Complex sentence: Another early turboprop powerplant that became available for the PC-6 was the Garrett Air Research TPE 331, some operators such as Air America chose to retrofit their Astazou II-powered PC-6s with the TPE 331 engine in its place.
Split into simpler sentences: Another early turboprop powerplant that became available for the PC-6 was the Garrett Air Research TPE 331. Some operators such as Air America chose to retrofit their Astazou II-powered PC-6s with the TPE 331 engine in its place.