Quick LinksVolcanic Ash - Deadly Small and Abrasive How do pilots know when a volcanic eruption might affect their flight? Still a major disruption to air travel.
Recently, a United Airlines Airbus A320 enroute to Mexico City International Airport was forced to return to George Bush Intercontinental Airport (IAH) due to volcanic ash in the air around Mexico City.
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Aircraft are built to fly through a menagerie of harsh environmental conditions and situations. From flying through thunderstorms, landing in smog, and flying in extreme cold, aircraft are quite robust.
Despite these advancements in modern aviation, all flights avoid volcanic ash clouds, no matter the cost. Why is this? What makes volcanic ash so dangerous for modern aircraft?
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According to the British Geological Survey, around 50 to 70 volcanoes erupt on Earth each year. Of those eruptions, few produce enough ash to have a significant effect on the aviation industry. Other significant volcanic eruptions may occur in areas that pose no significant threat to aviation.
The primary threat of volcanic eruptions arises from the ash that certain types of volcanoes emit during particularly large and explosive eruptions.
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The region on Earth that sees the most volcanic activity, deservedly called the "Ring of Fire," spans a ring-like shape around the Pacific Ocean. It's in this area that most of the world's active volcanoes (as well as some pretty violent volcanic eruptions) can be found.
Image: Gringer | Wikimedia Commons Volcanic Ash - Deadly Small and Abrasive
The word "ash" being used to describe the plumes of smoke that a volcano emits is somewhat of a misnomer. Unlike conventional ash emitted from burning, say, firewood, volcanic ash is hard, doesn't dissolve in water, and is particularly abrasive due to the sharp, microscopic rocks that comprise these tiny particles.
In larger amounts, volcanic ash has the ability to conduct electricity, disrupting the electromagnetic signals (low and high-frequency radio) that pilots use to communicate with air traffic control.
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When a volcanic eruption results in a large ash cloud, the height of that ash cloud depends on weather conditions, but typically ranges from anywhere between 10,000 feet all the way up to 65,000 feet. For reference, commercial airliners typically cruise at altitudes between 28,000 feet and 41,000 feet. The height of an ash and the direction the wind is blowing affects the impact the cloud will have on aviation.
Now imagine you're a captain at the helm of an aircraft flying between Toronto and London. Shortly after takeoff, you and your first officer get word that a volcano has erupted in Iceland and the explosion has resulted in ash reaching up to 50,000 feet along your route. If you decide to fly your aircraft through that ash cloud, here's what would most likely happen:
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Almost instantly after entering the ash cloud, your aircraft's nose, cockpit windows, leading-edge surfaces, and any other parts of the aircraft facing into the wind will be scratched and abraded by volcanic ash. After all, most aircraft are made from delicate carbon fiber and aluminum alloys, which aren't built to withstand high-velocity impacts from microscopic, razor-sharp particles.
Photo: Joao Carlos Medau | Wikimedia Commons
Not to mention, the small size of volcanic ash also leads to the clogging of the pedo tubes at the front of your aircraft, which results in a loss of instrument readings such as airspeed and altitude.
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All engines used on commercial airliners are air-breathing, meaning they require a constant flow of air to keep their running. When flying through a thick volcanic ash cloud, air-flow into a jet engine is disrupted by fine ash particles and other volatile gases entering the engine, scratching the engine fan-blades and its delicate insides.
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The operating temperature of a commercial jet engine is higher than the melting point of volcanic ash, causing ash to melt inside of jet engines, re-solidifying in deposits around the cooler back exhaust half of jet engines. This almost always leads to an in-flight compressor stall, such as with KLM Flight 867, causing your aircraft to lose engine power in what is known as a "flame-out".
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Aircraft source breathable oxygen for passengers and cabin crew via air filters on the outside of the aircraft. When flying through a volcanic ash cloud, these air filters would most likely be blocked by thick ash and smoke, and the 50/50 mix of internal and outside air that passengers and cabin crew breathe inside the aircraft would become laced with thick smoke. A tell-tale sign of volcanic smoke ingestion into the aircraft cabin is the smell of sulfur.
Photo: Smithsonian Institution National Museum of Natural History's Global Volcanism Program
By the time your aircraft emerges from that volcanic ash cloud that you and your first officer have decided to fly through, your aircraft will be severely damaged with scratched, sandblasted cockpit windows, no engine power, smoke in the cabin, problems with vital onboard instruments, and a lack of communications equipment (at least until the volcanic ash clears).
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All of this just to save some time re-routing your aircraft. Is it really worth it? Well, obviously, no. Has an aircraft ever flown into a volcanic ash cloud either on purpose or by accident? Yes, quite a few times, actually. The most notorious case of a flight crew flying their aircraft flying through a volcanic ash cloud and living to tell the tale is that of British Airways Flight 9.
Unlike in 1982, if pilots accidentally flies into a volcanic ash cloud for whatever reason, most major aircraft manufacturers and airlines have procedures in place to assist pilots in navigating through and out of ash clouds.
✕ Remove Ads How do pilots know when a volcanic eruption might affect their flight?
In many areas around the world where there are active volcanoes, geological agencies such as the United States Geological Survey (USGS) in the United States, or Icelandic Meterological Office in Iceland, monitor volcanoes for potential signs of an eruption. If an eruption occurs, or is deemed to be imminent, aircraft flying within a certain distance around the volcano will be re-routed around the area as a precaution.
If an eruption has occurred and there is a sizable volcanic ash cloud, flights may be canceled, diverted, or re-routed around the ash cloud (depending on the speed and direction of the wind).
Photo: USGS | Public Domain It is still a major disruption to air travel.
In the 21st century, volcanic eruptions (and the subsequent ash clouds that result from them) can and still do disrupt air travel. One notable example in recent times is the Eyafjallajökull Eruption that occurred in Iceland in 2010, forcing the majority of transatlantic and European flights to stay grounded for days.
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More recently, four United Airlines Tokyo bound flights were forced to divert due to the risks of ash coming from a volcanic eruption in the Russian region of Kamchatka. Volcanic eruptions emitting ash clouds are particularly dangerous for aircraft flying over remote regions of the world, such as the Northern Pacific, where Russian airspace is closed to western airlines.
The next time there is a disruption in aviation due to a volcanic eruption and your flight is delayed or canceled, now you know why.
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