Page last updated at 12:53 GMT, Thursday, 15 April 2010 13:53 UK

Volcanic ash incidents involving airliners

By Rob Corp
BBC News

Satellite image of ash plume from Eyjafjallajoekull eruption
The Eyjafjallajoekull eruption has sent volcanic ash into the upper atmosphere

Estimates suggest that more than 100 commercial airliners have encountered volcanic ash since the 1970s.

The impact on a jet cannot be over-stated. While commercial flights routinely operate in reduced visibility, arguably the greatest threat of ash is to the engines.

Particles have the potential to melt or burn, leaving deposits which can cause an engine to "flame out" - effectively shutting it down.

According to the US Geological Survey, melting volcanic ash can coat fuel nozzles, the engine's combustor and turbines, as well as seriously corrode moving parts - including turbine blades.

The problem is that while an aircraft's weather radar can detect most meteorological phenomenon, the same cannot be said of the potentially disastrous particles.

It was after the eruptions of Mounts Redoubt and Spurr in Alaska in 1989-90 and 1992 respectively that the International Civil Aviation Organisation (ICAO) acted to improve detection - and therefore avoidance - of volcanic ash clouds.

Now there is a worldwide network of Volcanic Ash Advisory Centres (VAACs), which monitor the effects of eruptions and advise the aviation industry about ash clouds.

While airlines, air traffic control services and national meteorological organisations are now much better placed to prevent aircraft entering ash clouds, there have been a number of significant incidents over the past 30 years.

BA 009 - 24 JUNE 1982
Captain Eric Moody in 1982
Capt Eric Moody was at the controls when his 747 hit a cloud of ash

British Airways flight 009 was on a commercial service from Kuala Lumpur in Malaysia to Perth in Australia when it entered a cloud of volcanic dust 150 miles (240km) south-east of Jakarta, Indonesia.

The dust had come from the eruption of Mount Galunggung on the Indonesian island of Java.

While cruising at 37,000 ft (11,300 metres), the crew of the Boeing 747 noticed St Elmo's fire - where charged particles from the dust cloud hit the aircraft, causing a fire-like glow extending from points around the jet. This was their first warning they had entered a volcanic ash cloud.

All four of the 747's engines failed, and the aircraft descended without power for four minutes over mountainous terrain, until reaching 12,000 ft (3,650 metres) when the crew, of Captain Eric Moody, First Officer Roger Greaves and senior engineer officer Barry Townley-Freeman, were able to re-start one of the aircraft's four engines.

They were then able to get power back on all the engines (although one was subsequently shut down), before making an emergency landing at Jakarta.

After landing safely - no-one on board was injured - the Boeing was seen to have been sandblasted by the particles.

The crew were later to receive a number of bravery awards, despite having made light of the incident at the time.

KLM 867 - 15 DECEMBER 1989
Mr Redoubt
After being quiet for months, Mt Redoubt may be re-awakening

Flight 867 of the Dutch airline KLM was flying at 25,000 ft (7,600 metres) en route to its destination of Anchorage, Alaska.

The Boeing 747-400 (just three months old at the time) flew into a normal-looking cloud, which was in fact ash from an eruption of Alaska's Mount Redoubt.

While the crew tried to climb out of the cloud, no more than 15 seconds later all four engines failed - along with the standby electrical system.

Now gliding downwards, the pilots were able to re-light two engines while at 13,000 ft, before the remaining two were re-lit at 11,000 ft.

The 747 was landed safely at Anchorage, but - as with the BA jumbo - the aircraft had been blasted by the ash, and also sustained damage to it windshields and internal equipment including instruments, navigation computers and flight management systems.

An investigation into the incident found that a lack of information about the ash cloud was a contributory factor.

Nasa DC-8 aircraft
Nasa's DC-8 landed safely after encountering ash in the north Atlantic

In February 2000, a Douglas DC-8 research aircraft belonging to the US aeronautical agency Nasa inadvertently flew into an ash cloud generated from the eruption of the Hekla volcano in Iceland.

The crew had been warned of the cloud, but predictions for the location of the plume were inaccurate.

Unlike previous encounters, there was no St Elmo's fire, and the aircraft did not lose power. After landing in northern Sweden, the DC-8's engines were replaced and those that had flown through the storm were found to have suffered damage from ingesting ash.


The US Geological Survey says at least 102 aircraft encountered volcanic ash clouds between 1973 and 2003.

The risk is naturally greater when aircraft fly in areas of volcanic activity. Studies suggest that ash from the eruption of Mount Pinatubo in the Philippines in 1991 was responsible for 20 incidents involving aircraft. One US airline grounded its aircraft at Manila for several days.

When Mount Popocatepetl in Mexico erupted in 1997, there was minor disruption to flights, with one crew experiencing such reduced visibility after landing they had to look through the flight deck's side windows to see where they were going.

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