Editing Model aircraft (section)

====Ducted fans====
[[Ducted fans]] are multi-blade propellers encased in a cylindrical duct or tube that may look like and fit in the same space as [[jet engine]]. They are available for both electric and liquid-fuelled engines, although they have become common with recent improvements in electric-flight technology. A model aircraft can now be fitted with four electric ducted fans for less than the cost of a single jet turbine, enabling affordable modelling of multi-engine airplanes. Compared to an unducted propeller, a ducted fan generates more thrust for the same area and speeds of up to {{cvt|200|mph}} have been recorded with electric-powered ducted fan airplanes, largely due to the higher RPMs possible with ducted fan propellers. Ducted fans are popular with scale models of jet aircraft, where they mimic the appearance of jet engines but they are also found on non-scale and sport models, and even lightweight 3D-flyers.
[[File:Nano Hummingbird.jpg|thumb|Small ornithopter, made to resemble a hummingbird]]