Keeping aircraft clear of volcanic ash

Nine Volcanic Ash Advisory Centres around the world advise the international aviation industry of the location and movement of clouds of volcanic ash. The area covered by the Darwin Volcanic Ash Advisory Centre includes Indonesia, Papua New Guinea and part of the Philippines. This area has seen some of the biggest eruptions known to history.

The above map shows the areas of the world that are covered by the nine Volcanic Ash Advisory Centres. The International Civil Aviation Organization has a downloadable Handbook on the International Airways Volcano Watch with details on how the warning system works - the Volcanic Ash Advisory Centres give specialist advice to Area Control Centres and Meteorological Watch Offices in the affected area, who then issue 'NOTAM' and 'SIGMET' warnings respectively to aircraft.

The effect of ash on aircraft

Volcanic ash in the air is composed of fine pulverised rock and accompanied by a number of gases which are then converted into droplets of sulphuric acid and other substances. It is potentially deadly to aircraft and their passengers. The most critical effect is caused by ash melting in the hot section of the engine, and then fusing into a glass-like coating on components further back in the engine, causing loss of thrust and possible "flame out" (engine failure). In addition there is an abrasion of engine parts, the airframe and parts protruding from the aircraft, and possible clogging of the fuel and cooling systems.

In June 1982 a British Airways 747 suffered severe damage and had all four engines flame out upon encountering ash from Mt Galunggung in Indonesia, descending to 12 000 feet before being able to restart some engines and make an emergency landing in Jakarta. Three weeks later the same thing happened to a Singapore Airlines 747, which this time lost two engines and also made an emergency landing. Since then, there have been many aircraft encounters with volcanic ash.

Since those incidents, a major international effort has been underway to track and warn aircraft of volcanic ash cloud. Quite apart from the safety consideration, volcanic ash has caused very expensive damage to aircraft; most estimates cite costs to aviation of over $250 million since 1982. International airlines are willing to undergo extensive and very expensive re-routing if there is any possibility of ash contact on their regular routes.

The Darwin Volcanic Ash Advisory Centre uses satellite information, ground reports from volcanological agencies, pilot reports, meteorological knowledge and numerical models to track and forecast ash movements so that aircraft can fly around the airborne ash safely. The Centre operates 24 hours a day. In this site you can read a bit about our satellite detection techniques, browse our eruption image gallery, and look at some scientific and general publications about volcanic ash. For aviation users and researchers we also have an archive of past messages and we display any current advisories on the site.