Rolls-Royce M250 / Allison 250 family

Rolls-Royce M250 / Allison 250 cross-configuration gas-turbine family, originally developed as the T63 and evolved through Series I, II, and IV turboshafts plus related turboprops. Rolls-Royce reports more than 31,000 engines produced, over 220 million flight hours, and 170+ civil and military helicopter and fixed-wing applications; current turboshaft offerings cover roughly 420–715 shaft horsepower, with Series IV FADEC and Value Improvement Package options. The global FIRST Network supports 16,000 M250/RR300 turboshaft and turboprop engines in service; exact models, installations, and historic Allison naming remain separate identities.