25-Jun-2021 Source: Russian Helicopters
60 years ago, on June 24, 1961, Mi-8 took off for the first time, ultimately becoming the most widely used twin-engine helicopter in aviation history. It is called the “helicopter with hundred professions” that can be seen all over the world: over 13,000 have been delivered to more than 80 countries.
The development of Mi-8 by Mil Design Bureau began in the second half of the 1950s. Chief Designer Mikhail Leontyevich Mil believed that gas turbine engines would achieve a revolution in helicopter construction and make a breakthrough both in flight performance and economic efficiency of rotorcraft, and therefore conceived to equip the new model with such engines.
The construction of initial five prototypes began in 1958 under the designation V-8. Domestic gas turbine engines for helicopters were still under development at that time, so the first prototypes used on V-8 were single-engine AI-24 aircraft engines, specially modified for installation on a helicopter.
On June 24 in 1961, the first V-8 prototype took and made a short hover. The crew was commanded by an experienced test pilot, veteran of the Great Patriotic War Boris Vladimirovich Zemskov. Two weeks later, on July 9, the prototype took part in the aviation parade at the Tushino airfield by flying a circle. In 1962, the prototype V-8A began flight tests equipped with two TV-2-117 engines specially designed for the helicopter.
The new model was initially intended as simple replacement for the Mi-4 transport helicopter, but ultimately Mi-8 received a completely different layout with reversed locations of the power plant and the cockpit. This design solution allowed a person of average height to walk through the cabin with a straight back, and the height of the tail was sufficient to let a car to pass inside the cargo compartment. During further development and testing, the new model started diverging even more from Mi-4: more extensive cockpit glass, a five-blade rotor, a three-wheel landing gear. This way, the chief designer Mikhail Mil laid the foundation for the long life of this helicopter. For decades, Mi-8 has served as a transport helicopter with virtually no alternatives in remote and inaccessible areas around the world.
In 1965, after necessary changes and improvements, the serial production of the new helicopter was launched at Kazan Helicopter Plant (back then called Factory no. 387). The civilian passenger modification was named Mi-8P, and the airborne troop transport version Mi-8T. The helicopter quickly became highly in demand, and in 1970 its production began at the Ulan-Ude Aviation Plant. Thus started the long life of the legendary model.
Since then, over 13,000 civil and military Mi-8/17s have been built, and even the number of their various modifications is approaching to hundred. This list includes passenger, transport, multipurpose, ambulance, agricultural helicopters, air command posts, electronic warfare helicopters, minelayers and many other. Outstanding flight performance, the ability to work in the most extreme weather conditions, a spacious and comfortable cargo compartment, flexibility and ease of control ensured the worldwide success of the helicopter.
The design and flight characteristics of Mi-8 have been constantly improving since its creation. The initial design assumed that the carrying capacity of the helicopter would be 2 tons, but as the engine power increased, it increased to 3-4 tons, and on the latest modification of the Mi-171A2 it reached 5 tons. The development of Mi-8 series is continued by the Russian Helicopters holding company of Rostec State Corporation and new engines, avionics, main and tail rotor, navigation systems, as well as the introduction of composite materials allow Mi-8 helicopters to meet the latest aviation standards. In the class of heavy civilian helicopters (maximum take-off weight from 10 to 16 tons), Mi-8/17 have been covering more than 90% of the world market in quantitative terms for several years.