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 AE 2100 Rolls-Royce AE 2100 The Rolls-Royce AE 2100 is a turboprop developed by Allison Engine Company, now part of Rolls-Royce North America. A derivative of the Allison AE 1107C-Liberty (Rolls-Royce T406) turboshaft engine, the AE 2100 shares the same high-pressure core as that engine, as does the Rolls-Royce AE 3007 turbofan. The engine is a two-shaft design, and was the first to use dual FADECs (full authority digital engine control) to control both engine and propeller. There are four variants of the engine: the civil AE2100A, and the military variants which include the AE 2100D2/D2A, AE 2100D3, AE 2100J and AE