Pace:
Quote:
Scientists have no standard for what concentration of ash is safe and what is a danger to aircraft, but ash cloud does scatter enough with time and distance to not threaten jets. Fallout from Mount St. Helens actually circled the globe three times before fully dispersing, but flights were grounded only within a couple hundred miles of the source.
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Alaska airlines have been dealing with this and flying for years. They have built up their own operating procedures.
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I am not an engineer or scientist but would have thought specialised engine testing, ground based in a wind tunnel where engines could be run for hours in various concentrations of ash would give a better answer?
i believe the answer was already given earlier down this thread: the tests you are mentioning, even if being a good idea, can not be done due to simple fact that it would be technically and scientifically difficult to decide on what type of ash to use for tests: harder or softer, more silica or less, with sulphus gases or without, etc.etc.
The amount of known ash types is so wide that it would be commercially not possible to select appropriate representatives for testing. And it would be difficult to extrapolate the results to different ash types without extensive test.
And hence the zero allowable ash concentarion directive - simple and effective.
Looking from the Alaska experience - they are simple avoiding any ash! OK Europe is smaller so we may have to invent a more creative way - but it may come at a cost. Hopefully just the cost of earlier engine replacement and not a a cost of passenger/crew lives.