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More trouble ahead from volcanic ash?

More trouble ahead from volcanic ash?

The full effects of volcanic ash on the aviation industry have yet to be seen, according to an aviation expert from the University of Leeds.

Aviation lecturer Stephen Wright believes the impact of ash on airplane air-conditioning systems could be serious and will build over the next few weeks as planes begin to 'hoover up' the additional ash in the atmosphere.

Air-conditioning systems provide fresh air to pressurise the cabin as well as the warming the internal temperature of the plane. Once clogged with dirt, they can overheat, forcing the pilot to shut the system down and make an unscheduled or emergency landing.

Overheating of the system can be serious, as on many planes the air-conditioning units are sited underneath the central fuel tank. "As planes taxi round airports, the air-conditioning systems suck up dirt which then clogs up the heat exchangers," says Stephen Wright, who worked in the aviation industry before joining the University's Faculty of Engineering.

"Sometimes dirt levels are so high, systems are having to be changed after just three to four months, whereas they're expected to last around 18 months. The planes will now be sucking up ash as well which will put these systems under very high stress."

Low concentrations of ash are deemed low risk by the UK Civil Aviation Authority as they have minimal effect on airplane engines. But air conditioning cooling systems filter all dirt out, so there will be a cumulative build up even when low levels of ash are present.

"Once the air-con unit is clogged up, it is less effective and so tries to work harder to maintain pressure and temperature - and so begins to overheat," says Stephen Wright. "The systems have built-in safety controls, so they're unlikely to catch fire. 

However, overheating will mean pilots have to shut down the affected system, and as this provides fresh air to the cabin, the loss will normally result in either an unscheduled or emergency landing. "At the very least, the air industry will be looking at much higher maintenance on these systems to keep them working, at a time when the grounding of planes has put them under severe financial pressure." Stephen Wright is available for interview.

For further information:

Please contact the University of Leeds Press Office on +44 (0)113 343 4031 or email

Notes to editors:

Mr Stephen Wright is a lecturer in the Energy and Resources Research Institute in the Faculty of Engineering at the University of Leeds. He lecturers on the Aviation with Pilots studies programme at Leeds - a significant source of UK pilots entering the industry. He specialises in pilot and engineering instruction, crew resource management and safety issues for the aviation industry. He is currently completing his PhD, looking at the impact of particulate matter levels on commercial aircraft air-conditioning systems.

The Faculty of Engineering at the University of Leeds is ranked 7th in the UK for the quality of its research (2008 Research Assessment Exercise); an impressive 75% of the Faculty's research activity rated as internationally excellent or world leading. With 700 academic and research staff and 3,000 students the Faculty is a major player in the field with a track record of experience across the full spectrum of the engineering and computing disciplines. 

The Faculty of Engineering is home to five schools: civil engineering; computing; electronic and electrical engineering; mechanical engineering; process, environmental and materials engineering. Two thirds of students are undergraduates with the remaining third split evenly between taught masters and research degrees.  The Faculty attracts staff and students from all around the world; one third of students are from outside the UK and representing over 90 different nationalities. The 2008 Research Assessment Exercise showed the University of Leeds to be the UK's eighth biggest research powerhouse.

The University is one of the largest higher education institutions in the UK and a member of the Russell Group of research-intensive universities. The University's vision is to secure a place among the world's top 50 by 2015.

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