An interesting related fact, one tip jet helicopter actually made it into the production, the Sud-Ouest S.O.1221 Djinn (http://en.wikipedia.org/wiki/Sud-Ouest_D

An interesting related fact, one tip jet helicopter actually made it into the production, the Sud-Ouest S.O.1221 Djinn (http://en.wikipedia.org/wiki/Sud-Ouest_Djinn http://en.wikipedia.org/wiki/Sud-Ouest_Djinn). According to Wikipedia 178 of them were built. In this case the tip jets were simply powered by compressed air.