Design and development Following the incomplete development of the heavier Mil Mi-12 (prototypes known as Mil V-12) in the early 1970s, work began on a new heavy-lift helicopter, designated Izdeliye 90 (“Project 90”) and later allocated designation Mi-26. The new design was required to have an empty weight less than half its maximum takeoff weight. The helicopter was designed by Marat Tishchenko, protégé of Mikhail Mil, founder of the OKB-329 design bureau. The Mi-26 was designed as a heavy-lift helicopter for military and civil use, and was to replace earlier Mi-6 and Mi-12 heavy lift helicopters, with twice the cabin space and payload of the Mi-6, then the world’s largest and fastest production helicopter. The primary purpose was to move military equipment like 13 metric ton (29,000 lb) amphibious armored personnel carriers, and mobile ballistic missiles, to remote locations after delivery by military transport planes such as the Antonov An-22 or Ilyushin Il-76. The first Mi-26 flew on 14 December 1977 and the first production aircraft was rolled out on 4 October 1980. Development was completed in 1983, and the Mi-26 was in Soviet military and commercial service by 1985. The Mi-26 was the first factory-equipped helicopter with a single, eight-blade main lift rotor. It is capable of flight in the event of power loss by one engine (depending on aircraft mission weight) thanks to an engine load sharing system. While it is only slightly heavier than the Mi-6, the Mi-26 can lift up to 20 metric tons (44,000 lb). It is the second largest and heaviest helicopter ever constructed, after the experimental V-12. The tail rotor has about the same rotor diameter and thrust of the four-bladed MD 500 main rotor. The Mi-26’s unique main gearbox is relatively light but can absorb 19,725 shp, which was accomplished using a non-planetary, split-torque design. Because Mil’s normal gearbox supplier said that such a gearbox could not be designed, the Mil Design Bureau designed the VR-26 transmission itself. As of 2013, the Mi-26 still holds the FAI record of greatest mass lifted to 2,000 metres – it lifted 56,768.8 kg in 1982. In July 2010 a proposed Russian-Chinese development of a 33-ton heavy-lift helicopter was announced. The Russian helicopter manufacturer, Rostvertol, is in the process of refurbishing and upgrading the entire fleet of Mi-26s serving in the Russian Air Force. The fleet is estimated to total around 20 helicopters. The upgraded aircraft will be comparable to a new variant, the Mi-26T. Contract completion is planned for 2015. The contract also covers the production of 22 new Mi-26T helicopters. Eight new-built helicopters were delivered to operational units by January 2012. Under the 2010 contract, 17 new-production helicopters have been delivered through 2014.