AIRFOIL COOLING PASSAGES HAVING HOURGLASS SHAPE

An airfoil (78) includes pressure and suction side walls (86, 88) that extend in a chord-wise direction between leading and trailing edges (82, 84). The pressure and suction side walls (86, 88) also extend in a radial direction to provide an exterior airfoil surface. A cooling passage (106, 107, 109) that has an hourglass shape is arranged between the pressure and suction walls (86, 88). The cooling passage has a first width (W) in the chord-wise direction near the suction side wall (88), a second width (W) in the chord-wise direction near the pressure side wall (86), and a third width (W) between the pressure and suction side walls (86, 88). The third width (W) is smaller than the first and second widths (W, W).