This invention relates to winged aircraft having tiltable propulsive thrust producing means providing a vertical and/or short take off and landing capability.

Such aircraft have the disadvantage that undesir¬ able effects resulting from the interaction of efflux, ground and/or wing can reduce their operational effectiveness.

An object of the present invention is to provide an aircraft in which such undesirable effects are mitigated.

According to the present invention an aircraft includes a fixed"region, a wing region pivoted to the fixed region about a first axis such that the angle of incidence with reference to the fixed region may be increased, and propulsive thrust producing means pivoted to the wing region about a second axis such that downward thrust may be provided.

Whilst the pivot axes may be close together or even co-axial enabling the wing region angle of incidence to be increased during the provision of downward thrust so that a reduction in any adverse interaction effects between the wing, the ground, and the efflux can be effected, preferably the first axis is so spaced from the

second axis that an increase in the angle of incidence of the wing region appreciably raises the location of the second axis; the thrust producing means is accordingly bodily raised.

Conveniently the pivot arrangement is such that when substantially vertical downward thrust is provided, the wing portion requires only to be tilted through a moderate angle of incidence.

One preferred embodiment of the invention is described by way of example with reference to the accompanying drawings in which:-

Figure 1 is a part plan view of an aircraft,

Figure 2 is a cross sectional view in the direction of the arrows on the plane II-II of Figure 1, plane II-II being coincident with the longitudinal axis of symmetry of the aircraft, and.

Figure 3 is a cross sectional view in the direction of the arrows on the plane III-III of Figure 1.

In the specification reference to the relative disposition of the various aircraft components assumes that the aircraft is in a straight and level flight attitude.

Referring to the drawings, an aircraft has a fixed region comprising a fuselage"!, and a wing having a centre portion 2 which carries outboard portions 3.

The centre portion has leading edges 4 and 5 and

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a trailing edge 6. The outboard portions 3 have leading edges 7 and trailing edges 8. Structural integrity of the wing is ensured by inclusion of a spanwise spar 9 (that is to say a torsion box) which extends continuously through the centre portion and the outboard portions at a chordwise station intermediate the leading and trailing edges.

The wing, and hence the spar 9, extends across an upper region of the fuselage. It is pivoted to the fuselage 1 about a transverse axis 10 (the first axis) which lies well aft of the spar 9, the fuselage being provided with pivot means in the form of a spaced brackets 11, and the wing being provided with spaced arms 12 rearwardly extending from the spar 9. A transverse pin arrangement couples the brackets 11 to the arms 12. Wing pivotal movement (that is to say, tilt) in the sense to increase its angle of incidence with reference to the fuselage about the axis 10, is effected by jack assemblies 13 pivoted both to the fuselage and to the spar 9. Conveniently, the jack assemblies 13 are of the scre type. The maximum angle of incidence of the wing is of the order of 30 as illustrated in broken outline at X in Figures 2 and 3; the wing at about 20 angle of incidence is shown at Y.

At the outboard extremities of its centre portion 2, the wing carries twin power plant units 14, symmetrically

spaced from the fuselage. Each power plant 14 comprises a pod housing a jet propulsion engine, an intake shown generally at 15, and an exhaust efflux outlet shown generally at 16.

The power plant units 14 are pivoted about an axis 17 (the second axis) parallel to the axis 10, the spar 9 being provided with pivot means in the form of forwardly extending brackets 18, and the power plants 14 being provided with brackets 19. Transverse pin arrange ments couple the brackets 18 to the brackets 19.

Pivotal movement (that is to say, tilt) of the pow plants 14 about the axis 17 in the sense to direct the efflux outlets downward from a rearward position is effec for each power plant .by twin jack 20 assemblies lying on opposite sides of the power plant and pivoted both to the spar 9 and the power plant. Conveniently the jack assemblies 20 are of the screw type and in this case are driven from a common centrally mounted motor 21 by spanwis extending drive shaft 22 carried to the rear of the spar 9

The axis 17 lies forward of the spar 9 but to the rear of the local leading edges 4 and 5 of the wing centre portion and accordingly a leading part 23 of the wing cent portion immediately above each power.plant is carried by a moves with.the tilting power plant.

In Figure 3, the tilted wing may have the power plants 14 un-tilted about axis 17 in which case in

position Y they lie at position A with their thrust directed part rearwards and part downwards.

Alternatively, the power plants may be tilted with respect to the wing about axis 17 so that their efflux is directed' generally vertically, in which case they lie at positions B and C, the former being when the wing is at position Y and the latter when the wing is at position X.

As can be seen in Figure 1 in plan view, to minimise out of balance forces due to the changes of thrust line and weight distribution associated with wing and power plant tilt, the axis 17 is positioned close to the centre of gravity 24 of the aircraft as a whole. The centres of gravity 25 of the power plants 14 are also positioned close to the axis 17. Since the centres of gravity 25 of the power plants when viewed from the side are below the pivot axis 17, they are located forward of the pivot axis 17 so that during tilting of the power plants 14 about that axis the centres of gravity remain in the same general position in plan.

In use, the aircraft can operate conventionally. In other words it can take-off, perform its mission, and land with the wing generally horizontal and with the power plants directing their efflux generally horizont¬ ally and rearwardly, as shown in unbroken outline in

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the Figures .

For relatively short take off and/or landing, the wing can be tilted about the axis 10 to about 20 angle of incidence without tilting the power plants with respect to the wing about the axis 17 so that their efflux is directed part rearwardly and part down- . wardly as shown at A in wing position Y in Figure 3. Because the wing is at a high angle of incidence, the fuselage can be maintained at a generally horizontal attitude which is advantageous fr m the piloting aspect.

For vertical take off and/or landing, assuming that the power plant thrust to aircraft weight ratio is greater than unity, the power plants 14 can be tilted with reference to the wing about the axis 17 so that their efflux is directed vertically downwards. As before described, this can be achieved in both the position Y and also position X of the wing; the two vertical thrust positions of the power plants being shown at B and C respectively. As is evident, the efflux outlet regions 16 are raised well above that position which would be adopted if the wing remained untilted. This hypothetical position is shown for reference at Z in Figure 3. It is also evident that if the power plants 14 were not pivoted to the wing and

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remained fixed, the wing itself would require to be tilted upwards to a vertical position in order to direct the efflux vertically downwards.

It is found that with the described arrangement, the mere tilting of the wing itself about the axis 10 reduces any adverse effects of efflux, ground and wing interaction, but when coupled with the raising of the power plant during tilting relatively to the wing about the axis 17 so that the efflux outlets are well above the ground, any adverse effects are yet further reduced; there is less interaction between ground and efflux. There is also less ground erosion. Moreover these beneficial effects occur without the necessity of excessively lengthened undercarriage.

After short or vertical take-off the wing and power plants are moved to their un-tilted positions for conventional flight until the mission is accomplished and short or vertical landing is required. However, should a special manoeuvring capability be required this can be provided by selective tilting of wing and/or power plants.

Fine control in the pitch and yaw sense during thrust borne flight is effected by efflux deflection means (not shown) used either differentially or together. Coarse control is effected by tilting the power plants about the axis 17.