An Improved Aircraft

5 This invention relates to an improved aircraft and is an improvement in and modification to the aircraft disclosed and claimed in British Patent 2011848 and United States Patent 4336913..

In accordance with one aspect of this invention 10 there is provided an aircraft having swept back anhedral foreplane and forward swept aftplane, the outboard sections thereof forming a dihedral.

Preferably the aftplane has inboard sections which in combination with the outboard sections thereof form a 15 cranked wing. In an advantageous embodiment the inboard sections of the aftplane have an anhedral configuration.

In accordance with another aspect of this invention, not essentially in combination with the aforesaid aspect, 20 there is provided an aircraft having a swept back anhedral foreplane and a forward swept aftplane of which outboard sections at least thereof form a dihedral, the wing tips of the foreplane being connected to the wing tips of the aftplane through an articulated linkage. 25 With an embodiment constructed in accordance with

the f rst aspect of this invention the aftplane when cranked using an inboard anhedral portion provides lateral surfaces which can be used for directional, i.e. yaw, control of the aircraft. Such surfaces may incorporate movable control surfaces forming effectively a rudder for directional control with the outboard sections of the aftplane having further movable surfaces forming aileron/elevator control.

When the aftplane is formed as a cranked wing with inboard anhedral and outboard dihedral surfaces, the juncture between said surfaces forming the crank serves as a location for mounting an engine. The underside portion at the crank also serves for supporting an undercarriage. In a preferred embodiment incorporating the articulated linkage between the oreplane and aftplane wing tips a further advantage accrues in that performance is augmented as the aftplane is prevented from twisting. The wing tips themselves may be connected through a strut member forming part of the linkage. The invention is now further described and illustrated with reference to the accompanying drawings showing one embodiment by way of an example only. In the drawings: Figure 1 shows a plan view of an aircraft

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constructed in accordance with the invention, Figure 2 shows a side elevation, Figure 3 shows a rear perspective view, and Figure 4 shows diagrammatically an articulated linkage joining the wing tips. In this invention and with particular reference to the preferred embodiment to be described, an aircraft is provided having no tail fin as such but employing a cranked forward swept wing as the main lifting surface in which the anhedral central section is intended to provide directional control and stability. The forward swept wing is linked at or near the tips to a swept back canard foreplane by means of an articulated strut. As shown in Figures 1 to 3 of the drawings , an aircraft has a fuselage 1 with a foreplane 2 mounted above the fuselage and having a swept back anhedral configuration. An aftplane 3 is mounted below the fuselage and has an inboard cranked portion 4 of an anhedral configuration and an outboard portion 5 of dihedral configuration. The outboard portion 5 at least is forwardly swept.

High speed aileron control surfaces 6 may be provided on the trailing edge of the foreplane. The cranked portion 4 at the inboard section of the

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aftplane may include rudder control surfaces 7 and the dihedral outboard portions 5 of the aftplane may include an aileron/elevator control surface 8 together with augmentary low speed aileron control surfaces 9.

As shown in Figures 2 and 3 , within the angle of the crank between the inboard aftplane section 4 and the outboard section 5 are provided propulsion engines 10 mounted on the fuselage or mounted on the wing and the underside of the crank may include an undercarriage 11 being either fixed or retractable. A nose wheel undercarriage 12 is provided at the forward end of the fuselage 1.

The foreplane and aftplane wing tips are connected through a strut member 13 which is articulated to allow wing flexing in the vertical plane. The strut also permits the canard foreplane incidence to be varied in flight and the torsional tendency of the forward swept wing will at the same time be suppressed by the articulated strut which is secured in a system of bearings or bushes in a wing tip reinforcing member.

A diagrammatic example of the articulated wing tip strut is shown in Figure 4 wherein the end of the foreplane 2 includes a universal joint or spherical bearing 14 bolted to a wing tip reinforcing member and carrying a titanium tubular strut 15 which has the other

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end secured in bearings 16 on the tip of the aftplane outboard wing portion 5. The bearings 16 allow pivotal movement about a generally longitudinally extending axis whereas the bearing 14 allows universal movement. This arrangement reduces or minimises torsional effects occurring in the forward swept wing and in practice a fairing will be provided covering the actual tubular strut member 15 shown in the drawings.

The arrangement provides an efficient wing having low weight and cost and in addition there is inherent stability in roll and yaw. Stability is a problem associated with a forward swept wing which is otherwise of high efficiency.

Although a connection is shown and described- between the tips of the foreplane and aftplane the primary requirement is for the wing tips to be separated and held at a constant distance apart in order to minimise aerodynamic interference. In the embodiment shown this distance is maintained by means of a streamlined articulated strut which permits restricted vertical aerodynamic flexing of the wings.

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