Disadvantages
- Less efficient than a propeller at cruise (at lower thrust level).
- Good efficiency requires very small clearances between the blade tips and the duct.
- Requires high RPM and minimal vibration.
- Complex duct design, and weight increase even if constructed from advanced composites.
- At high angles of attack, parts of the duct would be stalled and producing drag.
Read more about this topic: Ducted Fan