THE cause of flight AF447鈥檚 destruction over the Atlantic last week remains unknown, but one factor that the aviation industry will be hoping to rule out is structural failure. If they cannot, they may be forced to rethink the next revolution in aviation: replacement of metal aircraft with those made from lightweight composite materials.
The move to carbon-fibre reinforced plastic (CFRP) is the biggest shift in aircraft design since the introduction of all-aluminium pressurised aircraft in the 1950s. It is much lighter than metal, so planes can carry more passengers with the same amount of fuel. Airlines have been introducing carbon-fibre parts, such as rudders and tail fins, over the last two decades, and in a few weeks the first aircraft with a pressurised CFRP fuselage, the Boeing 787, will make its maiden flight. The Airbus A350 follows in 2012.
Questions have been raised before about the safety of carbon-fibre parts. Aircraft are designed to handle 1.5 times the highest force they are ever expected to experience, including vertical accelerations of up to 2.5 g. But estimates of the forces an aircraft could experience may have been underestimated. In 2003, the US National Transportation Safety Board studied turbulence-damaged planes and 鈥渁irplanes may be exceeding design and certification loads more frequently than previously known鈥�. One jet it cited had seen 4.3 g.
Advertisement
As New 杏吧原创 went to press, AF447鈥檚 flight recorders had yet to be recovered. The Airbus A330 鈥� which had a carbon-fibre rudder and tail fins 鈥� off Brazil, encountering fierce updrafts moving at 160 kilometres per hour. Some have speculated that ice-blocked airspeed sensors may have fooled the aircraft鈥檚 computer into flying too slow or too fast. is the force of the storm broke the plane apart.
Structural failure has been implicated in several recent incidents involving carbon-fibre components. In 2001, an Airbus A300 climbing out of New York hit heavy turbulence from the wake of a preceding jet. To try to control the craft, the panicking pilot moved the rudder from side to side, creating high forces that snapped the carbon-fibre tail fin. The plane crashed, killing 265 people. In 2005, passengers on an Airbus A310 had a lucky escape when the pilot managed to land despite the aircraft鈥檚 carbon-fibre rudder breaking apart mid-flight. While metal parts tend to deform before they break, carbon-fibre components can snap suddenly.
Another failure would increase pressure to revisit safety rules, particularly for the next generation of carbon-fibre planes, which have yet to rack up the millions of flight hours during which metal planes have proved themselves. That鈥檚 one thing the industry is hoping won鈥檛 be necessary.
