At least three airlines canceled flights between Australia and Bali this week after a volcanic eruption in eastern Indonesia sent a huge plume of volcanic ash into the air.
But while holidaymakers are naturally upset to have their plans disrupted, it’s worth remembering that flying a plane through volcanic ash is not safe.
So, how do airlines decide it’s not safe to fly when a volcano erupts? And why is volcanic ash so dangerous for planes anyway?
What effect does volcanic ash have on aircraft?
Volcanic ash particles are very abrasive. They can cause permanent damage to windscreens in aircraft and can also make windscreens opaque – as if someone has sandpapered them.
Imagine taking glasses and rubbing them repeatedly with sandpaper – this is what you would see if you were sitting in the cockpit.
Volcanic ash can also block or damage external sensors, causing inaccurate readings, and can infiltrate aircraft ventilation systems. This can affect cabin air quality and cause potential respiratory problems.
But really the main issue is the effect volcanic ash has on engines.
A jet engine works by drawing air, compressing it, mixing it with fuel, and igniting it. This creates high-pressure exhaust gases that are expelled to the rear, propelling the engine (and the aircraft) forward.
The correct balance of fuel and air flow is important. When you obstruct the air flow, it can cause the engine to stall.
Ash particles that get inside the engines will melt and accumulate, obstructing air flow. This may cause the engine to “burn out” or stall.
Volcanic ash contains a lot of silica, so when it melts it turns into something like glass. It won’t melt unless it’s exposed to very high temperatures – but inside a jet engine, you get very high temperatures.
A famous incident occurred in 1982 when a British Airways Boeing 747 aircraft flying around Indonesia lost all four engines after encountering volcanic ash spewing from Mount Galunggung in Java.
Fortunately, the pilot was able to restart the engine and land safely, although the pilots were unable to see through the front windscreen.
How do airlines decide it’s not safe to fly when a volcano erupts?
The decision is made by each airline’s operational staff. Each airline’s operational team will look at the situation in real time today and make decisions based on their risk assessment.
Every airline has a risk management process, which is required by Australia’s Civil Aviation Safety Authority.
Different airlines may deal with risk management in slightly different ways; Some of your flights may get canceled earlier than others. But, in the broader context, more sophisticated airlines will reach similar conclusions and they are probably all communicating with each other.
Most often, they make decisions based on the extent of the plume – how big the ash cloud is and where it’s going, taking into account that winds vary with altitude. As winds get stronger with altitude, ash can be blown far from the source.
There is also a United Nations agency called the International Civil Aviation Organization, which issues guidance on the dangers of volcanic ash. Various meteorological agencies around the world work together and liaise with aviation authorities to spread the news immediately when an eruption occurs.
For airlines to resume flights, the ash needs to be cleared and the possibility of further eruptions must be reduced.
Passenger safety is priority
The main reason behind these flight cancellations is security. If your engine fails and you can’t see out the window, the threat to passenger safety is obvious.
Naturally, people are upset about their holiday plans being put on hold. But it is actually in the best interest of travelers not to fly through volcanic ash.
(Patrick Murray, Emeritus Professor of Aviation, University of Southern Queensland
This article is republished from The Conversation under a Creative Commons license. Read the original article.)
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
