The National Air Traffic Services say there is "no threshold" at which volcanic ash is acceptable for aircraft. If particles are ingested into a jet engine, they clog it with molten glass, causing the engine to shut down. The International Civil Aviation Organisation recommends a no-fly zone if volcanic ash is detectable. (The Times, Tuesday April 20th)
Good news. NATS, the UK's national air traffic control service, has discovered the concept of a concentration level. Up until Tuesday evening this week, the organisation entrusted with the safe and expeditious control of aircraft within UK airspace, appeared unable to grasp the concept that a contaminant present in the atmosphere at detectable levels is not necessarily a contaminant present at hazardous levels.
Throughout this period, NATS attempted to counter growing objections within the aviation industry, with the standard, jet-out-of-jail-free card, that "Safety is paramount." Or, to complete the implicit thought process underlying such statements:
"In a risk averse culture, an uncritical, blanket approach to safety is paramount for preserving and promoting the lucrative careers of the managers and executives responsible for large industrial and technological enterprises."
On Sunday, McCabism noted that by assuming a contaminant detectable at any level must be a hazardous contaminant, NATS and the media were committing the same fallacy displayed after the Chernobyl explosion in 1986. Then, as now, the cloud of contamination was represented as homogeneous blanket extending over almost the whole of Europe. In fact, the analogy is stronger than suspected, for it transpires that the computer model used by the Met Office to predict the dispersion of the volcanic ash cloud, was actually developed in the wake of the Chernobyl accident, to model the distribution of radioactive fallout.
McCabism asked NATS last Friday to specify the maximum safe concentration level of volcanic ash, and is still awaiting a response. Happily, however, the Civil Aviation Authority has now been able to obtain an initial estimate of this figure as 0.002 grams per cubic metre.
It's good to know that the cream rises to the top, and we've got our best minds on the job at all times.