Rolls-Royce Merlin exhaust flow and waste-gates, meant that this option was rejected in favour of the two-stage supercharger. Fitted with the two-stage two-speed supercharger, the Merlin 60 series gained 300 horsepower (224 kW) at over the Merlin 45 series, at which altitude a Spitfire IX was nearly faster than a Spitfire V. The two-stage Merlin family was extended in 1943 with the Merlin 66 which had its supercharger geared for increased power ratings at low altitudes, and the Merlin 70 series that were designed to deliver increased power at high altitudes. While the design of the two-stage supercharger forged ahead, Rolls-Royce also
Rolls-Royce Trent April 1996. Initially Rolls-Royce had difficulty selling the engine; British Airways, traditionally a Rolls-Royce customer, submitted a large order for the competing General Electric GE90 engine. The breakthrough came when it won orders from Singapore Airlines, a staunch Pratt & Whitney customer, for its 34 Boeing 777s. The Trent 800 has a 41% share of the engine market on the 777 variants for which it is available. In 1998 Boeing proposed new longer range variants of the 777. Taking advantage of the Trent 800's growth capability, Rolls-Royce designed and built an improved engine designated "Trent 8104", which was later scaled