A ducted fan is an arrangement of a propeller-driven aircraft where the propeller is mounted inside the fuselage, within a duct. The term "ducted fan" is sometimes also used to refer to an aircraft powered by such an installation. By limiting the amount of air affected by the propeller to that which is in front of it, the ducted fan is more efficient than a conventional propeller of equivalent size. Ducted fans are favored in VTOL and other low-speed designs for their high thrust-to-weight ratio. An additional advantage is due to the fact that a ring airfoil is vastly more efficient than a conventional wing. A ducted fan is also quieter than a normal prop.

The high-bypass turbofans found in modern jets are a highly-refined and developed variation on the ducted fan, optimized for high-speed flight.

Ducted fans are particularly popular with hobbyists who build and fly radio controlled model aircraft, as a way of representing a jet powered aircraft without the great expense of buying and operating a miniature jet engine.

Ducted fan installations in full-size aircraft are much rarer but not unknown. Examples include the Vertol VZ-2 and the Edgley Optica . Many hovercraft are also powered by ducted fans.

Ducted Fan Design