Ducted Fan - Disadvantages

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