Definition
A turbofan engine in which the fan is mounted at the rear of the engine rather than at the front. The fan blades are driven by a separate turbine stage at the back of the engine, and the air they move bypasses the core and exits at the rear, adding to thrust.
Plain English
A jet engine where the big fan that helps produce thrust sits at the back of the engine instead of the front.
Context Anchor
Seen in powerplant and aircraft maintenance material when comparing different turbofan engine layouts.
Derivation
‘Aft’ is an old nautical word meaning ‘toward the rear,’ still used in aviation to mean the back of an aircraft or engine. So an aft-fan engine simply means the fan is at the back end.
Why Pilots Care
Most modern turbofans use a front fan, so recognizing the aft-fan layout helps a technician or pilot understand older or unusual engine designs and how airflow and thrust are produced differently.
Intuition Check
Do not read “aft-fan” as “after-fan.” Here, “aft” means rear, so the term describes where the fan is located on the engine.
Example Sentence 1
The General Electric CJ805-23 was an aft-fan engine, with its fan blades mounted on the rear turbine stage.
Example Sentence 2
Aft-fan engines were common on early airliners before front-fan designs became standard.