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Effect Of Smoke On Engines

Sat Dec 18, 2004 11:32 am

This summer, interior Alaska was plagued with wildfires which caused Fairbanks to be covered in dense smoke for several months. On many days, there was significant ashfall. I remember that most of the planes (especially the 732's) were much louder than normal when taking off in the smoke.

I was wondering what effect smoke and ashfall has on jet engines and any other parts of a plane.
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RE: Effect Of Smoke On Engines

Sat Dec 18, 2004 12:25 pm

I know ash is very bad for the engines, and would probably shut them down if the plane flew through a thick cloud of it. I assume this is one of the reasons planes were routed away from Mt. St. Helens when it recently was showing volcanic activity.
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RE: Effect Of Smoke On Engines

Sat Dec 18, 2004 1:04 pm

Well, smoke is particulate pollution, essentially, which isn't really a big deal. I don't think there are any significant performance issues that would arise in smoky air, unless it is really really bad, in which case there could be a drop in power if there wasn't enough oxygen to combust the fuel. All told, though, there shouldn't be issues with that. There might be some dirt buildup of some sort inside the engine or other abrasion, but still... not a big deal I don't believe.

As for volcanic ash, that is a whole different story. Since that is little bits of rock, there are serious damage issues with abrasion, because it is kind of like sanding down the inside of the engine. In addition, the ash can become hot enough in the engine that it will liquefy, and then you essentially have volcanic magma floating around in the engine, which can lead to a buildup of rock in there, which causes the engine to stop running altogether. It's as if someone had poured concrete into the engine, essentially.

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RE: Effect Of Smoke On Engines

Sat Dec 18, 2004 11:21 pm

Meister808 pretty much nailed it right on the head.

To answer the secondary question. Yes the smoke would make aircraft sound louder, because the sound waves are reverberating of the smoke particals (or the water in Fog).
The same kind of thing happens when an airport is covered by an overcast sky.

A simmiler effect can with air masses that are diffrent tempatures, ever notice how jet aircraft sound louder on cold days. (Might not mean much being that you live in alaska)
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RE: Effect Of Smoke On Engines

Sat Dec 18, 2004 11:55 pm

the main problem with ash or just dirty air is that if it gets too much it begins too build up on the blades and it will spoil the airflow, this can lead too stall/surge.
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RE: Effect Of Smoke On Engines

Sun Dec 19, 2004 12:01 am

Flying through smoke- ie: firebombing- has a significant effect on Turbine engine performance. I'm no expert on this but talking to several fire Tanker pilots they prefer an old radial engine in thick smoke- supposedly turbine engines have a bad habit of loosing power or flaming out in thick smoke. Although I'm not familiar with any accidents caused by this- the general opinion is to fly as close to the smoke as possible but don't get buried in it!
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