US Patent 7713029 Turbine blade with spar and shell construction

A turbine blade with a spar and shell construction in which the spar includes a blade tip and a dove-tail on the root end of the spar. A pair of platform halves form a fir-tree attachment capable of sliding into an attachment slot formed within a rotor disk. The platform halves form a slot within the fir-tree configuration that will pinch the dovetail slot of the spar and secure the spar to the platform halves against radial displacement. The shell is secured between the spar tip and the platform of the platform halves when assembled together. The spar includes cooling air passages and impingement cooling holes to provide backside impingement cooling of the shell. A fastener secures the two platform halves together so that the spar and shell blade assembly can slide into the attachment slot within the rotor disk.