The present invention relates to an aircraft component which is exposed to streaming surrounding air, in particular to a wing with perforations in the outer skin for boundary layer suction.

Boundary layer suction from the surfaces of aircraft components that are exposed to streaming air is used to reduce the flow resistance and to increase the achievable lift by avoiding early change from a laminar flow to a turbulent flow. In unfavourable environmental conditions there is a danger of the perforations in the outer skin, which perforations are used for boundary layer suction, icing up, or for an undesirable quantity of water entering the vacuum channel system that is connected to said perforations.

It is an object of the present invention to design an aircraft component according to the precharacterising part of claim 1 in such a way that icing up and thus blocking of the perforations may be avoidable.

According to the invention, this object may be met in that the above-mentioned aircraft component is designed with two walls and in the space between an inner and an outer wall element partition walls are inserted which with the incorporation of some sections of the wall elements adjoin each other so that alternately pressure channels and suction channels form, wherein first regions, serviced by the suction channels, of the outer wall element take up a significantly larger area than second regions, serviced by the pressure channels, and wherein by means of a control device the pressure channels can be connected to a hot air reservoir, and the suction channels can be connected to a vacuum reservoir.

The aircraft component designed according to the invention meets the above object in that hot pressurised air, e.g. bleed air from an aircraft engine, is fed into the pressure channels and exits to the environment through the perforations in the second regions of the outer wall element. Because the second regions are considerably smaller in area than the first regions of the perforated outer wall element, which areas are connected to the suction channels, enough heat can be supplied in the outer wall element without interfering with the boundary layer suction.

A preferred embodiment of the invention is characterised in that the partition walls are formed by an integral sheet with trapezoidal corrugations, with the base areas of said sheet alternately resting against the outer wall element and against the inner wall element of the component and comprising openings which communicate with the perforations of the outer wall element. This design of the partition walls has advantages predominantly relating to production technology because a single component, namely the integral sheet with trapezoidal corrugations, forms a multiple number of pressure channels and suction channels, and provides the structure with adequate rigidity. Fixing the sheet with trapezoidal corrugations in the space between the inner and the outer wall element can take place by connection means known from the state of the art, such as riveting, soldering, bonding etc.

A further advantageous embodiment of the invention consists of the open side of the trapezoidal contour of the sheet with trapezoidal corrugations being longer by a multiple than the closed baseline. With such a design of the sheet with trapezoidal corrugations, a construction is achieved in a simple way in which the formed suction channels, which include the first regions of the outer wall elements, communicate with a significantly larger area of the perforations of the outer wall elements. In other words direct suctioning off of the boundary layer by the suction channels can take place on a significantly larger part of the outer wall element.

According to a further embodiment of the invention, controllable valves are provided in the supply lines to the pressure channels or suction channels, by means of which controllable valves the negative pressure in the suction channels can be set by the control device. When substantial quantities of water arise on the outer skin, be it as a result of rain or as a result of the melting of ice, with this design said water can be prevented from being sucked into the suction pipe network as a result of excessive negative pressure in the suction channels, and icing over of the perforations can be prevented. It can be advantageous if the quantity of water arising at the outer skin is registered by suitable detectors, and if corresponding signals for controlling the negative pressure are transmitted to the control device.

The drawing shows one embodiment of the invention. The figure shows a diagrammatic cross-section of an aircraft wing.

Only the air flow region of the wing 1 is shown. The wing skin is double- walled comprising an outer wall element 4 and an inner wall element 6. On its pressure side, the outer wall element 4 comprises microperforations 3. While this is not shown in the figure, the microperforations 3 extend across the entire width of the wing. A sheet 2 with trapezoidal corrugations has been inserted into the space 5 between the outer wall element 4 and the inner wall element 6. The open side 29 of the trapezoidal contour of the sheet 2 with trapezoidal corrugations is several times longer than the closed baseline 28. The closed sides 28 of the sheet 2 with trapezoidal corrugations rests against the inner surface of the outer wall element 4 and of the inner wall element 6. The regions of the sheet 2 with trapezoidal corrugations, which regions rest against the inside of the outer wall element 4, comprise openings which communicate with the microperforations 3 in the outer wall element 4.

In this way, the sheet 2 with trapezoidal corrugations or its partition walls forms adjacent channels which taper off towards the outer wall element, which channels, due to the openings in the baseline of the sheet with trapezoidal corrugations, communicate with the microperforations, and alternately forms channels which extend towards the outside, with the outer walls of said latter channels being directly formed by the perforated wall element 4. These latter channels are suction channels designated 22 which are connected with the regions A of the microperforations of the outer wall element 4. The channels which taper off outward towards the wall element 4 are pressure channels 21 which communicate with region B of the microperforations by way of the openings in the sheet 2 with trapezoidal corrugations.

Through suction lines 12 the suction channels 22 are combined and connected to a vacuum reservoir U by way of a suitable suction pipe system S. The suction pipe system comprises a check valve 14. Through corresponding pressure lines 11, the pressure channels 21 are combined and connected to a hot-air reservoir W by way of a pressure pipe system P. The pressure pipe system P comprises a controllable pressure valve 13 which can be activated by a control unit by way of the control line 15. Finally, the embodiment shown also provides for a short-circuit line between the suction pipe system S and the pressure pipe system P in that there is a controllable short-circuit valve 16 which can be activated by the control unit 20 by way of a control line 12.

In the stationary flight state, in which there is neither ice formation nor excessive quantities of water arising from the environment, the controllable valve 13 is closed, and the check valve 14 is open, and the short-circuit valve 16 is optionally open so that sucking-off of the boundary layer from the region A and if applicable also from the region B by way of the two suction channels 22 and 21 and the two suction lines 12 and 11, towards the vacuum reservoir U, takes place.

As soon as the danger of icing or of excessive quantities of water on the outside of the wing occurs, the controllable pressure valve 13 is opened and the check valve 14 is closed so that from the hot-air reservoir P, which can for example be supplied with bleed air from an aircraft engine, hot air is introduced, by way of the pressure pipe 11 and if applicable 12, to the pressure channels 21 and 22 from which it flows outward through the microperforations in the regions A and B. In this arrangement, the pressure valve 13 should be controllable such that not too large a quantity of pressurised air is introduced into the pressure channels 21 and 22 so as to prevent the boundary layer on the outside of the wing from being disturbed. Controlling the valves 13 and 14 can take place in an attuned way and can additionally be supported by the short-circuit valve 16.

It should be noted that the term "comprising" does not exclude other elements or steps and the "a" or "an" does not exclude a plurality. Also elements described in association with different embodiments may be combined.

It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims. List of reference characters

1 Wing 2 Partition wall (sheet with trapezoidal corrugations) 3 Microperforations 4 Outer wall element (of the wing) 5 Space 6 Inner wall element 11 Pressure line 12 Suction line 13 Controllable pressure valve 14 Check valve 15 Control line 16 Short-circuit valve 20 Control unit 21 Pressure channels 22 Suction channels 28 Baseline of the sheet with trapezoidal corrugations 29 Open side of the sheet with trapezoidal corrugations