Few inventions this century changed the world like the jet engine. The story began with Frank Whittle's first jet engine patent in 1930, but as his concept was not embraced by the UK Government, Hans von Ohain's jet engine would fly first in Germany in 1939. That began the jet age.

General Electric built the first US turbojet in 1941, based on a Whittle design. Those first engines were mainly centrifugal compressor designs and they were not efficient. Axial-flow compressor turbojets, introduced by the Germans, proved a breakthrough in performance.

GE ran the first axial-flow turboprop late in the Second World War. Turboprops were considered a more efficient solution than the turbojet for powering commercial aircraft - until the turbofan. After the war, the UK led the world in commercial jet airliners with the de Havilland Comet, powered by the de Havilland Ghost, a centrifugal-flow turbojet. The 1950s saw advances in efficiency. GE's CJ805-23 aft-fan engine for the Convair 990 was the first truly efficient bypass engine. It stimulated Pratt & Whitney's JT3 and Rolls-Royce's Conway, very low bypass engines which powered the Boeing 707 and Douglas DC-8.

The JT3D led to the JT8D, a breakthrough engine, and the first truly reliable commercial turbojets. In the 1960s, high bypass jet engines arrived after advances in metallurgy and turbine cooling. The first high-bypass engine was GE's T39, introduced in the mid-1960s for the C-5 transport. Then P&W introduced the JT9D for the Boeing 747.

Through its RB211 family, R-R introduced the three-spool engine and composite carbonfibre fan blades.

Commercial turbofans routinely stay on wing for more than 20,000h. I can remember when 500h was considered excellent.

Source: Flight International