Helicopters were flying vehicles that used a rotor on top to get off the ground. They could take-off and land in areas where planes could not.
The concept of a helicopter originated with Leonardo da Vinci in the 1480s. Along with other flying machines, the helicopter took a while to be successful. The word helicopter was originally a French word derived from Greek. Helicopters were built throughout the early 20th century. However, it was not until 1942 that Igor Sikorsky built the first successful helicopter.
Tech Level: 9-10
With the advent of the R-4, helicopters entered mass production. The R-4 was the only helicopter used in World War II. With the advent of the turboshaft engine, more and more helicopters were being produced. They were larger, faster, and had a higher performance. But there was a problem. The rotor blades caused the helicopter to torque. A tail-rotor was used to stop that. Soon, however, more advanced designs would come.