FLAPTRACK FAIRING ON THE WING OF AN AIRCRAFT

This application claims the benefit of the filing date of German Patent Application No. 10 2006 015 727.3 filed February 25, 2006, the disclosures of which is hereby incorporated herein by reference.

The invention relates to a flaptrack fairing on the wing of an aircraft.

Normally, the flaps that are provided on the wing of an aircraft in order to increase lift for takeoff or landing are operated by flaptracks, in most instances arranged on the underside of the wing, that extend in longitudinal direction of the aircraft and are enclosed by a more or less aerodynamically shaped flaptrack fairing (FTF). Such a flaptrack fairing is, for example, known from DE 26 11 918 Al or from DE 36 41 247.

Figure 1 shows a typical arrangement of such flaptrack fairings according to the state of the art, wherein half of an aircraft is shown in an oblique perspective view from below. On the underside of the wing shown, there are three flaptrack fairings that extend in longitudinal direction of the aircraft. Figure 2 shows a top view of one of these flaptrack fairings of the conventional type. The illustration shows that the flaptrack fairing has a front part that closes off said flaptrack fairing towards the front, a rear part that closes off said flaptrack fairing towards the rear, as well as a middle part that is located in between. The width of the middle part remains constant in longitudinal direction of the aircraft; i.e. said middle part extends parallel in the top view or according to the horizontal section view of said wing. DE 26 11 918 Al in Figure 9 and DE 36 41 247 in Figure 4 each shown a top view of one of these conventional flaptrack fairings.

The known flaptrack fairings of the shape described above are associated with a disadvantage in that, beyond a certain limit that depends on the aerodynamic design of the aircraft configuration, the aerodynamic interference drag cannot be reduced any further.

It may be a need to create an improved flaptrack fairing on the wing of an aircraft, which flaptrack fairing is improved in particular in relation to its aerodynamic interference drag.

This need may be met by a flaptrack fairing with the characteristics of claim 1.

Advantageous improvements and exemplary embodiments of the flaptrack fairing according to the invention are stated in the subordinate claims.

The invention creates a flaptrack fairing on the wing of an aircraft, which flaptrack fairing in the direction of the longitudinal axis (x) of the wing partly protrudes beyond the trailing edge of the wing. The invention provides for the width of the flaptrack fairing, which width extends in the direction of the wingspan (y) of the aircraft, to increase in the region of the trailing edge of the wing with progressive x- direction towards the rear.

Preferably, the largest width of the flaptrack fairing is in a region which, in relation to the local wing profile depth, starts at 15% in front of the trailing edge of the wing and extends beyond said trailing edge of the wing.

Advantageously, the invention provides for the flaptrack fairing to comprise a front part that closes off said flaptrack fairing towards the front, a rear part that closes off said flaptrack fairing towards the rear, as well as a middle part that is located in between, wherein the middle part in the direction of the longitudinal axis (x) of the aircraft extends beyond the trailing edge of the wing both forwards and rearwards, and wherein the width of the middle part, which width extends in the direction of the wingspan (y) of the aircraft, increases towards the rear as the x-direction progresses.

The width of the middle part can increase slightly monotonically with progressive x- direction.

As an alternative, the width of the middle part can increase strictly monotonically with progressive x-direction.

A preferred exemplary embodiment of the invention provides for the angle ε between the tangent to the outside of the flaptrack fairing and the x-axis at the location of the trailing edge of the wing on both sides of the flaptrack fairing to be positive.

At the location of the trailing edge of the wing, the angle ε can be identical on both sides of the flaptrack fairing.

As an alternative, at the location of the trailing edge of the wing, the angle ε can be different on each side of the flaptrack fairing.

The flaptrack fairing can be provided as original equipment in an aircraft when it is first constructed.

As an alternative, the flaptrack fairing can be provided for retrofitting to an aircraft.

A significant advantage of the flaptrack fairing according to the invention may consist of it resulting in a measurable reduction in the overall aerodynamic drag of the aircraft.

Below, one exemplary embodiment of the apparatus or method according to the invention is explained with reference to the drawing.

The following are shown:

Figure 1 a perspective view of part of an aircraft with flaptrack fairings arranged on the wing;

Figure 2 a top view of a flaptrack fairing or a horizontal section of a flaptrack fairing on the wing of an aircraft, according to prior art;

Figure 3 a top view of a flaptrack fairing or a horizontal section of a flaptrack fairing on the wing of an aircraft, according to one exemplary embodiment of the invention;

Figure 4 a top view of a flaptrack fairing or a horizontal section of a flaptrack fairing on the wing of an aircraft, according to another exemplary embodiment of the invention.

One can assume that a load-bearing structure for transferring the flap loads, as mentioned in the introduction, is usually enclosed by a flaptrack fairing (FTF). Also possible is an aerodynamically favourable shape of the load-bearing structural component itself, so that, if needed, a flaptrack fairing in its entirety or in part is no longer necessary. The invention described below also refers to this embodiment, which below is designated a load-bearing flaptrack fairing.

Figures 3 and 4 show a flaptrack fairing 3 on the wing 2 of an aircraft 1 , compare Figure 1 , wherein said flaptrack fairing partly protrudes beyond the trailing edge 7 of the wing in the direction of the longitudinal axis (x) of the wing. Generally speaking, the invention provides for the width of the flaptrack fairing 3, which width extends in the direction of the wingspan (y) of the aircraft, to increase towards the rear in the region of the trailing edge 7 of the wing with progressive x-direction.

The flaptrack fairing 3 comprises a front part 4 that closes off said flaptrack fairing 3 towards the front, and a rear part (6) that closes off said flaptrack fairing 3 towards the rear, as well as a middle part 5 that is located in between, wherein the middle part

5 extends in the direction of the longitudinal axis (x) of the aircraft beyond the trailing edge 7 both towards the front and towards the rear, and wherein the width of the middle part 5, which width extends in the direction of the wingspan (y) of the aircraft, increases towards the rear with progressive x-direction. In other words, instead of the flaptrack fairing 3 having a constant width as is the case in prior art, i.e. instead of the middle part 5 of said flaptrack fairing 3 extending parallel with progressive x-direction, the invention provides a true widening, towards the rear, of the flaptrack fairing 3 in the region of the trailing edge 7. The maximum thickness of the flaptrack fairing 3 or the widest width of the flaptrack fairing 3 is thus in a region which in relation to the local wing profile depth, starts at 15% in front of the trailing edge 7 of the wing and extends beyond said trailing edge 7 of the wing.

The width of the middle part 5 can increase strictly monotonically with progressive x-direction, as shown in Figure 3, or it can increase slightly monotonically with progressive x-direction, as is the case in the exemplary embodiment shown in Figure 4.

Figures 3 and 4 show the angle ε between the tangent to the outside of the flaptrack fairing 3 and the x-axis at the location of the trailing edge 7 of the wing. Preferably, the angle ε between the tangent to the outside of the flaptrack fairing 3 and the x-axis at the location of the trailing edge 7 of the wing on at least one side of the flaptrack fairing 3, for example on both sides of the flaptrack fairing 3, is positive. For both exemplary embodiments shown in Figures 3 and 4, at the location of the trailing edge 7 of the wing the angle ε is identical on both sides of the flaptrack fairing 3.

As an alternative, at the location of the trailing edge 7 of the wing the angle ε can be different on each side of the flaptrack fairing 3.

The flaptrack fairing 3 can be provided as original equipment in an aircraft 1 when it is first constructed, or said flaptrack fairing 3 can be provided for retrofitting to an aircraft, which retrofitting is associated with considerable advantages.

List of reference characters

1 Aircraft

2 Wing

3 Flaptrack fairing

4 Front part

5 Middle part

6 Rear part

7 Trailing edge of the wing