Definition
A turbofan engine is a type of jet engine in which a large fan at the front of the engine pushes a substantial volume of air around the outside of the engine core, while a smaller portion of air passes through the core where it is compressed, mixed with fuel, ignited, and expanded through a turbine. The combined thrust comes from both the bypassed fan air and the hot exhaust from the core. Turbofans are the standard powerplant on most modern airliners and many business jets.
Plain English
A jet engine with a big fan up front. Most of the air the fan moves goes around the engine, not through it, which makes the engine quieter and more fuel-efficient than a pure jet.
Context Anchor
Seen in aircraft systems discussions, especially when comparing engine types used on transport aircraft, business jets, and some training or military aircraft.
Derivation
The name combines 'turbo' (from turbine, the spinning bladed wheel driven by hot exhaust gases) and 'fan' (the large bladed wheel at the front). The fan is driven by the turbine, hence turbofan.
Why Pilots Care
Turbofans power most modern jets and many training aircraft, delivering better fuel efficiency, reduced noise, and reliable high-speed performance compared with earlier engine designs.
Grounding Statement
A turbofan engine makes thrust by accelerating air backward, with the front fan moving a large share of that air.
Intuition Check
A turbofan engine is not just a normal fan attached to an airplane. It is a jet engine in which a turbine turns a large fan to help produce thrust.
Example Sentence 1
Most modern airliners are powered by turbofan engines because they offer a good balance of thrust, fuel efficiency, and lower noise.
Example Sentence 2
Most light jets used for instrument training rely on turbofan engines for their balance of speed and fuel economy.