Ka-20 Harp / Ka-25 Hormone
The Kamov Ka-20 (NATO codename Harp) was a Soviet specialised anti-submarine helicopter that was a precursor of the Ka-25. The Ka-25 was the end result of a 1957 Soviet navy requirement for a shipborne anti submarine warfare helicopter. In response Kamov developed the Ka-20 which flew for the first time during 1960. In July 1961 the Kamov Ka-20 Harp appeared for the first time during the Soviet Aviation Day celebration carrying two mock air-to-surface missiles.
The Kamov Ka-20 was a twin-turbine helicopter powered by two Glushenkov 670kW turboshaft engines providing a top speed of 220 kmh and a range of 650 km. The Ka-20 was much larger than the Ka-18. Although larger and with twin turbine powerplant, it was clearly derived from the Ka-15 and Ka-18, and judging by a search radar housing beneath the forward fuselage was considered to be a new anti-submarine helicopter. It has since come to be regarded as the prototype of the Ka-25 (NATO reporting name 'Hormone').
The Ka-25 helicopter was a major milestone in the history of the naval combat shipboard and carrier-borne aviation. This was the first dedicated combat helicopter designed in the Soviet Union. The emergence of the Ka-25 was inseparably connected with the creation of the ocean-going Navy and with ensuring a reliable anti-submarine defence. The deployment of the Polaris naval strategic nuclear missile system in the USA acted as a catalyst accelerating development of aircraft carrying ships in the USSR. The Ka-25 Hormone helicopter was developed to meet a Soviet Naval Air Force specification for an anti-submarine helicopter for ship or shore-based use. Its main role is the destruction of nuclear submarines.
The first Ka-25 prototype flew in 1961 with test pilot D.K.Yefremov at the controls. The State acceptance trials of the Ka-25 were completed in 1968. Designed by the world's leading pioneer of co-axial helicopters, Nikolai I. Kamov (1902-1973) this Soviet AV-MF (naval aviation) anti-submarine warfare rotary wing aircraft was assigned to the Soviet Helicopter Carrier Moskva. The Hormone is powered by two GTD-3F turboshaft engines developed by V.A.Glushenkov, installed side-by-side above the cabin, that drive two, three-bladed coaxial, contra-rotating rotors. The contra-rotating rotors eliminated the need for an anti-torque tail rotor, and made a very compact design possible, with obvious benefits for shipboard operations. Hormone cannot hover or dip at night.
For the Ka-25 the OKB developed a co-axial rotor system which was fully up to the latest achievements of scientific knowledge and to the technologies currently in use in the country. In subsequent co-axial helicopter types only minor changes were made to some elements of the rotor system to improve their design, production technologies and maintainability. The co-axial helicopter''s aerodynamically symmetrical layout, coupled with the autopilot, sophisticated avionics suite and good handling qualities, enabled one pilot to fulfil long-endurance combat tasks under any weather conditions.
For the first time, Kamov designers fitted a rotary-wing aircraft with a mission avionics suite and weapons system which allowed the helicopter to navigate above water surface devoid of any reference points and fulfill the task of locating and destroying a submarine, both in manual and automatic mode. They achieved this by skilfully joining the efforts of a large number of cooperating enterprises. During prototype construction the designers - for the first time in OKB history - had to adapt it to the ship. One of the big problems was the fact that space on a ship is extremely limited and every square metre has to be used to the full. The company''s specialists were well aware of that - and achieved an excellent result: the Ka-25''s take-off weight increased 5-fold compared to that of the Ka-15 for an increase in dimensions by a factor of only 1.6. To reduce the rotor-craft''s dimensions for hangar stowage during cruise, the designers created an electromechanical rotor blade folding system. This made the helicopter quite compact; e.g., overall length with the blades folded was only 11.0m.
Most of the Ka-25 helicopters are equipped with pneumatic "shoes" at each of the four pillars of seating, providing the necessary buoyancy, and automatically inflate during an emergency landing on water.
Two versions of the helicopter were designed in parallel: the Ka-25PL and the Ka-25Ts. The former is a submarine hunter equipped with weapons, the latter is a reconnaissance platform tasked with seeking out surface targets and designating them to the powerful artillery and rockert weapons placed on ships and at coastal bases. The airframe, rotor system and powerplant of these helicopters were designed with a maximum degree of commonality. Three variants were in operation. These options were: "Hormone-A" - the main deck anti-helicopter, "Hormone-B" - a helicopter for electronic discovery purposes, which, using its radar data to provide guidance and control ship dozvukovymi missiles, "Hormone-C" - a helicopter search rescue and general stores.
About 460 were built between 1966 and 1975. They replaced the piston-engined Mi-4s in the Soviet Navy and Naval Air Force. All in all, 18 different modifications of the Ka-25 were designed and built, i.e. the Ka-25PL basic ASW version, the Ka-25Ts over-the-horizon (OTH) targeting version, the Ka-25PS SAR version, the Ka-25BT mine countermeasures version, the civil Ka-25K flying crane etc. The Ka-25PL was exported to India, Syria, Bulgaria, Vietnam and Yugoslavia. 12 Soviet Navy Ka-25BTs took part in minesweeping operations in the Suez Gulf.
Late serial options to be equipped with two engines turbovalnymi Glushenkov GTD-3BM capacity of 738 kW (990 hp). Civilian version of the Ka-25K is still in flight operation and is used as a flying crane or as a passenger aircraft with 12 passengers on the deployment of folding seats along the walls of the cabin. Such an arrangement is allowed to use a helicopter and a cargo.
Even in the life Of N.I.Kamova in 1968 the OKB accepted participation in the competition of preliminary designs to the army transport- combat helicopter. To Defense Ministry was proposed modification KA-25 the KA-25F on ski landing gear. The armament of the combat apparatus included 23- mm mobile gun with the fire unit of 400 cartridges, six blocks OF BUNKS UB-16, of six PTUR "phalanx" and bombs. Project KA-25F obtained the positive conclusion of institutes VVS; however, the final decision of customer was nevertheless in favor another participant in the competition - the Mi-24 helicopter.
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