co-planar (i.e. overlapping stacked) wings, carefully positioning the centre of mass of the aircraft relative to its aerodynamic centre would become problematic without translating the body/fuselage horizontally to accommodate variations of its centre of mass resulting from an uneven distribution of the aircraft payload, such as an under occupied aircraft, for example only 3 passengers in a 5 seat aircraft, or uneven distribution of passenger mass, for example children seating in some seats and adults in other seats, or an uneven distribution of the aircraft cargo, in the cargo hold.

Unlike a biplane (or its equivalents with a multiplicity of stacked wings), the tandem wing aircraft of the present invention does not require a dedicated horizontal stabiliser and/or vertical stabiliser, such as a tail or tail plane, for stable flight. This type of aircraft features a set of staggered and offset wings also known as tandem wings. The staggered and offset tandem wings are positioned fore and aft of the fuselage when viewing the aircraft in its horizontal flight configuration.

A tail plane, such as a horizontal stabiliser vertical stabiliser combination is a structure typically at the rear of an aircraft that provides stability and control during flight and does not provide significant lift.

The tandem wing aircraft of the present invention preferably does not have a tail plane.

Unlike bi-plane with their co-planar or overlapping stacked wing arrangement, the tandem wing aircraft do not require an additional horizontal stabiliser for longitudinal stability, as both wings are significantly offset from one another to ensure that one of the wings, typically the aft wing, acts as the main wing and a fore wing acts to balance the mass moments with aerodynamics moment as is normally the case with a horizontal stabiliser plane. Unlike bi-plane with their co-planar or overlapping stacked wing arrangement, the tandem wing aircraft do not require an additional vertical stabiliser for longitudinal stability, as this function can be assumed by one of the two staggered and offset wings Preferably, in the tandem (or staggered/offset) wing arrangement of the present invention, the centre of mass of the aircraft is located forward of the aft wing, in between the fore and aft wings when viewing the aircraft in flight horizontal configuration. Not only does this wing arrangement confer the aircraft with acceptable longitudinal stability, it also makes it more tolerant to variations of its centre of mass and therefore a practical solution for the transport of multiple passengers, in particular in cases of under-occupancy or uneven passenger weight or cargo weight distribution.

Consequently, when viewing the aircraft in its horizontal position (see FIG 1), the first wing (also referred to as fore wing) is positioned in front of the pod/fuselage and the second wing (also referred to as aft wing) is positioned behind the pod/fuselage.

As depicted, in Fig 9 for example, the first (fore) and second (aft) wings do not necessarily have the same size (span, surface, chord or thickness). In the particular embodiment depicted throughout, it should be noted that the pivot point of the pod/fuselage is biased towards the second (aft) wing when viewing the aircraft in its horizontal configuration, as is depicted in Fig. 9 or Fig. 10.

This is to assist passenger embarkation (as discussed later) but it also shifts the centre of mass of the aircraft to the rear. As a result, and to maintain the centre of mass of the aircraft in front of the aerodynamic centre of the aircraft, the rear wing surface has to be larger than the front wing surface to offset the aerodynamic centre rearward and keep it behind the aircraft centre of mass when viewing the aircraft in its horizontal configuration.

This confer the aircraft with an acceptable longitudinal stability and tolerance to variations in aircraft centre of mass unlike the wing arrangement of prior inventions US 2014/0097290, US 2011/0042509 or US 2018/0093765 or EP 3263445.

In an effort to ease passenger access (in particular without the need for a ladder for example), the pod is located as close to the ground as possible, similarly to EP 3263445.

However, with the present invention, this is enabled without the need for an additional mechanism or motion designed to lift/translate the pod in position between the wings as required in EP 3263445. Unlike prior invention EP 3263445 where both co-planar are above the fuselage when in vertical position (see claim 4 and Fig 4), the staggered and offset wing arrangement means that the second wing (aft of the fuselage) in the present invention is positioned lower than the fuselage when viewing the aircraft in its vertical configuration whereas the first wing (fore of the fuselage) is located above the fuselage. As such, the fuselage and its centre of mass is already located between both wings.

It is important to note that due to the staggered and, optionally, offset wing configuration of the present invention, the fuselage centre of mass is very preferably located between the two wings, both in vertical configuration as mentioned above, and in horizontal configuration.

The features of staggered wings and of offset wings are combinable and the combination of staggered (fore/aft) separation and offset (up/down) wing separation by the first and second aerofoils is particularly preferred as it provides both stable flight, good pilot visibility and, with a suitable support, a VTOL confirmation analogous to tail sitting giving a small footprint and hence landing area combinable with ease of access and egress on the ground.

The present invention is preferably configured in a tail-sitting configuration to facilitate vertical flight from take-off and landing.

A tail-sitter or tail-sitter is a type of VTOL aircraft that takes off and lands on its tail, then tilts horizontally for forward flight.

In the present invention there is preferably not tail as such and hence the term tail-sitting configuration related to the use of a support member suitable for supporting the aircraft in a vertical configuration on the ground, vertical in comparison to the horizontal configuration of horizontal flight. The support member may be a dedicated horizontal stabiliser in addition to the second aerofoil.

In order to alleviate the historical practical limitations of past tail-sitting aircraft, a tilting body is provided to ensure that passengers are always in a level or quasi-level position. As such the pod /fuselage of the present invention features a pivot and preferably a mechanism to control the pivoting motion.

Another category of winged VTOL aircraft, known as Tail-sitters allows for a seamless transition, effected by a forward pitching moment (resulting from differential thrust, differential aero-dynamic moments from control surfaces or a combination of both) without resorting to safety critical mechanisms such as necessary with tilting wings, tilting rotors and similar arrangements.

Tail-sitter aircraft have historically been rather impractical for passengers to embark and disembarks safely when the aircraft is in vertical configuration, and in particular unsafe to evacuate in an emergency. In addition, a conventional tail-sitting configuration limits the visibility of the pilot during vertical flight phases and present a safety hazard to the aircraft and its surroundings.

Detailed description

Figures The present invention will now be illustrated by means of the following figures, in which: Figure la -Present invention in a vertical configuration whilst on the ground; Figure lb -Present invention during Level Flight; Figure lc -Present invention fitted with skids for ground support; Figure ld -Present invention fitted with skids and winglets on the aerofoils; Figure 2a -Depicts close-up of wheel actuator Figure 2b -Present invention fitted with skids, winglets and wheel actuators in horizontal configuration Figure 2c -Present invention fitted with skids, winglets and wheel actuators in vertical configuration Figure 3a -Steering controls in straight line Figure 3b -Steering controls turning Figure 4a -Depicts direct drive and brake Figure 4b -Depicts geared actuator and brake Figure 5 -Depict the aircraft converting from vertical to horizontal configuration Whilst the above figures and the description below describes combinations of features those features may be present separately as defined in the description or in the claims.

The above drawings provide isometric views of the present invention. These drawings illustrate the fore and aft staggered wings, an example of eight distributed electric motor propellers, fuselage capable of housing passenger(s), the yoke with its structure of beams that link the fore and aft wings together as well as the pivot that allows the fuselage to rotate about the yoke assembly.

In the following figures like numerals represent like features. The aircraft 100-103 of the present invention has the following features: A tail-sitting, tandem wing vertical take-off and landing aircraft; 101 to 103 A tail-sitting, tandem wing vertical take-off and landing aircraft variants; passenger fuselage; 202 alternative payload' fuselage; 210 nose of the fuselage; 220 a yoke; 230, 230' port and starboard arms of the yoke; 240 fore aerofoil; 240' swept aerofoil example; 242 fore extremity of yoke arm 230 joins to fore aerofoil 240; 244 fore portion of the yoke; 250 aft aerofoil; 250' aerofoil example; 252 aft extremity of yoke arm 230 joins to aft aerofoil; 260, 260' etc., propulsion unit; 270 pivot; 280 canopy; 290 pilot; 400 landing skids; 400 spherical landing skids; 402 aft aerofoil with downward winglets; 404 fore aerofoil with upwards winglets; 410 fore landing skids; 420, 422 aft landing skids; 430, 430' landing skid support member; 440 landing wheel support member; 450 wheel assembly; 452 landing wheel; 454 landing wheel motor housing; 500 direct drive actuator; 510, 510' motor and brake assembly; 512 motor; 514 brake; and 520 wheel assembly gearing.

In the following figures the aircraft are displayed without propellers for clarity, hence, the propellers shown in figures la and lb are understood to be present in the further depictions of the aircraft.

The present invention provides a system that may be used for ground handling of a tandem wing tail-sitting aircraft, including ground taxi as well as automatic conversion from vertical to horizontal position on ground and without external ground support equipment.

Figure la shows an aircraft in the form of a tail sitting tandem wing aircraft suitable for implementing the present invention in a vertical configuration whilst on the ground.

Figure lb shows an aircraft in the form of a tail sitting tandem wing aircraft suitable for implementing the present invention in a horizontal configuration during Level Flight.

The aircraft may be parked in a horizontal position as depicted in figure lb for storage in a low ceiling hangar, or to protect the aircraft from being blown over by strong winds during adverse weather conditions. Analogous parking arrangements may also be used for the aircraft as shown in figure lc and ld.

Figure lc shows a further variation of a tail sitting tandem wing aircraft suitable for implementing the present invention in which a (non-passenger) payload fuselage 202 is present in the aircraft (such of the aircraft as a drone) together with landing skids 400 equipped proximate to the end of support members 430' attached to a pivot 270 of the aircraft.

Figure 1 d shows a yet further variation of a tail sitting tandem wing aircraft suitable for implementing the present invention in which fuselage 200' is supported in a yoke 220 attached to fore and aft aerofoils 240 and 250. The aircraft includes landing skids 400 proximate to the end of support members 430.

The ground support arrangement shown in figures lc and ld are particularly preferred because they allow for ground handling when moving the aircraft to embarkation zone or to take-off zone, by letting the pilot maneuverer the aircraft on the ground. The skids 400 will also reduce the likelihood of damaging the aircraft, especially the aerofoils 240',250' and yoke 220, when moving on the ground by introducing a barrier between the aircraft and the ground, thus reducing the friction on these parts of the aircraft when moving along the ground.

The ground support arrangement of the figure ld is preferable as there are multiple sets of skids 400,410,420. With one set of skids 420 near the aft foil 402 for use in the aircraft's vertical configurations, as shown in figure 1D. And another set of skids 410 near the fore aerofoil 404 for use in the aircraft's horizontal configuration as shown in figure 2b. The landing skids 400, proximate to the end of support members 430, are in contact with the ground in either configuration allowing the ground support system to function in either configuration.

A second aspect of the present invention provides a tandem wing tail sitting aircraft comprising a fuselage 200 pivoted between arms of a yoke 220, the yoke comprising landing skids on fore and aft portions, the yoke 220 having a further landing skids 400 proximate to the end of support members 430, the support members being an extension of the yoke 220 in the region of the pivot 270 from which the fuselage 200 is pivoted.

Where it may be considered as the first aspect in which the landing skids 400 equipped proximate to the end of support members 430 are in the form of rotatable wheel assemblies 450. These wheels may be unpowered, allowing the aircraft to be moved without the necessity to access the controls within the fuselage 200. It is preferable that the wheels 452 be lockable by means of a brake 514 or other locking mechanism. This mechanism will allow motion of the aircraft on the ground to be controlled, such as locking one wheel to allow the aircraft to turn, and readily stopped, permitting the pilot to carryout emergency stops if necessary.

Tandem wing aircraft A tandem wing aircraft has two wings. The wings are staggered That is one wing, the first aerofoil, is located fore of the other, second, aerofoil which is aft of the first aerofoil, when viewing the aircraft in its horizontal flight configuration. For the present invention this means that the trailing edge of the fore aerofoil is fore, i.e. ahead of and does not overlap the leading edge of the aft aerofoil. The wings of the present invention may be described as significant stagger, that is they do not overlap horizontally in the horizontal flight configuration.

Fore and aft refer to the front and rear potions of the aircraft in its horizontal flight configuration.

The wings are preferably positioned fore and aft of the fuselage when viewing the aircraft in its horizontal flight configuration. By being positioned fore and aft of the fuselage the leading edge of the fore, or leading wing (the first aerofoil), is ahead of the nose of the fuselage and the trailing edge of the aft or trailing wing (the second aerofoil) is behind the tail of the fuselage Preferably by being positioned fore and aft of the fuselage the trailing edge of the leading wing is ahead of the nose of the fuselage and the leading edge of the aft or trailing wing is behind the tail of the fuselage.

A horizontal flight configuration is when the cords of the wings are parallel or substantially parallel to the ground in flight. If the cords of the wings are no parallel the fore wing is the wing by which horizontal flight configuration is to be judged.

As stated, tandem wing aircraft has two wings. The wings may be offset. That is one wing, the first aerofoil, is located above or below of the other, second, aerofoil which is correspondingly below or above the first aerofoil, when viewing the aircraft in its horizontal flight configuration. For the present invention this means that the top of the fore aerofoil at its maximum thickness and its highest point is below the bottom of the aft aerofoil at its maximum thickness and its lowest point (so located below) or that the top of the aft aerofoil at its maximum thickness and its highest point is below the bottom of the bottom of the fore aerofoil at its maximum thickness and its lowest point (so located above).

The fore aerofoil is preferably below the aft aerofoil when viewing the aircraft in its vertical configuration. This provides a clearer view for the pilot. Similarly, by raising the first (fore) wing significantly above the ground and therefore significantly above the pod, the present invention confers to the pilot improved visibility during vertical flight phase, visibility that is crucial in this phase of the flight to the safety of aircraft and its occupants. In prior inventions US 2014/0097290, US 2011/0042509 or US 2018/0093765, pilot visibility is impaired by the presence of the co-planar first wing, in front of the pod cockpit.

When using co-planar or quasi co-planar wings, carefully positioning the centre of mass of the aircraft relative to its aerodynamic centre would become problematic without translating the body/fuselage horizontally to accommodate variations of its centre of mass resulting from an uneven distribution of the aircraft payload, such as an under occupied aircraft, for example only 3 passengers in a 5 seat aircraft, or uneven distribution of passenger mass, for example children seating in some seats and adults in other seats, or an uneven distribution of the aircraft cargo, in the cargo hold.

Unlike a biplane (or its equivalents with a multiplicity of stacked wings), the tandem wing aircraft of the present invention does not require a dedicated horizontal stabiliser such as in the form of a tail plane for stable flight. This type of aircraft features a set of staggered and offset wings also known as tandem wings. The staggered and offset tandem wings are positioned fore and aft of the fuselage when viewing the aircraft in its horizontal flight configuration.

A horizontal stabiliser, such as a tail plane is a structure typically at the rear of an aircraft that provides stability and control during flight and does not provide significant lift.

The tandem wing aircraft of the present invention preferably does not have a horizontal stabiliser, such as tail plane. Unlike bi-plane with their co-planar or quasi-coplanar wing arrangement, the tandem wing aircraft do not require an additional horizontal stabiliser for longitudinal stability, as both wings are significantly offset from one another to ensure that one of the wings, typically the aft wing, acts as the main wing and a fore wing acts to balance the mass moments with aerodynamics moment as is normally the case with a horizontal stabiliser plane.

Preferably, in the tandem (or staggered/offset) wing arrangement of the present invention, the centre of mass of the aircraft is located forward of the aft wing, in between the fore and aft wings when viewing the aircraft in flight horizontal configuration. Not only does this wing arrangement confer the aircraft with acceptable longitudinal stability, it also makes it more tolerant to variations of its centre of mass and therefore a practical solution for the transport of multiple passengers, in particular in cases of under-occupancy or uneven passenger weight or cargo weight distribution.

Figure 2a to 2c, depict the proposed invention in a preferred variant of the second aspect.

Specifically, a pair of electrically powered motorised wheel assemblies 450 are located proximate to the end of the aircraft support members 430 as depicted in figure 2b and 2c. Fore and aft skids pads 410, 420 are also present to provide support in combination with the wheel assemblies 450. The motorised wheels would be controlled by a control unit within the aircraft or remotely controlled from outside the aircraft allowing ground crew to handle the aircraft without having to step inside fuselage 200. These wheels would allow more control over the movement of the aircraft on the ground. Using the wheels separately, or in combination with the propulsion units 260 to accelerate, decelerate and steer the aircraft on the ground.

In a preferred embodiment, fore and aft skids 410, 420 may be constructed from low friction material, such as low cost replaceable PTFE pads, to limit wear and resistance during ground manoeuvres.

In an alternative embodiment fore and aft skids 410, 420 pads are equipped with additional wheels, preferably un-powered to reduce manufacturing cost and improve reliability of the aircraft, more preferably lockable such as by means of a brake, or otherwise and free to caster in order to reduce wear on the fore and aft skids 410,420 during ground manoeuvring.

Figure 2a shows a close-up of a wheel assembly 450 comprising wheel 452 and landing wheel motor housing 454. The assembly may further comprise a motor for rotating the wheel 452 of the wheel assembly 450 such as to move the aircraft along the ground while the aircraft is supported by the wheel assemblies 450.

Figure 2b depicts a variant of the aircraft 103, wherein skids 400 on support member 430 of the yoke 220 are replaced with wheel assembly 450, with the aircraft 103 in a horizontal configuration. Whereas, figure 2c depicts the same aircraft 103 in a vertical configuration. The landing wheel 452 will be in contact with the ground in either configuration, allowing the wheel assembly to be used in either the horizontal or vertical configuration. The landing wheels 452 are preferable as they will have a lower rolling friction, reducing the wear on the support members 430.

The electrically powered wheels, controlled independently from each other, can be used symmetrically to move the aircraft forward and back in a straight line as depicted in figure 3a, or asymmetrically to steer the aircraft in any direction by means of a differential motion of both powered wheels as depicted in figure 3b.

The wheel assembly 450 taxi actuator may consist of a direct-drive actuator 500 (i.e. a high torque electric motor directly driving the wheel) or a geared actuator 520 (i.e. a low torque motor connected via a gearing arrangement to the wheel), as depicted in figure 4a and 4b respectively. The taxi actuator may include a brake, preferably powered-off or no-back brake, in order to prevent the aircraft from being unintentionally moved by an external force such as high wind.

Figure 4a shows a functional schematic of landing wheel assembly 450 in a first configuration providing direct drive and brake using a direct-drive actuator 500. In this configuration wheel 452 is driven by wheel and brake assembly 510, comprising motor 512 and brake 514 mounted on a common axle 516.

Figure 4b shows a functional schematic of landing wheel assembly 450 in a second configuration providing direct drive and brake using a geared actuator 520. In this configuration wheel 452 is driven by wheel and brake assembly 510', comprising motor 512, and brake 514 mounted on a common shaft 516 which is coupled to wheel assembly gearing 520 conveying power to the wheel 452.

The present invention further includes a method and system for operating the aircraft, as previously described, with the actuation system of the aircraft cabin to optionally transition between horizontal and vertical configurations on the ground, throughout figures 5a to 5f.

Using the horizontal configuration to allow the aircraft to park and manoeuvre in areas with low ceilings. This can also allow the aircraft to preform horizontal landings and takeoffs if necessary. This would be beneficial in certain situations such as; when the aircraft does not have sufficient power or propulsion to perform a vertical take-off or landing, or if a failure meant the aircraft could no longer change configuration mid-flight.

Figures 5a to 5f depict the aircraft in various stages during the convertion from vertical to horizontal configuration, it being understood the process can occur in the reverse direction also: Figure 5a depicts the aircraft in a vertical configuration, which is used during vertical take-offs and landings, for instance in situations such as when there is insufficient runway for horizontal take-offs and landing. In this configuration the aft skid 420 and support system skid 400, which may also be in the form of a landing wheel 452, are in contact with the ground only.

Figure 5b depicts the first phase in the reconfiguration, wherein the motorised pivot 270 rotates the fuselage 210 clockwise, lowering the nose of the fuselage 210 to be in contact with the ground. This redistributes the weight of the aircraft towards the nose of the fuselage 210 which is equipped with a friction pad to prevent the nose of the fuselage from skidding along the ground and away from the aft skid 420. Alternatively, if the friction between the nose of the fuselage and the ground is insufficient, the nose of the fuselage 210 may be temporarily tied to the ground. After which the motorised wheels 452 are rotated counter-clockwise and the motorised pivot 270 is controlled to provide a counterclockwise resistive torque on fuselage 200, to allow a controlled rotation of yoke 220. The yoke 220 is rotated by either the motorised pivot 270, or the motorised wheel 452, or both, in a direction that lifts the aft skid 420 away from the ground.

Figures 5c, 5d and 5e show the aircraft at later stages of the reconfiguration, wherein the yoke 220 continues to be rotated around the motorised pivot 270 in a direction that removes the aft skid 420 from the ground and brings the fore skids 410 towards the ground.

During these stages the aircraft's weight is supported by the support system skid 400 and the nose of the fuselage 210. As the weight of the aircraft is shifted forwards by the fore portion of the yoke 244 the fuselage 200 is rotated around the pivot 270 changing the angle between the fuselage 200 and the ground, this allows the aircraft to use the varying angle to redistribute the aircrafts weight, to remain upright throughout the reconfiguration, as the support system skids 400 move with the yoke 220 as the yoke 220 rotates.

To ensure that the aircraft remains in position during the conversion, the underside of the cabin may be equipped with a pad made of high friction material, such as a rubberised pad. This ensures that the conversion manoeuvre may be executed safely, without the fuselage, and in turn the aircraft sliding or falling over. Alternatively, if the friction between the nose of the fuselage and the ground is insufficient, the nose of the fuselage 210 may be temporarily tied to the ground.

Another reason a wheel assembly 450 is preferable for the support system skid 400, is that the wheel assembly 450 can comprising a braking mechanism 415 which can be used to moderate the reconfiguration, i.e. to slow it down and remove energy when required.

Figure 5f shows the end phase of the reconfiguration, with the aircraft in a horizontal configuration. At this stage the support system skid 400 and fore skid 410 are brought in contact with the ground, and the yoke 220 rotation stopped. At this stage the pivot 270 rotates the fuselage 200 to bring the nose of the fuselage 210 out of contact with the ground. With the fuselage 200 off of the ground the aircraft is free to move in the horizontal configuration.

It should be noted that the aircraft may perform a taxiing manoeuvre on the ground in either vertical or horizontal configuration.

An alternative embodiment of the invention (not depicted) may feature detachable actuators that would be attached for ground handing and detached before flight to avoid flying unnecessary extra weight. The detachable actuators may either be powered and controlled externally, or powered and controlled by the aircraft computer and the aircraft on-board energy source (typically high energy batteries).

Although the latter embodiment essentially requires additional ground support equipment (i.e. the detachable wheel actuators), it provides a bespoke and compact solution to safely manoeuvre the aircraft on the ground and safely convert the aircraft from vertical to horizontal configuration (and conversely) without the use of external equipment such as hoist or overhead cranes.

In a further embodiment of the invention, designed solely to assist moving the aircraft from its vertical configuration to its horizontal storage configuration, the underside of fuselage 210 may be equipped with a powered wheel and skids 430 may be fitted with friction pads (e.g. rubberised material). In this particular embodiment, the rubberised friction pads 400 at the extremity skid support member 430 ensures that there is no relative movement of the skid 430 with respect to the ground, whilst motion of fuselage 210 powered wheel, together with the resisting action of motorised pivot 270 ensure a controlled reconfiguration of the aircraft from a vertical configuration to a horizontal configuration in a similar motion to that depicted in figure 5. Conversely, the aircraft can be reconfigured from its horizontal storage configuration to its vertical storage configuration by reversing the steps illustrated in figure 5. It should be noted that this particular configuration does not readily permit taxiing and would be limited to assisting ground crew in reconfiguring the aircraft without external ground equipment, either for storage in a low ceiling hangar or to protect the aircraft from strong winds during adverse weather.