Doblhoff WNF 342

The Doblhoff WNF 342, which first flew in 1943, was the first jet helicopter. It utilized a unique system where a mixture of fuel and air was compressed and burned through nozzles at the tips of its hollow rotors for vertical takeoff and landing. A conventional piston engine powered its horizontal flight. This design was an early step in helicopter development, exploring alternative power sources for vertical flight capabilities. While autogiros were experimented with before World War II, they were eventually replaced by conventional aircraft and the more advanced helicopter designs that emerged in the late 1930s.12