Under the ash cloud

Added on 07 January 2011 by Royal Aeronautical Society

In 2010 an ash cloud from an eruption of the Eyjafjallajökull volcano in Iceland caused the closure of much of Europe’s airspace for six days from 16-21 April. A conference at the Royal Aeronautical Society on 9 November focused on the events and their consequences and looked at what lessons could be learned for the future. BILL READ reports.

This is a full article published in Aerospace International: January 2011

The Eyjafjallajökull eruption paralysed European air traffic for six days. (Finnur Malmquist).

On 14 April 2010 the Eyjafjallajökull volcano in Iceland erupted, sending a huge cloud of ash into the sky. The volcano had been active since 20 March but had only produced lava with little explosive activity. In the second eruption, although still relatively minor by volcanic standards, magma from the volcano erupted through a glacier, melting the ice into water and causing an estimated 250 million m3 of ash and gas to be ejected in a volcanic plume over 10km (33,000ft) high. Much of the ash consisted of very fine particles which stayed in the atmosphere rather than settling on the ground. Moved by prevailing winds, the ash cloud drifted towards northern Europe, arriving first over Scotland and Scandinavia and then moving rapidly across England and the European mainland.

Aerospace International Contents - January 2011
News Roundup - p4
Plane Speaking - p12
Exclusive interview with one of crew of Qantas A380 QF32
Missile masterclass - p16
Anglo-French joint defence research
Under the ash cloud p 18
RAeS volcanic ash conference report
Small but perfectly formed  - p22
Isle of Man has big aerospace ambitions
Anglo-Italian magic- p26
A profile of SELEX Galileo
Under pressure- p31
BAE Systems Brough and the F-35 JSF
The last word - p34
Keith Hayward on Anglo-French co-operation
Letters - p35
Preserving the UK’s technology base

Concerned that the ash cloud could damage or even stop jet engines on aircraft, aviation authorities imposed no-fly zones across most of Europe. The ban lasted for six days between 16-21 April, during which time 313 airports were closed and 100,000 flights were cancelled. The closure of European airspace left an estimated 7m passengers stranded around the world — 6m in Europe and 1m in the rest of the world — a worse disruption to air transport even than the events of 9/11. Figures from the European Commission claim that passenger and air cargo traffic across the 27 European states during the ‘ash days’ fell by 64% and 61%, respectively.

Following rapid consultations between the aviation regulators, air traffic controllers, airlines and engine manufacturers, the regulations regarding ash clouds were changed, air traffic control operators began to lift flight restrictions and most flights resumed from 22 April. Between 4-17 May, the ash cloud moved again towards Europe and there were further temporary airspace closures over Ireland, northern England, western Scotland, Portugal, western Spain, southern France and parts of Italy resulting in the cancellation of a further 5,000 flights.

Learning process

On 9 November around 120 delegates attended the RAeS ‘Flying through an era of volcanic ash’ conference which looked back at what happened as a result of the Eyjafjallajökull eruption together with its regulatory, economic and other implications. However, as RAeS President David Couzens explained, the aim of the conference was not just to look back at what had happened in April but to look forward on the lessons learned for the future.

The conference speakers take questions and answers from the audience.

“While the April eruption caught us unawares, the good news was that safety was maintained and no lives were lost,” observed Dr Guy Gratton, head of facility at the Facility for Airborne Atmospheric Measurements at Cranfield University. “The future will still emphasise safety but seek balance against economic costs,” added Padhraic Kelleher, head of airworthiness at the UK Civil Aviation Authority (CAA).

Looking at the economic costs of the Eyjafjallajökull eruption, the revenue loss for scheduled airlines between 16-21 April has been estimated by IATA at $1.7bn. British Airways and Air France-KLM both estimated that they lost £20m each day. Even after the ash cloud began to clear, airlines faced increased maintenance costs, as aircraft engines were removed to be checked for signs of ash. Some carriers substituted longer-range aircraft on Atlantic routes which better capable of taking long diversions (such as Boeing 757s being replaced by 767s) but which used more fuel.

However, it was not just airlines that suffered a loss of business. “Air transport is an integral part of the world production system,” explained John Sharman, executive director of Spectrum Capital London. The knock-on effect of the airspace closure also hit hotels, the tourist industry, perishable goods, such as fruit, vegetables and flowers, and global industries dependant on the supply of high value just-in-time (JIT) electronic and machine sub-assemblies and spare parts from around the world. A report commissioned by Airbus and published by Oxford Economics estimated that the April ash cloud closures cost the global economy $4.7bn with the May closures adding a further $0.3bn. The report estimated that the April closures resulted in net losses for the global aviation business of $2.2bn, lost revenues from visitor spending of $1.6bn, productivity losses from stranded workers of $490m and losses from perishable and JIT goods of around another $200m. The economic impact did not just affect Europe but was felt around the world. Kenya lost an estimated $3m from lost sales of flowers, fruit and vegetables and had to temporarily lay off thousands of workers. Nissan and BMW car plants in Germany, Japan and the US also had to suspend production due to a shortage of parts while South Korea reported losses estimated at $10m for its mobile phone industry.

The effects on airlines are still continuing. “Eyjafjallajökull was an event ‘with a very long tail’,” said Sharman. “While there has been no long term fall in demand for air transport, there has been an effect on costs.” He quoted the example of an unnamed airline which saw the price of buying a narrowbody aircraft rise during April by $2.7m because the banks lending the money ‘got jittery’ and increased the cost of the loan by 1%.

Ash and aircraft don’t mix

No one denies that volcanic ash is bad news for aircraft. Not only are ash particles abrasive but also corrosive and statically charged. If ingested into jet engines, the particles can melt in the temperatures of up to 2,000°C within the engine core and then solidify to clog cooling vents and distort turbine blades, causing the engine to surge or seize up. However, this is not the only risk. Ash can also cause erosion damage to compressor blades and linings as well as the leading edge of the wings or the fuselage, blank out the cockpit windscreen, clog the airspeed pitot, stop bleed air from entering the cabin or damage pneumatic, oil, cooling and electrical systems. Corrosive gases could also enter the aircraft and incapacitate passengers and crew.

The risk to aircraft from volcanoes has been known for a long time. John Sharman highlighted the fact that the airlines had received warnings about the effect of volcanoes long before April 2010. The United States Geological Survey had publicised the risks as long ago as 1993 while the Aer Lingus prospectus for 2006 included a reference to its operations running the risk of being adversely affected by ‘natural disasters’. Guy Gratton quoted a long list of incidents, dating back as far as WW2 when 78 B-25s from the USAF 340th Bombardment Group were damaged on the ground in Italy by an eruption of Mt Vezuvius in 1944. According to an International Civil Aviation Organization (ICAO) database, there were around 100 ash encounters between 1973 and 2000. Several serious incidents occurred during the 1980s. On 24 June 1982 a British Airways 747-236B flying close to Jakarta at night flew into a volcanic ash cloud from Mt Galunggung and lost all four engines. Fortunately, the flight crew were able to restart three of the engines and land the aircraft safely. A second incident occurred two weeks later when a Singapore Airlines 747 lost three engines from ash from the same volcano, again without loss of life. On 15 December 1989 a KLM 747-400 lost all four engines after flying into the plume from Mt Redout in Alaska. In 2000 a NASA DC-8 flew through a plume from the Icelandic Hekla volcano causing $3.2m worth of damage.

Avoid Avoid Avoid

The memory of such incidents and their closeness to disaster has led aviation authorities to err on the side of caution and to require that aircraft should steer clear of any kind of ash clouds — the so called ‘Avoid Avoid Avoid’ rule. Given enough space in the sky, pilots can steer around an ash cloud or, depending on the height of the cloud, fly over or under. However, there are risks — overflights have no safe place to descend in the event of trouble and underflights are nearer the ground.

Damage to the interior of an engine of a Finnish Air Force F-18 Hornet fighter that flew on the morning of 15 April. (Finnish Air Force).

However, in the congested skies over Europe where many aircraft have to share the same airspace, such avoiding options were not practical and the decision was taken to close the airspace to commercial traffic entirely. “We don’t believe that it was an over reaction,” said Richard Deakins, chief executive of NATS. “The threat from the ash cloud was real.” During the time of the ban, there were a number of reported incidents relating to military aircraft which were not grounded. Just before the ban was imposed on 15 April, Finnish Air Force F-18s were found to have ash damage in their engines.

On 21 April RAF Typhoons on non-essential flights were briefly grounded following the discovery of ash damage while USAF F-16s from an unnamed NATO air force were also reported to have been effected. Even after the restrictions to commercial airspace had been lifted, the first three aircraft to land at Heathrow reported a smell of sulphur and burning while descending.

Ash advice

The decision to close the airspace over Europe was taken following advance warnings from the UK Met Office on the approaching ash cloud. The Met Office oversees one of nine regional Volcanic Ash Advisory Centres (VAACs) which were set up in 1995 by ICAO, as part of its International Airways Volcano Watch Operations Group. Located in Anchorage, Buenos Aires, Darwin, London, Montreal, Tokyo, Toulouse, Washington and Wellington, the task of the VAAC centres is to detect, track and forecast the movement of volcanic eruption clouds within their areas of jurisdiction and to advise meteorological offices that they need to issue warnings to aircraft. While the London VAAC is responsible for a relatively small area over the UK, Iceland and the northeastern Atlantic, it covers some of the busiest airspace in the world which was effected by the ash plume from Eyjafjallajökull.

Advance warning of the eruption came from the London VAAC’s volcanic eruption detection system which was based on data from advanced very high resolution radiometer (AVHRR) on board polar orbiting satellites, as well as images from the Meteosat Second Generation geostationary satellite series. The system utilises a space-matching technique to issue automated alerts that an eruption has occurred and the volcanic ash detection tool that uses a detection algorithm that uses a brightness temperature difference between two spectral channels to detect and monitor the movement of ash clouds.

The London VAAC also runs the NAME atmospheric dispersion model which, in addition to volcanic ash, can also be used to forecast the spread of chemicals, nuclear materials or even airborne diseases. Using input from land and sea observation, radar, aircraft and satellites on the location, start time, release height and top and bottom of the plume (if known), the NAME programme generates a map of where ash concentrations can be expected over the next 24 hours. In addition to the basic chart the CAA asked VAAC to provide a number of supplementary charts, including three-hourly updates and five-day ash concentration zoned charts.

Location of the nine Volcanic Ash Advisory Centres.

It was on the VAAC map and its predictions that the aviation authorities had to base much of their decision making. “NAME is a very accurate model which is good at predicting background winds,” remarked Doug Johnson, head of transport programme, Met Office. “Data from both satellites and observation flights found ash where we predicted.” However, the VAAC model could only predict information within certain margins of error which made planning very difficult. “VAAC was the only show in town,” commented CAA chief executive, Andrew Haines. “However, while the VAAC model was not at fault it needed more input.” “Operators wanted to know what was up there,” added Guy Gratton. “To make any kind of decision whether to fly, they needed information on how dense the ash cloud was, what was in it, where it was and where was it going to be in the future.”

The problem is that getting information on exactly what is coming out of a volcano and what it has put into the atmosphere isn’t easy. “Obtaining data on ash particles inside a volcanic plume is very difficult, particularly in real time,” said Dr Sue Loughlin, head of vulcanology at the British Geological Survey. The plume can be monitored from the air or from space but such observations will not reveal everything about exactly what is in it. It is not practical to take samples directly from the plume, as this would involve a danger to any manned aircraft involved. Samples of ash particles can be collected from the ground but these may not have the same properties as the ash still left in the air.

The plume was also volatile, constantly changing its position, both horizontally and internally, with different layers within it. One flight of a specially equipped Dornier 228 over East Anglia and the North Sea on 16 April with a UK National Environment Research Council team on board identified three distinct layers of residue in the plume — heavy gritty particles at 8,000ft, below which were sulphurous chemicals and finer dust particles.

As the airspace ban continued, the CAA, NATS and other authorities came under increasing commercial and political pressure to re-open European airspace with some countries beginning to waive their own national restrictions. Several airlines conducted their own test flights over Europe, including a KLM 737-800, a British Airways 747, an Air Berlin A330, an Air France A320 and a Lufthansa A340-600. Airbus also conducted its own tests using an A340-600 and an A380. None of these flights found any evidence of ash. Meanwhile, Rolls-Royce inspected over 350 engines and found no evidence of ash contamination.

A series of meetings were arranged between the CAA, airlines, aircraft and engine manufacturers, airports and other interested parties to try and find a way to end the crisis. “The CAA acted as an independent arbitrator pulling together different and often competing bodies,” explained Andrew Haines. As a result of the discussions, the CAA announced a change of the ash cloud rules on 20 April, based on new data collected from test flights and technical input from aircraft and engine manufacturers. The previous fly/no fly rules were changed to introduce three graded tolerance thresholds of ash — Black zone (no flying), Grey zone (fly with approval from competent national authority of the operator with certain operational or technical restrictions) and Red zone (fly subject to conducting engine checks after each flight). Using these new rules, flights were able to recommence shortly afterwards.

Lessons learned

What has been learned for the future? One fact that is clear is that there will be more volcanic incidents in the future. The day of the RAeS conference coincided with the eruption of another volcano — Mt Merapi in Indonesia which was causing the rerouting of flights over south east Asia. On 28 October a Thomas Cook Scandinavia A330-300 flying from Solo City to Bantam suffered engine damage after flying into the Merapi ash cloud — fortunately without incident. Sadly, by the time the Merapi eruption finished in late November, a total of 324 people on the ground had been killed.

There are many other volcanic ‘hot spots’ around the world, including several in Europe. Further eruptions will occur in Iceland which has already had 205historically-recorded eruptions. According to Sue Loughlin of BGS, Iceland has a 140-year cycle in volcanic activity which has been at a historical low level and is expected to rise. Whether a future volcanic eruption in Iceland will have the same effect on European airspace as Eyjafjallajökull in April depends on many different factors, including the location of the eruption, its scale and duration, location, composition and the wind direction.

Meanwhile, ICAO is working on new regulations regarding the management of flight operations with known or forecast volcanic ash contamination — a draft version of which was published on 6 October 2010. Says Padhraic Kelleher: “The CAA is working within the ICAO Volcanic Ash Task Force to develop a structured and regulated airline safety assessment approach supported by improvements in understanding ash, the airworthiness threat it poses and how ash clouds can be tracked.”

Meanwhile, Rolls-Royce and other engine manufacturers have also conducted investigations to determine the risk to engines from different concentrations of ash. One topic of debate at the conference was whether aero engines could be designed to be more ash resistant and if ash-ingestion could be included as one of the standard engine certification tests. However, David Lambourne, airworthiness specialist at Rolls-Royce, highlighted two problems. A certification test for ash ingestion is not as simple to arrange as, say the bird ingestion test which all engines currently have to undergo. The closest that engine manufacturers can get to ash cloud conditions is to test aircraft in dusty desert conditions. The other problem is that a more ash-tolerant engine design would require an increase in fuel burn which would result in a less efficient engine with more fuel consumption and emissions.

The conference agreed that more work was needed to improve the availability of data on the position and composition of volcanic plumes — not just for ash particles but also for SO2 gas content. “Economically we need to fly but safety must be maintained,” said Guy Gratton. “We need better forecasting to reduce levels of uncertaincy.”

To create better VAAC forecasts, more research is needed on volcanoes and plumes with additional monitoring equipment to create more robust statistical descriptions. “To model a dispersion model for prediction of volcanic ash, accurate data is required for: the type of eruption, the evolution of the plume, the weather and the gaseous and particulate properties of the plume,” said Professor Stephen Mobbs, director, National Centre for Atmospheric Science (NCAS). “The greatest challenge is in obtaining information on the near-source part of the plume.”

Image from NASA's Terra satellite taken on 11 May showing the ash plume streaming south from Eyjafjallajokull (red rectangle) over the North Atlantic. (NASA Goddard / MODIS Rapid Response Team)

New technology is on the way. Future Earth observation satellites due to be launched by the European Space Agency (ESA) will include sensors which could be adapted to monitor ash clouds. The Met Office has plans to acquire a specially equipped twin-piston engined Cessna 421 Civil Contingencies Aircraft (MOCCA) from March 2011, as well as having more radar observations and more sophisticated processing of satellite imagery. Research is also being carried out on a new system capable of detecting volcanic ash clouds from a commercial aircraft. Developed by the Norwegian Institute for Air Research, NILU, the Airborne Volcanic Object Imaging Detector (AVOID) system uses passive infrared radiation to detect and quantify micron-sized silicate ash particle concentrations capable of damaging engines. Capable of operating both during the daytime and night, AVOID can allow pilots up to six minutes advance warning of ash clouds.

Another area for future research is into the future applications of UAVs. It was remarked by more than one speaker that ash monitoring is an ideal application for an unmanned aerial vehicle which can stay up for a long time and could take more risks flying close or into a volcanic plume than a manned aircraft ever could.

However, research and equipment all costs money and agreement has yet to reached as to who will pay for it. It was remarked during the conference that the UK government had not compensated any of the operators of research aircraft that were taken off other research projects to monitor the ash clouds. Another problem is that of communication. People involved with the crisis often had to spend much of their time answering questions for government and the media when they could have been working to solve the problem. There also needs to be more sharing of information. Rolls-Royce reported that, from all the test flights conducted by airlines, the engine manufacturer was only able to get data from two of them. There also needs to be more communication between interested parties. “We need to improve interdisciplinary communication between vulcanologists, meteorologists, research aircraft, air traffic controllers, regulators, pilots, airlines, manufacturers, governments and the general public,” commented Sue Loughlin.

When the next volcano goes off, no one can say that we haven’t been warned.

This is a full article published in Aerospace International: January 2011. As a member, you recieve two new Royal Aeronautical Society publications each month - find out more about membership.

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One Response to “Under the ash cloud”

  1. John Thompson says:

    Having re-read ‘Under the Ash Cloud’, I remain convinced that the UK’s Aviation executive (including RAeS)reponse to the event was very poor. How the decision was taken to close all UK airspace is not really covered. We went to bed with no mention of ash on any media and woke up the next morning with NATS having closed down all our airspace. Who made the decisions and on what evidence? ‘Zero tolerance to ash’ is and was clearly a rediculous policy on which to base such an important decision.
    I also find the brief statement under the Avoid, Avoid, Avoid section that seeks to explain why it was not possible for at least some aircraft to fly over, under or around the dangerous elements of the ash cloud rather pathetic in 2011.
    John Thompson AM (Retd)

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