turboshaft

lang=en|thumb|right|upright=1.5|A simplified turboshaft engine. The compressor Spool (aeronautics)|spool (turbine) is shown in green and the free/power spool (turbine) in purple.

A turboshaft engine is a form of gas turbine that is optimized to produce shaft horsepower rather than jet thrust. In concept, turboshaft engines are very similar to turbojets, with additional turbine expansion to extract heat energy from the exhaust and convert it into output shaft power. They are even more similar to turboprops, with only minor differences, and a single engine is often sold in both forms.