The Heinonen HK-1 Keltiäinen[1] is a Finnish single-seat, single-engined sport aircraft of the 1950s. Only a single example was built, which was used by its designer to set a class distance record in 1957 that stood for 18 years before being beaten.

HK-1
Role	Sport aircraft Type of aircraft
National origin	Finland
Designer	Juhani Heinonen
First flight	August 1954
Status	Sole example in the Finnish Aviation Museum
Number built	1

Design and development

Juhani Heinonen, an aeronautical engineer who had previously worked for the Valmet aircraft factory at Tampere, and then for Finnair, designed a single-seat, single engined aerobatic sport aircraft, the Heinonen HK-1. It was a low winged monoplane of all-wooden construction, powered by a Walter Mikron air-cooled inline engine rated at 48 kilowatts (65 hp) driving a two-bladed propeller. Split flaps were fitted to the wings, while the aircraft had a fixed tailwheel undercarriage, with a steerable tailwheel but no brakes. The pilot sat under a sliding perspex canopy.[2][3] A prototype was built at the glider school at Jämi,[4] first flying in August 1954.[2]

Operational history

The HK-1 was displayed at the 1955[5] and 1957 Ypenburg airshows.[6] On 10 July 1957, Heinonen flew the HK-1, fitted with an additional ventral fuel tank,[3] non-stop between Madrid, Spain and Turku in Finland, covering a distance of 2,844 kilometres (1,767 mi) in 17 hours 1 minute, setting a class world distance record for aircraft of less than 500 kilograms (1,100 lb) take-off weight.[7][8] For this flight, Heinonen was awarded a Louis Blériot medal by the Fédération Aéronautique Internationale.[9] This record was not broken until 2 July 1975.[10]

The aircraft is now preserved at the Finnish Aviation Museum near Helsinki Airport.[1]

Specifications

Data from Jane's All The World's Aircraft 1956–57[2]

General characteristics

• Crew: 1
• Length: 5.35 m (17 ft 7 in)
• Wingspan: 6.86 m (22 ft 6 in)
• Height: 2.08 m (6 ft 10 in)
• Wing area: 7.0 m² (75 sq ft)
• Aspect ratio: 6.8:1
• Empty weight: 250 kg (551 lb)
• Gross weight: 400 kg (882 lb)
• Fuel capacity: 58 L (13 imp gal; 15 US gal)
• Powerplant: 1 × Walter Mikron III air-cooled inverted four-cylinder inline engine, 48 kW (65 hp)

Performance

• Maximum speed: 215 km/h (134 mph, 116 kn) at sea level
• Cruise speed: 185 km/h (115 mph, 100 kn)
• Range: 700 km (430 mi, 380 nmi)
• Rate of climb: 4.5 m/s (880 ft/min)
• Take-off distance to 15.25 m (50 ft): 240 m (790 ft)
• Landing distance from 15.25 m (50 ft): 350 metres (1,150 ft)

See also

Aircraft of comparable role, configuration, and era

• PIK-11

Notes

References

Wikimedia Commons has media related to Heinonen HK-1.

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