A core structure used to form a cooling configuration in a gas turbine engine airfoil comprising: a first core element including a leading edge section, a tip section integral with the leading edge section, and a turn section integral with the leading edge and tip sections (30, 32) and joining the leading edge and tip sections (30, 32), the first core element adapted to be used to form a leading edge cooling circuit in a gas turbine engine airfoil, the leading edge cooling circuit including a cooling fluid passage comprising: a leading edge portion formed by the first core element leading edge section, the leading edge portion extending radially through the airfoil adjacent to a leading edge (L E) of the airfoil; a tip portion formed by the first core element tip section, the tip portion extending chordally from adjacent to the leading edge (L E) of the airfoil to adjacent to a trailing edge (T E) of the airfoil; and a turn portion formed by the first core element turn section, the turn portion facilitating fluid communication between the leading edge portion and the tip portion of the cooling passage; wherein each of the leading edge portion, the tip portion, and the turn portion of the cooling fluid passage are adapted to be formed concurrently in the airfoil by the first core element, characterized in that the leading edge section of the first core element includes a plurality of helical ridges extending circumferentially and radially with respect to a radial axis (R AC) of the leading edge section, the ridges forming corresponding helical grooves extending into a surface of the airfoil defining an outer boundary of the leading edge portion of the cooling passage, wherein the grooves effect a helical flow pattern for cooling fluid flowing radially outwardly through the leading edge portion of the cooling passage. a first core element including a leading edge section, a tip section integral with the leading edge section, and a turn section integral with the leading edge and tip sections (30, 32) and joining the leading edge and tip sections (30, 32), the first core element adapted to be used to form a leading edge cooling circuit in a gas turbine engine airfoil, the leading edge cooling circuit including a cooling fluid passage comprising: a leading edge portion formed by the first core element leading edge section, the leading edge portion extending radially through the airfoil adjacent to a leading edge (L E) of the airfoil; a tip portion formed by the first core element tip section, the tip portion extending chordally from adjacent to the leading edge (L E) of the airfoil to adjacent to a trailing edge (T E) of the airfoil; and a turn portion formed by the first core element turn section, the turn portion facilitating fluid communication between the leading edge portion and the tip portion of the cooling passage; a leading edge portion formed by the first core element leading edge section, the leading edge portion extending radially through the airfoil adjacent to a leading edge (L E) of the airfoil; a tip portion formed by the first core element tip section, the tip portion extending chordally from adjacent to the leading edge (L E) of the airfoil to adjacent to a trailing edge (T E) of the airfoil; and a turn portion formed by the first core element turn section, the turn portion facilitating fluid communication between the leading edge portion and the tip portion of the cooling passage; wherein each of the leading edge portion, the tip portion, and the turn portion of the cooling fluid passage are adapted to be formed concurrently in the airfoil by the first core element, characterized in that the leading edge section of the first core element includes a plurality of helical ridges extending circumferentially and radially with respect to a radial axis (R AC) of the leading edge section, the ridges forming corresponding helical grooves extending into a surface of the airfoil defining an outer boundary of the leading edge portion of the cooling passage, wherein the grooves effect a helical flow pattern for cooling fluid flowing radially outwardly through the leading edge portion of the cooling passage.