Why Volcanic Ash is a Hazard to Aircraft?

Why Volcanic Ash is a Hazard to Aircraft? Flights across Europe crippled and high paced life grounded to a halt due to volcanic eruption in Iceland.

Volcanic eruption in Iceland recently spewed tonnes of ash clouds into the atmosphere. The result, a great part of Europe was declared a no fly zone by the aviation authorities. Thousands of flights across Europe have been cancelled on Thursday. Thousands of air passenger stranded were clueless when the flight will resume. Aviation authorities were not in position to say when it will become safe to fly again.

Why then volcanic ash is hazard to flights? It is not the problem of visibility but the abrasive effect of the ash. Volcanic ash is a cloud of ash released during volcanic eruption. It consists of tiny particles of glass, silicates and pulverized rocks.  The pulverized rocks and other particulate debris have the potential to strip off the vital surface of engine on collision with a high speed moving aircraft. The particulate matter can penetrate and cause the engine to stop functioning by damaging the avionic and electronic systems of an aircraft. Worse still, expert says volcanic ash is often in combination of sulphuric and hydrochloric acid. So, 120 nautical mile (1 nautical mile is equal to 1852 meters) from the point of plume is considered a danger zone and flights are banned from flying within this perimeter, as there is high possibility of winds carrying the ash across the flight path.

How man came to know about the volcanic ash as hazard to an aircraft? As usual, on June 24, 1982 British Airways jumbo jet was enroute to Perth, Australia from Kuala Lumpur, Malaysia. At around 37,000 feet altitude, captain of the aircraft calmly told the 247 passengers onboard through the flight speaker system that all the four engines have failed. One can imagine what the passengers might have thought or how they might have reacted to the captain’s announcement. But what billed as miracle in aviation history, Captain Eric Moody glided the aircraft for more than 20000 feet, somehow managed to restart one of the engine at around 13000 feet followed by others and allowed aircraft to safely land. Later the investigators found that the engine failure was caused by flying through the cloud of volcanic ash from the eruption of mount Galunggung, West Java, Indonesia. This incident prompted drafting of new flight procedures and international  aviation exercises.