The erstwhile Soviet Union had a penchant for things that were big, and they built huge radars, jets and helicopters. The biggest helicopter ever built, according to the Guinness Book of Records, is the Mil V-12 built in the early ’60s. This helicopter looked much like an airplane. Two rotors, each with a diameter of roughly 35meters, were mounted side by side at the end of large wings. The distance between the two rotor disks was almost 67 meters, which is more than the wingspan of a 747! Mil V-12 was a very strong machine and set the record for carrying the biggest payload (40,205kg) for a helicopter. Despite its huge size and great lifting capacity, the Soviets deemed this project a failure. Ironically, its huge size, which brought it into the Guinness Book, was found too difficult to maneuver and be a practical machine. Only two Mil V-12 prototypes were built. [Via: Spluch] Video