I have just completed a project to build a helicopter with a gasoline engine, controlled by Arducopter (of course!) This helicopter serves as a test bed for future gas heli development work for a client of mine. The goal was to prove out that it could be done. Gas engines pose a unique challenge for Arducopter due to the heavy vibration they produce. But they also present a lot of promise for UAV applications as it can allow heavy payloads, long duration flight, and high speeds.