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How ash particles can damage aircraft

While it may be of little comfort to the thousands of  frustrated airline passengers whose planes have been grounded because of the volcanic ash swirling over much of Europe

Experts claim that it is better to be safe than sorry.

According to experts, there have been at least three high-profile incidents of jet engines damaged by volcanic grit since the early 1980s, and two of the flights nearly ended in tragedy.

In these instances, the pilots didn't realize the extent of the threat until they had entered the danger zone contaminated by the ash.

There is also concern that even the most sophisticated computers and satellite sensors may not always provide detailed enough images to help pilots avoid a repeat of those events.

Volcanic particles can scour the windshields and pit the flight-control surfaces of speeding planes. In the most dangerous situations, they can abrade turbine blades, clog the insides of modern jet engines and plug their cooling systems, causing them to burn out and stop running.

In milder incidents they can suffer extensive damage and have to be replaced.

The concerns about volcanic ash stretch back to 1982 when a British Airways Boeing 747 temporarily lost power from all four engines and descended for more than 24,000 feet before the pilots managed to restart the engines and land safely. The crew had no idea they had entered a volcanic cloud. Other incidents involved a KLM jumbo jet preparing to land and refuel in Alaska and a KLM jetliner which lost more than 12,000 feet of altitude.

In 2000, a McDonnell Douglas DC-8 operated by NASA suffered significant engine damage en route to Sweden from California, after flying through a cloud of volcanic ash near Iceland. The engines on the research plane didn't fail, but the nearly new engines had to be replaced.

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