MIL MI-26

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 as the Izdeliye 90 (“Project 90”)[4] and later allocated designation Mi-26.

The new design was required to have an empty weight less than half its maximum takeoff weight.

The Mi-26 was designed to replace earlier Mi-6 and Mi-12 heavy lift helicopters and act as a heavy-lift helicopter for military and civil use, having twice the cabin space and payload of the Mi-6, then the world’s largest and fastest production helicopter. The primary purpose of the Mi-26 was to transport military equipment such as 13-metric-ton (13,000 kg; 29,000 lb) amphibious armored personnel carriers and mobile ballistic missiles to remote locations after delivery by military transport aircraft 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 by 1985, the Mi-26 was in Soviet military and commercial service.

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) because of an engine load sharing system. It is the second largest and heaviest helicopter ever constructed, after the experimental Mil V-12. The tail rotor has about the same diameter and thrust as the four-bladed main rotor fitted to the MD Helicopters MD 500.

The Mi-26’s unique main gearbox is relatively light at 3,639 kg (8,023 lb)[9] but can absorb 19,725 shaft horsepower (14,709 kW), which was accomplished using a non-planetary, split-torque design with quill shafts for torque equalization.

Aircraft of comparable role, configuration and era: Boeing CH-47 Chinook, Mil Mi-6, Mil V-12, Sikorsky CH-53E Super Stallion