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/MAN Turbo RB193 Rolls-Royce/MAN Turbo RB193 The Rolls-Royce/MAN Turbo RB.193 is a vectored thrust turbofan engine designed and manufactured by Rolls-Royce and MAN Turbo in the mid-1960s. The engine test flew in its sole application, the VFW VAK 191B VTOL fighter aircraft but production did not follow after cancellation of the associated aircraft project. The RB.193 was a joint development project by Rolls-Royce/MAN Turbo originally designed to meet a requirement for the VFW VAK 191B project, design work commenced after a contract from the Federal German Ministry of Defence was signed in December 1965. Bristol Siddeley (from 1966 part of Rolls-Royce) were sub-contracted