ICAO - 9691
Manual on Volcanic Ash, Radioactive Material and Toxic Chemical Clouds
|Publication Date:||1 January 2015|
On 24 June 1982, the aviation community and much of the world learned of the drama involving a British Airways B747 aircraft which lost power on all four engines while flying at 11 300 m (37 000 ft) from Kuala Lumpur, Malaysia to Perth, Australia. During the ensuing sixteen minutes, the aircraft descended without power from 11 300 m to 3 650 m (37 000 ft to 12 000 ft), at which point the pilot was able to restart three of the engines and make a successful emergency landing at Jakarta, Indonesia.
Over the next few days the civil aviation authorities, engine manufacturers and the airline company involved mounted an urgent investigation into the cause of the four-engine flame-out. On-site inspection of the airframe and engines revealed a general "sand-blasted" appearance to the leading edges of the wing and engine inlet surfaces, the radome and the cockpit windows. Borescope inspection of the engines revealed no apparent mechanical damage and no fuel problem, but heavy deposits of an unknown material were found on the concave surfaces of the high-pressure turbine and nozzle guide vanes.
The report of the incident by the pilot indicated that an acrid electrical smell had been noticed in the cockpit at the time and what appeared to be very fine dust or smoke entered the cockpit. St. Elmo's fire was observed on the leading edge of the engine nacelles and around the cockpit windows, and a "search light" effect was visible shining out of the engines through the fan blades. Moreover, when the aircraft was making its emergency landing at Jakarta, it was immediately apparent that the cockpit windows were almost completely opaque and the landing had to be completed by the pilot looking through a small side- section of the cockpit window that had remained relatively clear.
Piecing together the available evidence and knowing that a large Indonesian volcano, Mt. Galunggung, had been erupting at the time of the incident, suspicion quickly focused on a volcanic ash cloud as being the likely culprit. This suspicion gained further support some three weeks later when another aircraft, a B747 of Singapore Airways bound for Melbourne, Australia, reported a similar incident. This time power was lost on two engines and the aircraft also diverted successfully to Jakarta.
Subsequent strip-down inspection of the engines from the British Airways aircraft revealed general evidence of "sand-blasting", erosion of compressor rotor paths and rotor blade tips, erosion of the leading edges of high-pressure rotor blades and fused volcanic debris on the high-pressure nozzle guide vanes and turbine blades. It was clear that the engines on the aircraft had all stalled due to ingestion of volcanic ash and that a restart had only been achieved because the aircraft, in descending without power, happened to fly out of the high-level volcanic ash cloud into clear air.
The seriousness of these two incidents was not lost on the aviation community. While it was known that aircraft had encountered difficulties in the past when inadvertently flying through volcanic ash cloud, these incidents had generally been restricted to the sand-blasting effect of the ash on cockpit windows and to blocked pitot-static tubes. It was now perfectly clear to all that such ash clouds had the potential to cause a major aircraft accident.
To meet this newly recognized threat, the ICAO Air Navigation Commission moved swiftly to develop a set of interim guidelines to assist States in the dissemination of information on volcanic ash to pilots and the development of contingency arrangements for the diversion of aircraft around affected areas, pending the development of the necessary formal amendments to the relevant Annexes to the Chicago Convention and Procedures for Air Navigation Services (PANS). These formal amendments were subsequently developed, with the assistance of the ICAO Volcanic Ash Warnings Study Group (VAWSG), and were adopted by the ICAO Council in March 1987.
The initial amendments to the ICAO Annexes and PANS comprised international Standards, Recommended Practices and Procedures covering the observation and reporting of volcanic activity, eruptions and ash cloud, the issuance to aircraft of warnings and, as necessary, information regarding the closure of air routes and the activation of alternative contingency routes, and the reporting by pilots to air traffic service units of any observed volcanic activity or encounter with volcanic ash cloud. These initial provisions essentially formed the framework for the ICAO International Airways Volcano Watch (IAVW), the establishment of which was made possible by the cooperation of States and a number of international organizations.
In addition, the need to develop guidance material on volcanic ash in the form of an ICAO circular was identified by the Air Navigation Commission. During the next few years, however, events moved faster than anticipated with a number of explosive eruptions occurring including Mt. Redoubt and Mt. Spurr in Alaska in 1989 and 1992, respectively, Mt. Pinatubo in the Philippines and Mt. Hudson in Chile in 1991, all of which affected aviation. The experience gained in conducting aircraft operations during these and other eruptions permitted the development of detailed regional procedures to cope with the situations. In view of this, the Air Navigation Commission agreed that the guidance material on volcanic ash should be issued as an ICAO manual and not as a circular.
Further amendments to the ICAO Annexes and PANS were made to provide for the issuance by meteorological watch offices (MWOs) of information concerning en-route weather and other phenomena in the atmosphere that may affect the safety of aircraft operations (SIGMETs) encountering a volcanic ash cloud, to assist operators at the flight planning stage in the dispatch of aircraft on long-haul routes and to include provisions relating to Volcanic Ash Advisory Centres (VAACs). In this regard, international arrangements were made, in cooperation with the World Meteorological Organization (WMO), to designate nine regional volcanic ash advisory centres having the capability to detect, track and forecast the movement of volcanic ash clouds and provide advice to meteorological watch offices in their areas of responsibility. The role and responsibilities of the VAACs were introduced into Annex 3 by Amendment 71 which became applicable on 5 November 1998.
Since the eruptions of Mt. Galunggung in Indonesia in 1982 there have been numerous explosive volcanic eruptions around the world, many of which have affected aircraft operations. With the occurrence of each new eruption, the opportunity has been taken to focus on and review the local and international arrangements for the issuance of information to pilots and, where necessary, fine-tune these arrangements based on actual operational experience gained in dealing with the impact of the eruptions on aircraft operations. In this way, the IAVW is being steadily expanded and strengthened.
There have been many difficulties faced in the establishment of the IAVW, most of which have been of a technical or procedural nature which, with the cooperation of States and international organizations, have since been resolved. There is, however, a more general difficulty that is unlikely to ever be eliminated completely and which, therefore, requires constant attention. This concerns the fact that the IAVW depends entirely on cooperation between a number of different disciplines such as air traffic services, communications, meteorology and vulcanology and numerous and varied national observing sources such as forestry stations, customs/immigration border posts, etc., within sight of active volcanoes. Constant attention is required by States to maintain effective communications channels from the various observing sources to the relevant area control centres (ACCs)/flight information centres (FICs) and MWOs. Moreover, because explosive volcanic eruptions in any one State are, thankfully, comparatively rare events, maintaining the currency of the local procedures during numerous staff changes and over long periods when the procedures may never have had to be activated under the circumstances of a real volcanic eruption in a particular State, is extremely difficult.
In addition to its potential to cause a major aircraft accident, the economic cost of volcanic ash to international civil aviation is staggering. This involves numerous complete engine changes, engine overhauls, airframe refurbishing, window re-polishing and/or replacement and pitot-static system repair, etc., and the inevitable loss of revenue due to aircraft down-time while the foregoing is accomplished. Delays to aircraft and their rerouting around volcanic ash has caused considerable expense to airlines operating in regions prone to volcanic eruptions. Also to be included is the cost of volcanic ash clearance from airports and the damage caused to equipment and buildings on the ground. Various estimates have been made, most citing costs to aviation well in excess of $250 million since 1982.
The Meteorology (MET) Divisional Meeting (2002), held conjointly with the Twelfth Session of the Commission for Aeronautical Meteorology (CAeM) of WMO, recommended the establishment of the International Airways Volcano Watch Operations Group (IAVWOPSG) to coordinate and develop the international airways volcano watch (IAVW) with a global perspective. Since then, the IAVWOPSG has held several meetings in various ICAO regions making considerable progress on the refinement of existing, and the development of new, Standards and Recommended Practices, procedures and associated guidance material, thereby placing the IAVW as a mature system to support international air navigation in ensuring the availability of up-to-date and relevant information on volcanic ash in the atmosphere.
In April 2010, the explosive phase of the Eyjafjallajökull eruption in Iceland provoked an unprecedented disruption of air operations, which paralyzed aircraft operations in the western and northern parts of the European (EUR) and eastern parts of the North Atlantic (NAT) regions for many days. This event prompted the establishment by ICAO of an International Volcanic Ash Task Force (IVATF) tasked to urgently address, in close coordination with the IAVWOPSG, issues relevant to the Eyjafjallajökull eruption. The IVATF was tasked to, inter alia, review the guidance material, establish volcanic ash contingency plans, improve ash detection systems and develop ash concentration thresholds. Without reaching agreement on ash concentration thresholds, the IVATF was disbanded in 2012 after completion of most of the assigned tasks and prompting several legacy tasks to the IAVWOPSG. As a result of recommendations stemming from the MET Divisional Meeting (2014), the IAVWOPSG was disbanded and its tasks were assigned to the Meteorology Panel (METP). Today, ICAO, with the assistance of the METP, continues the development of the IAVW in order to ensure that it continues to meet evolving operational requirements.
Given the safety and economic implications of volcanic ash to aircraft operations, it is necessary to maintain the ICAO International Airways Volcano Watch much in the same way that the aerodrome fire services are maintained: in constant readiness but with the fervent hope that it rarely has to be used.
Generally speaking, volcanic ash in the atmosphere is of little direct safety concern to anyone except aviation. It falls upon the aviation community, therefore, to take the lead in establishing and maintaining the essential channels of communication between volcano-observing sources and the relevant ACCs, FICs and MWOs and maintaining the currency of the local staff instructions and procedures. The main purpose of this manual, therefore, is to assist States and international organizations in this effort by gathering together in one document information on the problem of volcanic ash and provide guidance regarding what each of the parties in the IAVW is expected to do and why.
Since the aircraft incidents involving volcanic ash described above, which prompted the development of the IAVW, aviation has been faced with two other newly recognized hazards. These concerned radioactive materials and toxic chemicals discharged into the atmosphere following industrial accidents. The accident at the Chernobyl nuclear power plant in 1986, in which a cloud of radioactive debris spread across international borders, caused difficulties for aircraft operations in neighbouring States and drew attention to the potential risk for aircraft en-route to destinations which lay in the path of such a cloud. Similar accidents have occurred at industrial chemical plants and during the transport of toxic chemicals which so far have caused only local operational problems, but which also have the potential to affect international aircraft operations.
The Air Navigation Commission considered that, given the operational similarities in the provision of warnings to aircraft for radioactive materials and toxic chemicals on the one hand and for volcanic ash on the other, it would be expedient for the VAWSG to advise the Secretariat on the development of the necessary international arrangements and procedures for warning aircraft in flight of radioactive materials and toxic chemicals accidentally discharged into the atmosphere.
Accidents at nuclear or chemical facilities, in which hazardous materials are discharged into the atmosphere, present a danger to the general public, including those travelling by air, and are already the subject of detailed emergency procedures in States concerned, and regular international tests of the procedures are made. It is not the purpose of ICAO, therefore, to develop separate procedures for aviation, but to ensure that due account is taken of the special needs of international civil aviation, especially aircraft in flight, in the relevant Annexes to the Convention and in international arrangements developed to deal with such emergencies. 29
In addition to addressing the problem of volcanic ash, a secondary purpose of this manual, therefore, is to provide information concerning the requirements for the provision of warnings to aircraft of radioactive materials and toxic chemical clouds and guidance regarding how these requirements may be satisfied.
There is little point in having such guidance material unless it is used in the relevant training courses for staff whose duties are involved in any way with the provision of operational information to aircrew, and in the training courses for the aircrew themselves. States are, therefore, requested not only to make this manual available to staff concerned, but also to ensure that relevant training courses adequately cover the subject matter contained therein.