GB2055729A - Aircraft - Google Patents

Abstract

An aircraft having, for example, a tailplane (4, 5) at least part of which is movable with reference to a fuselage (1) to effect control requires the control effect, that is to say lift, to be enhanced in a certain control position. Accordingly, fixed vanes (8, 9) are provided on the fuselage forward of the tailplane to form a substantially continuous leading edge roof extension only when the tailplane is in a given control position, e.g. in a nose-down position (Figure 4, not shown). The vanes may be used in conjunction with a wing having a movable leading edge, and arranged to be effective when the leading edge is drooped, but ineffective with the wing in its normal cruise configuration. The vanes may be foldable into or against the fuselage sides. <IMAGE>

Description

SPECIFICATION Aircraft This invention relates to aircraft in which the effectiveness of a lift-producing member (such as a wing ortailplane) having at least a tiltable leading edge requires to be enhanced in certain conditions.

According to the present invention an aircraft includes a fixed member, a lift-producing member, having a leading edge region, extending from the fixed member, at least the leading edge region being tiltable with reference to the fixed member, and a lift-enhancing member, having a trailing edge region, extending from the fixed member, the trailing edge region being shaped and positioned to match the leading edge region when that region is in a position of tilt such that the lift-enhancing member then forms a forward extension to the lift-producing member.

Preferably the lift-enhancing member is set at or near zero angle of incidence to the local airflow in cruising flight so that it produces only a small drag effect in such flight. The actual incidence setting chosen must however be commensurate with an angle relative to the tilted leading edge which gives a desired lift-enhancing effect.

By this arrangement the lift-enhancing member has the effect of leading edge root extension on the lift-producing member when such an effect is most required; conversely since it is not attached to the lift-producing member it does not contribute to its weight or area.

Preferably, the lift-enhancing member is of low aspect ratio with a sharp leading edge of high average sweep-back; it thus produces a vortex sheet which extends rearwards over the lift-producing member at least when it is substantially continuous with the tilted leading edge.

An aircraft according to the invention is described with reference to the accompanying drawings in which Figure lisa pictorial view of an aircraft in flight, Figure 2 is a plan view of a tailplane to fuselage junction region of the aircraft, Figure 3 is a view upon Arrow III of Figure 2, Figure 4 is a sectional view, the section being upon line IV-IV of Figure 2, Figure 5 is a plan view of a wing to fuselage junction region of the, or a further, aircraft, and Figure 6 is a sectional view, the section being upon line VI-VI of Figure 5.

Referring initially to Figures 1 to 4, an aircraft has a fuselage 1 to which is attached the two halves 2 and 3 of awing and the two halves 4 and 5 of a tailplane.

The two halves of the tailpiece pivot about axes 6 and 7 respectively from a cruise position shown in broken outline in Figure 4to various other positions for control in the pitch sense. One such control position is shown in continuous outline at 'X' in Figure 4. This position is with the leading edge tilted downwardly and the trailing edge raised to give the aircraft a pitch up effect.

To enhance this effect the tailplane halves have lift-enhancing members 8 and 9, respectively, mounted upon the fuselage 1 in such a position that they form substantially continuous leading edge root extensions in the 'X' position of the tailplane halves.

The lift-enhancing members 8 and 9 are in the form of vanes and each have a wide chord root 10 fixed to the sides of the fuselage, a curved leading edge 11 of high average sweepback, and a trailing edge 12 shaped (with straight sweepback) to closely match the adjacent leading edge regions of the tailplane halves when in the position 'X'. The members 8 and 9 are of much greater sweepback than the tailplane and are of much less span.

The leading edge is sharp as shown in Figure 3. It is found in this illustrated embodiment that the members 8 and 9 delay tailplane stall just when necessary and that their effect decreases smoothly as the tailplane moves away from its 'X' position of substantial continuity.

Referring now to Figures 1,5 and 6, the aicraft wing, comprising the halves 2 and 3, is of variable geometry having leading edge regions 13 tiltable downwards from a cruise position shown in broken outline in Figure 6 to various other positions for high lift purposes. One such high lift position is shwon in continuous outline at 'Z' in Figure 6 and as can be seen the leading edge is tilted downwardly.

To enhance the high lift effect the wing halves have lift-enhancing members 14 and 15, mounted upon the fuselage 1 in such a position that they form substantially continuous leading edge root extensions in the 'Z' position of the leading edge regions 13.

The members 14 and 15 are similar to those referenced 8 and 9, being in the form of vanes with a wide chord root 16 fixed to the sides of the fuselage, a curved leading edge 17 of high average sweepback, and a trailing edge 18 shaped to closely match the adjacent leading edge regions of the wing halves when in the position 'Z'. Again, the members 14 and 15 are of much greater sweepback than the wing and are of much less span. The leading edge 17 is sharp.

The pairs of members 8,9 and 14, 15 may be fitted additionally or alternatively to one another depending upon whether the wing or the tailplane, or both, require lift enhancement. Thus, although Figure 1 shows both pairs of members 8, 9 and 14, 15 fitted for descriptive purposes, only one pair may well be fitted in practice. The members are applicable not only as illustrated to an all moving tailplane or tiling leading edge wing but also to a tilting leading edge tailplane or an all moving wing.

The lift-enhancing members 8,9 and 14, 15 are positioned on the-fuselage to be at or near zero incidence with reference to the local airflow in aircraft normal flight so that drag is relatively low in this condition.

In a further embodiment, not shown, the members 8,9 and 14, 15 are foldable either into or adjacent the fuselage when not required.

If the wing or tailplane of the aircraft are carried by a body other than a fuselage, for example, the tailplane may be carried by a vertical fin, then the lift-enhancing members are positioned on that body.

In this specification the term 'lift' refers to all aerodynamically generated forces irrespective of their direction.

Claims (7)

1. An aircraft including a fixed member, a liftproducing member, having a leading edge region, extending from the fixed member, at least the leading edge region being tiltable with reference to the fixed member, and a lift-enhancing member, having a trailing edge region, extending from the fixed member, the trailing edge region being shaped and positioned to match the leading edge region when that region is in a position of tilt such that the lift-enhancing member then forms a forward extension to the lift-producing member.

2. An aircraft according to claim 1 wherein the lift-producing member has a greater span than the lift-enhancing member.

3. An aircraft according to claim 2 wherein the lift-enhancing member has a leading edge region of higher average sweepback than that of the leading edge region of the lift-producing member.

4. An aircraft including a fixed body, a tail plane with a leading edge region, pivot means pivoting the tailplane to the fixed body, a vane member, with a trailing edge region, extending from the fixed body, the trailing edge region being shaped and positioned such that it matches the leading edge region when the tailplane is in a position of tilt and the vane member then forms a forward extension to the tail plane.

5. An aircraft according to claim 4wherein the tailplane has greater span than the vane member.

6. An aircraft according to claim 5 wherein the vane member has a leading edge region of higher average sweepback than that of the leading edge region ofthe tailplane.

7. An aircraft substantially as described with reference to the accompanying drawings.