MATCHING studies of three turboprop engine configurations were made for flight conditions from sea-level static to 600 mph at 40,000 ft.
It is concluded that turbine frontal area, stress, and pressure ratio requirements made exhaust-area adjustment desirable. Sfc depended primarily upon flight conditions and turbine temperature, with lowest sfc occurring at highest turbine temperature, flight velocity, and altitude.
Free turbines restricted turbine temperature range and produced critical turbine requirements. Increasing a two-spool engine's outer-compressor pressure ratio increased turbine temperature range and made turbine requirements less critical.