12/31/2010. Remarks by Johan Visschedijk: "Dipl.-Ing. Juhani Heinonen was a Finnish aeronautical engineer and former designer at the Valmet Oy Aircraft Factory in Tampere. While employed by Finnair (Aero Oy) at Helsinki, he designed and built in his spare time at the Jämi Soaring School the HK-1. The small single-seat monoplane was powered by a 65 hp Walter Mikron III four-cylinder inverted in-line air-cooled engine, and was first flown in August, 1954.
On July 10, 1957, Heinonen set up an international distance record for light aircraft weighing less than 1,100 lb (500 kg) by flying his HK-1 from Madrid, Spain to Turku, Finland, 1,766 mls (2,844 km) non-stop in 17 hours 1 minute. The aircraft is presently part of the collection of the Finnish Aviation Museum near Helsinki airport.
Heinonen subsequently designed the HK-1B with a 65-85 hp Continental engine and revised cockpit, two examples were produced, OH-HKB c/n 002 and OH-HKC c/n 003. The HK-2 Valkuainen was a two-seater with a "stepped down" rear fuselage and an 115 hp Lycoming O-235-C1 engine. Registered OH-HKX (c/n 1) the aircraft was first flown on March 29, 1963. No further examples were produced."