With it's prototype designed and tested in 1926, The Curtiss Aircraft Company's SX-5-1 was one of the earliest ''Rotary Wing'' Aircraft (Helicopter) produced for potential US Military use. Although only one was built, and it's propulsion system was seen as too dangerous, The SX-5-1 served to spur future design prototypes of the now widely used Helicopter Aircraft. A central Engine (Pratt & Whitney Wasp), produced 420-HP. Shafts coming from the Engine generated air force which was caught by one of (4) 35-foot curved Blades (positioned over the Craft's fuselage). The resulting movement of the turning blades, created enough momentum and pull to launch the prototype several hundred feet into the air. A Pilot, using levers to angle the position of the blades, caused forward movement. The prototype achieved 70-mph and reached 1,000-feet.