WO1988000556A1

WO1988000556A1 - A vtol aircraft and components

Info

Publication number: WO1988000556A1
Application number: PCT/AU1987/000221
Authority: WO
Inventors: Kimberley Vere Sadleir; Donald Mathieson Devenish
Original assignee: Kimberley Vere Sadleir; Donald Mathieson Devenish
Priority date: 1986-07-16
Filing date: 1987-07-16
Publication date: 1988-01-28
Also published as: CN87105599A; IL83205A0

Abstract

A VTOL aircraft (10) comprising a fuselage (12) having a wing (14) fixed to it, a turbine fan (48) rotatably housed within the wing (14) and a plurality of sets of stator vanes (30, 38, 46, 52) disposed above and/or below the turbine fan (48) to control the direction of flow of air therethrough, the turbine fan (48) being disposed such that the centre of lift of the turbine fan (48) substantially coincides with the centre of lift of the wing (14).

Description

TITLE A VTOL Aircraft and Components DESCRIPTION The present invention relates to a VTOL aircraft and components thereof.

FIELD OF THE INVENTION In general VTOL aircraft may be categorized into those with pivot assemblies to pivot a thrust unit between a vertical propulsion condition and a horizontal forward propulsion condition and those with a single thrust unit and means to vary the direction of such thrust to cause vertical through to horizontal propulsion; and those with dual thrust units, one for vertical propulsion and one for horizontal propulsion. The present invention relates to a VTOL aircraft of the latter type and particularly of the type with a first thrust unit housed within a wing of the VTOL aircraft to provide vertical propulsion together with some horizontal propulsion. In prior art VTOL aircraft there has been difficulty in providing good control over the aircraft in vertical flight and in transition between vertical and horizontal flight and vice versa.

Prior art VTOL aircraft have provided very complicated means to attempt to achieve control over the aircraft in vertical flight.

SUMMARY OF THE INVENTION The present invention provides a VTOL aircraft with relatively uncomplicated means to control vertical flight. In accordance with the present invention there is provdied a VTOL aircraft characterised in that it comprises a fuselage having a wing fixed to it, a turbine fan rotatably housed within the wing and a plurality of sets of stator vanes

5 disposed above and/or belcw the turbine fan to control the direction of flow of air therethrough the turbine fan being disposed such that the centre of lift of the turbine fan substantially coincides with the centre of lift of the wing. BRIEF DESCRIPTION OF THE DRAWINGS

10 Figure 1 is an upper perspective view of a VTOL aircraft in accordance with the present invention;

Figure 2 is a plan view of the VTOL aircraft of Figure 1 showing outer upper stator vanes; Figure 3 is a further view of Figure 2 with the outer upper

15 stator vanes rearward to show inlet radial stator vanes and • a swatch plate;

Figure 4 is a further view of Figure 3 with the inlet radial stator vanes removed to show a turbine fan; Figure 5 is a further view of Figure 4 with the turbine fan

2.0^' removed to show outlet radial stator vanes;

Figure 6 is a further view of Figure 5 with the outlet radial stator vanes removed to show outer lower stator vanes and a drive shaft for the turbine fan shown in Figure 4; Figure 7 is a cross sectional view of a wing of the VTOL

25 aircraft of the present invention showing the outer upper stator vanes _r the inlet radial stator vanes, the turbine fan, the outlet radial stator vanes and the outer lower stator vanes of Figure 2 to 6 respectively; Figure 8 is an upper perspective view of the inlet radial stator vanes and the swash plate shown in Figure 3 but at an enlarged scale;

Figures 9 and 10 are schematic side views of the inlet radial stator vanes and the swash plate of Figure 8 shown in two conditions of operation, each Figure showing three inlet radial stator vanes to represent such vanes disposed half way around the turbine fan; and

Figure 11 is a cross sectional view of a tip of a blade of the turbine fan of Figures 4 and 7 showing two air bearings. DESCRIPTION OF THE INVENTION

In Figure 1 there is shown a VTOL aircraft 10 comprising a fuselage 12 upon which is fixed a wing 14. The fuselage 12 comprises a cockpit 16 and may comprise a stiffening member 18 disposed from the cockpit 16 to a rear -edge 20 of the wing 14. ^* •

A first thrust unit (described hereinafter) is mounted within the wing 14 and a second thrust unit 22 is mounted upon the wing 14 or the fuselage 12 adjacent the rear edge 20. The second thrust unit 22 in the examplary embodiment shown in Figure 1 is of the engine driven propeller type. The second thrust unit 22 comprises an engine housing 24 having an air intake port 26 disposed toward the cockpit 16 and a propeller 28 fixed to a rotatable output shaft of an engine (not shown) mounted in the engine housing 24.

It is envisaged that the wing 14 could comprise two fins 29, as shown in Figure 1, disposed at opposite edges of the wing 14 and at an angle thereto. The fins 29 are preferably substantially parallel to longitudinal axis of the VTOL aircraft 10. The fins 29 serve to reduce the spill of air over the edge of the wing 14 and hence reduce contribute to increasing the lift of the wing 14. It is envisaged that the wing 14 have a substantial delta shape so as to receive a first thrust unit of relatively planar dimension.

It is also envisaged that the second thrust unit 22 could be of the jet engine type. It is further envisaged that an inflatable air bag could be provided in a lower portion of the fuselage 12, the air bag being disposed to be inflated to absorb the impact of the VTOL aircraft 10 striking the ground at an excessive speed, such as for example in a crash situation. The wing 14 comprises a plurality of outer upper stator vanes 30 as shown in Figures 1, 2 and 7, such as, for example, eight outer upper stator vanes 30 on each side of the stiffening member 18.

As shown in Figures 2 and 7 the outer upper stator vanes 30 cover a cavity 32 formed in the wing 14 and seal an upper end of the cavity 32 to provide an upper lift surface for the wing 14. The outer upper stator vanes 30 are pivotally fixed adjacent the upper end of the cavity 32. The outer upper stator vanes 30 each comprise a leading edge 34 and a tracking edge 36 and being of an asymmetrical aerofoil shape.

Preferably, the trailing edge 36 of one of the outer upper stator vanes 30 overlaps with the leading edge 34 of an adjacent one of the outer upper stator vanes 30. Such overlap is preferred to achieve a relatively smooth upper surface for the wing 14, which smoothness is required where a relatively fast VTOL aircraft 10 and therefore aerodynamically efficient is to be produced. The outer upper stator vanes 30 comprise pivots (not shown) disposed to allow pivoting of each of the stator vanes from a first condition wherein they cover the cavity 32 to a second condition wherein they are disposed with their leading edges directed upwardly and forwardly and their trailing edges directed downwardly and rearwardly. It is envisaged that the pivots may be fixed to the wing 14 at a location adjacent but displaced from the trailing edge 36 of each of the outer upper stator vanes 30. It is envisaged that the angle of pivotal disposition of adjacent ones of the outer upper stator vanes 30 could vary such that the outer upper stator vanes 30 located toward the cockpit 16 are disposed more uprightly than the others. Also it is envisaged that the asymmetry of the outer upper stator vanes 30 could vary from more asymmetric toward the cockpit 16 to less asymmetric toward the rear edge 20. Preferably, the outer upper stator vanes 30 are transversely disposed on the wing 14 so as to be substantially normal to the path of oncoming bodies of air to direct the air into the cavity 32.

The wing 14 also comprises a plurality of outer lower stator vanes 38 as shown in Figures 6 and 7. The outer lower stator vanes 38 are pivotally fixed to the wing 14 at or adjacent their leading edges 40. Trailing edges 42 of the outer lower. stator vanes 38 overlap with adjacent leading edges 40 to provide a relatively smooth lower lift surface for the wing 14.

The outer lower stator vanes 38 may be of symmetric aerofoil shape and may be disposed to direct air out of the cavity 32. Preferably, the outer lower stator vanes 38 are also disposed transversely on the wing 14. Also it is preferred that a part set of the outer lower stator vanes 38 be independently controllable of a starboard set of outer lower stator vanes 38 so that yaw control and some steerage of the VTOL aircraft 10 may be effected.

The cavity 32 also receives a first thrust unit 44 comprising a plurality of inlet radial stator vanes 46, a turbine fan 48 having a plurality of turbine blades 50 and a plurality of outlet radial stator vanes 52 as shown in Figures 3, 4, 5 & 7.

The inlet radial stator vanes 46 are disposed below the outer upper stator vanes 30 and above the blades 50 of the fan 48. The outlet radial stator vanes 52 are disposed below the blades 50 of the fan 48 and above the outer lower stator vanes 38.

Each of the inlet radial stator vanes 46 has a substantially symmetrical aerofoil shape.

As shown in Figures 7 and 8 the inlet radial stator vanes 46 are each pivotally connected between the wing 14 and to an inner hub 54, which hub 54 is also fixed to the wing 14. A swas plate 56 is mounted within the hub 54 and connected to each of the upper radial stator vanes 46 via a crank rod 58. Each crank rod 58 is conveniently shaped with two substantially parallel and offset shafts joined by a further shaft disposed at an angle to the two first mentioned shafts .

Each of the crank rods 58 is fixed at one end to a leading edge of a respective one of the inlet radial stator vanes 46. The other end of each crank rod 58 is rotatably fixed to the swash plate 56. The shaft of each of the crank rods

58 which is fixed to a corresponding one of the inlet radial stator vanes 46 extends through the inner hub 54 and is in rotatable engagement therewith. A drive means (not shown) is provided to displace the swash plate 56 upwardly and/or downwardly. Such displacement causes the crank rods 58 to .rotate and thus causes the inlet radial stator vanes 46 to rotate through an angle. The angle of rotation is dependent upon the amount of displacement of the swash plate 56.

As shown in Figure 9 the swash plate 56 may be raised, by the drive means, to rotate the inlet radial stator vanes 46 through an angle in a counter clockwise direction. Such rotation, in use, pre-conditions the direction of flow of air to the fan 48 and can therefore be used to increase and/or reduce the effective lift of the fan 48.

As shown in Figure 10 the swash plate 56 may be raised at one end and lowered at another end so as to be angled. Such angling of the swash plate 56 causes some of the inlet radial stator vanes 46 to rotate through an angle counter clockwise, some to be unmoved and some to be rotated through an angle clockwise. o Precondition of air flow by angling the swash plate 56 causes increased lift in part of the fan 48 and reduced lift in. another part of the fan 48 with a relatively gentle or smσαth. transition between the areas of differing lift. Such variations in the lift of the fan 48 about its area generates pitch and roll control. It is envisaged that a joy-stick could be configured to control the drive means to produce a tilting of the swash plate 56 to counter or induce a desired amount of pitch or rail in the VTOL aircraft 10.

It is envisaged that a further control lever could be provided to effect raising and lowering of the swash plate

56 to increase and decrease the effective lift of the fan

48.

It has been found that the transition between the areas of differing lift .must be gradual as sudden abrupt changes in air flow create unacceptable turbulence. The swash plate 56^" has been found to produce a blade angle which varies substantially continuously about the fan 48 and hence which is less likely to produce turbulence.

Further, the swash plate 56 is relatively simple in construction and controls all of the inlet radial stator vanes 46 simultaneously.

The fan 48 is in the form of a low speed turbine type fan 48 as shown in Figures 4, 7 and 11 and comprising a plurality of radially disposed blades 50, such as, for example, between 20 and 200 blades 50.

Preferably, the blades 50 are relatively small in area so that the wing 14 is not relatively thin. β

As shown in Figures 7 the fan comprises a fan head 48a to which one end of all of the blades 50 is fixed. The fan head 48a is rotatably fixed in the wing 14.

As shown in Figures 4 and 11 the first thrust unit comprises an anngular ring 48b which is connected to free ends of each of the blades 50. The annular ring 48b is maintained between annular air bearings as described hereinafter to keep the fan 48 rotating in a fixed plane. It is envisaged that each blade 50 could comprise a plurality of endwise disposed segments (not shown) . Each of the segments is intended to be maintained in the wing 14 with air bearings and the fan head 48a as described, and with two annular rings for each segment excepting a segment fixed at one end to the fan head 48a.

Innermost ones of the segments are connected for rotation with 'the fan head 48a and are supported by mechanical bearings (not shown) .

As shown in Figure 7 the VTOL aircraft 10 may comprise a drive shaft 60 fixed to an output shaft of the engine (not shown) . A pinion 62 is provided to connect the drive shaft 60 to an output 64. The output shaft 64 is connected to thefan 48 to cause same to rotate.

It is also envisaged that the fan 48 be rotated by the output shaft 64 at a speed between 2% and 10% of the speed of the engine, such as for example a speed of between 1000 to 2000 rpm. Lower fan speeds are to be used for larger fans.

It is recommended that the angular velocity of the tips of the blades 50 be kept below the speed of sound. It is envisaged that the fan 48 could be driven via a drive means disposed to drive the annular ring 48b of the fan 48. Such drive could be a belt, a friction drive or a cog drive. It has been found that such drives are suited to only very low speed fans with relatively low load applied. The fan 48 could be driven by a plurality of turbine blades fixed to the annular ring 48a and disposed to be subjected to the efflux of an air pump or jet engine or the like. Such, construction is particularly suited to faster fans with larger" applied loads. Air" exhausted from the fan 48 has a downward thrust component and a twist component. The former serves to raise the VTOL aircraft 10 the latter tends to cause the VTOL aircraft 10 to rotate in a direction opposite to that of the fan 48. Preferably, the outlet radial stator vanes 52 have a longitudinal twist directed to oppose and substantially cancel the torque produced in the VTOL aircraft 10 by the rotating fan 48. Torque is generated as the air resists being rotated and forced downwardly by the blades 50 of the fan 48. In order to cancel the effects of the torque it is necessary to at least partially redirect the air exhausted from the fan 48 to a direction substantially perpendicular to the wing 14.

The lift generated by the blades 50 of the fan 48 increases toward the tips of the blades 50. Thus, the force required by the outlet radial stator vanes 52 to cancel the torque generated by the fan 48 increases towards the tips of the blades 50. Accordingly, the outlet radial stator vanes 52 may be longitudinally twisted. It is envisaged that the outlet radial stator vanes 52 will be fixed to the wing 14. It is to be noted that the cancellation of torque by the outlet radial stator vanes 52 is not linearly fixed to the volume of air flowing over them. The limit occurs when the outlet radial stator vanes 52 can no longer straighten up the exhaust air flow.

It is to be noted that the outlet radial stator vanes 52 could also be controlled by a swash plate similar to that described hereinabove. Alternatively, coupling means could be provided to control the outlet radial stator vanes 62 with the swash plate 68.

In the above configuration the fan 48 is preferably of the fixed pitch type. Such is preferred since there has been found to be much added complexity and practical difficulties in using a variable pitch fan in the present invention. If a variable pitch fan was employed the inlet radial stator^' vanes 46 are still required to give wall and pitch control, unless means is provided to alter the pitch of the blades 50 of the fan 48 so that the pitch of the blades 50 as they pass a particular location is one angle and differing angles as the blade 50 rotates.

It is envisaged that where the fan 48 is driven by its annular ring 48b a central rotation axle or the like may be omitted. The fan 46 in such a case is held in rotation within the wing 14 by two of the air bearings. It has been found that the outer regions of the fan 48 generate a substantial proportion of the lift. Consequently, the inner hub 54 and the fan head 48a may be relatively large, thus allowing cabling, connecting rods and the like to pass through it to for the wing 14, the outer upper stator vanes 30, the upper radial stator vanes 46 the swash plates 44, the fan 48, the lower radial stator vanes 52 and the outer lower stator vanes 38. In Figure 11 there is shown two air bearings 68 each comprising a bearing pad 70 having one or more air passages 72 leading to a bearing face 74. The bearing face 74 is intended to locate adjacent the outer most annular ring 48b of the first thrust unit. The passages 72 lead to secondary air chambers 76 and via further passages 78 to a major air chamber 80.

A flexible connector 82 joins the bearing pad 70 to beam 84, one of the air passages 78 passes through the flexible connector and to the air chamber 80 in the beam 84. The beam 84 is fixed to the wing 14 and hence provides support for the air bearing 68.

Preferably the air bearing 68 follows the annular ring 48a around the fan 48.

Preferably the air bearing 68 is split into discreet lengths about the annular ring 48. One of the air bearings 68 is located adjacent an upper side of the annular ring 48b and the other of the air bearings 68 is located adjacent a lower side of the annular ring 48b. It has been found that the upper air bearing 68 supports most of the lead of the annular ring 48b, whereas the lower air bearing 68 is provided to substantially restrain the annular ring 48b in the plane of the fan 48. When the fan 48 is in operation and the VTOL aircraft is in the vertical flying condition the blades 48 tend to bow upwardly. Such bowing causes the annular ring 48b to angle slightly downwardly toward its outermost region. The flexible connectors 82 are provided to allow the air bearings 68 to also deflect to keep the bearing faces 74 substantailly parallel to the annular ring 48b and hence to keep the load of fan 48 substantially evenly distributed over the air bearings 68.

Preferably the primary air chamber 80 and the secondary air chambers 76 are so dimensioned that there is a substantial pressure drop from a supply of compressed air to the primary air chamber 80 and a further substantial pressure drop from the primary air chamber 80 to the secondary air chambers 76. Such pressure drops are preferred so as to reduce the likelihood of pressure differences at differing segments of the air bearings.68 due to partial blockages or the like. Since there is a substantial pressure drop the two secondary chambers 76 may be considered as indpeendent and thus the two bearing faces 74 operate substantially to share the load of the fan 48 between them.

An exhaust passage 86 is provided in the bearing pad 70 to allow escape of air caught between the two bearing faces 74. The air pressure at the bearing faces 74 is between 100 and 1000 kpa such as for example about 200 kpa. The annular ring 48b also preferably comprises an annular rim 90 disposed substantially at right angles to the annular ring 48b and adjacent the blades 48. The wing 14 comprises two annular flanges 92 and 94 adjacently aligned with the annular rim 90 to substantially seal off the cavity 32 from the air bearings 6β. Air passages 96 and 98 are formed by the adjacency of the annular ring 90 and the annular flanges 92 and^" 94. The air passages 96 and 98 are angled downwardly toward the outlet radial stator vanes 52 so that air passing from the relatively high pressure region of the air bearings 68 to the relatively low pressure area of the cavity 32 does not flow parallel to the blades 48.

Where air exhausted from the air bearings is allowed to travel parallel to the blades 48 stalling of the fan 48 at its tips may occur and which would result in reduced controlability of the VTOL aircraft 10.

Preferably, the ckentre of the first thrust unit is located forwardly in the wing 14 so.that the centre of lift of the first thrust unit and the centre of lift of the wing 14 _^ substantially coincides. Preferably, the centre of gravity of the VTOL aircraft 10 substantially coincides with the centre of the wing 14 and/or the first thrust unit.

It is envisaged that means could be provided to compensate for insufficient coincidence of the centre of gravity and the centre of lift. For example, the position of the payload of a part of the payload could be alterted by slidable movement upon rails.

The above preferments aid in achieving stability of the VTOL aircraft 10 during transition between horizontal and vertical flight.

The centre of gravity may be located slightly forward of the centre of lift so that if power is lost the VTOL aircraft 10 may glide cockpit 16 first with the wing 14 providing some lift and drag. In vertical flight the inlet radial stator vanes 46 and the outer lower stator vanes 38 could be adjusted to adjust the centre of lift to substantially coincide with the centre of gravity. 5 In use, the VTOL aircraft 10 of the present invention can be operated in a vertical propulsion condition and in a forward propulsion condition.

The vertical propulsion condition is used when the VTOL aircraft 10 is stationed on the ground and it is desired to 10 take off or is airborne and desires to land. Next, air pressure is applied to the air bearings 68 to generate an air cushion between the bearing faces 74 and the annular ring 48b. Then the engine (not shown) is started and the inlet radial stator vanes 46 to angle air drawn in by the 15 rotation of the fan 48 in the same direction as the rotation- of the fan 44 to reduce the effective lift thereof. Then the outer upper stator vanes 30 are pivoted to be normal to the surface of the wing 14 so taht air may pass downwardly through the wing 14. The pitch of the inlet radial stator 2.0, vanes 46 is then altered so that air is directed into the fan 44. The fan 44 forces the air downwardly and in a spiral. Accordingly, the blades 50 and the annular ring 48b are forced upwardly against the air bearings 68. The upward force against the air bearings 68 is transmitted to the 5 fuselage 12 via the wing 14. When the upward force exceeds the weight of the VTOL aircraft 10 it rises off the ground and becomes airborne.

The VTOL aircraft 10 is propelled by supplying power from the engine to the second fan unit 22. Some forward velocity whilst in the vertical flight condition may be achieved by angling the outer upper stator vanes 30 forwardly ande upwardly and the outer lower stator vanes 38 downwardly and backwardly. Such is used to gain increase in rate of forward propulsion during transition between vertical flight and horizontal flight.

When the desired altitude is reached and sufficient forward air velocity is reached the outer upper stator 30 and the outer lower stator vanes 38 may be closed and the fan 48 stopped to make the wing 14 relatively streamlined. Then the wing 14 provides alift to maintain the altitude of theVTOL aircraft 10 as the second thrust unit propells it.

The reverse process is employed in landing. By raising and lowering the swash plate 56 the effective lift of the first thrust unit may be altered.

By tilting the swash plate 56 banking may be induced into the VTOL aircraft 10 since the lift from the first thrust unit varies around its circumference. By independently tilting the port and starboard halves αf the outer lower stator vanes 38 the VTOL aircraft may be turned about a substantially vertical axis.

Preferably the wing comprises a rear outlet 98 to allow escape of air from the air bearings 68. It is envisaged that the air bearings could be made to generate their own air cushion once a set speed of rotation is reached.

It is envisaged that the second thrust unit 22 could be a jet engine and the efflux thereof could drive a turbine to drive the fan 48.

It is expected that should all power to the fans be lost then the relatively large area of the wing 14 and the low centre of gravity of the VTOL aircraft 10 may result in a natural parachute effect and/or glide effect which is expected to substantially reduce the free fall speed of the VTOL aircraft 10 and to a survivable speed. It is further expected that the operational noise of the VTOL aircraft 10 may be less than that of a helicopter, for example, since the fan 48 of the VTOL aircraft 10 operates at a lower speed.

Furthermore, it is expected that since the fan 48 is housed within the wing 14 and air bearings 68 provided to resist the upward force of the blades 50 there may be far less likelihood of an embkarking or disembarking passenger or pilot from being struck by the blades 50 since the blades 50 tend not to drop at idle speeds. Such dropping is a common problem with helicopters.

Furthermore, it is expected that since the fan 48 is housed within the wing 14 the wing 14 may strike an obstacle, such as, for example, a tree, during the takeoff or landing without the VTOL aircraft 10 necessarily crashing into the ground as a result.

Modifications and variations such as would be apparent to a skilled addressee are deemed within the scope of the present invention

Claims

CLAIMS 1. A VTOL aircraft characterised in that it comprises a fuselage having a wing fixed to it, a turbine fan rotatably housed within the wing and a plurality of sets of stator vanes disposed above and/or below the turbine fan to control the direction of flow of air therethrough, the turbine fan being disposed such that the centre of lift of the turbine fan substantially coincides with the centre of lift of the wing.

2. A VTOL aircraft according to Claim 1, characterised in that the plurality of sets of stator vanes comprise outer upper stator vanes .disposed -transversely of the wing and covering a cavity, and outer lower stator vanes disposed transversely of the wing and covering a lower end of the cavity.

3. A VTOL aircraft according to Claim 2, characterised in that the plurality of sets of stator vanes comprise inlet radial stator vanes disposed radially in the cavity and located between the outer upper stator vanes and the turbine fan, and inlet radial stator vanes disposed radially in the cavity and located between the turbine fan and the outer lower stator vanes, the inlet radial stator vanes being of variable pitch configuration.

4. A VTOL aircraft according to Claim 2 or 3, characterised in that the outer upper stator vanes each comprise a leading edge and a trailing edge, the outer upper stator vanes being pivotable adjacent their trailing edge, the outer upper stator vanes being disposed upwardly from the wing and protruding above an upper surface thereof, in a vertical propulsion condition, and downwardly from the wing and protruding below a lower surface thereof, the outer upper stator vanes being disposed with the trailing edge of one of the outer upper stator vanes overlapping a leading edge of an adjacent one of the outer upper stator vanes.

5. A VTOL aircraft according to Claims 3 or 4 characterised in that it comprises a swash plate having each of the inlet radial stator vanes rotatably fixed to it, the swash plate being displaceable to cause rotation of each of the inlet radial stator vanes.

6. A VTOL aircraft according to Claim 5, characterised in that it comprises a crank rod to conect each of the inlet radial stator vanes to the swash plate and means to displace the swash plate in a direction non-parallel to the inlet radial stator vanes to effect rotation of the inlet radial stator vanes which rotation is dependant upon said displacement, displacement of the swash plate preconditioning the angle of approach of air into the fan to vary the effective lift generated by the fan.

7. A VTOL aircraft according to Claim 6, characterised in that it comprises means to tilt the swash plate with respect to the inlet radial stator vanes to effect varying degrees of rotation of the inlet radial stator vanes to provide effective variation of the lift generated by the fan about its circumference.

8. A VTOL aircraft according to any one of the Claims 2 to 7, characterised in that means is provided to independently pivot a port side group of the outer lower stator vanes and a starboard side group of the outer lower stator vanes.

9. A VTOL aircraft according to any one of the preceding Claims, characterised in that the turbine fan comprises a plurality of blades, each of the blades being disposed between a fan head at one end and an annular ring at another end, the annular ring receiving an air bearing on an upper face and a lower face thereof.

1Q. A VTOL aircraft according to Claim 9, characterised in that the air bearings each comprise a bearing pad having one or more bearing faces, each of the bearing faces being supplied with air under pressure by an air passage, said air passages leading to a supply of air under pressure, the air bearing being provided with a primary air chamber and one or more secondary air chambers connected to the air passages to -substantially lower the air pressure.

11. A VTOL aircraft according to Claim 10, characterised in that the air bearings each comprise a flexible joint to flexibly fix the bearing pad to the wing, the flexible joint disposed to allow substantially upright bending displacement of the blades of the fan by keeping the bearing face substantially parallel to the annular ring.

12. A VTOL aircraft according to Claim 11 or 12, characterised in that it comprises a barrier means. disposed to at least partly isolate the air bearings from the cavity to reduce the incidence of air flow from air bearings flowing parallel to the blades.

13. A VTOL aircraft according to any one of the preceding Claims, characterised in that the centre of gravity thereof substantially coincides with the centre of the left wing.

14. A VTOL aircraft according to Claim 13, characterised in that means is provided to alter the position of masses in the VTOL aircraft to achieve substantial co-incidence between the centre of gravity and the centre of lift.

15. A VTOL aircraft according to Claim 13, characterised in that means is provided to angle the swash plate to achieve substantial co-incidence between the centre of gravity and the.- centre of lift of the turbine fan.