The rest of the description can be found with the original engine, search for 2L6
.
This version adds a clutch, reduction gear and a turboshaft engine. To engage the clutch, just stage, open context menu of one of the clutch elements (airplane landing gear) and pin it. Now change focus until you have full options on the menu and engage the parking brake. Use the brakes slider to adjust the clutch slip.
Action group 1 toggles the turboshaft engine.
Action group 2 toggles the piston engine.
Built in the SPH in KSP version 1.3.0.