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Ash fall may severely disrupt transportation systems over extremely large areas for hours to days, including roads and cars, airports and aircraft, and railways. An ash fall of 1-3 mm can seriously reduce visibility on highways, make roads slippery for cars, strand travelers, damage vehicles and aircraft that operate in ashy conditions, and result in the temporary shut down of airports and highways. Returning transportation systems to normal service following an ash fall requires the removal and disposal of ash and the cleaning of vehicles, aircraft, and facilities. Cleanup operations will be most efficient when a disposal site for the ash is identified before ash begins to fall (see considerations for identifying an ash dump site) and residents, businesses, and utilities coordinate their activities.

Mitigation strategies for reducing the effects of volcanic ash to transportation systems are described for each category shown above.

Roads & Highways  || Driving conditions || Safety strategies || Drainages || Ash cleanup & removal  ||

Driving conditions

Poor visibility
Visibility on roads is typically poor during and after an ash fall, and total darkness may result during a heavy ash fall. During such conditions vehicle headlights and brake lights are often ineffective and barely visible to other drivers, and driving may become difficult or impossible. After an ash fall, fast-moving vehicles will stir up ash along roads and create billowing ash clouds a few tens of meters tall.

For example, following an eruption of Mount St. Helens in Washington on 25 May 1980 that deposited 1-4 cm of fine ash within about 120 km of the volcano, hundreds of vehicle accidents were likely caused by such stirred-up ash. This description appeared in the newspaper Seattle-Post Intelligencer on 28 May:

"Brake lights could be faintly seen through the dust which rose 30 feet (9 m) above the freeway. Often, though, lights couldn't be seen, and all that could be heard was the tinkle of broken glass and the crunch of crumpled metal as cars from the rear headed into the ash clouds, and rammed vehicles already hidden in the clouds" (Blong, 1984, p. 291-292).

Slippery surface
Ash deposits will absorb a considerable amount of water before being eroded and washed away. When ash on roads become wet, the mud-like mixture can cause vehicles to lose traction and drivers to lose control of steering. During such conditions, the braking ability of vehicles may be significantly reduced.

Dry ash also cause roads to be slippery.

Road markings covered
Ash deposits thicker than about 1 mm will obscure or completely cover markings on roads that identify lanes, road shoulders, direction of travel, and instructions to drivers (for example, stop or slow). When such road markings are not visible, drivers may become confused and disoriented.

Safety strategies

Before ash is removed from roads, several actions can help reduce vehicle accidents and lower the amount of ash that is constantly being stirred up by moving vehicles. The following actions were taken in communities and for major highways in eastern Washington following an ash fall that deposited between 1 and 5 cm of ash from the 18 May 1980 eruption of Mount St. Helens:

Drainages and waste-water systems

Drainage canal cleared of volcanic ash, Mount Pinatubo, Philippines
Ash was removed first from drainage ditches, Philippines
Ash fall may also result in the clogging of roadside ditches and culverts. During rainfall, poor or nonexistent drainage along a highway or road can cause erosion of the shoulder and road surface. During ash clean-up operations, prevent ash from accumulating in such drainages or entering underground waste-water or storm-drain systems.

Ash cleanup & removal from roads

Most communities and organizations tackle the ash cleanup of roads and highways using their available road-cleaning equipment and, sometimes, from the help of those not affected by ash fall. If ash is pushed to the side of the road instead of removed, wind and vehicle movement will cause it to stir or billow, creating clouds of ash for weeks or months.

Ash typically is removed from urban areas even for accumulations of only a few millimeters. A number of factors will influence the removal method employed, the ease with which ash can be removed, and the cost of any clean-up operation. These include ash thickness, grain-size, availability of equipment, and the degree of cooperation and assistance from residents.

Removing ash from paved roads and urban streets
  • Provide direction to property owners along roads and streets to be cleaned to move ash from roofs and the rest of their property to the street. The ash should be placed away from waste-water drains and gutter downspouts that enter the road to avoid blockages.
  • Coordinate the various road, residential, and building clean-up efforts to prevent the need for more than one ash-cleaning sweep in each area.
  • Before starting cleanup activities, build small dikes (for example, using sandbags filled with ash) around catch basin inlets and waste-water drains or sewer systems to prevent ash from entering the drains.
  • Encourage residents to organize into neighborhoods on a block by block basis in order to sweep and water down roofs and pile dampened ash in windrows on the street at the same time. Such windrows can reach one meter tall and a few meters wide. Coordinate street cleanup when neighborhood teams have completed their work.
  • Moisten the ash using a sprinkling system. Avoid getting the ash too moist because a wet ash slurry is difficult to isolate and collect.
  • Use motorized graders to scrape or blade ash to the middle of the road into berms or windrows. Collect, load, and transfer the ash to trucks, then haul the ash to approved disposal sites.
  • For a thorough cleaning of paved roads with storm sewers, after the ash is removed, use power brooms on the remaining dampened ash.
  • To remove the remaining ash on paved roads without storm sewers, flush the roads with water (see next section below).
  • As soon after the street cleanup as possible, remove ash deposits from catch basin inlets with vacuum trucks or machines with jet prodding and vacuum systems. Long delays in cleanup allows time for the ash to develop a surface crust or compact into pieces, making it harder to remove.

Modified from, FEMA, 1984

Removing ash from paved or oiled roads that have no curbs or sewers
  • Sprinkle ash with water and use motorized graders to blade it onto the shoulders or into the ditches. Collect, load, and transfer the ash to trucks to be hauled to dump sites. Remove the residue by sweeping or flushing the road with water, if necessary.
  • If gravel shoulders exist, replace lost gravel in order to maintain the integrity of the roadway.

Modified from, FEMA, 1984

Removing ash from gravel roads
  • Use motorized graders to blade the ash into roadside ditches, being careful to avoid unnecessary loss of surface materials (gravel).
  • If the existing right-of-way is wide enough, spread the ash along the back slopes outside the ditch. (Note that much of the ash may become integrated into roadside vegetation and that the ash in these areas will blow for some time during windstorms. 
  • Remove ash blocking the drainage in ditches and culverts, and transport it to a disposal site.
  • A considerable amount of ash will remain on the roadbed surfacing, creating a serious visibility problem for traffic. Nothing can be reasonably done to eliminate it totally, but it will decrease with time.
  • On the roadbed, place a thin layer of rock consisting of graded material 5/8 inch or less and crushed to standard specification. This layer can be added and processed into the existing surface to achieve the binding effect that will stabilize the surface under traffic. (While this expensive method will not provide total dust control, it is, nevertheless, the most suitable method available for achieving visibility levels so that traffic operations can be restored.)

Since the roadway and visibility problems vary in each ash-affected area, no specific thickness criteria for gravel blankets can be provided. However, in determining thickness, the following factors should be considered:

  • Prevailing depth of ash deposit.
  • Functional classification of the road—its importance as a service arterial and acceptable speed restrictions.
  • Traffic characteristics—average daily traffic; variation in volumes; operation of intersections; turning conflicts.
  • Condition of existing surface—undulations, washboards, and ruts affecting loss of material if ash is bladed to shoulders.
  • Existing surfacing material—depth, quality and gradation as determinants for integrating the ash by scarification, mixing, blading and processing existing material.

Modified from, FEMA, 1984

Vehicles || damage || special maintenance ||

Damage to vehicles

Because volcanic ash consists of tiny pieces rock and volcanic glass, ash can infiltrate nearly every opening and abrade or scratch most surfaces, especially between moving parts of vehicles. Ash particles easily clog air-filtration systems, which can lead to overheating and engine failure. Small concentrations of ash particles inside an engine can cause extra engine wear. Even transmissions experience extra wear after ingesting minute ash particles.

Seals on hydraulic components may wear out faster than usual, and brakes and brake assemblies are especially vulnerable to abrasion and clogging from ash. Trucks used to transport ash to disposal sites and other vehicles subjected to heavy ash exposure may require constant brake attention.

Ash caught between windshields and wiper blades will scratch and permanently mark the windshield glass, and windows are susceptible to scratching each time they are raised, lowered, and cleaned. Corrosion of paintwork and exterior fittings may also result where ash is in contact with the exterior.

Special maintenance

Strategies for reducing the effects of ash on machinery involve frequent oil changes, cleaning or replacing air filters often, using air pressure (< 30 lbs/in2) to blow ash from electrical equipment and other essential engine components (for example, alternator, starter, wiper motor, and radiator), and frequently cleaning vehicles with water to wash away the ash. During such cleanup, care should be taken to ensure the ash does not enter a waste-water or drain-water system.

The list below provides some protective measures for vehicles driven in ashy conditions based on the experience of the 18 May 1980 eruption of Mount St. Helens. Vehicle owners and operators are encouraged to obtain maintenance manuals and manufacturers' recommendations that may be available for operating vehicles in ashy or dusty conditions. For example, in June 1980 General Motors Corporation issued a public service announcement to drivers in ash fallout areas from the Mount St. Helens eruption.

Suggested measures for reducing effects of ash to vehicles


  • Avoid driving in heavy ash conditions unless absolutely required.
  • When required to drive in ashy conditions keep speed below 55 km per hour (35 mph) or lower. Do not follow too close to the car ahead, and use headlights on low beam.

Oil change and air filters

  • Change oil often. In very dense ash conditions change oil at 80-160 km (50-100 mi) intervals. In light ash conditions change oil at 800-1,600 km (500-1000 mi) intervals. Lubricate all chassis components at each oil change.
  • Clean air filters by back-flushing filter paper with compressed air (30 lbs/in2). Caution—blow element from inside (clean side) to outside (dirty side). DO NOT strike filters against anything. Air clean only. If unsure, have a qualified mechanic perform the air filter service. Inspect filters for dents or torn paper. Clean the inside of filters and the filter cover with damp cloth before reinstalling filter. Reinstall filter in housing and tighten on cover very tight, approximately one full turn with pliers after tightening. Do not exceed one full turn with pliers or you may damage the system.
  • Commercial truck filters can be installed to increase the filtering capacity of the cleaner. This would be beneficial for vehicles operating continuously in extreme dust conditions.
  • Air filter restriction gauges can be installed by qualified mechanics. The gauge will tell you when your air filter requires servicing in order to avoid over-servicing.
  • DO NOT install hose from carburetor air intake (air clean) to inside of car. Outside dust and ash will be drawn into vehicle.
  • Rags, or any other intended filtering material, should not be placed over the carburetor inlet inside the air cleaner element; serious damage to the engine and/or loss of vehicle control may result.

Outside vents

  • Cover passenger compartment vent inlet (located at base of wind-shield and usually under hood) with thick, loosely woven felt-type material to filter air into vehicles. With vent filter in place, keep heater blower high. Blower will slightly pressurize inside of vehicle and keep dust from entering through body gaps or holes. If a vent filter is NOT installed, keep air conditioner and heater blowers off.


  • Have a service garage clean wheel brake assemblies every 50-100 miles for very severe road conditions, or every 200-500 miles for heavy dust conditions. The brake assemblies should be cleaned with compressed air.
  • Have service garage clean alternators winding with compressed air after heavy accumulation or every 500 to 1000 miles or after severe dust exposure.
  • Clean the vehicle, including the engine, radiator, and other essential parts daily, if necessary, using water to flush the ash.
  • Wash the engine compartment with a garden hose or steam cleaner. Be sure to seal off air intakes and electrical components before cleaning.

After running vehicles in heavy concentrations of ash, the equipment life of properly serviced vehicles, as outlined above, may be somewhat reduced, but the equipment probably will not have catastrophic failures. Failures attributable only to ash fall can be expected to occur within 30 days following the exposure period.

Modified from, FEMA, 1984

Railways || damage || temporary shutdown ||

Rail transportation is less vulnerable to volcanic ash than roads and highways, with disruptions mainly caused by poor visibility and breathing problems for train crews. Moving trains will also stir up fallen ash, which can affect residents living near railway tracks and urban areas through which railway lines run.


Fine ash can enter engines and cause increased wear on all moving parts. Light rain on fallen ash may also lead to short-circuiting of signal equipment.

Temporary shutdown

Disuptions caused by poor visibility and breathing problems for train crews, and potential damage to engines and other equipment, can result in the temporary shutdown of rail services or the delay in normal schedules. For example, ten trains in western Montana (USA) were shut down for nearly a day because of 1-2 mm of ash fall resulting from the eruption of Mount St. Helens volcano, 625 km to the west (Blong, 1984). The rail services were back to normal operations within 3 days, however.

Airports  || effects || mitigation strategies & cleanup ||


Worldwide, approximately 500 airports lie within 100 km of volcanoes that have erupted since 1900 AD. Ash fall has caused about 40 airports to close temporarily for periods lasting from one hour to as long as three weeks since 1944. The majority of closures have occurred since 1980. Ash falling on airports will affect runways, taxiways and aprons, buildings, ground services, electrical utilities, communication facilities, and airplanes parked on the ground. Also, electronically-activated badges used to gain entry to restricted areas may not permit access during power disruptions or if the badges become severely abraded by ash. Before these facilities and airplanes can return to normal service following an ash fall, the ash must be removed and cleaned from all surfaces, facilities, and airplanes.

Problems at airports include:

(a) difficult landing conditions due to reduced runway friction coefficient, especially when the ash is wet,
(b) loss of local visibility when ash on the ground is disturbed by engine exhausts during take off and landing,
(c) deposition of ash on hangars and parked aircraft, with structural loading considerably worsened if weight is added by precipitation absorbed by ash, and
(d) contaminated ground-support systems.

List of cities, towns, and military bases in which airport operations were disrupted by volcanic activity, from 1944 to mid-2003, organized by country (Guffanti and others, 2003).


Airport operations disrupted at city, town, or military base

Antigua Saint John's
Argentina Buenos Aries, Comodoro Rivadavia, Cordoba, Jujuy, Mar del Plata, Neuquen, Puerto Deseado, San Julian, Salta
Colombia Pasto
Dem. Rep. of Congo Goma
Dominica Roseau
Ecuador Ambato, Quito, Riobamba
France Unnamed airport(s) on Guadeloupe
Guatemala Guatemala City
Indonesia Bandung, Gorontola, Manado, Medan, Surabaya, Unnamed airport west of Gamalama volcano
Italy Catania, Reggio di Calabria, Naples, Sigonella Naval Air Station
Japan Kagoshima, Mijake-jima
Mexico Colima, Mexico City, Puebla, Unnamed airports in SE Mexico
Netherland Antilles Sint Maarten
New Zealand
Auckland, Tauranga
Paraguay Asuncion
Philippines Basa Air Base, Clark Field, Cubi Point, Legaspi, Manila, Puerto Princesa, Sangley Pt. Air Base
Papua New Guinea Kimbe, Kavieng, Port Moresby, Rabaul
St. Kitts
Unnamed airport
United Kingdom Unnamed airport on Anguilla, Bramble (Montserrat), Stanley (Falkland Islands)
USA and Territories Anchorage, Elemendorf Air Force Base, Grant County, Guam, Kenai, Merrill Field, Missoula, Portland, Pullman, Roosevelt Roads Naval Air Station (Puerto Rico), Saipan (Mariana Islands), San Juan (Puerto Rico), St. Croix (US Virgin Islands), St. Thomas (US Virgin Islands), Spokane, Unnamed airports on south Texas coast, Yakima

Mitigation and cleanup

A workshop, Impacts of Volcanic Ash on Airport Facilities, was convened 26-28 April 1993 in order to enhance aviation safety through the exchange of information about proper removal and containment of volcanic ash at airport facilities (Casadevall, 1993). Several common recommendations emerged during discussions in the four working groups. These recommendations have a direct practical bearing on ash and airport operations. Many of these were also included in the working group recommendations and considerations listed below.

Impacts of Volcanic Ash on Airport Facilities, Summary Recommendations:

  • Make plans for dealing with ash fall and cleanup operations ahead of time, and make sure the plan is practiced, staff are trained, and the equipment works. The ash plan should be coordinated with airport response plans and regional emergency plans.
  • Systems that provide water for cleanup, especially under pressure, are extremely useful and important in most situations.
  • Move ash only once; ash is not snow, it won't melt and disappear—pick ash disposal sites carefully (plan ahead).
  • The right equipment is needed for cleanup, ranging from trucks to graders to brooms, plastic covers, and tape.
  • Airplanes should be moved away from the airport before ash starts to fall.
  • Do not start cleanup operations until the ash fall is over (except when buildings are threatened by overloading of roofs).
  • In light ashy conditions, aircraft can land and take off, but flight crews should exercise proper care and procedures such as tow-in and tow-out from ramp areas.
  • Ash can be slippery when wet; aircraft and ground vehicles need to exercise caution.
  • Personal protection gear and logistical support is needed for people working on roofs, aircraft wings, and during ashy conditions. For example, filter masks, respirators, eye protection, hats or helmets, food and water, auxiliary lighting, and portable toilets to minimize walking traffic into airport buildings.
  • Innovation is needed to identify solutions to problems that emerge.


During the workshop, four working groups met to address four topics key to airport facilities and identified several action items (see below).

Surfaces-working group recommendations and considerations.

  • Prepare an ash-response plan that is part of established emergency plans; for example plans that spell out coordinated responses to fire, runway incursions and other incidents, earthquakes, and severe weather events.
  • Identify staff familiar with airport facilities; for example, the drainage and electrical systems.
  • Establish a control and communications center to coordinate cleanup activities and disseminate ash and eruption cloud notices and information.
  • Provide educational materials about ash to staff regarding physical properties and health effects, and personal protective equipment.
  • Prioritize and sequence areas for cleanup. For example, experience at Anchorage International Airport during the 1992 ash cleanup from the eruption of Mount Spurr suggests that cleanup is most effective in the following order: runways first, taxiways second, airport buildings third (using a top-down strategy), areas between parking ramps and taxiways fourth; and roadways and non-aircraft movement areas last.
  • Once a cleanup operation begins, continue 24 hours a day until airport operations are back to normal in order to limit the likelihood that some areas will have to be cleaned two or more times. 
  • When using water for cleanup, be careful not to compromise the water supply needed for fighting fires.
  • Sweep or push ash on runways into windrows along sides of paved runways for pickup; if ash is dry, wet the ash to minimize billowing. After windrows are removed, use high-pressure water to clean runways.
  • Cover the ash to prevent it from being blown back into airport facilities and runways; recommend use of emulsions to stabilize berms if they cannot be scooped up right away.
  • Select ash-disposal sites carefully so the ash does not have to be moved again. At the U.S. Naval Air Station Cubi Point after the 15 June 1991 eruption of Mount Pinatubo in the Philippines, about 57,000 truck loads of ash had to be moved!
  • Be prepared to provide increased maintenance to vehicles and equipment used in cleanup (see vehicle maintenance).
  • Identify short-term and long-term equipment availability and needs; consider resources that might be available elsewhere.
  • Use ash-filled sand bags to help control drainage and storm runoff (prevent ash from entering drainage system).
  • Allow grass along runways and infields to grown longer than usual.

A 3.5-hour-long eruption of Mount Spurr on 18 August 1992 formed an eruption cloud that moved over the Anchorage area and deposited 1-3 mm (1/16-1/4 in) of ash between 8:10 p.m. and 11:00 p.m. The ash fall led to the closure of Anchorage International Airport (AIA), Elmendorf Air Force Base, and Merrill Field. Total cost of removing the ash from the airports, including the cost of protecting and cleaning aircraft caught on the ground is estimated between about $650,000 and $683,000.

At AIA, crews found the best technique for removing ash from runways and taxiways involved four steps: (1) completely saturate the ash with water in order to "float it with large quantities of water" (photos, lower left and center); (2) sweep the water-saturated ash into windrows or berms using graders and runway sweepers (photo, lower right); (3) loading the ash onto trucks and then hauling the ash to a disposal site at the airport; and (4) with water trucks, flushing the areas that the graders and runway brooms had swept over. One runway was re-swept and flushed with water more than six times before it was considered safe for use by aircraft. For more about the effects on the Anchorage-area airports and cleanup operations, see testimonials in Casadevall, 1993.

Water is sprayed on ash-covered taxiways and runways, Anchorage International Airport
| med | large |
Water is sprayed on ash-covered taxiways and runways, Anchorage International Airport
| med | large |
Water is sprayed on ash-covered taxiways and runways, Anchorage International Airport
| med | large |


Electronics and communications systems group recommendations and considerations.

  • Shut down all nonessential equipment. If you don't need it, turn it off.
  • Cover up equipment to prevent ash from settling directly onto equipment surfaces and from entering inlet systems.
  • Pre-planning is vital. Identify and prioritize equipment and resource needs before the emergency.
  • Evaluate specific mitigation techniques.
  • Evaluate past experiences.
  • Electronically-activated badges that provide access to restricted areas may not work if there is a disruption of power or the badge is damaged due to ash abrasion.

Emergency services group recommendations and considerations.

  • Plan ahead and practice plans. Set priorities for the efficient use of staff and equipment during ash fall and cleanup operations. 
  • Become involved in regional planning and coordination with other agencies and communities also involved in responding to ash fall and other emergencies. Evaluate how essential the airport facility is for the operation of the region.
  • Volcanic ash is not like snow (it doesn't melt), and special techniques are required to handle and remove it.
  • Move ash once, and consider ecological impacts of disposal sites. Identify long-term disposal sites in advance.
  • Lots of water are needed to control ash, but care is needed to prevent turning the ash and water mixture into a slurry.
  • Plans need to be flexible. Staff may need to experiment with cleanup techniques to determine best way to remove the ash.
  • Shut the airport off and close it up—a primary goal is to limit or prevent ash from entering the heating, ventilation, and air-conditioning systems.
  • Survey building structures for load capability of roofs ahead of time—if heavy ash fall occurs and the low load-bearing roofs cannot be swept clean of ash, consider evacuating people from the buildings or the contents within.
  • Consider special safety and personal equipment needs of staff during ash fall and cleanup operations (for example, eye goggles and filter masks).
  • Be prepared to take care of all the extra people involved in cleanup, including food and temporary lodging.
  • Document procedures used to respond to ash fall and cleanup operations and share the information in various ways, including participation in workshops, writing articles, and taking photographs.
  • Develop strategy to secure support for equipment and staff training, including storage and maintenance of inventory.

Airplanes and support vehicles group recommendations and considerations.

  • Develop plans ahead of time for dealing directly with aircraft on the ground and ground-support vehicles, including needed equipment and staff, personal protective materials, tape, and plastic coverings.
  • Keep informed of the location of eruption clouds and estimated times of ash fall; know how to find such information ahead of time.
  • Because ash is abrasive, a primary concern is damage to moving parts. Protect aircraft and equipment not needed for cleanup by covering, wrapping, sealing, or storing them in hangars and other buildings (caution—thick accumulations of ash may collapse roofs that are not designed to sustain heavy loads; see buildings). 
  • Monitor vehicles and equipment and be prepared to increase maintenance schedules; service and replenish water, oil, and air filters.
  • Identify how to get supplies and equipment needed for ash cleanup operations and staff on short notice.
  • Prioritize storage locations; store equipment in the sequence needed (last in, first out); position equipment where it's going to be needed in advance.
  • Coordinate equipment support and use with the general airport operations and management and carriers.
  • During cleanup, clean top to bottom (roof to ground).
  • Follow manufacturers' recommendations and maintenance manuals.
  • Brief staff on protective measures to be taken before ash fall, techniques for removing ash during cleanup, emphasize safety and encourage innovative ideas.
  • Remove ash from the cooling fins of air-cooled engines. 

Aircraft  || effects || safety measures || ash cleanup ||

From 1973 through 2000, about 100 encounters of aircraft with airborne volcanic ash have been documented (Guffanti and Miller, 2002). That number can be considered a minimum value, because not all encounter incidents are publicly reported. Aircraft have been damaged by eruptions ranging from small, recurring episodes (e.g., Etna, Italy, 2000) to very large, infrequent events (e.g., Pinatubo, Philippines, 1991). Severity of the encounters has ranged from minor (acrid odor in the cabin and electrostatic discharge on the windshield) to very grave (engine failure requiring in-flight restart of engines). Engine failures have occurred 150 to 600 miles from the volcanic sources. Fortunately, engine failure leading to crash has not occurred.


Boeing 747 jet on takeoff Life-threatening and costly damages can occur to aircraft that fly through an eruption cloud. Based on reported damages from ash encounters, the hazard posed to aircraft may extend 2,000 km (3,200 miles) from an erupting volcano. The actual effects of ash on aircraft depend on several factors, including the concentration of volcanic ash and gas aerosols in the cloud, the length of time the aircraft actually spends in the cloud, and the actions taken by the pilots while in the eruption cloud.

Numerous instances of jet aircraft flying into volcanic ash clouds have demonstrated the serious damage that can be sustained. Ash particles are angular fragments having the hardness of a pocket-knife blade and, upon impact with aircraft traveling at speeds of several hundred knots, cause abrasion damage to forward-facing surfaces, including windscreens, fuselage surfaces, and compressor fan blades. Moreover, the melting temperature of the glassy silicate rock material that comprises an ash cloud is lower than the operating temperatures of modern jet engines; consequently, ingested ash particles can melt and then accumulate as re-solidified deposits in the engine. The overall result of an aircraft's flying into an ash cloud can be degraded engine performance (including flame out), loss of visibility, and failure of critical navigational and operational instruments.

Experimental tests (Dunn and Wade, 1994) determined the following mechanisms that can affect aircraft performance due to exposure to a volcanic ash cloud:

(a) Deposition of material on hot-section components.
(b) Erosion of compressor blades and rotor-path components.
(c) Blockage of fuel nozzles and cooling passages.
(d) Contamination of the oil system and bleed-air supply.
(e) Opacity of windscreen and landing lights.
(f) Contamination of electronics.
(g) Erosion of antenna surfaces.
(h) Plugging of the pitot-static system which indicates the airspeed of the aircraft.

An ash cloud eventually dissipates in the atmosphere, and ash concentrations drop. However, the threshold concentration at which ash poses no harm to aircraft is not known, and indeed, may never fully be characterized for all situations involving aircraft. It is usually assumed that ash identifiable on satellite images continues to present a hazard to aircraft. Accordingly, the consensus of the aviation community is that if an ash cloud can be discerned, it should be avoided.(Guffanti and Miller, 2002).

Safety measures

Eruption column at Mount St. Helens volcano on 18 May 1980 Flight crews and dispatchers
Complete avoidance of volcanic ash by aircraft and the quick exit of an eruption cloud if ash is encountered are the only courses of action for flight crews and dispatchers that guarantees flight safety. Updated information about ways to ensure safe operations and minimize damage to an aircraft during a volcanic-ash encounter is available from Aero, Advances in Volcanic Ash Avoidance and Recovery, (No. 9, 1999) a quarterly magazine published by Boeing Commercial Airplane Group.

International Cooperation and Communication

Keeping aircraft away from eruption clouds involves international cooperation and communication between volcanologists, meteorologists, airline dispatchers and pilots, and government aviation and meteorologic organizations. Since the early 1990s new procedures and systems have been devised to disseminate quickly and widely information about (1) volcano status, especially new activity that includes eruption columns and downwind clouds of ash; (2) forecasts of eruption cloud movement; and (3) pilot reports regarding possible and actual eruption clouds. Because the ash hazard to aircraft is greatest within the first few hours following an eruption, the speed of notification between all links in the chain of communication is critical.

Procedures handbook. Operational procedures for disseminating such information is identified in a report by the International Airways Volcano Watch (IAVW) under the auspices of the International Civil Aviation Organization (ICAO), Handbook on the international airways volcano watch—operational procedures and contact list (first edition, 2000), available in pdf (for procedures, see p. 17-27).

Volcanic Ash Advisory Centers. As a key part of the IAVW, in 1995 nine regional Volcanic Ash Advisory Centers (VAAC) were established around the world under ICAO auspices to advise Meteorological Watch Offices on the issuance of volcanic ash warnings to aircraft. The VAACs have been specifically tasked with the detection, tracking, and forecasting of the movement of eruption clouds within their respective areas of responsibility. Link to VAACs and messages.

Pilot Reports. Verbal and written pilot reports are critical for identifying the airspace where volcanic ash or sulfur aerosols are located at a specific time and also where ash is not located. Verbal pilot reports provided to the air control center are critical for informing other pilots and dispatchers of ash-contaminated airspace. Written pilot reports prepared after the flight has ended are also important to help scientists improve their forecasts of eruption cloud movement.

Ash cleanup

Each of the major airframe and engine manufacturers has developed operational and maintenance related procedures for dealing with volcanic ash. These may be found in the appropriate Flight Crew Operating Manuals (FCOM) and Aircraft Maintenance Manuals (AMM). Interested parties are urged to consult the appropriate manuals for their respective operational needs. A number of manufacturers' suggested procedures are derived from the Aerospace Industries Association Volcanic Ash Committee (Casadevall, 1993).


Air transport

Casadevall, T.J., 1993, Volcanic ash and airports: discussions and recommendations from the workshop on impacts of volcanic ash on airports facilities, Seattle, Washington, April 26-28, 1993: U.S. Geological Survey Open-File Report 93-518, 58 p.

Casadevall, T.J., ed., 1994, Volcanic ash and aviation safety: Proceedings of the first international symposium on volcanic ash and aviation safety, Seattle, Washington, July, 1991: U.S. Geological Survey Bulletin 2047, 450 p.

Casadevall, T.J., and Krohn, M.D., 1995, Effects of the 1992 Crater Peak eruptions on airports and aviation operations in the United States and Canada, in Keith, T.E.C., ed., The 1992 eruptions of Crater Peak vent, Mount Spurr volcano, Alaska: U.S. Geological Survey Bulletin 2139, p. 205-220.

Dunn, M. G., and Wade, D. P., 1994, Influence of Volcanic Ash Clouds on Gas Turbine Engines, in Casadevall, T. J. (ed.). "Volcanic Ash and Aviation Safety - Proceedings of the First International Symposium on Volcanic Ash and Aviation Safety" U.S. Geological Survey Bulletin 2047, p. 107-118.

Gibson, N.W., 1999, Trip report to Quito, Ecuador, November 9-12, 1999: unpublished report, 3 p.

Guffanti, M., Mayberry, G.C., and Miller, T.P., 2003, Impact of volcanic activity on airports: presentation at the 3rd International Workshop on Volcanic Ash, Toulouse, France.

Guffanti, M., and Miller, E.K., 2002, Reducing the threat to aviation from airborne volcanic ash: presentation at the 55th Annual International Air Safety Seminar, Dublin, Ireland.

Labadie, J.R., 1994, Mitigation of volcanic ash effects on aircraft operating and support systems, in Casadevall, T.J., ed., 1994, Volcanic ash and aviation safety: proceedings of the first international symposium on volcanic ash and aviation safety: U.S. Geological Survey Bulletin 2047, p. 125-128.

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