Mil Mi-1 "Hare", Mi-2 "Hoplite", & Mi-4 "Hound" (2024)

* Soviet efforts in helicopter design after World War II paralleled those ofthe West, with a range of experimental rotorcraft finally leading to workableproduction machines. The most prominent of Soviet first-generationhelicopters, the piston-powered "Mi-1 Hare", was the product of theexperimental design bureau (OKB) led by Mikhail Mil. It led in turn to amuch larger helicopter, the piston-powered Mil "Mi-4 Hound", which wasstrongly influenced by the American Sikorsky S-55, and to a turbine-poweredderivative of the Mi-1, the "Mi-2 Hoplite". This document provides a historyand description of these early Mil helicopters, as well as the Polish PZL"W-3 Sokol" follow-on to the Mi-2.

[1] IVAN BRATUKHIN & THE ORIGINS OF SOVIET HELICOPTERS

* Soviet rotary-wing efforts began in the 1920s, under the direction of theCentral Aero-Hydrodynamic Research Institute (TsAGI in its Russian acronym).Initial work focused on autogyros, then moved on to helicopters. EarlySoviet helicopter experiments were conducted by TsAGI staff such as BorisYuriev, who had built primitive helicopters before World War I in parallelwith Igor Sikorsky's early efforts, as well as by three men who wouldestablish the Soviet helicopter industry: Ivan Bratukhin, Mikhail Mil, andNikolai Kamov.

The early history of Soviet helicopter design is muddy and confused. Itappears that a number of autogyros were developed at TsAGI during the 1930s,leading to a set of more or less unworkable experimental helicopters. Thehistorical trail becomes more solid with Bratukhin's "Omega" demonstrationprototype, with work on this machine formally authorized at Bratukhin's"OKB-3" experimental design bureau in the summer of 1941, shortly after theNazi invasion of the USSR. The Omega had a general configuration not toodifferent from the contemporary German Focke-Achgelis helicopters, withside-by-side rotors.

Development was protracted, but considering the magnitude of the militaryemergency being faced by the Soviet Union at the time, it is surprising thatany work was being done at all on such a speculative technology. In anycase, by 1944 Bratukhin was flying an improved prototype, the "Omega II",also known as the "G-2", where "G" meant "helicopter". The Omega 2 led inturn to a handful of "G-3" machines, flown in 1945, which differed mostly inbeing powered by two Pratt & Whitney Wasp Junior radial engines salvaged fromUS-supplied Lend-Lease aircraft, instead of less powerful Soviet-built MG-31Fradials available to Bratukhin. The G-3 was supposed to be used forartillery spotting, but it saw little or no operational use.

Bratukhin continued to refine his designs, but none of them would enter massproduction. A handful of "G-4" helicopters, much like the G-3 but with morepowerful Soviet-built engines, were built in 1947 and 1948, to be followed bythe scaled-up "B-5", with the "B" in honor of Bratukhin. Only one B-5 wasbuilt, flying in 1947 and proving unsatisfactory. A single "B-9", which wasa medical evacuation version of the B-5, was also completed in 1947 but it isnot thought to have flown. One "B-10", which was a largely redesignedderivative of the B-5 with an entirely new fuselage, was completed in 1947 aswell and did meet expectations. However, by this time, the authorities werebecoming discouraged with progress in helicopters in general, and theside-by-side rotor scheme in particular.

Bratukhin's final helicopter was the "B-11", with two built in 1948. It wasapparently intended just to provide a reference design for more promisinghelicopters then being built by Mil and Kamov. One of the B-11s crashed on13 December 1948, killing both aircrew on board. By that time, Sovietofficials had generally written off Bratukhin's efforts. His OKB wasdisbanded in 1951, and he went to work for other organizations.

[2] MIL MI-1 "HARE"

* The most prominent early Soviet helicopter designer, Mikhail Mil, beganwork on rotorcraft in the 1930s, when he was on the staff of TsAGI. In 1947,the Soviet state authorized Mil to form his own OKB to design helicopters.In September 1948, the Mil OKB performed the initial flight of the "GM-1"helicopter; in 1950, the state began a competition for a fully operationalhelicopter, and Mil submitted the GM-1 design. The GM-1 contended againsttwo rivals for the award, including the Bratukhin B-11 and the "Yak-100",designed by the Yakovlev OKB, well-known for their piston-engine fighters ofWorld War II.

The Mil design won the competition. Yakovlev remained in the helicopterbusiness for a few years longer, designing the "Yak-24", which was atandem-rotor helicopter along the lines of the American Piasecki "FlyingBananas" but substantially bigger, with a capacity of 40 passengers. It wasunsuccessful, with only 100 built, and the Yakovlev OKB then got out of thehelicopter business.

The first two Mil GM-1 prototypes were lost in accidents, the second killingthe pilot, but the bugs were worked out, with the machine going into Red AirForce service in 1951 as the "Mi-1". It was publicly unveiled at the TushinoAir Display in 1951. NATO assigned the type the reporting name "Hare".

The Mi-1 was comparable to the Sikorsky S-51 Dragonfly in size, capability,and broad configuration, though it was clearly different in appearance(arguably more attractive, in fact) and absolutely not a clone. It featureda main rotor / tail rotor configuration, with a three-blade wooden main rotorand a similar small tail rotor; a fully-enclosed, metal-skinned fuselage;fixed tricycle landing gear, with single wheels on all gear assemblies; andaccommodations for a pilot and three passengers. It was powered by aseven-cylinder air-cooled radial Ivchenko AI-26V piston engine, providing 430kW (575 HP).

An estimated total of 1,800 Mi-1s was built in the USSR up to 1955. Alongwith the standard three-passenger Mi-1, a number of variants were built inRussian production:

• Mi-1 Moskvich: Basic Mi-1 produced with soundproofing, a metal rotor, and other refinements for Aeroflot use. Eventually, this version became standard production, and it was simply referred to as the Mi-1.
• Mi-1T: Later Soviet standard production machine. It could only carry two passengers but had a number of small refinements.
• Mi-1U: Dual-control flight trainer.
• Mi-1P: Amphibian with floats.
• Mi-1NKh: A civil utility version, which was used for agricultural spraying; light cargo and transport duties; mail carriage; and as an air ambulance, with a stretcher carried on either side of the fuselage.

The Mi-1 was used as a light general-purpose helicopter, operating in a widerange of roles such as observation, liaison, search and rescue (SAR), airambulance, and flight training. The Mi-1 was used by several branches of theSoviet armed forces, as well as Aeroflot, the state airline, and DOSAAF, theyouth air corps. It was exported to Warsaw Pact nations, Soviet clientstates around the world, and Finland.

 ___________________________________________________________________ MIL MI-1 "HARE": ___________________________________________________________________ main rotor diameter: 14.3 meters (46 feet 11 inches) fuselage length: 12.0 meters (39 feet 4 inches) footprint length: 16.95 meters (55 feet 7 inches) height: 3.30 meters (10 feet 10 inches) empty weight: 1,800 kilograms (3,970 pounds) max loaded weight: 2,400 kilograms (5,290 pounds) maximum speed: 185 KPH (115 MPH / 100 KT) service ceiling: 3,000 meters (9,840 feet) range: 620 kilometers (385 MI / 335 NMI) ___________________________________________________________________

In 1955, production was transferred to the PZL factory at Swidnik in Poland,as per a Soviet custom of assigning production of various light utility andtraining aircraft to Warsaw Pact nations. The PZL Swidnik factory built anestimated additional 1,700 Mi-1s up to 1965. They were given the designation"SM-1" and were powered by a license-built copy of the AI-26V engine with thedesignation of "LiT-3". PZL Swidnik built an improved variant, the "SM-1W",with metal blades, which was used as the basis for the "SM-1WS" airambulance, the "SM-1WZ" cropduster, and the "SM-1WSZ" dual-control trainer.

The Poles also built a substantially redesigned version of the SM-1designated the "SM-2", featuring a "fat" cabin with accommodations for apilot and four passengers. Initial flight was in 1959, with the SM-2 goinginto production in 1961 and being built in a number of different versions.

* The Mi-1 was not very powerful, but that was true of many of the earlyhelicopters in its class such as the Bell Model 47 and the Hiller Model 360,and that didn't stop the Mi-1 from being put to extensive good use in lighttransport, medical evacuation (medevac), and agricultural roles. It remainedin service long after the end of production. It is unclear if any remain inoperational service.

[3] MIL MI-2 "HOPLITE"

* In September 1961, the Mil OKB test-flew the first of two "V-2" or "Mi-2"prototypes. The Mi-2 was the USSR's answer to the US Bell UH-1 Huey and wasmore or less a turbine powered derivative of the Mi-1 with twin IsotovGTD-350 turboshaft engines, each providing 300 kW (400 SHP). The Mi-2leveraged off some Mi-1 assemblies, but the engines were mounted on top ofthe fuselage, while the Mi-1's engines had been inside the fuselage. The newengine arrangement provided much more cabin space and also made the machineless sensitive to changes in center of gravity from load arrangements.

The twin engines drove a three-blade main rotor, and a two-blade tail rotor.The main rotor blades featured a metal spar with either metal or fiberglassskinning. Both the main and tail rotors had electrical de-icing. The Mi-2had fixed tricycle landing gear, with twin wheels on the nose gear and singlewheels on the main gear. Skis could optionally be fitted over the wheels.There were two forward-hinged doors on the right and one on the left. Therewas a rubber fuel tank under the floor with a capacity of 600 liters (158 USgallons), while an auxiliary fuel tank with a capacity of 238 liters (63 USgallons) could be fitted on each side of the fuselage.

The Mi-2 had seating for a pilot on the left, but no second seat for acopilot. As a utility transport, it could carry eight passengers plus thepilot in an air-conditioned cabin; or 700 kilograms (1,545 pounds) of cargointernally; or 800 kilograms (1,765 pounds) of cargo externally on a slinghook. It could be fitted with a door winch with a lifting capacity of 150kilograms (330 pounds) for the SAR role. In the medevac role, it could carryfour stretchers and a medical attendant, and in the agricultural role itcould be fitted with a hopper on each side with a capacity of 450 kilograms(990 pounds) of dry chemicals or 500 liters (132 US gallons) of liquidchemicals. When the type became known in the West, it was assigned the NATOreporting name of "Hoplite".

 ___________________________________________________________________ MIL MI-2 "HOPLITE": ___________________________________________________________________ main rotor diameter: 14.5 meters (47 feet 7 inches) fuselage length: 11.4 meters (37 feet 5 inches) footprint length: 17.42 meters (57 feet 2 inches) height to rotor head: 3.75 meters (12 feet 4 inches) empty weight: 2,424 kilograms (5,344 pounds) max loaded weight: 3,700 kilograms (8,157 pounds) maximum speed: 200 KPH (125 MPH / 110 KT) service ceiling: 4,000 meters (13,125 feet) range, max payload: 170 kilometers (105 MI / 92 NMI) ___________________________________________________________________

* The Mi-2 was only produced in Poland. An agreement was signed with the PZLSwidnik organization in January 1964 for production, with PZL building theIsotov engines as well. The first PZL Mi-2 performed its first flight inNovember 1965. At least 5,520 were built in all to end of production in theearly 1980s. As with the Mi-1, the Mi-2 went into widespread service withSoviet forces, Warsaw Pact nations, and Soviet client states. Some Mi-2soperated by Arab forces may have fallen into Israeli hands.

Civil Mi-2s were used as utility transports, cargolifters, air ambulances,and photographic survey platforms. Military variants included:

• Mi-2RM: Naval support variant, possibly for maritime SAR.
• Mi-2US: Infantry support gunship, with fixed 23-millimeter NS-23KM cannon on the right side of the fuselage, twin 7.62-millimeter machine gun pods, and twin 7.62-millimeter machine guns on pintle mounts. A second seat was fitted to the right of the pilot's seat for a gunner, with a PKV gunsight fitted in the co*ckpit. The "Mi-2URN" was similar, but replaced the two machine gun pods with two 57-millimeter unguided rocket pods, with 16 rockets per pod.
• Mi-2URP: Antitank gunship, with pylons on each side to carry a total of four AT-3 "Sagger" (9M14M Malyutka) wire-guided antitank missiles, plus four reload missiles in the cabin, and a sighting system arrangement similar to that of the Mi-2US/UR. These machines were later fitted to carry up to four SA-7 "Grail" (9M32 Strela 2) light air-to-air missiles (AAM) for operation in the helicopter escort role. Apparently this variant was fitted with a defensive radar warning receiver (RWR) system.

A slightly improved "Mi-2B" was introduced late in production, featuring abetter electrical system and new navigation aids. It was manufactured in arange of variants similar to those of the original Mi-2, though apparentlythe number of Mi-2Bs built was relatively small. In the late 1970s, PZLSwidnik also developed a variant of the Hoplite with US Allison turboshafts,known as the "Kania (Kittyhawk"), with about a dozen built.

The Mi-2 appears to have been a straightforward, reliable, and effectivehelicopter, and many still remain in service. Indeed, the Mil and Rosvertolorganizations are now offering an "Mi-2A" upgrade, with modern turboshaftengines and avionics.

* The Mil organization did design an "Mi-3" variant in the mid-1950s, butsources are confused and confusing on the matter. Descriptions give it as anenhanced Mi-1, presumably piston-powered, with a four-blade rotor, biggercabin, and improved avionics. Whatever it really was, it did not enterproduction.

[4] MIL MI-4 "HOUND"

* The Mi-2 was actually produced out of numeric sequence, with thechronological successor of the Mi-1 being the "Mi-4", which resembled ascaled-up Sikorsky S-55 and had a similar engine arrangement, with a pistonengine providing 1,270 kW (1,700 HP) mounted in the nose and driving thefour-bladed rotor through a driveshaft running up between the pilot's andcopilot's seats. It also had a four-wheel landing gear arrangement along thelines of that of the S-55. Initial flight of the Mi-4 was in April 1952,with the type going into service in 1953. It was assigned the NATO reportingname of "Hound" -- later "Hound-A", after other variants were introduced.

The Sikorsky S-55 had gone into production in 1950, and it's hard to believethat the Mil OKB engineers weren't heavily influenced by it -- but all thatis saying is that the Soviets were smart enough to adopt good ideas when theysaw them. The S-55-type engine arrangement permitted a large cabin and easedmaintenance, since the service crew didn't have to clamber up on top of thehelicopter to work on the engine.

In any case, the Mi-4 was different from the S-55 in almost all specificdetails, as well as substantially larger, empty weight being nearly twice asmuch. The Mi-4 was powered by a Shvetsov ASh-82V two-row 14-cylinderair-cooled radial providing 1,270 kW (1,700 HP). It was originally fittedwith wooden-skinned rotor blades with an unsatisfactory lifetime of only 100hours, but that was increased to 300 hours in 1954, doubled to 600 hours in1957, and then extended to 1,500 hours in 1960 with the introduction ofall-metal rotor blades.

The Mi-4 was the first Soviet helicopter to feature hydraulically-boostedflight controls. The pilot and copilot climbed up kick-out steps to enterthe helicopter through the large sliding co*ckpit side windows, or they couldenter through the passenger door on the left. The landing gear could befitted with skis or inflatable pontoons.

The standard Mil-4 military transport version also had features not found onthe S-55, including clamshell rear loading doors and a ventral tub, with thetub used for navigator observation. Typical loads for the Mil-4 included 14fully equipped troops, or 1,600 kilograms (3,530 pounds) of internal cargo;loads could also be carried on a sling hook.

 ___________________________________________________________________ MIL MI-4 "HOUND-A": ___________________________________________________________________ main rotor diameter: 21.0 meters (68 feet 11 inches) fuselage length: 16.79 meters (55 feet 1 inch) footprint length: 25.02 meters (82 feet 1 inch) height: 4.40 meters (14 feet 5 inches) empty weight: 5,355 kilograms (11,805 pounds) max loaded weight: 7,800 kilograms (17,195 pounds) maximum speed: 210 KPH (130 MPH / 115 KT) service ceiling: 6,000 meters (19,700 feet) range: 590 kilometers (370 MI / 320 NMI) ___________________________________________________________________

A confusing range of different variants was built. Sources tend to disagreein their descriptions and designations, but highlights included:

• An "airliner" version, the "Mi-4P", was built for Aeroflot, with a capacity of 11 passengers in normal seating configuration, or 16 passengers in a high density configuration. It had larger rectangular cabin windows, in contrast to the round windows of military variants; no ventral tub; and sometimes spats over the wheels. It is unclear if it had the rear clamshell doors. There was also an "Mi-4S" VIP transport.
• An "Mi-4Skh" AKA "Mi-4A" agricultural version that was fitted with an internal dust hopper with a load of 1,000 kilograms (2,200 pounds) or a liquid dispenser with a capacity of 1,600 liters (422 US gallons); dust spreader or spray bars were fitted to each side of the machine. The "Mi-4L" was a similar fire-fighting variant.
• The "Mi-4M" was a land-based antisubmarine warfare (ASW) variant that featured a radome under the nose, and could carry sonobuoys, homing torpedoes, and possibly depth charges. An export version was built under the designation of "M-4ME". An improved version was introduced as the "Mi-4RI". It was designated "Hound-B" by NATO. There were apparently other specialized ASW fits.
• The "Mi-4MK" AKA "Mi-4PP" was a battlefield electronics warfare platform, apparently mostly used for communications jamming, and featuring dipole arrays sticking out the sides. It was introduced in 1977; given that this was very late in the Mi-4's operational lifetime, when it had been generally rendered obsolete by turbine-powered helicopters, the Mi-4MK was almost certainly a conversion of older machines.
• Relatively late in the Mi-4's service life, the type was fitted out as a gunship, designated the "Mi-4AV", designated "Hound-C" by NATO -- though some sources attribute that reporting name to the Mi-4MK jammer platform. It featured an outrigger fitted to each side that could carry six pylon stores, most generally 57-millimeter rocket pods, with four antitank guided missiles mounted on top. A machine gun could also be fitted to a flexible mount in the door on one side and a window on the other.

There were a number of special fits, including winterized and high-altitudemachines, a SAR variant, a battlefield minelayer, a variant intended to helplay gas pipelines, trials platforms, and even target drone conversions.

* About 3,500 Mi-4s were built in the USSR to end of production in 1968, andserved with Soviet forces, Aeroflot, Warsaw Pact nations, and Soviet clientstates. The Chinese built about 545 Hounds as the Harbin "Z-5", and the typewas heavily used by the People's Liberation Army.

The Soviets provided drawings to China in 1958 and the first Z-5 performedits initial flight at the end of 1959. However, Mao Zedong's government waspushing a aggressive "Great Leap Forward" economic development program at thetime -- which turned out to be a fiasco that emphasized quantity at theexpense of quality, and the Z-5 program suffered accordingly. Essentiallythe Harbin factory had to start all over again, receiving new drawings in1961 and flying a second "first prototype" in August 1963. Metal rotors wereintroduced in 1966.

The Chinese appear to have built a range of variants of the Z-5 similar tothe Mi-4 variants built by the USSR, and may have built a few unique variantsas well. They did re-engine at least one Z-5 with a Pratt & Whitney CanadaPT6T-6 "TwinPac" turboshaft in 1979.

[5] FOOTNOTE: PZL SWIDNIK W-3 SOKOL

* The Polish PZL Swidnik organization followed up production of the popularMi-2 Hoplite with a much improved successor, the "W-3 Sokol (Falcon)". Thefirst of five prototypes made its initial flight on 16 November 1979, withthe second, which featured many changes, following on 6 May 1982. The otherthree flew in 1984 and production began in 1985.

The Sokol had certain broad configurational resemblance to the Hoplite, butwas clearly more modern and capable. Like the Hoplite, it had a main-tailrotor configuration, twin side-by-side turboshafts on top of the fuselage,and a tricycle landing gear arrangement that seemed to have been inheritedfrom the Mi-2 with little change. The two PZL Rzeszow TWD-10W turboshaftswere much more powerful than the Hoplite's Isotov engines, providing 769 kW(900 SHP) each; and the rotorcraft was fitted with a modern four-blade mainrotor system, the blades featuring swept tips, along with a three-blade tailrotor.

The fuselage featured hinged co*ckpit doors, sliding doors on both sides, andaccommodation for 12 passengers. Including fuel, the Sokol could handle aload of up to 2,100 kilograms (4,630 pounds). There were fuel bladders underthe floor providing a total internal fuel capacity of 1,700 liters (449 USgallons), and an auxiliary fuel tank with a capacity of 1,100 liters (290 USgallons) could be carried as well.

 ___________________________________________________________________ PZL SWIDNIK W-3 SOKOL: ___________________________________________________________________ main rotor diameter: 15.7 meters (51 feet 6 inches) fuselage length: 14.21 meters (46 feet 8 inches) footprint length: 18.79 meters (61 feet 8 inches) height to rotor head: 4.12 meters (13 feet 6 inches) empty weight: 3,300 kilograms (7,275 pounds) normal take-off weight: 6,400 kilograms (14,110 pounds) maximum speed: 235 KPH (145 MPH / 125 KT) service ceiling: 4,650 meters (15,250 feet) range: 1,225 kilometers (760 MI / 660 NMI) ___________________________________________________________________

A total of 51 standard W-3 transports was built, with this total including13 sold to Myanmar / Burma, and the rest flying in Polish service. Two ofthe Burmese and one of the Polish machines were built as VIP transports,sometimes referred to with the designation "W-3P". Other variants of thebaseline W-3 included:

• The "W-3W" armed assault transport, with a GSh-23 two-barrel 23-millimeter cannon mounted on the right side of the fuselage; hardpoints for bomblet dispensers, mine dispensers, or unguided rockets; and six ports in the windows to allow infantry to fire assault rifles or light machine guns. 5 were built for the Polish Air Force and 16 were built for the Polish Army. There were various confusing incarnations of a dedicated gunship, the "W-3H Huzar (Hussar)", but nobody bought off on it.
• The "W-3RM Anakonda", an offshore SAR variant, with seven built for the Polish Navy, including one that ended up in Ukraine. The Anakonda featured a watertight fuselage, six flotation bags, a winch, and modified doors with extra windows. From 2010, the Polish Navy decided to upgrade six Anakondas -- one having been lost in a crash -- plus two transport W-3s to an improved Anakonda standard, in particular getting rid of Russian-made avionics. The eight upgraded machines were redelivered from 2017 to 2020.
• A single "S-1RR" electronic intelligence variant for the Polish Air Force, followed by at least one "SRR-10" machine built to a slightly improved standard.

* With the fall of the Soviet Union, the Poles quickly turned their attentionto the West, with following Sokol variants built with Westernized avionics.The type is still in production and it seems that PZL Swidnik is making a tidy business from it, though its sales are modest relative to those ofhelicopter giants such as Sikorsky and Airbus Helicopter. Incidentally,as of 2010 PZL Swidnik is an arm of the Leonardo defense group, previouslyAgusta Westland. Modern variants of the W-3 include:

• The "W-3PL", an improved W-3W combat transport with modernized avionics, including a "glass co*ckpit"; Rafael Toplite sensor-sighting system; a 12.7-millimeter machine gun in an undernose turret, instead of the 23-millimeter cannon; a weapons management system, with the option of using guided munitions; and defensive countermeasures. It is available as new-build or as an upgrade to the W-3W.
• The "W-3RL", a combat SAR variant, with two upgraded from standard W-3 transports for Polish service. The W-3RL featured NATO-compatible radios and IFF, plus a GPS navigation receiver; a searchlight; a rescue hoist; accommodations for two stretchers and a medic; and internal auxiliary fuel tanks. Apparently three more CSAR machines were obtained by the Poles that were fitted to an improved avionics standard, based on the W-3A variant, described following.
• The "W-3A", basically a baseline transport with Westernized avionics for foreign sales, first flown in 1992. 11 were sold to the Czech Air Force, two to the German police, three to South Korea, and three to various Polish organizations. A "W-3AM" variant, similar to the W-3A but with six inflatable flotation bags, was also built, with six sold to South Korea and one sold in Poland. In addition, a "W-3AE" medevac variant was offered as well.
• The "W-3WA", an armed variant of the Westernized W-3A featuring a similar weapons configuration to the W-3W, with at least 19 delivered to the Polish Air Force, Army, and Navy.
• The "W-3PPD", a flying command post for the Polish Army featuring items such as a MIL-STD 1553B databus and color workstations, with provision for defensive armament. Four were obtained from 2001.
• The W-3RM Anakonda naval SAR variant has been followed by work on the W-3 "Gluszec" armed multi-role naval helicopter, capable of transport, SAR, surface warfare, and ASW missions.

Studies were conducted for a stretched "Sokol Long" assault transport, withseating for 14 fully-equipped troops. It didn't happen, but with the Sokolstill in production, it may not be entirely dead.

[6] COMMENTS, SOURCES, & REVISION HISTORY

* Soviet-era aircraft tend to be "under-documented" in the West, though thathas been changing since the fall of the USSR, and documentation onhelicopters in general tends to be scarce as well. The result is that thisdocument still leaves much to be desired in terms of completeness, and likelyaccuracy as well. In its defense, for the moment there doesn't seem to bemuch better data available, and it also provides a useful framework forplugging in more information as it becomes available.

* Sources include:

• HELICOPTERS & OTHER ROTORCRAFT SINCE 1907 by Kenneth Munson, 1968
• MODERN FIGHTING HELICOPTERS by Bill Gunston & Mike Spick, Crescent Books, 1986
• THE ENCYCLOPEDIA OF WORLD MILITARY AIRCRAFT, edited by David Donald & Jon Lake, Barnes & Noble, 2000

Some details were also scavenged from various editions of JANE'S ALL THEWORLD AIRCRAFT.

* Revision history:

 v1.0.0 / 01 feb 05 v1.0.1 / 01 feb 07 / Review & polish. v1.0.2 / 01 feb 09 / Review & polish. v1.0.3 / 01 jan 11 / Review, added Ansat helicopter. v1.0.4 / 01 dec 12 / Review & polish. v1.0.5 / 01 nov 14 / Review & polish. v1.0.6 / 01 oct 16 / Review & polish. v1.0.7 / 01 sep 18 / Review & polish. v1.0.8 / 01 jul 20 / Review & polish. v1.0.9 / 01 may 22 / Review & polish. v1.1.0 / 01 apr 24 / Review & polish.