Firestone Model 45, better known as the XR-9, an American experimental helicopter of the late 1940s.

The Focke-Wulf Fw 61 was, however, an experimental helicopter and only two samples were ever built.

Headed by Ivan Pavlovich Bratukhin, the bureau built several experimental helicopters over the next decade.

In 1943, they provided the finances for the construction of the W.9, an experimental helicopter, to Air Ministry requirements.

January 29 - Pateras Pesara flies an experimental helicopter in Paris.

Their goal was the development of an experimental helicopter, the Gyroplane Laboratoire.

Other uses included rotor tip propulsion for experimental helicopters.

The Flettner Gigant was an experimental helicopter built in Germany during the early 1930s.

McDonnell Model 38 experimental lightweight helicopter, two built.

The e-volo VC2 is a single place experimental electric multirotor helicopter.