The Doblhoff-WNF WN 342V4, seen here, was the fourth and last prototype of this the world's first jet-driven, or hot-cycle helicopter. Conceived by the Austrian engineer Friedrich von Doblhoff. the first WN 342 made its maiden flight in the spring of 1943, around six months after development had been initiated. Initially powered by a 60hpWith a Mikron to power the air compressor that fed air to the rotor tip combustors, the last WN 342 was a two seater powered by a 140hp BMW Bramo Sh14A.The close-up shows the rotor tip combustor with its internal atomizer ring. Here fuel and compressed air, both fed down the rotor were mixed and ignited by glow plug, the overall unit, with no moving parts, being, in effect, a small, self-starting ramjet. Interestingly, a number of key Doblhoff staff were to continue with their work after the war as employees of the Fairey Aviation Company in Britain, while Doblhoff, himself, went to the US, where he worked with Kellett, later to become Hughes, and McDonnell.