Porous structure having laminar flow control and contamination protection

The leading edge (22) of a nacelle (20) for an aero-engine (10) is porous. The porous leading edge (22) has laminar flow control and contamination protection. At take off and landing a liquid is selectively distributed through channels (30) to regions D and F of a layer of porous material (24). The liquid permeates slowly through the pipes (32) located in the channels (30). The pipes (32) resistance to the flow of liquid therethrough causes a pressure to develop which is sufficient to dispense the liquid through the layer of porous material (24). The exuded liquid provides contamination protection at the leading edge (22) of the nacelle (20). At cruise a chamber (36) adjacent inner surface (26) of the porous layer (24) is evacuated to selectively suck air through the porous layer (24). The suction provides laminar flow control by preventing the onset of turbulence in the boundary layer air flow passing over the nacelle (20).