Icelandic ash and its implications for aircraft

Air traffic across Europe, including flights from Britain to New Zealand and Australia, was halted in April as ash from an Icelandic volcano drifted towards the continent. The volcano under the Eyjafjallajokull glacier erupted Wednesday 14 April for the second time in less than a month. While the volcanic ash is high up in the stratosphere, the risk to humans has been described by scientists as negligible. However, what about the effect on plane engines?

Dr Rob Howell, Department of Mechanical Engineering, University of Sheffield, said: "There are a number of potential issues regarding engine contamination with volcanic ash. One occurs where ash builds up on some of the internal parts of the jet engine, specifically the compressor, and changes the aerodynamics of that compressor. It is possible, with enough contamination, for the engine to enter a condition called stall and eventually surge where the engine loses power and can also be damaged.

"Another problem, more often seen in industrial jet engines, is where the turbine cooling holes become blocked. This will cause the turbine blades to increase in temperature and fail, potentially destroying the engine. A further problem area is the combustion systems of the engines, which can become clogged and again the engine loses power."

Dr Tim Fox, Head of Energy and Environment at the Institution of Mechanical Engineers, said: "Modern jet engines are highly technological machines that work by sucking air in through a large fan and using it in a combustion process to generate thrust. If, for example, foreign objects such as the introduction of large amounts of grit or volcanic ash were to be sucked into the air, this would result in serious damage to the fan blades and internal surfaces of the engine. In turn, this would interfere with combustion, ultimately resulting in engine failure.

"In the event of such a failure, which would likely occur to all engines, the aircraft would be forced to make an emergency descent. The best policy if large amounts of volcanic ash are known to be present in the air is clearly not to fly through it."