Shifting gears

That jet engines have evolved over the past few decades will be apparent to any seasoned air traveller. Early jet engines had narrow inlets and were very noisy, but as the diameter of the fans at the front increased, the engines became quieter. Compared with a rowdy 1960s jet, a modern turbofan is some 80% quieter and burns as little as half as much fuel — thus producing fewer greenhouse gases.

The aviation industry has set itself a tough target: a 50% reduction in fuel consumption by 2020, to cut CO2 emissions in half. The solution devised by Pratt & Whitney (P&W), a division of United Technologies, is a “geared turbofan” engine called the PurePower PW1000G.

Some airlines, however, are wary of gearboxes. They worry that replacing a simple shaft with a complex gearbox will increase maintenance costs and make it more likely that something will go wrong.

Internet: <www.economist.com> (adapted).

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