Back in February there was a conversation with a Richard Sohn. The subject was the Blokow Bo-103 single-bladed rotorcraft, since he had worked on the controls for the flying version many, many moons ago.
He now owns or runs a small airport in Florida. During the conversation the subject of Wankel engines briefly came up. As I recall, he said that there were approximately a dozen Wankel driven rotorcraft and aircraft at the airport, plus a Wankel development association. The subject of high fuel consumption was mentioned and he said that the Wankel is an idea engine for rotorcraft since rotorcraft engines run at a constant rpm. He said that the fuel consumption of a Wankel varies greatly over the normal automobile operating range but the fuel consumption is the same as a reciprocating engine at its optimal rpm.