Page 15 - 2018-Issue1

VOLCANIC ERUPTIONS & AVIATION 15

Far left: Mount Etna, Italy. Middle and right: Popocatepetl, Mexico. All photos by Klaus Sievers

or very large amounts of gas (SO2), or they VOLCANIC ASH ADVISORY CENTERS blades.
may reach very high, 20km or more, and form The task of the 9 Volcanic Ash Advisory • Adherence of molten or partially molten
a mushroom-shaped cloud. The details of the Centers is to collect information on eruptions ash particles to parts of the hot section of the
eruption are highly important as input to from all available sources. This includes, for engine, which can lead to engine failure as the
models that follow the dispersion of volcanic example, reports from aircraft, observers on flow of air through the engine is disturbed or
ash and gas clouds. At some volcanos, a high the ground, satellite images, infrasound blocked when air passages are restricted by the
amount of investment has flowed into the observations, and lightning detection network accumulating molten ash. Additionally, cooling
determination of eruption-cloud properties, information. The information is then reviewed, systems inside engine blades may get blocked,
into measurement devices like lidar and special and the dispersion of ash is modelled. finally, leading to temperatures beyond the design
radar, infrared SO2 cameras or aircraft/UAV volcanic ash advisories are issued on the point with resultant failures of blades. Note
with air sampling capability. Examples are the websites of the Ash Advisory Centers, but that an engine failure will lead to loss of
European Supersites in Iceland and Sicily, as primarily to the Meteorological Watch Offices, systems which are vital for the operation of an
well as other locations: Area Control Centers, and aircraft operators. aircraft such as electric, hydraulic or
http://supersites.earthobservations.org/ The VAAC London maintains links to all other pneumatic systems.
Volcano Observatories generally VAACs on their website: • A more long-term but no less costly effect
communicate the status of a volcano to www.metoffice.gov.uk/aviation/vaac on engines is due to the aggressive chemical
aviation by means of the Aviation Volcano Complicating matters is the fact that properties of heated volcanic ash and aerosols.
Alert Status Colour Code. It should be besides ash, volcanic SO2 aerosol can be These substances diffuse, infiltrate into the
included in ASHTAMs or NOTAMs issued for emitted by volcanoes in large quantities. No extremely heat-resistant protective layers of
volcanic activity. According to ICAO DOC information from VAACs is presently available special metal covering turbine blades. At first,
9766, the Handbook on the International on this, although the smell can disturb only tiny areas are affected, but after the
Airways Volcano Watch (IAVW), this code passengers, play a role in long-term engine protective layer of “thermal barrier coatings” is
should be used: damage, and in larger concentrations, may breached, damage to the turbine blade itself
even pose a health risk. ICAO is in the process may occur. Maintenance checks can identify
GREEN of considering the inclusion of SO2 the early signs and repairs can be initiated in
Volcano is in a typical background, measurements and forecasts into the official time, however, some engine failures have been
non-eruptive state. documents. A good source of near real-time connected to this failure mechanism.
information on SO2 in the atmosphere, as well Contamination of the air inside an aircraft,
YELLOW as ash clouds, can be found at: which can be due to volcanic ash as well as
Volcano is exhibiting signs of elevated unrest http://sacs.aeronomie.be/ aerosol/gas may lead to use of oxygen masks by
above known background level. the crew, nuisance smell events in the cabin,
DANGERS OF VOLCANIC CLOUDS and can also cause health effects. The volcanic
ORANGE • Purely mechanical, due to the abrasive material can settle on electronics, reduce
Volcano shows heightened or escalating properties of the volcanic ash. Effects may cooling efficiency and potentially induce
unrest with increased potential for eruption. include completely opaque windshields, failures in electronic components due to
blocking of pitot and static sensors, with corrosion.
RED secondary effects, like unreliable airspeed • Contamination of the air system of an
Eruption is imminent or in progress. Signifi- information, loss of efficiency or decrease in aircraft, which may be very difficult to clean.
cant emission of ash into atmosphere is likely. engine-stall margins due ot abrasion of turbine

InterPilot | The Safety and Technical Journal of IFALPA ISSUE 1 | 2018