This prototype, the first successful STOL aircraft built in the United States, was controllable down to 27 mph.
Engine: Continental A-65, 65 hp (Smithsonian caption)
President of Helio Aircraft Corp., Lynn L. Bollinger, described Helio No. 1 as first successful pioneering attempt in US to develop short-field airplane with sufficient control and stability to permit day-to-day STOL operations even in unfavorable wind conditions. Had good control characteristics down to 28 mph. Aircraft is highly modified Piper Pioneer. Successor, Helio Courier, used identical high-lift and control devices to make short takeoffs and landings (under 40 mph) practical under operational conditions. Bollinger claims first US design capable of taking off and landing within 500 ft over 50 ft barriers with adequate control and stability. Automatic slat used in combination with high- lift slot and flap not new when first Helioplane built. A unique factor in Helio design was use of lateral roll control augmentor which appears physically similar to a spoiler. Although functions as spoiler, more importantly, is aerodynamically placed so controls flow of air through slat gap and, thus, influences pressure pattern for leading edge slat. Bollinger credits Prof. Koppen's skillful design and placement of other aerodynamic control surfaces (in combination with roll control augmentor) as basis for successful and practical STOL aircraft.