is discharged through the rows of film cooling holes associated with each impingement cavity most of the cooling air from the supply channel 11 is metered into the adjacent p s impingement cavity 19 and then flows to the remaining impingement cavities of the rest of the airfoil s s impingement cavity 20 is connected to the p s impingement cavity 19 through the metering hole to produce impingement cooling the spent cooling air then being discharged through the row of film cooling holes onto the suction side wall cooling air from p s impingement cavity 19 flows in series along the impingement cavities along the pressure side wall 22 24 through metering holes p s cavities are connected to adjacent s s impingement cavities through the metering holes that also produce impingement cooling each p s and s s impingement cavity also includes a row of film cooling holes to discharge the spent impingement cooling air the last p s impingement cavity 24 is connected to the t e cooling circuit that includes p s impingement cavities 26 27 28 that each are connected to the one long s s impingement cavity 29 through separate metering holes the spent impingement cooling air from the long s s impingement cavity 29 is discharged out through the row of p s exit slots 30 to enhance the internal cooling performance rough surfaces are formed on the outer walls of each impingement cavity the cooling flow rate.