GB2051706A - Aircraft wings - Google Patents

Abstract

An aircraft wing 1 having a lift increasing flap 2 which, when in high lift position, forms a vortex generating discontinuity has vanes 9 arranged to modify the development of any such vortex. The vanes 9 or 9a may be mounted directly on the ends of the flap, as shown, or on booms secured to the flap ends or to the fixed wing structure adjacent the flap ends and extending rearwardly from the flap or wing trailing edge, (Figures 2, 4, not shown). <IMAGE>

Description

SPECIFICATION Aircraft wings This invention relates to aircraft wings having lift increasing flaps movable between an inoperative position in which they lie generally within the wing contour and an operative position in which they increase wing lift.

It is found that, in the operative position of the flaps, vortex generating discontinuities are formed; moreover the vortices produce drag with detrimental effect upon the performance of the aircraft.

It is an objective of the present invention to reduce such drag woth attendant advantages in aircraft operation. For example, if such a drag is reduced, a given lift gain due to flap operation will be achieved with reduced drag, so that take off weight (and hence payload) can be increased for the same power setting and, as a corollary, an increased margin of safety in at least some 'engine out' situations.

It is known to modify the vortex flow from aircraft wing tips, as is evidenced by United States patents 4,172,574 (Spillman) and 4,190,219 (Hackett) but these make no discussion of such wings when associated with lift increasing flaps.

According to the invention, an aircraft wing having a fixed structure and a lift increasing flap movable relatively to the fixed structure between an inoperative position in which it lies generally within the wing contour and an operative position in which lift is increased, but in which a vortex generating discontinuity is formed, includes van means arranged to modify the development of a vortex generated by the discontinuity.

The vane means may be carried directly by the flap itself or by rearwardly directed members extending from either the flap or the wing fixed structure.

Some embodiments of the invention are described with reference to the accompanying drawings, in which Figure 1 illustrates a trailing edge region of an aircraft wing with a lift increasing flap in an operative position, Figure 2 is a similar view view incorporating one embodiment according to the invention, Figure 3 is a similar view incorporating further embodiments, Figure 4 is a similar view incorporating yet a further embodiment, and, Figure 5 shows diagrammatically the generation of a forward thrust component from a vortex.

In the figures, an aircraft wing has a fixed trailing edge region 1 and a lift increasing flap 2. The lift increasing flap 2 lies generally within the wing contour in an inoperative position but when in an operative position is angled downwards to provide an increase in lift. In moving from the inoperative position, the flap can be merely angled downwards or it can be both angled downwards and moved bodily rearwards depending upon the operating mechanism provided. In either case, when in the operative position, discontinuities are formed in the wing contour and in the spanwise lift distribution of the wing which cause rearwardly trailing vortices to be formed.Particularly strong vortices 3 and 4 are formed by the spanwise extremities 5 and 6 of the operative flap, that referenced 3 having a clockwise circulation and that referenced 4 having an anticlockwise circulation when viewed from the rear.

Such vortices produce drag and to reduce such drag it is proposed that vane means be positioned to modify the development of that vortex.

Figure 2 illustrates one arrangement for positioning suitable vane means. In this case, three vanes 7 are mounted upon a boom 8 carried by the flap 2 at or near its spanwise extremity 5 and extending aft in such a manner that the vanes 7 lie generally within the vortex 3 when the flap is operative. The extremity 6 is similarly equipped. Also in Figure 3 a further alternative arrangement is shown in broken outline.

In this alternative arrangement, a single vane 9a is mounted upon the flap at or near its spanwise extremity 5, the vane extending downwardly but angled away from the flap. The extremity 6 is similarly equipped.

Figure 3 illustrates a further arrangement. In this case twin vanes 9 are mounted upon the flap 2 at or near its spanwise extremity 5, one vane extending upwardly and the other downwardly. Conveniently, both vanes are angled to extend toward the far extremity of the flap so that the vanes do not foul any adjacent wing structure. The extremity 6 is similarly equipped.

Figures 2 and 3 both illustrate vane means attached either indirectly or directly to the flap 2 and movable with it. Figure 4, however, illustrates an embodiment in which the vane means are mounted upon a boom 10 carried by the fixed trailing edge region of the wing. In this case, the boom includes a downwardly and rearwardly extending side wall 10a extending from the trailing edge region 1 adjacent the spanwise extremity 5 of the flap. Since the flap 2 is movable, that surface of the sidewall 1 Oa closely adjacent the flap extremity lies in a vertical plane so that the flap can be freely moved between the operative and the inoperative positions.If desired, sealing means (not shown) can be furnished between the flap and the sidewall 10a. The boom 10 has, at its rear-most extremity, a vane 11 protruding in a direction away from the flap, generally within the vortex 3 formed when the flap is inoperative.

Again, that extremity 6 is similarly equipped.

In modifying the development of a vortex, these vanes 7, 9, or 11 generate forward thrust and figure 5 illustrates the generation of such forward thrust from a vortex. In this figure a vane 7, 9, or 11 viewed in chordwise cross section is shown diagrammatically adjacent a triangle of velocities. That side referenced 12 of the triangle represents the longitudinal velocity within the vortex, this being approximately the same as the velocity of the free airstream, that side referenced 13 represents the local transverse velocity of the flow within a vortex, whilst that side referenced 14 represents the resultant local velocity of the airstream. As can be seen, this is at a positive angle of incidence to the vane.

The aerodynamic thrust generated by a vane, represented by line 15, is shown normal to that side referenced 14 and this can be divided into two components, one referenced 16 being substantially normal to the vane, and the other (referenced 17) being substantially parallel to the free airstream, that is to say, the line 17 represents a forward thrust component.

The vane 9a is fouhnd to develop little, if any, forward thrust; it does however modify the development of a vortex at source in a particularly favourable manner.

Since the vortices associated with the flap disappearwhen the flap is moved to its inoperative position, it is envisaged that the vanes may themselves be retractable or at least have their configuration modified to minimise any drag they might cause during, say, cruising flight.

It is further envisaged that drag in flight with the flap in its operative position, for example, during the approach to landing, could be varied by the use of the vanes, so that the aircraft could be caused to more closely follow a chosen flight path and as a corollary, reduce any noise nuisance.

A secondary advantage resulting form the use of the vanes is that the strength of the trailing vortices may be significantiy reduced, so that any danger to following aircraft is also reduced.

Claims (8)

1. An aircraft wing having a fixed structure and a lift increasing flap movable relatively to the fixed structure between an inoperative position in which it lies generally within the wing contour and an operative position in which lift is increased but in which a vortex generating discontinuity is formed, including vane means arranged to modify the development of a vortex generated by the discontinuity.

2. An aircraft wing according to claim 1 including a rearwardly extending boom member, said vane means being mounted upon the boom member.

3. An aircraft wing according to claim 2 wherein the boom member is carried upon the flap.

4. An aircraft wing according to claim 2 wherein the boom member is carried upon the fixed structure.

5. An aircraft wing according to claim 1 wherein the flap has a spanwise extremity and the vane means is mounted upon that extremity.

6. An aircraft wing according to claim 5 wherien the vane means comprises a vane angled away from the flap.

7. An aircraft wing according to claim 5 wherein the vane means comprises at least one vane angled toward the flap.

8. An aircraft wing substantially as described with reference to any one of Figures 2, 3 or 4 of the accompanying drawings.