How Much Is Too Much?

Commentary By Ron Beasley

Airline passengers are inconvenienced, airlines are losing money, the Europeans don't have fresh produce and everyone is unhappy. 

To fly through ash or not? That's no easy question 

Six days after volcanic ash shut down the skies over much of Europe, planes are back in the air, but science still can't answer the question:

Is it safe to fly again?

Mother Nature has given Europe a lesson in risk, aviation technology, scientific uncertainty and economics. And how these fields intersect is messy.

Watching the same people who earlier said it was too dangerous to fly now say it's safe "is just more proof that risk is a subjective idea," said David Ropeik, a risk perception expert at Harvard University.

When people turn to science for answers, they get a lot equivocation.

"We really don't have as good a handle as we should on the ash particle size, the ash concentration and most important, just exactly how high the ash got up into the atmosphere," said Gary Hufford, a U.S. government volcano expert based in Anchorage, Alaska.

So how much ash is too much?  Nobody knows:

Ever since a Boeing 747 temporarily lost all four engines in an ash cloud in 1982, the International Civil Aviation Organization (ICAO) has stipulated that skies must be closed as soon as ash concentration rises above zero. The ICAO's International Airways Volcano Watch uses weather forecasting to predict ash cloud movements, and if any projections intersect a flight path, the route is closed.

But although it is certain that volcanic ash like that hanging over northern Europe can melt inside a jet engine and block airflow, nobody has the least idea about just how much is too much. After a week of losing millions every day, airlines are starting to ask why we can't do better.

It need not be this way, concedes Jonathan Nicholson at the UK's aviation regulator, the Civil Aviation Authority. "There may be a non-zero safe ash level for commercial jets, of so many particles of a certain size per minute," he told New Scientist, "but we just don't know."

How much is too much?  The only people who can make that call are the aircraft engine manufacturers and they haven't.  And perhaps they won't.  It could be they don't want to do the necessary testing or it may be their legal departments won't let them.  What would happen if they said a concentration of X was safe and a plane went down when flying through such an ash cloud - they would have a lawsuit to deal with.  But even if parameters were established we lack a method to measure ash concentration and particle size.  So for the foreseeable the tolerance is likely to remain zero.