The volcanic ash threat to Australian flights

The Darwin Volcanic Ash Advisory Centre is one of the world’s busiest. Last financial year it issued over 1700 advisories to airlines on threats from active volcanoes in the region. (You can see the latest here.)

Because Indonesia has so many active volcanoes, planes routinely have to fly around ash plumes in the region. The graphic above shows how, just in recent decades, there have been numerous examples of plumes affecting major air corridors.

Below is an enlarged version of the map showing volcanic plumes between 1979 and 2001, and how they intersect with major air routes.

Because prevailing winds tend to be on east-west lines above the active volcanoes, it’s unlikely a major eruption would disrupt domestic air travel across Australia. But while the ash monitoring system has proven effective, two key risks remain:

• Insufficient warning to airlines as a result of a surprise eruption from an unknown or unmonitored volcano, and
• A cataclysmic eruption, such as the 1883 Krakatau incident, which could create an ash plume so large it could be difficult to navigate around

Tupper said the “critical thing in this region is because so many of the volcanoes are unmonitored, it can be a matter of two to three hours” before an eruption is recognised and the warnings passed on to the aviation industry. The risk with Indonesia’s volcanoes is “the next one that affects us is one we’ve never heard of,” he said.

The other threat – a cataclysmic eruption – could put severe restrictions on travel in and out of Australia at significant cost to the economy, but these could be among the least of anyone’s worries in the wake of such an event.

Tupper said there had been “numerous examples” of incidents in recent decades where volcanic ash had damaged aircraft. Some airlines have been forced to replace engines at costs of millions of dollars.

Since the eruption of the unpronounceable Icelandic volcano - Eyjafjallajokull - last month, the story of the British Airways jumbo which suffered complete engine failure and plunged 12,000 feet after flying into an ash plume has been cited as the most unnerving example of the threat volcanoes pose to passenger jets.

The BA flight’s destination was Perth and the incident happened just south of the Indonesian coast. It flew into an ash plume from Mt Galunggung, one of the 129 active volcanoes in Indonesia, prompting pilot Eric Moody to tell the passengers in a now-celebrated address: “Ladies and gentlemen, this is your captain speaking. We have a small problem. All four engines have stopped. We are doing our damnedest to get it under control. I trust you are not in too much distress.” (Watch a video recreation of the incident below.)

Aircraft that fly into a volcanic plume are at risk from the build-up of ash in the engines. And if the engines keep running the pilots can be left trying to land with a film of ash across the windshield, as happened to the BA flight in 1982. The pilot on that flight, Eric Moody, sent this photo of his windshield to Tupper.

In the wake of the disruption caused by the Eyjafjallajokull plume, airlines – notably BA – were critical of the decision to effectively shut down all airports in Britain and western Europe.

While the restrictions were in force BA chief executive Willie Walsh said his company’s test flights had provided “evidence that the current blanket restrictions on airspace are unnecessary”. Other airlines, including Ryanair and Virgin, were also dubious about whether the restrictions were necessary.

Australian airlines, Dr Tupper said, were traditionally conservative in their approach to handling ash warnings. “The history of Australian airlines is they are very engaged with the warning system, especially Qantas,” Tupper said.

“As aviation grows, the airlines and (global civil aviation body) the ICAO will be very good at responding to volcanic ash problems.”

The trouble is, large-scale civil aviation has only been around for less than a century. Volcanoes operate on different timescales and eventually the region will be due a big one.

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