Modern jet engine. Front view of a jet engine used in a small airliner. The large set of forward fan blades is seen clearly. In a turbofan engine such as this, the fan blades produce thrust like a multi-bladed propeller. The fans are turned by a small 'core' jet engine, which also contributes to the overall thrust. Modern turbofans are much quieter than their predecessors in order to meet ever-tighter noise restrictions, and are far more fuel efficient. The engine seen here is an Avco- Lycoming ALF-502, mounted on the No.1 position (port outer) of the four-engined British Aerospace 146 regional airliner.