MORE power is continuously being demanded from aero‐engines and a leading feature of the Rolls‐Royce RB 211 series of turbofans is the progressive development of this unit from its original design rated at 42,000 lb thrust to the Trent which in its fully developed form, will be able to deliver 95,000 lb thrust. The RB 211 initially powered the short range TriStar and the latest model has already been ordered for the MD‐11 and Airbus A330 and is being considered for the so‐called MD‐12X and the Boeing 777.