Pull the cowling off a King Air and the PT6 looks like somebody installed it backwards. They did not. It is a reverse-flow engine, and every bit of that layout is deliberate. Air enters a scoop near the propeller, travels aft along a duct, then turns 180 degrees through a screened annular inlet at the very back of the engine. From there it flows forward, against the direction of flight. The internal running order, front to back: - Propeller and epicyclic reduction gearbox - Exhaust stubs, sitting just behind the spinner - Power turbine - Compressor turbine - Annular reverse-flow combustor - Centrifugal impeller - Three or four axial compressor stages - Inlet screen and accessory gearbox Air moves forward through the axial stages, then the impeller flings it radially outward into a ring of diffuser tubes. Those tubes turn the flow aft into the combustion liner. Fuel is added, the mixture burns, and the gas reverses a second time to head forward into the compressor turbine nozzle. T...