Helio STOL Experimental

Helio was founded 1948 as Helio Aircraft Corporation to develop the two-seat Koppen-Bollinger lightplane. Otto Koppen may best be known as the creator of the Helio, the first modern short-takeoff airplane. "We built the Helio before STOL was invented," Koppen remembers. "I felt that an effective short-field airplane shouldn't have to fly at the obstacle, it should be able to fly around it." Koppen wanted an airplane that could climb steeply and maneuver safely at low airspeeds and high angles of attack.
The Helio development model, put together in 1944, was a Piper Vagabond with an 80-horsepower engine swinging a nine-foot prop. Leading-edge slots and full-span flaps completed the rig. With the propeller turning at a maximum 960 rpm, the airplane took off in 125 feet. It climbed steeply with two people aboard, and it flew quite happily at 26 mph.