Slashdot Mirror
EU Conducts Test Flights To Assess Impact of Volcanic Ash On Aircraft
chrb writes "As we discussed on Friday, the eruption of Eyjafjallajökull in Iceland has led to flights being canceled across the EU. With travel chaos ensuing and the airlines losing an estimated $200 million per day, EU authorities are coming under increasing pressure to re-open the airways. Test flights conducted on Saturday were apparently successful, with no problems encountered during flight. Following the test flights, Peter Hartman, CEO of KLM, said, 'We hope to receive permission as soon as possible after that to start up our operation and to transport our passengers to their destinations.' Evidence possibly opposing this move comes from the Finnish Defense Forces, which released photos and a statement after F-18 Hornets flew through the ash cloud, saying, 'Based on the pictures, it was discovered that even short flights in ash dust may cause significant damage to an airplane's engine.' Is it safe to resume flights so soon, or should planes remain grounded until the ash cloud has dissipated?"
There is satellite imagery however. Both NASA and ESA traces the ash cloud based on satellite data, ESA even compiled an informative animation.
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The ash allegedly contains shards of glass, and I can see how this would cause serious problems for turbines... but I think it's obvious that just like any other phenomena of weather, the ash will be non-uniform. It makes perfect sense that one test would have completely different results from another. Thus, broadly-based testing would be necessary to derive any useful result...
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Ash is abrasive. Any idiot who has washed their hands with LAVA soap can attest to that.
Q:So then, what happens when you put abrasives into parts manufactured to close tolerances?
A: Tolerances are widened.
Q: What happens when tolerances are widened on machinery that spins at high RPM?
A: Centers are lost and jitter occurs speeding disappearing tolerances and adding heavy vibration.
Q: What will that heavy vibration do Cap'n fly?
A: Titaniums can shatter, Waspalloy and Hastalloy parts will tear away from Titaniums and Aluminums, H60 coated bearings will fly as though fired from a gun.
Q: What are you really saying, fly?
A: Assume the crash position, put your chin on your taint and kiss your @ss goodbye!
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Actually the problem, as I understand it, is that the silica particles in the ash cloud (similar to very fine grains of sand, or glass) are melted by the heat of the engine, then then collide with the leading edge of the turbine blades and condense. This is bad for a number of reasons, firstly it expands that surface and significantly reduces the efficiency of the engine. More importantly however, it has a different coefficient of thermal expansion to the titanium blade, and very quickly it will start to crack and break away. In this process it takes small chunks of the blade with it. The process causes a lot of pitting in the leading edge of the blade.
The thermal spraying department at my work do a lot of research into repairing blades that have suffered from this problem. Most often it has been caused by planes flying through sand storms in a desert, but the effect is just the same. One of the methods of repairing the blade is to remove enough of the titanium so that you can plasma spray a ceramic in its place to make the blade the right size again.