A bifurcation aerofoil having a leading edge portion and flanks where the leading edge portion is mounted to an inner wall of the bypass duct using a floating seal which permits circumferential movement of the leading edge. A cowl has a wall that provides the flanks of the aerofoil. On closing of the cowl into its flight position any contact between the flanks and the leading edge portion enables realignment of the leading edge portion to the inner wall of the bypass duct.