Airfoil with tapered radial cooling passage

A turbine engine airfoil comprising:

• an airfoil structure having an exterior surface and an end portion, and a cooling passage extending a length radially within the structure in a direction towards the end portion, a wall portion provided between the cooling passage and the exterior surface, the cooling passage providing a convection surface on the wall portion along the length adjacent to the exterior surface, the convection surface including a generally uniform width along the length in an airfoil chord-wise direction, and the cooling passage having generally decreasing cross-sectional areas along the length in the direction, the width and the cross-sectional areas are generally perpendicular to the length, wherein the convection surface is generally fiat, and the cross-sectional areas are generally rectangular in shape, the wall portion having a uniform thickness in an airfoil thickness direction extending from a root toward a tip of the airfoil structure.