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 RB162 change from vertical to horizontal installation. With the RB162 fitted the Trident 3B had a 15% increase in thrust over the earlier variants for an engine weight penalty of only 5%. A design study for a turbofan version of the RB162 was designated RB175. Another projected derivative, the RB181 was to be a scaled-down version of the RB162 producing approximately 2,000 lbs of thrust. Seven of these lift engines were to power the unbuilt Lockheed/Short Brothers CL-704 VTOL variant of the F-104 Starfighter. Rolls-Royce RB162 The Rolls-Royce RB162 was a simply constructed and lightweight British turbojet engine produced by Rolls-Royce