Barrie writes:

How does this compare with the present form of propulsion, such as in the
B747, which I've heard being called "Fanjet"? Is it the same but turbine
blades replace propellor blades while serving a similar function?

Essentially, yes. A turbofan is a jet engine with a very large front
fan in a duct. This fan, which is driven by a turbine in the
combustion section that in turn is driven by hot exhaust gases,
provides most of the thrust. It's like a many-bladed propeller in a
duct (whence the term "ducted fan," which is occasionally used). It's
much more efficient than a pure turbojet, and it also has advantages
over an open prop. It's the preferred mode of propulsion for
commercial airliners these days.

However, turbofans don't work well at transonic and supersonic speeds,
although I understand that these problems have been fixed in recent
years. Likewise, they don't have significant advantages for low speed
flight like that of a small GA plane.

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