What distinguishes a turboprop engine from a turbojet?

The distinction between a turboprop engine and a turbojet revolves primarily around how they generate thrust. A turboprop engine generates thrust primarily using a propeller, which is driven by a turbine. This means that while a turbojet produces thrust by expelling high-speed exhaust gases directly, a turboprop leverages the efficiency of a propeller, making it particularly suited for lower speed flight.

In terms of operational efficiency, turboprops excel at lower speeds compared to turbojets, which typically operate best at higher altitudes and speeds. This efficiency allows turboprops to be widely used for regional flights and shorter air routes where lower speed and fuel economy are critical.

Concerning fuel efficiency, turboprops are indeed more fuel-efficient at lower speeds, contradicting any notion that they would be less efficient in such conditions. The reliance on steam for propulsion is not applicable to turboprop engines, which operate on a different principle altogether. The correct identification of how cursory understanding of turboprop engines highlights their reliance on propellers as the primary thrust source sets the stage for understanding their design and application in aviation.