A case study into the performance of two-spool turboprop engines, used the Pratt & Whitney PW120A to evaluate fuel efficiency, range, and economic savings. The results indicate that such two-spool models improve fuel efficiency by about 5% over a single-spool. The extended range by 65 km per flight saves ~26, 800 annually per aircraft. These figures confirm the relative efficacy of two-spool engine architectures.
Rahul Basu (Fri,) studied this question.