KUALA LUMPUR: Flying through a volcanic ash cloud is dangerous for airliners as it could lead to a complete engine failure.
This, an aviation expert said, is because an erupting volcano spews ash and particles into the sky, predominantly made up of silicates.
Malaysian Pilots Association president Captain Abdul Manan Mansor said the very high temperature inside a jet engine will melt these particles but in cooler parts of the engine, they will solidify again forming a glassy coating.
"This disrupts the airflow which can lead to the engine stalling or failing completely."
He said that if the engines were to fail during take-off or landing, there wouldn't be enough time to react, increasing the likelihood of a crash.
Drawing from a previous case, he mentioned a British Airways flight en route from Kuala Lumpur to Perth in 1982.
"The Boeing 747, carrying 247 passengers, inadvertently flew through an ash cloud over Indonesia. The pilots observed fire on the windscreen, and within minutes, all four Rolls Royce engines failed."
"The plane glided from 11,300 metres to 3,650m before the engines started working again and the plane was able to make a safe landing in Jakarta," he said. Aside from shutting down the engines, he said that ash clouds can affect many of the sensors on the plane, resulting in, for instance, faulty speed readings.
"It affects visibility for the pilots and can also affect air quality in the cabin, making oxygen masks a necessity. The sharp particles in the ash also cause abrasions and damage to the exterior of the plane, though this is not an immediate danger to the flight."
Abdul Manan also said that ash clouds can be hard to spot for pilots, and their small particles are not visible on a weather radar.
"At high altitudes, volcanic ash does not look like the dense cloud currently seen above Gunung Ruang. As such, the first action recommended at that point is to simply turn the plane around, hoping to escape the area quickly," he said.
"The pilot can also reduce the thrust of the engines, which will lower engine temperatures, making a failure less likely. Ideally, though, pilots shouldn't even find themselves in that situation," he added.
There are nine Volcanic Ash Advisory Centres around the world, each responsible for a specific region.
Earlier, multiple flights to and from Kuala Lumpur International Airport to Sabah and Sarawak today were cancelled due to the Gunung Ruang volcanic eruption in Indonesia.
Gunung Ruang, a stratovolcano in North Sulawesi Province, erupted several times on Tuesday and Wednesday.
Authorities had raised the alert level to its highest point after the dome spewed a column of smoke more than 1.6 kilometres into the sky, and forced hundreds to evacuate.
The alert level for the volcano, which has a peak of 725 metres above sea level, was then raised on Wednesday evening from three to four, the highest level in the four-tiered system.
Meanwhile, Universiti Kuala Lumpur Aviation Technology Institute search and rescue department head Associate Professor Major Dr Mohd Harridon Mohamed Suffian the volcanic ashes are very disruptive to the performance of the aircraft engine.