I was thinking about the design of the ring craft. It would probably be stable when it is ascending vertically with power., kind of like a helicopter with small rotor. However, horizontal flight lends itself to instability, because wm hen there is no power, the control surface in the front would drop, and will cause the craft to dive. And as Zak mentioned, it has no aileron control, because there is no control surface that's far enough from the central axis that will produce any effective roll.

To get a ring wing to fly horizontally, I think, we should try to put stab, fin, elevator, and rudder on the other side of engine, to give them stable control authority. So, if the engine is in the front, put control surfaces in the back. If the control surfaces is in the front, put the engine in the back.

This still doesn't address the lack of roll control. Perhaps put a horizontal wing in the middle of the ring wing. Then the horizontal wing could have some aileron which could roll the craft.

This is just my brainstorming, which may not work at all. I have MSME from UCLA, but it doesn't mean all that much when it comes to practical aircraft design. The only thing I've ever self-design and flown was a stick-type design, which was not much of original design at all. I just enjoy flying and dreaming about new types of flying.

If the original designer would share the purpose of this aircraft, maybe the brains in this forum can help achieve an air-worthy design.