- Fit all kind of engine, electric, piston and turbine;
- Can build it by any size, Two seater or Four seater even more bigger;
- More safety and hard, because all rotating part inside the frames. It's easy to add armor more than traditional helicopter, probably became a real flying tank in war or counter-terror. Or safely through the many high-rise in down-town;
- Easy to build. It isn't dependent on any new technology, just let some old technology combine together.
- The Mechanical complexity was more lower than traditional copter;
- Efficiency and flying range probably is much lower than traditional helicopter, but i guess too much people had can't stand heavy traffic. So it's fault isn't important.