with two rows of circumferentially spaced cooling holes 94a and 94b at their upstream end and three rows 94c 94d and 94e at their downstream end the upstream rows 94a 94b are spaced a short distance from the upstream flange 76c for maximum cooling effect two of the downstream rows 94c and 94d are similarly spaced from the downstream flange 76d but the third row 76e is formed in the inwardly facing portion 84 of the flange the cooling holes which define the two upstream and two downstream rows 94a d are inclined with respect to the tile surface by substantially equal amounts preferably these rows are angled 25 degrees to the tile surface 92 but other angles may be selected if desired the tiles forming the final row of cooling holes have a shallower angle in the example shown the holes in row 94e are formed at 15 degrees to the tile surface 92 this angle is determined by the shape of the adjoining side edge the angle is such that the holes promote a parallel flow of effusion film cooling air over the upstream edge of the neighbouring tile this flow ensures that there is a continuous film of cooling air.