Technological advances in the Rolls‐Royce RB 211 family of turbofan engines have broadened the scope of applications and, at the same time, embodied improvements such as lower specific fuel consumption (sfc) which make the powerplants more viable in the current environment. The RB 211‐22B was the first to enter service in the TriStar at a thrust rating of 42,0001b and since that time two lines of development have become evident. One relates to improved sfc and higher thrust levels for the ‐524 variant used in later TriStars and the Boeing 747 and the other to the ‐535 engines for varying thrust level applications among which the first enters service in the Boeing 757 early next year.