A study performed by research firm Conklin & de Decker for GE Aviation found “significantly increased operating efficiency, reduced variable costs and net savings” for buyers of the Power 90 engine upgrade. The Power 90 program replaces the King Air C90’s original Pratt & Whitney Canada PT6A-20/21 engines with the GE M601E-11A. Smyrna Air Center of Tennessee owns the STC for conversion of the King Air to the M601E. The upgrade costs $532,000, and the M601E has a 3,000-hour TBO with no midlife or hot-section inspection. Compared with the King Air’s PT6As, the M601E costs less to overhaul, too, and thus its reserve set-aside is $94 per hour versus $161.67 for the PT6A, according to the study. Features of the M601E make it easier to maintain and thus less costly, including no nozzle maintenance because the engine has a diffuser ring instead of fuel nozzles and an electronic limiting unit that can prevent hot starts. The 820-shp M601E is flat-rated to 705 shp for the Power 90 conversion and in an average year uses 14 percent less fuel than the PT6A-21 and 8 percent less fuel than the Blackhawk King Air PT6A-135A mod.