The claim

“The absence of any volcanic ash in the atmosphere supports Ryanair’s stated view that there is no safety threat to aircraft in this mythical ‘red zone’.”
Ryanair spokesman, May 24 2011

The background

Does volcanic ash really pose a safety threat to passenger planes? It’s a subject that’s becoming as murky as the skies above Iceland.

The row that broke out last year when the Eyjafjallajökull eruption grounded aircraft for six days burst back into life this week, with the ash cloud from Grimsvotn threatening airlines’ profits again.

Although fewer flights have been affected this time, airline bosses have been quick to go on the offensive, with both BA and Ryanair accusing the Civil Aviation Authority (CAA) of excessive caution.

With claim and counter-claim flying around like lumps of smouldering volcanic debris, what are the facts when the ash has settled?

The analysis

The Met Office has been tracking the cloud of ash from Grimsvotn as it drifts across British airspace, and it drew a “red zone” over Scotland earlier this week, marking an area of high ash density.

On Tuesday, Ryanair sent one of its planes up with no passengers on board to assess the risk itself. The company said the flight took off from Glasgow Prestwick, climbed to 41,000 feet and flew to Inverness, Aberdeen and Edinburgh before touching down at Glasgow again one hour later.

A strongly-worded press release swiftly followed, with a spokesman for the budget carrier saying: “During the flight there was no visible volcanic ash cloud or any other presence of volcanic ash and the post flight inspection revealed no evidence of volcanic ash on the airframe, wings or engines.

“The absence of any volcanic ash in the atmosphere supports Ryanair’s stated view that there is no safety threat to aircraft in this mythical ‘red zone’ which is another misguided invention by the UK Met Office and the Civil Aviation Authority.”

Ryanair sent another plane up later on Tuesday with the same results, and BA also carried out a flight in the red zone for 45 minutes and “found nothing”, according to chief executive Willie Walsh.

The CAA looked at radar tracking of the first Ryanair flight carried out by air traffic control company NATS and said that not only had the plane not entered the red zone, its height of 41,000 feet put it 20,000 feet higher than where the Met Office thought the volcanic ash would be.

A spokesman told FactCheck: “We know for definite that the first flight went nowhere near the red zone. We haven’t looked at the second flight yet.” The BA flight took off with the CAA’s approval and its route appeared to be more credible.

But the fact that individual flights have so far avoided the dreaded ash plume is not evidence that it isn’t there, he added.

The Met Office make their predictions about where the ash is likely to drift using complex modelling techniques backed up with radar and satellite imaging as well as measurements from balloons and other instruments and observations from pilots.

It’s far from an exact science, the spokesman added, saying: “The ash could be at different levels and at different locations. And of course it’s moving all the time, with changes in the wind and atmosphere.”

Academic experts on the subject go further.

Dr Guy Gratton, Senior Visiting Research Fellow in Aeronautics at Brunel University’s School of Engineering and Design, said airlines who simply send aircraft up without instruments on board that can measure ash density are “being really quite unhelpful”.

Dr Gratton, who is also a test pilot, said: “You could equate it to a game of Russian roulette. You have got one bullet in the gun, as you have got a certain amount of height that’s got ash in it. If you haven’t got instruments telling you where you are, you just don’t know if you’re safe.

“This volcanic ash sits in layers. You can actually fly from one end to the other of the concentrated area and if you get lucky, you wouldn’t see any ash at all. An aircraft right above you might be In the centre of it and might suffer significant damage.

“Doing that with passengers on board is just downright stupid.”

Professor Jon Davidson, Chair of Earth Sciences at Durham University, said: “You can fly an aircraft up and down and land it and say: ‘It’s fine’ but no – you can’t be absolutely sure. It’s possible that there’s a higher concentration up there that they didn’t fly through.

“There have been incidents in the past – fairly serious incidents – that have made it quite clear that this is, in principle, an accident waiting to happen.

“A short flight is just a one-off test that isn’t a well-constrained, well-conducted piece of research. What needs to be done is research in which the amount of ash is known. We really don’t know what the tolerances for aircraft are – how much ash can be in a cubic metre of air before it becomes a safety issue.”

A group of scientists from Iceland and Denmark published the first major study on ash from Eyjafjallajökull last month, concluding that the aviation authorities had been right to ground planes.

Geochemist Dr Susan Stipp said particles from the 2010 eruption were so sharp they could have “sand-blasted” flying planes and could have melted in jet engines, causing them to fail.

She said: “The air authorities made the right decision last time based on the fact that these particles were dangerous in certain proportions. There were a lot of people frustrated and a lot of money lost, but there were no lives lost as a result of plane failure.

She expressed the opinion that airlines shouldn’t fly planes through ash-filled skies, saying: “Neither you nor I would like to get on a plane where there would be any experimenting.”

After the events of last year the CAA has moved away from blanket no-fly zones, putting more emphasis on the airlines to carry out their own tests and present a case to aviation authorities if they think it’s safe to fly.

Ryanair now say they have received written confirmation from their airframe and engine manufacturers that it is safe to operate in the red zones.

If that’s the case, it would mean the aviation industry is finally making a serious effort to test the tolerances of passenger planes and has come up with credible findings, something that experts say would represent real progress.

FactCheck asked the airline to show us the correspondence they have had with their manufacturers, but the company has so far declined to go public.

If they did, it would be a significant step forward in the debate and could boost confidence in the flying public over the safety issues of volcanic ash.

Our request still stands. Watch this (air)space.

The verdict

Until we hear from Ryanair, the FactCheck-o-meter is going to have to stay on fiction, as the overwhelming consensus from the scientific community is that there are far too many unknowns in the saga of volcanic ash to say that there is “no safety threat to aircraft”.

By Patrick Worrall