An airfoil for a gas turbine engine, comprising: a first side wall; a second side wall joined to the first side wall at a leading edge and a trailing edge, the first and second side walls extending in a radial outward direction from a base coupled to an airfoil platform; a tip cap extending between the first and second side walls such that the tip cap and at least portions of the first and second side walls form a blade tip; and an internal cooling system arranged within the first and second side walls configured to direct cooling air through and out of the airfoil, the internal cooling system including a first cooling circuit comprising: an acceleration channel generally extending in a radial outward direction and receiving cooling air from a first source, wherein at least a first section of the acceleration channel decreases in cross-sectional area along the radial outward direction such that the cooling air is accelerated through the first section of the acceleration channel and the acceleration channel is at least partially defined at a radial outer end by a transition at least partially formed by a portion of a generally chordwise wall, and the generally chordwise wall includes at least a first crossover hole angled in the chordwise aft direction; a trailing edge chamber fluidly coupled to receive at least a portion of the cooling air from the acceleration channel and extending generally in a chordwise aft direction from the acceleration channel to the trailing edge; and a tip cap passage extending between the tip cap and the generally chordwise wall in the chordwise aft direction to the trailing edge, and wherein the first crossover hole fluidly couples the acceleration channel to the tip cap passage, wherein the tip cap defines an exit hole aligned with the first crossover hole. a first side wall; a second side wall joined to the first side wall at a leading edge and a trailing edge, the first and second side walls extending in a radial outward direction from a base coupled to an airfoil platform; a tip cap extending between the first and second side walls such that the tip cap and at least portions of the first and second side walls form a blade tip; and an internal cooling system arranged within the first and second side walls configured to direct cooling air through and out of the airfoil, the internal cooling system including a first cooling circuit comprising: an acceleration channel generally extending in a radial outward direction and receiving cooling air from a first source, wherein at least a first section of the acceleration channel decreases in cross-sectional area along the radial outward direction such that the cooling air is accelerated through the first section of the acceleration channel and the acceleration channel is at least partially defined at a radial outer end by a transition at least partially formed by a portion of a generally chordwise wall, and the generally chordwise wall includes at least a first crossover hole angled in the chordwise aft direction; a trailing edge chamber fluidly coupled to receive at least a portion of the cooling air from the acceleration channel and extending generally in a chordwise aft direction from the acceleration channel to the trailing edge; and a tip cap passage extending between the tip cap and the generally chordwise wall in the chordwise aft direction to the trailing edge, and wherein the first crossover hole fluidly couples the acceleration channel to the tip cap passage, wherein the tip cap defines an exit hole aligned with the first crossover hole. an acceleration channel generally extending in a radial outward direction and receiving cooling air from a first source, wherein at least a first section of the acceleration channel decreases in cross-sectional area along the radial outward direction such that the cooling air is accelerated through the first section of the acceleration channel and the acceleration channel is at least partially defined at a radial outer end by a transition at least partially formed by a portion of a generally chordwise wall, and the generally chordwise wall includes at least a first crossover hole angled in the chordwise aft direction; a trailing edge chamber fluidly coupled to receive at least a portion of the cooling air from the acceleration channel and extending generally in a chordwise aft direction from the acceleration channel to the trailing edge; and a tip cap passage extending between the tip cap and the generally chordwise wall in the chordwise aft direction to the trailing edge, and wherein the first crossover hole fluidly couples the acceleration channel to the tip cap passage, wherein the tip cap defines an exit hole aligned with the first crossover hole.