THE worlds biggest wind tunnel can generate a windspeed that is 12 times that of sound. Journalists were offered a glimpse of the 24-metre-girth steel tubes at the National Centre for Aeropsace Research (Onera), where propellers, weighing over a tonne each, power the huge gusts of wind. Despite their size, the fans can get up to speeds of 230 revolutions every minute, nearly four a second, at the worlds largest wind tunnel that tests aircraft to their limits. The simulations last for just a matter of seconds, but the four tunnels in Modane, France, allow manufactures and defence ministries to test hypersonic flight, sometimes exceeding 12 times the speed of sound, the Daily Mail reports. The huge site was built out of sight with extreme precision after it was discovered during World War Two. Jean-Paul Becla, test director at the site in Modane, said: The site, chosen for its air quality, also has the advantage of being close to dams producing enough energy for the wind tunnels, which alone consume one thousandth of Frances electric capacity. Patrick Wagner, site director who last opened the doors to journalists in 2003, said: Thanks to them, the tests, close to real conditions, improve the quality of the aeroplanes so that they consume less fuel and improve their sound. Economic Times