Recent volcanic eruptions are creating a minefield for pilots who have to be on watch for volcanic ash clouds capable of shutting plane engines down completely.
The Calbuco volcano in Chile, one of 1,500 active volcanoes worldwide, erupted in late April and forced major cancellations and delays at Buenos Aires' Ezeiza International Airport.
In December of 1989, 231 passengers aboard KLM Flight 867 - a 747 jetliner headed for Anchorage, Alaska - dropped through 2 miles of air after all four of the aircraft's engines blew out when it entered a cloud of ash from the erupting Redoubt Volcano, according to United States Geological Survey.
"People spend time and energy so that 747s never lose power, but volcanic ash is one of the ways they can," said John Power, an Alaska Volcano Observatory scientist and geophysicist supervisor at the Alaska Science Center.
The aircraft's pilots were able to restart the engines and land the plan safely in Anchorage, but Power said, the plane required $80 million in repairs.
"Volcanic ash is kind of like grit or sandpaper," said John Hansman, a professor of Aeronautics and Astronautics at MIT. "If it goes into the engines and is the right size, it can cause the engines to shut down."
The ash is sucked into the engines, where it is melted by the heat of the engine, Power said. The melted ash then coats the inside of the engine, ultimately leading to engine failure.
Volcanic ash is actually highly abrasive and can scratch and erode plastic, glass and metals; Power described it as "putting an engine in front of a sand blaster."
Aside from engine shutdown, Hansman said the gas created during eruptions can cause the plastic glass on the windows to degrade and slowly crack.
As the windows in the cockpit become scratched, pilots can have increasing difficulty seeing the runways and landing the plane safely.
Other effects include damaging control systems and contaminating the cabin, requiring passengers to use oxygen masks, according to the International Civil Aviation Organization.
The amount of damage that occurs is dependent on the concentration of volcanic ash, the gas aerosols in the cloud, the length of time the aircraft is in the cloud of volcanic ash and the action taken by the pilots, according to NOAA.
There have not been any fatalities to date. If pilots find themselves in an ash cloud, they can attempt to restart the engine or avoid the area all together, which is ultimately the best option, Hansman said.
However, ash clouds are difficult to distinguish from ordinary clouds and can drift great distances from their source, according to the USGS.
The volcanic ash that could have brought KML Flight 867 crashing into the Talkeetna Mountains traveled 150 miles from the erupting Redoubt Volcano, according to a USGS fact sheet.
The ash cloud from the 1991 eruption of Mount Pinatubo in the Philippines traveled more than 5,000 miles and damaged more than 20 airplanes, USGS reported.
The incident in 1989, among others including the eruption of Iceland's Eyjafjallajökull volcano in 2010, which shut down air traffic in Europe, has ushered endeavors to reduce the risk and consequences that volcanic activity poses to air travel.
The 2010 eruptions of Eyjafjallajökull in Iceland caused about 20 countries to shut down air traffic for a week, affecting more than 10 million travelers and costing the industry billions of dollars.
But Hansman said that the forecast models, which these countries used to determine their shutdown procedures for the Eyjafjallajökull eruption, were too conservative.
Particles in the ash cloud come in varying sizes, with the smaller particles staying in the atmosphere for longer, he said.
"One of the issues there is that no one really knew the sizes of particles," Hansman said. "So they had to shut down much of the airspace over Europe."
Hansman said that Iceland now hosts a program where airplanes intentionally fly into the ash cloud to sample particles during eruptions.
Airborne Volcanic Object Imaging Detector (AVOID) is a device that provides real-time imagery of hazards ahead of an aircraft and supplies the information directly to the cockpit.
Infrared cameras can detect volcanic ash particles that are up to 62 miles ahead of the aircraft, giving the pilot a seven- to 10-minute warning period, according to Nicarnica Aviation, a Norwegian company that specializes in the developing solutions to detect volcanic ash that helped develop AVOID.
This type of software, which was developed in 2013, could help airlines save money and avoid the risks of flying through an ash cloud.
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