Can we fly safely through volcanic ash?
来源：未知 作者：籍乐昴 时间：2018-02-19 06:01:19
By Paul Marks If airlines and aircraft makers did not understand the economic case for Fred Prata‘s invention a week ago, they will now. Since 1991 the atmospheric physicist has been developing a sensor to warn pilots about volcanic ash clouds up to 100 kilometres ahead of their plane so they can thread a safe path around it. But despite successful ground tests (see image), he has not been able to secure the funding to test it in the air. With an estimated 6.8 million passengers grounded by airborne ash cloud from Iceland’s Eyjafjallajökull volcano, and millions of pounds at stake, serious questions are being asked about the technological shortcomings of the current approach to protecting flights. 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 computerised pollution dispersal models 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.” Denis Chagnon, spokesman for the ICAO, agrees, but says that isn’t regulators’ fault. “This has to be established by the engine makers themselves, because they produce the affected equipment. And that has not been done,” he says. Two of the biggest aero engine makers – Rolls-Royce in the UK and General Electric in the US – did not return phone calls or emails asking for comment on if, how and when they plan to establish safe thresholds. When the ash settles, it seems likely that they will be asked to think seriously about doing so. The wisdom of allowing computer models alone to ground flights is also being questioned. Frustrated companies including KLM, Lufthansa, BA, and aircraft maker Airbus have launched their own aircraft to explore how the reality in the air matched the models keeping them on the ground. None suffered any damage, and some carried sampling instruments that found no ash in places where models predicted it, sparking strong complaints from the airline trade body IATA. Yet in a reminder of the risks, some military jets did encounter ash last week and sustained engine damage. Prata says sensors like those he is developing at the Norwegian Institute for Air Research (NILU) in Kjeller could keep planes flying by letting them finesse the educated guesses of models to reveal ash-free patches and routes. A spokeswoman for the British air-traffic control agency NATS said she was not aware of Prata’s work, but said the idea of in-flight detection sounded “handy”. However, Nicholson suggested that it could cause traffic problems if many flights ended up switching course to sidestep ash. Whatever happens, one fallout from the ash cloud that has grounded Europe looks likely to be a fresh look at just how dangerous volcanic ash is, and whether planes can be given the smarts to dodge around it. More on these topics: