Chaos indeed – but it could have been much worse

Geoffrey Thomas’ article in the August issue of Australian Aviation brought out many of the challenges in dealing with a major volcanic ash event such as the eruption in June of Chile’s Cordón Caulle volcano into a jet stream headed for Australia.

As Thomas noted in his article, an article published in The Australian during the event implied that volcanic ash wouldn’t cause damage at a distance.

Volcanic ash encountered at distance has in fact caused damage on various occasions.

For example, ash encountered more than 1000km from the Pinatubo, Philippines, eruption in 1991 resulted in replacement of all the engines. In an extreme example in 2002, an ash encounter north of Papua New Guinea 20 days after the source eruption (Reventador, Ecuador) caused abrasion and pitot tube contamination, despite the cloud having faded from view on satellite imagery.

Overall, there have now been well over 130 reported encounters with volcanic ash in flight, with 79 of these having various degrees of airframe or engine damage, and nine with engine shutdown inflight. It’s therefore probably not surprising that original equipment manufacturers do not recommend flying into ‘visible ash’ at any concentration or distance.

The Darwin Volcanic Ash Advisory Centre monitors the extremely active volcanic region to our north – the ‘ring of fire’, which includes Indonesia, Papua New Guinea and the Philippines – issuing around 1500 volcanic ash advisories each year. It’s a tough region to cover, as many of the more than 150 active volcanoes are not monitored from the ground, and they are also frequently invisible to satellite detection due to the heavy cloud cover.

Because of these challenges, since the mid 1980s key airlines operating in the region have been meeting at least once a year with Australian government agencies such as the Bureau of Meteorology, CASA, and Airservices Australia to discuss volcanic ash and the development of the International Airways Volcano Watch in this region. Thanks to the efforts on all sides, and despite not having any volcanoes of our own to play with, Australia is one of the world’s leading countries on this issue.

In this context, the choice that the airlines made, although different, were based on a good understanding of the advisories and the science behind them.

European style advisories, which include supplementary guidance based on modelled ash concentrations, are not issued as there is concern about their accuracy and potential to increase disruption. Indeed, theWorld Meteorological Organisation’s expert team on volcanic ash has debated the model charts intensely, and advised the International Civil Aviation Organisation (ICAO) that the concentration values are not currently accurate to better than an order of magnitude in each direction at best.

So to be clear, it is not a lack of ability that prevents publishing these charts, but a deliberate decision to avoid even greater disruption. These charts in fact suggest ash is present, where it has not been observed. The focus in the Australian advisory is to lean heavily on evidence – pilot and satellite observations – and our post analysis so far suggests this worked pretty well, although not perfectly.

What could have been done better? Different strategies used by different airlines are arguably a natural consequence of allowing the airlines to make their own decisions about managing risk. The principle that operators are in the best position to As soon as airlines start making different decisions, the pressure on every player in the warning system increases.

eruption disruption Probability says it will be two decades before we experience another ash cloud circumnavigation of the Southern Ocean. (AAP Image) decide what works best based on all available advice – safety, business and maintenance – has been heavily debated and is now internationally accepted.

As soon as airlines start making different decisions, the pressure on every player in the warning system increases, as well as the frustration of the travelling public. In my opinion, the best way to support the most consistent possible decision making is to keep improving the warning system to keep operators well informed and part of a collaborative process.

Doing that in a globally consistent manner is not easy, and this is where the discussions at ICAO are critically important. Its Volcanic Ash Task Force has made some decisions, and will hand down its final report mid next year.

As soon as airlines start making different decisions, the pressure on every player in the warning system increases.

MER0087 Ansett Press 210x148_REV_OL. indd 1 14/09/11 11:56 AM On the balance of probability, it will be 20 years before we have another ash circumnavigation of the Southern Ocean. However, the odds are near certain that within that 20 years there will be many more large eruptions and the potential for serious incidents in the tropics to our north. The risk posed by unmonitored or poorly monitored volcanoes also continues to be a concern, and strong Australian engagement with this issue will remain a top priority. n Dr Andrew Tupper is the Bureau of Meteorology’s Regional Director for the Northern Territory, co-chairs the World Meteorological Organisation’s Volcanic Ash Science Advisory Group, and represents Australia on ICAO’s International Volcanic Ash Task Force.