eion wrote:UnderAGreySky wrote:Here's a question: Would it be possible to operate airliners at 10,000 feet till they can get out of the clag? From what it seems the particles are between FL200 and 550. General aviation aircraft at the airport where I live are operating as always.. so I was wondering.
There's also the danger that should they hit a low flying ash cloud (and let's remember that often these ash clouds are invisible) their engines will go out and they’ll crash before they can restart them. If I recall correctly the two incidents where an airliner lost all 4 engines due to ash happened at around 25,000ft, and by gliding and running air through the engines to clean them out they were able to restart around 13,000 ft.
If the same thing happened at 10,000ft you'd be 2,000ft in the ground before you could restart. Efficiency isn't the only good reason to fly so high.
I touched on the "increased risk" aspect but yes, this is a real danger. If your jet's engines quit at 30,000 feet not only is there time to attempt a restart, but so far the track record for dead sticking airliners from that altitude has produced some surprising success stories in regards to safe landings
because you have time to deal with the situation.
If your jet's engines quit at 10,000 feet... you probably can't restart them before you run out of sky and hit the ground. You CAN land a big plane without engine power and walk away, but I guarantee it will be one of the more unpleasant rides you experience in life, and there's a good chance you will die because a certain amount of luck as well as skill is required. That's why KLM was moving big jets
without passengers on board - bad enough to lose a crew, worse to lose a hundred or two hundred people.
Another factor is that, remember, that ash is abrasive as all hell - it can
also get into moving parts like hinges needed for flight controls like ailerons and rudder and flaps and stuff and potentially
jam them. Frankly, as a pilot I'd rather lose an engine than to lose my steering. You
can fly without an engine - you
can not control the airplane without the flight controls.
Sometimes you can compensate for damaged flight controls with engine power, but
only if the engine is working!
Now, by no means does every airplane that encounters volcanic ash fall out of the sky. It DOES fuck them up. It
always causes damage. Hell,
normal air, without ash in it, erodes the paint off airplanes, cause wear on the moving parts, and so forth, it just does so slowly and maintenance can keep up with it. Volcanic ash causes the equivalent of
decades of wear in mere minutes.
I know it is extremely frustrating, even incomprehensible, for people to look up at a clear blue sky and be told it's not safe to fly but it
really isn't. You can't see the danger but it really is there.
