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Mi-4 Helicopter Modifications

In the course of its operational life the Mi-4 was constantly upgraded. From 1958 the baseline troop-carrier version was built under the designation Mi-4A (Mi-4ADT, desahntno-trahnsportnyy). It differed from the original production Mi-4 in having rotor blades of improved design, increased stabilizer area and the AP-31 autopilot. The service life of the Mi-4A's main assemblies exceeded 600 hours. By the mid-1970s the helicopter's designated service life exceeded 10,000 hours.

The Mi-4 and the Mi-4A served as a basis for more than 30 military and civil versions. Some of them are described below:

  • The Mi-4GF was the factory designation for a "demilitarised" version of the Mi-4 intended for use in the Civil Air Fleet (hence the GF for Grazhdahnskiy [vozdooshnyy] flot).
  • The Mi-4M (Mi-4VM) was an anti-submarine warfare (ASW) developed in 1953 (originally designated VM-12, the M standing for morskoy - maritime). The ventral gondola of the Mi-4M accommodated a navigator/WSO; a Koors (Heading) search radar, later replaced by the Rubin-V (Ruby-V, pronounced roobin) radar in the updated Mi-4MR version, was installed under the nose; the fuselage housed the Baku sonar system, an extra fuel tank and a rescue dinghy. The armament comprised depth charges carried externally on the fuselage sides, and sonobuoys were dropped through a hatch in the floor of the cargo hold. In 1955 a mine-sweeping version designated Mi-4BT (booksirovschchik trahla) was evolved from the Mi-4M; it was equipped with inflatable floats for waterborne operations. A version produced in 1957 and equipped with the "Rion" experimental sonar, bore the manufac-turer's designation Mi-4RI
  • The Mi-4ME was brought out in 1964 as an export version of the Mi-4M ASW variant.
  • The Mi-4MT was a torpedo-carrying ASW attack ("killer") aircraft derived from the Mi-4M in 1963. It could carry a PLAT-1 air-launched ASW torpedo, or a Kondor rocket, or depth charges with a total weight of 520 kg (1,147 lb); due to the lack of a search radar it could only be used together with the Mi-4M. In 1963 the Mil OKB developed a "hunt-and-kill" weapons system comprising the Mi-4MU attack helicopter (U stands for oodahrnyy - attack, used attributively), the Mi-4MO search helicopter equipped with an Oka sonar (hence the O) and the Mi-4MS search helicopter equipped with a Soora infra-red sensor (hence the S) for initial detection.
  • The Mi-4P (Mi-4VP, passazheerskiy) was a passenger version developed in 1954. It dispensed with the ventral gunner's gondola; the clamshell doors of the cargo hold were replaced by a fairing and the circular windows gave way to rectangular ones. The passenger cabin was fitted out with sofas; a toilet and a baggage compartment were provided in the aft fuselage. The basic passenger version was designed to carry 8 to 11 passengers. In 1957 a 10-passenger version with seats from the Il'yushin Il-18 airliner was developed. In the 1960s a 13-seat version featuring wider windows was built in series. The Mi-4P became the first helicopter in the USSR to be used on scheduled passenger services. At that time it was operated on approximately 100 local passenger routes.
  • The Mi-4A (Mi-4VA, Mi-4SKh) was an agricultural modification developed in 1954. It had a spreader for dry chemicals instead of the ventral "bathtub", spraybars on the fuselage sides and a hopper for chemicals inside the cargo hold. Another agricultural version designated Mi-4s (with a lower-case "s", for sel'skokhoziai-stvennyy) appeared in 1968. It featured modernized equipment and strap-on chemical hoppers flanking the fuselage.
  • The Mi-4L (Mi-4VL) was a fire-fighting version built in 1954 to combat forest fires (L = lesopozharnyy). It could transport a landing party of up to 8 firemen and could extinguish a fire by means of a water cannon placed in a ventral gondola; besides, it could use chemical agents against a fire. Tanks with a fire retardant were installed in the cargo hold.
  • The Mi-4FV (Mi-4KV) "photographic and guidance helicopter" fitted with the Kvarts-49 (Quartz-49) device for remotely controlling a naval target boat was tested in 1955. The Mi-4Schch was a "polar version" developed in 1955 for working at the Soviet Arctic and Antarctic research stations.
  • The Mi-4M (second use of designation; M = meditsinskiy) was an ambulance version developed in 1956 for the Soviet Ministry of Health. Some examples of the Mi-4 were converted to "flying operating theatres".
  • The Mi-4SP (spasahtel'nyy) was a special rescue modification developed in 1956. It was fitted with a winch and a boom on port side of the fuselage and carried search radio stations and inflatable rafts and boats. The crew included a medical attendant.
  • The Mi-4PG was the first experimental version equipped with an external load sling system; it appeared in 1956.
  • The Mi-4SV (severnyy - "Northern") was a version with improved heat insulation developed in 1956 specially for working in the Far North.
  • The Mi-4 with the Pristavka (Add-on) radio equipment was deve-loped in 1957 for the guidance of remote-controlled reconnaissance balloons.
  • The Mi-4S (salon) with a VIP interior, the first of its kind. This seven-seat helicopter was built in 1957 for the government of Yemen. Two years later special six-seat "salon" versions were developed by the Mil OKB for the Soviet Government and the Soviet Air Force command. They had improved soundproofing and vibration protection and a more effective communications suite.
  • The Mi-4N "Filin" (Horned owl) was an experimental reconnaissance version intended for night-time operational use; it was built in 1958.
  • The Mi-4PS (poiskovo-spasahtel'nyy) was a search and recue version developed in 1958. It was equipped with the Rubin-V search radar, two additional fuel tanks in the cargo hold, a hoist, rescue means, and light beacons. Marker bombs producing colour spots on the water surface were carried on external racks. The helicopter was equipped with inflatable flotation gear enabling it to land on water.
  • The Mi-4 minelayer version was produced by converting troop-carrier helicopters. The rear clamshell doors were removed and a conveyor-type device for laying anti-tank mines was installed in the opening.
  • The Mi-4 modified for transporting and laying gas pipes was developed in 1961. This version was intended for use in the construction of gas pipelines.
  • The Mi-4KK and Mi-4KU were mobile command posts for uninterrupted control of Air Force units assigned for the support of Ground forces. The post comprised two helicopters: the Mi-4KK (Mi-4VKP) command post and the Mi-4KU (Mi-4VPU) heliborne post for controlling Air Force units. The two helicopters could operate both jointly and independently.
  • The Mi-4U was a target designator carrying the Oospekh (Success) system designed to detect ground and maritime surface targets and supply the target information to the Navy's missile systems. It was built in 1961.
  • The Mi-4GR was a version fitted in 1963 with the Grebeshok-3 (Haircomb-3) wide-range panoramic detection and relay radar.
  • The Mi-4TARK (televizionnyy aviatsionnyy razvedyvatel'nyy kompleks) was a TV-equipped artillery reconnaissance and spotting helicopter developed in 1963 to 1964.
  • The Mi-4MK (Mi-4PP - posta-novschchik pomekh) was an ECM version developed in 1964. It was equipped with the Mayak-3 (Beacon-3) jammer and additional antennas.
  • The Mi-4 with the Panorama 360 ciné camera system was produced by conversion in 1965.
  • The Mi-4AV (vo'oroozhonnyy, armed). The development of armed versions based on the Mi-4A began in 1958. Several versions were designed, featuring light, medium and heavy armament which included machine-guns, cannon, bombs and missiles. In 1960 two versions were built for demonstration purposes. One of them carried six UB-16-57 pods on outriggers, with sixteen KARS-57 unguided rockets apiece; the other one was armed with two pods, each pod containing six TRS-132 rockets stabilised by rotation due to canted jet nozzles. The lukewarm attitude of the Armed Forces command caused a delay in the service introduction of armed helicopters. Only in 1965, after the successful completion of firing tests conducted with two Mi-4As (each armed with eight UB-16-57 pods holding 16 KARS-57 rockets apiece), the Mil OKB received a go-ahead for developing a production version of the armed Mi-4. The result was the Mi-4AV battlefield support helicopter developed in 1967 for close air support of ground troops. It was fitted with the K-4V weapon system which included four 9M17M Falanga anti-tank guided rockets and 96 S-5M 57-mm (2.24-in.) unguided rockets in six UB-16-57U pods. Instead of the rocket pods, six 100-kg (220-lb) bombs or four 250-kg (551-lb) bombs or napalm containers could be carried on external racks. These racks could also be used for carrying cannon or machine-gun pods. In all, nearly 185 Mi-4A helicopters were converted to armed versions. Machine-guns were installed on flexible mounts to fire through the side windows and the door opening. Starting with the Hungarian uprising of 1956, the Mi-4 helicopters took part in all the military operations conducted by the armed forces of the USSR and some other states. Various "improvised" versions of armament were often fitted by foreign operators.
  • The Mi-4UM (oopravlyayemaya mishen') was a radio-controlled target drone version developed in 1979.

Mi-4s used as testbeds. Apart from the abovementioned versions, the Mi-4 and Mi-4A were widely used as testbeds of various kinds for testing subassemblies and systems of future aircraft, as well as equipment for other branches of industry.

The Mi-4's main rotor, swashplate, powerplant, main gearbox and some control system components were used, virtually unchanged, by the Yakovlev OKB in the design of the Yak-24 heavy tandem-rotor helicopter.




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