How volcanic ash jeopardizes an airplane's flight
There are about 1,500 active volcanoes in the world. However, a handful of these volcanoes poses a great danger to human life for one reason or another. Here are some of the most dangerous active volcanoes in the world.
Plumes of ash spewed into the atmosphere from volcanic eruptions can pose a significant flight safety hazard for planes.
The ash can cause significant damage to the engine, propellers, windows, fuel system and more because the ash fragments consist of pulverized rock, minerals and volcanic glass.
Mayon volcano erupts at dusk Thursday, Jan. 25, 2018 in Albay province around 200 miles (340 kilometers) southeast of Manila, Philippines. (AP Photo/Bullit Marquez)
Short-term effects of volcanic ash on planes may include damaged airspeed sensors, reduced visibility for pilots and polluted cabin air.
The long-term effects of ash contamination can also lead to failure of critical navigational and operational instruments.
"For the fuselage, it is mostly abrasion of glass to reduce visibility and in the absolute limit erosion of flying surfaces to induce thinning and failures," Dr. Colin Brown, engineering director of the Institution of Mechanical Engineers, said.
"For engines, the dust both clogs tiny passages as well as potentially fuses into a larger mass of material in a hot zone, that can then accumulate or even solidify elsewhere. The major risk is if these passages are for cooling air which means parts of the engine could then overheat and fail catastrophically," Brown said.
When the ash particles are sucked into an engine, it can melt quickly then accumulate as re-solidified deposits in cooler parts, degrading engine performance over time. The ash that gets into the plane's combustion chamber can melt, producing a substance like molten glass.
In most cases, if a plane goes through volcanic ash, it can be repaired.
"The fuselage can easily be re-painted, repaired and glass replaced if scratched – although very heavy abrasion can mean an almost total loss of vision through glass in the worst case. The engines would need stripping down and replacement of those parts affected and coated with ash," Brown said.
Due to the potential destruction ash can do to planes, the aviation industry formed the Volcanic Ash Advisory Centers (VAACs) in 1991 to serve as a liaison between meteorologists, volcanologists and the aviation industry.
In 2000, NASA unintentionally proved ash is bad for planes when a NASA DC-8 jetliner that was flying to Sweden flew right through an ash plume produced by Icelandic volcano Mt. Hekla.
The flight crew couldn't see due to the plume, yet they safely landed their plane at their destination without incident. At first, no visible damage was detected upon arrival; however, a closer inspection showed how devastating volcanic ash can be to an airplane.
The costs of air travel disruption in Europe after an Icelandic volcanic eruption in 2010 forced aircraft manufacturers to specify limits on how much ash they considered acceptable for a jet engine to ingest without damage.
Prior to 2010, aircraft engine manufacturers had not defined specific particle levels above which they considered engines at risk.
Airspace regulators took the general approach that if ash concentration rose above zero, they considered airspace unsafe and consequently planes were not allowed to fly.
A plane dusted in volcanic ash sits grounded at the San Carlos de Bariloche airport, southern Argentina, Tuesday June 7, 2011. The wind carried volcanic ash across the Andes to Argentina resulting in the closing of six airports, and the cancellation of flights in the capital city. The Puyehue volcano, dormant for decades, erupted in south-central Chile. (AP Photo/Alfredo Leiva)
Since the 2010 volcanic ash crisis that grounded United Kingdom flights, measures have been put in place to ensure that the U.K., and the aviation industry worldwide, is prepared for a similar event.
The U.K. Civil Aviation Authority (CAA), in agreement with engine manufacturers, set the safe upper limit of ash density at 2 mg per cubic meter of airspace.
In May 2010, the CAA revised the safe limit upwards to 4 mg per cubic meter of airspace.
To minimize further disruption that this and other volcanic eruptions could cause, the CAA created a new category of restricted airspace called a Time Limited Zone (TLZ).
Airspace categorized as a TLZ is similar to airspace under severe weather conditions, in that restrictions should be of a short duration. Any airspace where ash density exceeds 4 mg per cubic meter is prohibited airspace.
According to the CAA, any U.K. airline wishing to operate in areas of airspace forecast to be contaminated with volcanic ash will need to complete an assessment of the safety risks related to known or forecast volcanic ash contamination as part of its management system.
The United States Federal Aviation Administration (FAA) does not recommend engine operation or flight into a visible volcanic ash cloud.
The FAA's primary method of dealing with volcanic ash events is operator avoidance. According to the FAA, since the geographical location of areas that may be affected by volcanic ash is weather-dependent, their model of managing air traffic when confronted with volcanic ash is to treat it much like a major weather event.
Brown said there still isn't enough information about what gets ejected from volcanoes and how it disperses, as well as not enough aircraft testing in real situations.
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