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VOLCANIC ASH 
INTERNATIONAL TELECONFERENCES 
 
17-23 April 2010 
 
INFORMATION NOTE 
REPORT OF PROCEEDINGS 
 
 

Padhraic Kelleher 
Head of Airworthiness 
UK Civil Aviation Authority 
 
Report of Proceedings FINAL: 5 May 2010 v1 
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Context 
 
 
After three weeks of activity, Iceland’s Eyjafjallajokull volcano erupted on 14 April 2010 for 
the first time in almost 200 years.  The ejected debris plume reached over 30,000 feet into 
the atmosphere and was carried by the prevailing wind over the UK and Northern Europe. 
 
The aviation industry’s standing instructions for dealing safely with volcanic ash, published 
by ICAO, are to avoid all encounters with ash.  This advice has been incorporated into 
safety management systems operated by leading air traffic services and airspace 
management organisations.  The “zero tolerance” of ash inherent in this advice led directly 
to a sequence of decisions that reduced air traffic flow through UK, Irish and Continental 
European airspace to a “zero rate” in those sectors identified as falling within the London 
Volcanic Ash Advisory Centre (VAAC) contaminated area. 
 
The plume persisted over the British Isles and Northern Continental Europe for a number 
of days; the continued application of “zero rate” halted commercial aviation operations.  By 
18 April, commercial aviation movement through the airspace of 23 European countries 
had ceased and restrictions were in place in two other countries.  Over 300 airports, 
representing 75% of the European network, closed.  Precautions were taken to protect 
grounded aircraft from potential ashfall and to prepare aerodromes to deal properly with 
ashfall. 
 
Urgent confirmation was needed as to whether a “zero tolerance” of volcanic ash was 
necessary to maintain flight safety.  If not, then there was an urgent need to identify a 
density of ash which could be safely tolerated by commercial aircraft and engines; it was 
acknowledged that even if it could be established that operations in such ash densities 
were safe, there might be economic penalties in relation to an escalation in the 
engineering interventions necessary to sustain airworthiness standards. 
 
Response 
 
On 17 April, UKCAA hosted the first of a series of teleconference meetings aimed at 
gathering together the world’s leading aircraft and engine manufacturers to focus on this 
issue.  Supporting these discussions were leading scientific experts in meteorology, 
geology and volcanology, many of whom were directly monitoring the Eyjafjallajokull 
eruption and ash plume.  Air Traffic Services experts, airspace managers and leading 
airlines also supported the work.   
 
More than 60 organisations participated in a series of six teleconferences between 17 and 
23 April.  Instrumented flight test aircraft were made available to the group and the 
resulting data communicated after each flight sequence to the group. 
 
On 20 April, the aircraft and engine manufacturers determined that their aircraft and 
engines would tolerate operations in an ash density of 2x10-3g/m3.  Flight operations in the 
UK recommenced shortly after this consolidated position had been determined.  By 22 
April, activities had resumed across Europe apart from airspace in southern Finland. 
 
Eurocontrol has reportedly estimated that more than 100,000 flights were cancelled 
affecting the travel plans of around 10 million passengers.  The airlines estimate their 
Report of Proceedings FINAL: 5 May 2010 v1 
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losses in the order of €1.4 billion, the airports €250 million, ground handlers €200m and Air 
Navigation Service Providers €175 million with wider impacts beyond this grouping. 
 
Agreed Position 
 
The position agreed by the manufacturers on 20 April 2010 was presented in the following 
form: 
 
Statement from the international conferences of airframe and aero engine 
manufacturers, aviation safety regulators, operators and specialist 
meteorological and research agencies 
 
20 April 2010  
In response to the exceptional operational circumstances currently being experienced in 
the UK due to volcanic ash, the airframe and engine manufacturers have held extensive 
discussions with regulators, operators, research centres, air traffic control service 
providers and meteorological agencies with a view to finding a way to resume operations 
in UK airspace.  
1) The limited data available from previous volcanic ash encounters involving a variety of 
manufacturers’ products has been analysed.  
2) The understanding of previous volcanic ash eruptions is that flight operation restrictions 
have ensured that encounters with volcanic ash are minimised and appropriate 
precautionary inspections are carried out to identify whether encounters have occurred.  
3) Based on the available data, a consensus has been reached among the parties to 
permit operations initially in areas of volcanic ash with densities predicted by the UK Met 
 
Office, of up to 2 x10-3g/m3 subject to appropriate precautionary maintenance practices 
being applied and the avoidance of visible ash.  
4) The possible long-term effects of operation in volcanic ash are not known. In view of 
this, additional maintenance measures will be required to be developed by airframe 
manufacturers in conjunction with their engine suppliers to monitor for any possible long-
term airworthiness effects resulting from operations in volcanic ash concentrations up to 
this level.  
5) Industry and regulators are committed to continuing to work to acquire and analyse 
information arising from operational experience which would appear to offer an improved 
understanding of any longer term effects and to further modify maintenance programmes 
when appropriate.  
 
 
Report of Proceedings FINAL: 5 May 2010 v1 
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Implementation 
 
As well as defining a tolerable ash density level, the manufacturers group also considered 
how the tolerable level could be used to aid flight planning.  The majority view supported 
the creation of a "No Fly" zone at ash concentrations above 2x10-3 g/m3 with normal 
operations beyond this zone.  There was a significant minority view in support of adding an 
intermediate "enhanced procedures" zone (below 2x10-3 but above 2x10-4). 
  
The European National Supervisory Authorities (NSAs) and Air Navigation Service 
Providers (ANSPs) elected to adopt the 2 x 10-3 limit and to also apply a 60 nautical mile 
buffer around it in order to create an extended “No Fly” zone.  An intermediate “Enhanced 
Procedures Zone” (EPZ) was also introduced as shown in the diagram. 
 
To facilitate flight 
planning, the NSAs and/or 
ANSPs agreed to publish 
a NOTAM every 6 hours 
setting out the specific 
coordinates of the No Fly 
zone.   The Enhanced 
Procedures Zone was 
defined on a revised chart 
published by the UK Met 
Office in its role as the 
London VAAC.  Work to 
provide the necessary 
information in one 
published source 
continues. 
 
For UK commercial 
operators, the UK CAA required operators, in planning flights through the EPZ, to carry out 
a risk assessment.  CAA also encouraged operators to report any events they suspected 
could be linked to a volcanic ash encounter. 
 
The CAA also reaffirmed its belief that the manufacturers are best placed to decide what 
the appropriate maintenance procedures should be in preparation for, or following, a flight 
in the EPZ.  As no evidence existed of any additional safety concerns for operations within 
this zone, the CAA did not require enhancements to the instructions judged by the 
manufacturers necessary for their particular products. 
 
By 23 April, all participating manufacturers, and a wider range of companies worldwide, 
had issued to operators of their aircraft and engines the engineering instructions 
necessary to ensure continued airworthiness of aircraft operating in ash density up to 
2x10-3g/m3. 
 
 
Report of Proceedings FINAL: 5 May 2010 v1 
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Technical Assessment  
 
In deciding that 2x10-3g/m3 was a tolerable ash density level, the manufacturers were able 
to take account of information and advice regarding: 
•  The rationale behind the ICAO “zero tolerance” approach and confirmation that it was 
not based on known safety concerns at low concentrations of ash (as briefed by FAA 
and US Weather Service staff who participated in that work) 
•  The use by the London VAAC of a predicted ash density of 2x10-4g/m3 as the limit of the 
extant “no fly” zone and the value to restoring operations were it possible safely to 
reduce this limit to 2x10-3g/m3 (as briefed by UK Met Office and NATS staff) 
•  The London VAAC ash density forecasting process including modelling, measurements 
and data blending and, with help from experts from the FAA and US Weather Service, 
comparisons of the London VAAC techniques with those used at the Washington and 
Anchorage VAACs 
•  An independent assessment of the London VAAC forecasts by the UK National Centre 
for Atmospheric Sciences confirming confidence in the Met Office products 
•  Instrumented flight test measurements from the UK Facility for Airborne Atmospheric 
Measurements (FAAM) and NERC, the UK Natural Environment Research Council, 
LIDAR laser measurements and meteorological balloon data all confirming that the 
forecast levels accorded well with the peak values being measured in the atmosphere 
•  The physical and chemical properties of particulates in the plume based on information 
from the Icelandic Met Office 
•  The calculated rate of accumulation of ash within the core of turbine engines and its 
expected subsequent behaviour and effects 
•  The robustness of airframe systems (e.g. Total Air Temperature probes, pitot probes 
and static ports) in relation to ash intake and flow erosion 
•  The operational experience in the presence of ash after the Mount Redoubt eruption in 
1989 as reported extensively by Alaskan Airlines albeit that readily accessible data on 
the specific ash densities encountered was not available 
•  Detailed information on a range of specific encounters with ash including the KLM 
B747-400 incident in 1989 resulting in a four-engined flame out in a calculated ash 
density of 2g/m3   
•  Data from “pathfinder” flights flown by some European airlines between 15 and 19 April 
and for which manufacturers had had direct involvement in data acquisition pre and post 
flight; again there was typically a paucity of credible data on the specific ash densities 
encountered. 
 
The manufacturers were clear that although they were content that 2x10-3g/m3 represented 
a tolerable density level for their products, any further increase in this level would require 
more data on, and analysis of, the effects of ash contamination on airframes and engines.   
 
Report of Proceedings FINAL: 5 May 2010 v1 
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Future Work – near term 
 
By 26 April, the eruption from Eyjafjallajokull had subsided from a peak material ejection 
rate approaching 1,000 tonnes/second to a rate closer to 10 tonnes/second.  However, 
fresh eruptions from this volcano can be expected for some time to come.  Furthermore, 
the UK Geological Survey advises that 3 out of 4 eruptions of the current active volcano 
result in Katla, the larger volcano in that region of Iceland, also erupting.  Hence, further 
work in relation to tolerability at higher ash concentrations is advisable in the near term.   
 
It would seem sensible to consider assessing the tolerability of ash and other particulates 
at densities of the order of 10-2 g/m3
 
The Group also noted the potential value in examining the case for flights that transition 
through areas of contamination for a portion of the flight only.  It might be possible to 
accommodate such flights were it possible to specify not only a tolerable rate of 
accumulation per hour of exposure but also a maximum total accumulation per flight.  
Were such an approach possible, it could provide aircraft operators with a mechanism to 
permit safe flight planning and to anticipate the necessity for post flight actions. 
 
With this in mind, manufacturers are continuing to gather data from the current operations 
and from instrumented specialist atmospheric research aircraft in order to further validate 
current assumptions and to provide a basis for further work.   
 
Additional airborne research assets are being identified internationally and arrangements 
made to coordinate their efforts with those of the UK assets.  Early data acquisition is 
being aimed at exploring the outer edges of the no fly zone to confirm the forecast ash 
densities, to confirm the overall makeup of the ash plume and to provide information to the 
Health Protection Agency regarding health of aircraft occupants.  The data is being 
committed to the repository run by EUFAR, the European Facility for Airborne Research 
which coordinates European atmospheric research assets. 
 
In parallel, the UKCAA has alerted aircraft owners and operators, both private and 
commercial, of the need to report any actual or suspected encounters with ash.  These 
occurrence reports are being gathered, examined and made available through a data 
repository being established by Eurocontrol.  Manufacturers are also receiving such 
reports directly from the operators of their products. 
 
In addition, manufacturers have worked with some airlines to establish a data gathering 
programme involving a selected group of aircraft which are being specifically monitored 
and their condition reported on an ongoing basis as they continue to operate within and 
outside of the Enhanced Procedures Zone. 
 
Report of Proceedings FINAL: 5 May 2010 v1 
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Future Work – mid term 
 
The group established a specialist group to compare the forecasts produced by different 
VAACs, to identify any variations in approach that might exist and to recommend best 
practice taking into account such inputs as the manufacturers and operators would make 
in relation to the usability of the solutions generated. 
 
The specialist group is also drawing together such knowledge, data and research as they 
can find in order to contribute proactively to the development of new ICAO standards, 
practices or guidelines.   Again, the continued involvement of the manufacturers has been 
identified as a key aim. 
 
 
 
 
 
 
 
 
 
 
 
Padhraic Kelleher 
Head of Airworthiness 
UK CAA 
5 May 2010 
Report of Proceedings FINAL: 5 May 2010 v1 
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ATTENDANCE ON THE CONFERENCE CALLS 
 
This table summarises known participation in a series of conference calls from Saturday 
17 to Friday 23 April 2010.  There was no call on 21 April.  
 
•  Total number of organisations involved:  63. 
•  Total number of organisations actively participating in calls: grew from 20 to 43. 
 
It is likely that there were many more participants than recorded here due to difficulties for 
organisations in responding to the on-call registration process and because many 
organisations fielded teams of experts on each call: 12 from Boeing on Call 1, for example.  
“Linked” organisations were in contact with proceedings. 
 
 
Call 1 
Call 2 
Call 3 
Call 4 
Call 5 
Call 6  Linked
Airframe Manufacturers 
 
 
 
 
 
 
 
Airbus  






 
ATR 
     
 

BAE Systems – Regional Aircraft 
 
 
 
 


 
Boeing 






 
Bombardier 
Aerospace 
   3 


 
Bombardier Shorts Brothers  
 
 
 



 
Cessna 
Textron 
     
 

Dassault 
    3 

 
Embraer 
   3 


 
Gulfstream 
       3 
 
 
 
 
 
 
 
 
Engine Manufacturers 
 
 
 
 
 
 
 
General Electric 






 
Honeywell 
International 
   3 


 
International Aero Engines 
 
 
 
 
 

 
Pratt & Whitney 






 
Pratt & Whitney Canada 
 
 




 
Rolls Royce 






 
SNECMA  





 
Williams 
International 
       3 
 
 
 
 
 
 
 
 
Air Navigation Service Providers 
 
 
 
 
 
 
 
Eurocontrol 

 
 
 
 
 
 
FAA Air Traffic Control 
3 





 
Meteo France (Toulouse VAAC) 
 

 

 
 
 
Met Office, Iceland 
 
 
 
 
 
 
3 
Met Office, Netherlands 
 

 
 

 
 
Met Office, UK (London VAAC) 






 
National Oceanic and Atmospheric 






 
Administration (NOAA), US (Anchorage 
VAAC and Washington VAAC) 
NATS 


 
 
 
 
 
US Air Force Met Service 
 
 
 
 
 

 
 
Report of Proceedings FINAL: 5 May 2010 v1 
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Call 1  Call 2
Call 3 
Call 4 
Call 5 
Call 6  Linked
Scientific Agencies 
 
 
 
 
 
 
 
CEV, National Flight Test Centre of France 

 
 
 
 
 
 
Chief Scientific Adviser, UK 
 
 
 



 
FAA Weather Group  






 
Facility for Airborne Atmospheric 




 

 
Measurements, UK (FAAM) 
National Centre for Atmospheric Sciences, 
 





 
UK (NCAS) 
Natural Environment Research Council, UK 

 
 
 
 
 
 
(NERC) 
NLR, German Research Centre 
 
 
 
 

 
 
US Geological Survey 
 
 
 
 
 

 
 
 
 
 
 
 
 
Operators  
 
 
 
 
 
 
 
Air Canada 
 
 
 
 
 

 
Air France 
 
 
 
 
 

 
Astraeus  
 
 
 
 
 

British Airways 

 

 

 
 
easyJet  
 
 
 
 
 

FlyBe  
 
 



 
bmi  
 
 
 


 
Lufthansa  
 
 



 
Monarch  
 
 



 
Ryanair  
 
 
 
 

 
Thomas Cook 
 
 
 



 
Thomson Airways 
 
 
 

 
 
 
United Airlines 
 
 
 
 
 


Virgin Atlantic 
 
 
 
 


 
 
 
 
 
 
 
 
Representative Bodies  
 
 
 
 
 
 
 
Aerospace Industries Association 
 
 
 
 
 
3 
 
General Aviation Manufacturers 
 
 
 
 
 

 
Association 
Oil & Gas UK 
 
 
 
 
 
 

 
 
 
 
 
 
 
Regulators  
 
 
 
 
 
 
AESA, Spain 
 
 




 
CAA, Netherlands 




 
 
 
CAA, Norway 
 
 
 

 
 
 
CAA, UK 






 
DGAC France 






 
EASA 






 
FAA Airworthiness Certification 






 
Irish Aviation Authority 
 
 




 
MAA, UK Military Aviation Authority 
 
 
 



 
Transport Canada 
 
 
 


 
 
UK DfT 
 



 

 
 
ENDS 
 
Report of Proceedings FINAL: 5 May 2010 v1 
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Document Outline