To meet a Soviet Naval Air Force specification in the late fifties for an antisubmarine helicopter for ship or shore-based use, the Kamov bureau developed a helicopter powered by twin turbines installed side-by-side above the cabin, with two three-bladed coaxial, contra-rotating rotors as on their other aircraft. It was first seen at the Tushino air display in July 1961 and was assigned the NATO reporting name Harp.
The Harp was characterized by a large radome under the nose and a fairing beneath the tail boom. The armament consisted of two fixed machine guns in the nose and two small missiles at the sides of the fuselage.
The Ka-20 was later developed as the Ka-25 shipboard and shore-based antisubmarine helicopter. Despite the small number of changes made in the transition from prototype to production standard, the reporting name Harp was not continued, the Ka-25 being allocated the name Hor-mone.
Rotor diameter: 15.74 m (51ft 8 in)
Length: 9.83 m (32ft 3 in)
Weight: 7300 kg (16 100 lb)
Powerplant: 2900-shp Glushenkov GTD-3 turbo-shafts
Range: 400 km (250 miles)
Maximum speed: 220 km/h (137 mph)