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How the ash cloud affects flights – and how a flight to NZ changed the rules

Tens of thousands of people are stranded today as most of Europe’s airports close following a large volcanic eruption in Iceland.

The ash cloud is being pushed south eastwards towards the UK and Europe and has resulted in all UK airports being closed and a number of European airports closing. head weather analyst Philip Duncan says unlike a band of rain an ash cloud lingers much longer.  “The ash particles are very fine and once they reach high altitudes they fan out over a huge area.  It can take days for the winds to clear them and that means airports across Europe may stay closed right through this weekend”.

Mr Duncan says unlike ash created by a bonfire, volcanic ash is sharp and gritty.  “Volcanic ash isn’t soft like wood ash, it is actually fine pieces of rock.  The reason why planes can not fly in to a volcanic ash cloud is because the jet engines suck the ash in, heat it up and melt it into glass.  Eventually it builds up in the engines and “chokes” the engines to death”.

In 1982, a British Airways 747 flew into a cloud of volcanic ash in the middle of the night by an eruption of Mount Galunggung in Indonesia.  The 747 was enroute from England to New Zealand when all four engines failed – however the reason for the failure was not apparent to the crew or ground control.

The aircraft was diverted to Jakarta in the hope that enough engines could be restarted to allow it to land there. The aircraft was able to glide far enough to exit the ash cloud, and all engines were restarted (although one failed again soon after), allowing the aircraft to land safely.

When pilots came in to land the ash caused a sandpaper effect to the cockpit windows, much like looking out through a fogged up windscreen, however the plane landed safely.  The ash was so gritty it removed parts of the British Airways logo across the jet


The dry electrical ash also caused the plane to develop an electrical glow, much like St Elmos fire.

Since this incident planes have been diverted around ash clouds and airports closed when ash is in the airspace.

in 1995, on two occasions, Auckland International Airport was closed due to the eruption of Mt Ruapehu.  Several other airports were also closed, especially Rotorua and Taupo airports.

Track the ash plume by satellite – click the image to animate

satellite image of Iceland and ash plume from Eyjafjallajokull Volcano

The Eyjafjallajokull volcano in Iceland erupted Wednesday, April 14, for the second time this month. The volcano is still spewing ash into the air and the ash clouds are impacting air travel in Northern Europe.

NASA’s Terra satellite flew over the volcano the following day at 11:35 UTC (7:35 a.m. EDT) on April 15, 2010, and the Moderate Resolution Imaging Spectroradiometer, or MODIS instrument onboard Terra captured a visible image of the ash plume from Eyjafjallajokull Volcano.


– with, Wikipedia & NASA


Guest on 24/09/2011 6:00am

One interesting note is that pumice (volcanic rock) is sometimes used as a cleaning agent for aircraft jet engines. Engine is set to idle and ash is shoveled into the intake. I suspect the difference between this use and actual flying is that the engine generates much higher temperatures during flight resulting in a glass induced in flight engine seizure.

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