Mil Mi-8
The Mil Mi-8 is a medium twin-turbine helicopter, originally designed by the Soviet Central Aerohydrodynamic Institute in the 1960s and introduced into the Soviet Air Force in 1968. Russian production of the aircraft model still continues as of 2024. In addition to its most common role as a transport helicopter, the Mi-8 is also used as an airborne command post, armed gunship, and reconnaissance platform.
The Mi-8 is the world's most-produced helicopter, with over 17,000 units used by over 50 countries. As of 2015, when combined with the related Mil Mi-17, the two helicopters are the third most common operational military aircraft in the world.
Design and development
originally approached the Soviet government with a proposal to design an all-new two-engined turbine helicopter in 1959 after the success of the Mil Mi-4 and the emergence and effectiveness of turbines used in the Mil Mi-6. After design and development, the Mi-8 was subsequently introduced into the Soviet Air Force in 1967.The Soviet military originally argued against a new helicopter, as they were content with the current Mil Mi-4. To counter this, Mikhail Mil proposed that the new helicopter was more of an update to new turbine engines rather than an entirely new helicopter, which persuaded the council of ministers to proceed with production. Due to the position of the engine, this enabled Mikhail Mil to justify redesigning the entire front half of the aircraft around the single engine.
The prototype, which was named V-8, was designed in 1958 and based on the Mil Mi-4 with a larger cabin. Powered by an AI-24 2,010 kW Soloviev turboshaft engine, the single engined V-8 prototype had its maiden flight in June 1961 and was first shown on Soviet Aviation Day parade in July 1961.
During an official visit to the United States in September 1959, Nikita Khrushchev took a flight in the S-58 presidential helicopter for the first time and was reportedly extremely impressed. On Khrushchev's return, he ordered the creation of a similar helicopter, which was to be ready for the return visit by the American president, to save face. A luxury version of the Mi-4 was quickly created and Khrushchev took an inspection flight, during which Mikhail Mil proposed that his helicopter in development was more suitable. However, it would be necessary to have a second engine for reliability.
This gave Mikhail Mil the power under the orders of Khrushchev to build the original two-engined helicopter, which for the first time in Soviet history would need purpose-built turbine engines, rather than those adapted from fixed wing aircraft and an entirely new main rotor gear box that would be designed in-house for the first time. In May 1960, the order was given for Mikhail Mil to create his twin engine helicopter. The Sergei Isotov Design Bureau accepted the task of creating the engines.
The second prototype flew in September 1961.
Two months after the engines were completed by Isotov, the third prototype designated V-8A equipped with two 1,120 kW Isotov TV2 engines, made its first flight piloted by Nikolai Ilyushin on 2 August 1962, marking the first flight of any Soviet helicopter to fly with purpose built gas turbine engines. The aircraft completed its factory based testing in February 1963.
The fourth prototype was designed as a VIP transport, with the rotor changed from four blades to five blades in 1963 to reduce vibration, the cockpit doors replaced by blister perspex slides and a sliding door added to the cabin.
The fifth and final prototype was a mass production prototype for the passenger market. In November 1964, all joint testing had been completed and the Soviet government began mass production. Production started in the Kazan Production Plant, with the first aircraft completed by the end of 1965.
The Soviet military originally showed little interest in the Mi-8 until the Bell UH-1's involvement in the Vietnam War became widely publicised as a great asset to the United States, allowing troops to move swiftly in and out of a battlefield and throughout the country. It was only then that the Soviet military rushed a troop-carrying variant of the Mil Mi-8 into production. By 1967, it had been introduced into the Soviet Air Force as the Mi-8.
There are numerous variants, including the Mi-8T, which, in addition to carrying 24 troops, is armed with rockets and anti-tank guided missiles. The Mil Mi-17 export version is employed by around 20 countries; its equivalent in Russian service in the Mi-8M series. The only visible differences between the Mi-8 and Mi-17 are A) the position of the tail rotor the shape of the exhausts Dust shields in front of engine air intakes for the Mi-17. Also Mi-17 has some improved armour plating for its crew. The naval Mil Mi-14 version is also derived from the Mi-8.
The Mi-8 is constantly improving and the newest version still remains in production in 2024. However the second generation of the Mi-8 was changed to a tractor-tail rotor configuration as this configuration has increased yaw authority from the upwards advancing tail rotor blades into the downwash. The increase of the airspeed flowing over the rotor blades increases overall tail rotor effectiveness and yaw authority, whereas with the 'Pusher' tail rotor configuration the advancing rotor blade moves downwards. This decreases the airspeed across the rotor blade, reducing its overall effective yaw authority.
Operational history
Finland
The Finnish Defence Forces and the Finnish Border Guard began using Mi-8s in the 1970s, with the Finnish Air Force receiving its first, serialed HS-2, on 28 May 1973, and the second, HS-1, on 31 May 1973. Six Mi-8Ts were obtained at first, followed by further two Mi-8Ts and two Mi-8Ps. Three of the helicopters were handed over to the Border Guard Wing. One of these was lost after sinking through ice during a landing in April 1982. It was soon replaced by a new Mi-8.After their Border Guard service, the helicopters were transferred to the civil register, but shortly thereafter to the Finnish Air Force. In 1997 it was decided that all helicopters, including the remaining five Mi-8Ts and two Mi-8Ps, should be transferred to the Army Wing at Utti. All Mi-8s have now been retired. One Mi-8 is on display at the Finnish Aviation Museum in Vantaa, and one is at the Päijänne Tavastia Aviation Museum in Asikkala, near Lahti. One Mi-8T is The two final Mi-8Ts were given to Hungary in August 2011 with all the remaining spare parts.
Georgia
The Georgian air force started operating Mi-8 and Mi-17 helicopters from 1991 onwards. During the War in Abkhazia Mi-8 helicopters were used by both sides. Several were shot down, the first being a Georgian civilian Mi-8T which was destroyed in Sukhumi by an RPG-7. On 14 December 1992, a Russian Air Force Mi-8T was shot down by a SA-14 missile near Lata.On another occasions Abkhaz Mi-8MTVs were shot down by Georgian forces, by SA-14 in one case and by RPG-18 in a second case, both during 1993. In the final case, Georgian Mi-8MTV carrying civilian refugees was shot down, killing 25 people. Georgian Air Force and Police currently operate about 20 Mi-8T/MTVs.
India
The Indian Air Force inducted the Mi-8 in the 1970s as part of a growing rotary-wing fleet that evolved without centralised long-term planning. Acquired in the wake of geopolitical deals and stop-gap needs, the Mi-8 formed the backbone of medium-lift capability before being succeeded by the Mi-17.Iraq
Mi-8s were employed by the former Iraqi Army Aviation and Iraqi Air Force under Saddam Hussein. In the Iran–Iraq War of the 1980s, there were air-to-air combat between Iraqi and Iranian Army Aviation helicopters, including between Iranian Bell AH-1J Cobras and Iraqi Mi-8s.South Sudan
On 21 December 2012, a Nizhnevartovskavia owned Mi-8 working for the United Nations Mission in South Sudan was shot down and crashed near Likuangole in the South Sudanese state of Jonglei during the South Sudan internal conflict. All four Russian crewmembers on board were killed, and after some initial confusion, a UN spokesman said that the South Sudanese army confirmed on 22 December that it mistakenly fired at the helicopter.On 26 August 2014, a UTair Aviation owned Mi-8 working for the United Nations crashed as it approached a landing airstrip near Bentiu. Three of the Russian crew members died and one was injured. Rebel commander Peter Gadet claimed that his forces brought it down using a rocket-propelled grenade.
Soviet Union
The Mi-8 family of helicopters became the main Soviet helicopter, covering a large range of roles in both peace time and war time. Large fleets of Mi-8 and its derivatives were employed by both military and civil operators.Large numbers of Mi-8 family helicopters were used during the Soviet–Afghan War during the 1980s. Its rugged construction allowed easier in-theater operations and maintenance. A large number of Mi-8s were lost with several shot down by enemy fire, with the Mi-8 and its derivatives being the main aircraft model lost by the Soviet Union in Afghanistan.
Between April and May 1986, Mi-8s were used in large numbers to drop radiation-absorbing materials into the No. 4 reactor of Chernobyl Nuclear Power Plant after the Chernobyl disaster, and the fire was extinguished by the combined effort of helicopters dropping over 5000 metric tons of sand, lead, clay, and neutron-absorbing boron onto the burning reactor and injecting liquid nitrogen into it. Most of the helicopters were severely irradiated and abandoned in a giant junkyard, the so-called "machines cemetery" near Chernobyl, with several disappearing from the site in later years. During the initial operation, one crashed near the power plant after hitting a construction crane cable with all the crew of four being killed in the crash. It is now known that virtually none of the neutron absorbers reached the core.