Self-aspirating high-area-ratio interstage turbine duct assembly for use in a gas turbine engine

An upstream end (22) and a downstream end (24) of a channel (40) are connected to a port (44) and disposed within a low-pressure turbine nozzle (12), respectively. The channel forms a bypass fluid flow path (27) between the nozzle and an inter-turbine duct (20) comprising an annular structure. Independent claims are also included for the following: (1) gas turbine engine system; and (2) gas turbine engine performance optimization method.