Many of us in aviation watched in awe as the Eyjafjallajokull volcano on Iceland began erupting in earnest on April 14 and began disrupting air traffic all over Europe. According to Oxford Economics, that first week of disruption caused an estimated impact of $4.7B, not just limited to Europe, but extending to North America, Asia and other parts of the world. We realized the potential contributions that Air Traffic Flow Management (ATFM) could make and began prototyping specialized tools for use in this situation. But, more on that some other time.

Over the years, I occasionally have heard of volcanic events occurring in various parts of the world. Typically I heard only about the severe ones. You may recall the two major events from the 1980s involving Boeing 747 aircraft that encountered volcanic clouds. The clouds were of sufficient density to cause engine flame outs and a complete loss of engines. The first one occurred in 1982 when a British Airways 747 flying to Perth, Australia, encountered a volcanic cloud from an eruption in Indonesia, lost 20,000 feet and fortunately was able to restart three of four engines for an emergency landing in Indonesia. The second occurred in 1989 when a KLM 747 encountered a volcanic cloud from Mt. Redoubt south of Anchorage, lost 26,000 feet before managing to restart its engines. Although no lives were lost, the severe 1989 encounter resulted in $80M in repair costs to a $125M airplane – replacement of engines, aircraft skin, windows, and more.

Taking a closer look at aircraft damage, it’s interesting to note that in February 2000 an instrumented NASA aircraft encountered a volcanic cloud north of Iceland. It was flying from Sweden back to California at night following an ozone data collection mission. The DC-8 had been re-engined with modern, high bypass ratio, CFM-56 engines. It was packed with air quality measuring equipment, which was operating during the flight. The flight flew 200 miles north of the reported extremity of volcanic clouds emanating from Hekla, another Icelandic volcano. The sensitive air quality instrumentation detected an encounter with the volcanic cloud, which lasted for seven minutes. Since all engine functions and instruments appeared normal, the flight continued back to California without diverting. However, upon post-flight inspection, it was discovered that the engines had incurred some damage and required overhaul and refurbishment at a cost of over $3M.

While the public hears about the severest of events, few hear about the more subtle encounters. Yet, the magnitude of maintenance costs, even from brief encounters, can be substantial. How many revenue flights are needed to generate $3M in profit, the cost of overhauling engines from one incursion?

One of the problems encountered by the Europeans was the lack of useful aircraft and engine specifications for ash exposure. The current guidance from the manufacturers had been to simply avoid encounters of any kind. Simple enough to say, but seemingly too cavalier when an entire continent is shut down for days at a time. After several days of severely curtailed operations and mounting public pressure to deal with millions of stranded travelers, the manufacturers and regulators arrived at an interim ash density threshold of 2mg per cubic meter (the estimated ash concentration from the Mt. Redoubt encounter in 1989 was 2g per cubic meter, or 1000 times greater than the interim adopted level). This interim step at least allowed traffic to start moving again. No safety problems appeared to occur as a result.

However, considering the results of the NASA DC-8 encounter in 2000, a scientifically based set of standards appears to be vitally needed. Flying around volcanic clouds will likely be driven more by maintenance costs than safety, since maintenance costs will dictate ash density limits that are far lower than any safety limit. In addition, instead of a single density threshold, standards likely need to be a combination of density and duration of exposure. Finally, while most of the media attention has been on volcanic ash, it should be noted that volcanic clouds often contain significant amounts of sulfur dioxide or SO₂. Sometimes the ash and SO₂ are not in the same place. When combined with water in the atmosphere, SO₂ forms sulfuric acid, which corrodes aircraft skin and damages windows and other components, and thus results in substantial costs due to reduced aircraft service life. So, we have to pay attention to both ash and SO₂.

In response to the severe encounters in the 1980s, in 1995, ICAO established Volcanic Ash Advisory Centers (VAAC) as part of the International Airways Volcano Watch program. Nine VAACs were established under their respective host nation’s weather forecasting agency. The US has 2 VAACs (Anchorage and Washington) operating under NOAA. While VAACs have provided some degree of warning, they have a way to go. For instance, when Mount Pinatubo erupted in 1991, 20 aircraft were damaged due to inadvertent encounters, most over 600 miles from the eruption. There are numerous aircraft encounters in the absence of any warnings or advisories, sometimes requiring a lot of detective work to determine where the volcanic cloud might have come from.

In the case of Eyjafjallajokull, there was no confusion about the location of the eruption. While the images broadcast by the media might have suggested that there was complete understanding of the position and density of the cloud, in fact, there was great uncertainty about the current and forecast position and density. Many of the satellite sensing data required significant time to process before the resulting images could be produced. There was a lack of timely, accurate information and a lack of common situational awareness to support planning by air navigation service providers, airlines and other users, airport operators and regulators.

Many experts in European aviation, including the people who were directly involved, said that they were unprepared for this kind of event. Was this a rare event? Hardly. The diagrams below provide an idea of where active volcanoes are located, how often eruptions occur and how big they potentially could be. The USGS tracks 1500 active volcanoes worldwide.

Should we be doing more in the US and globally to be better prepared for these kinds of events? Do the financial losses incurred in the wake of Eyjafjallajokull suggest more investment to be better prepared? You be the judge.