Interesting... but comparing to X2... huge. And will pose some challenges with stability. The idea seems to be coming back - first with Focke-Wulf FW61, then Fa223, and than Ka-22 and Mi-12, not very practical then, but today a FBW should eliminate some problems.
Although the size...
Well, future looks interesting. With the Piasecki, Sikorsky and Bell concepts, wonder what's Boeing up to
