Crises are not like buses: they come along every decade ewind three months, to your last edition of The Log: a scientific explainer on the 10-year anniversary of the Eyjafjallajkull eruption of 2010. It was briefly noted in the wider press, but, fair to say, eclipsed by the latest crisis. If were all a little blas now about volcanoes, in 2010 there was no expectation that Europe could be brought to a standstill: it came out of the blue. With more than 20 nations closing airspace, 95,000 flights cancelled and losses estimated by IATA of US$1.7bn, 2010 wasnt small beer even if it feels so now. Compare Eyjafjallajkull and COVID-19 as challenges. There are obvious differences: cause, transmission, mortality, global reach and societal change. In similarities, both were unexpected examples of wider, known phenomena, very Europe-centric in damage, and in need of modelling and research. The 2010 rumblings about safe ash levels equate to discussions of distancing and lockdown. Ultimately, with both, it was easy to stop flying and far harder to restart requiring good, international collaboration. Weve weathered much in the past decade more than most professions? Was a pandemic (excluding other, more restricted outbreaks) the only thing left on a diminishing list? Regardless of scale, aviation has had a pivotal, mass shutdown nearly every decade since 9/11. Within this lie smaller crises single events or wider themes, all synonymous with a single word: Hudson/AF447 (2009); lasers (2010); MH370 (2014); Germanwings (2015); and drones (2018). We can add in the global belt-tightening of 2008, perhaps long forgotten until recently. All challenged industry and, at a broader level, governments and agencies on policy and practice, and continue to resonate. In short, theres a fair parallel here for the multidisciplinary mitigation of a threat, something in which aviation has a good track record. With authorities speaking of a recovery roadmap for 2020, how do we reboot and ensure lessons arent forgotten, having been left ashen-faced in 2010? By Captain Robin Evans, Senior Log Contributor Eruption of Eyjafjallajkull volcano In Iceland seen from an Icelandair B-757 climbing out of Reykjavik Engines As decades passed, it was considered that the effects of a shutdown would be vast, given modern traffic densities above north America, Europe and Asia. NASA reports that ash-ingestion testing took place as early as the 1980s, as outgrowth of nuclear bomb scenarios, using high concentrations of various contaminants. Particularly after the huge 1991 eruption of Mt Pinatubo in the Philippines, questions began to be asked in industry about engine ash tolerance. There was some reluctance to further the issue, however, reinforced by a scarcity of sizeable eruptions. Airlines had always deferred to the engine giants, who were not required to perform destructive tests with ash, unlike with bird strikes or fan-blade separation. A vehicle integrated propulsion research (VIPR) project run by NASA, the US Geological Survey and US Air Force, among others, changed this. Ash research became one facet of advancing engine health-management systems and sensors for next-generation engines. Ground runs were made using a modified F117 engine (a militarised Pratt & Whitney 2000) on a C-17 Globemaster. Across three phases, the project established baseline parameters (2011), using a spider rig to introduce neutral substances such as cereal and wax (2013) and then ash (2015) at concentrations around the visibility threshold. Blade-tip clearance (by microwave), temperature (by fibre optic/thermocouple), vibration (accelerometer), acoustics and emissions were all recorded. The effects of work such as this can be seen in the Rolls-Royce duration of exposure versus ash concentration (DEvAC) model (see box, right). The number of variables is great: engines and operating temperatures differ. Ash chemistry also varies: its toxicity to engines depends on the glass component, a function of geology at the location of the eruption. Using ancient ash deposits for testing is not ideal: glass chemistry changes over time and by weathering. An ideal might be a worldwide database of ash types and their particular damage coefficient. Airlines complained about blanket denial of airspace in 2010, but they now have tools to use and at a cost Airspace Advances in satellite monitoring and processing, or LIDAR usage, have helped decision-making for trained analysts. Waveband, timing of satellite passes and resolution all factor into the fitness for use of a particular method. Ash can be rained out or held aloft for different periods according to density. Visual reports have limited use for flight planning. Significantly downwind, there will be no obvious mushroom cloud: ash can be an invisible, intercontinental phenomenon. Research concludes that, in good light, suspended ash becomes visible somewhere between 0.01mg/m3 and 10mg/m3: you could experience it unknowingly. Ash is classified in three airspace contamination bands: Low: concentrations 0.2-2mg/m3 Medium: concentrations >2-4mg/m3 High: concentrations >4mg/m3 READ MORE Further Reading The pivotal events of the 1980s all occurred close to unknown eruptions, experiencing a far greater intensity than the 4mg/m3 high threshold here. The upper value of the low classification is significant: this was the value chosen as a benchmark in 2010. The 1mg/m3 contour fell across Gatwick, meaning it could only land and Heathrow would close. Consultation between the Met Office, the CAA and operators pushed this to 2mg/m3 around the primary shutdown. Concentration is only part of the story; flight duration through a contaminant gives equivalent flightpath dosage total exposure. Using a combination of in-service experience, engine test data and mathematical modelling, Rolls-Royce has established that, for all Trent and RB211 engine types, an ash dose equivalent to operating for 120 minutes in an actual ash concentration of 2mg/m3 will not lead to significant reductions in flight-safety margins providing all measures are taken to maximise engine operability margins. What does this mean, practically? Intake volume is another variable, but a quick visualisation at high power is ingesting a squash court per second: about 300m3. The maxima of the low limit, 2mg/m3 equates to 36g/minute or 2.1kg/hour. The CAA now requires an accepted safety case from airlines intending to transit airspace in excess of this: medium or high. Ash becomes another risk to quantify, via expertise and data, in a management system. The cost of long-term performance degradations (shorter component life, labour and maintenance downtime) would have to be considered. Airlines complained about blanket denial of airspace in 2010, but they now have tools to use if they wish and at a cost. Future When it comes to airborne ash detectors, a truth lost on airline PR was that miniaturising, certifying and plumbing a successful scientific research project into an Airbus was (and remains) another order of magnitude harder. Those same PR departments did their job: people considered the idea an immediate panacea. The costs of this development would need to be met: the intention even if it could be realised is that devices would only need to be fitted to a few tactically deployed assets across operators, not standard-fit. These difficulties reinforce the difference between direct measurement in situ and remote sensing. Future ideas being mooted are real-time ash collection by drone and ash-repellent coatings able to withstand internal compressor temperatures. Volcanologists would say a trait of natural hazards is the perceived risk diminishing over time. The current crisis has reinforced that political gears move slowly; for every layer of governmental or national authority involved, time, cost and complexity increase. All sources suggest we are now in a more informed position: a reduced amount of traffic could be kept flowing, akin to a weather event. Eyjafjallajkull is considered a catalyst of the single European sky and disaster management. Ultimately, industry benefited from knowledge gained before 2010 and the luxury of arguing about it over subsequent years, not during a prolonged shutdown. Origins Timescales vary, but the (relatively) short, sharp shocks of phenomena contrast with the much longer intervals between them; the first challenge of a 100-year event is recalling what was learned the last time. Commercial air travel began in 1919 by repurposing wartime hardware and battle-hardened pilots for peace. If the last pandemic of this magnitude was the 1918 flu, which ran until summer 1919, our knowledge of dealing with them is as old as our profession. In discussing 9/11, US Defense Secretary Donald Rumsfeld made his remark about known unknowns. Ash, like viruses, suggests were starting to get to grips with what we know: that we dont yet know. READ MORE FURTHER READING Rolls-Royce DEvAC model: Volcanic Ash and Aviation Rolls-Royce Position, May 2017, R Clarkson. Available online Nicarnica Aviation: nicarnicaaviation.com firm that devised the AVOID system in partnership with Airbus and easyJet Icelandic volcano catalogue: icelandicvolcanos.is extensive, map-based tool of the 32 Icelandic volcanic systems and their eruption histories. Daily tectonic data: en.vedur. is/earthquakes-and-volcanism/earthquakes Futurevolc: futurevolc.hi.is European consortium of scientific agencies, focused on Iceland. Includes ash-dispersal forecasting as one strand of a large, multinational research project. The eruption of Eyjafjallajkull was followed by dark days of abrasive fallout The volcanic ash distribution spider used to inject ash during the NASA VIPR project The Naples control centre for monitoring volcanic activity VO LCAN I C AS H Recovery roadmap