Flying through volcanic ash can be dangerous for aircraft and passengers.

[lisab]

This isn't purely an Earth science question, but I don't know where else to post it. Recently, the Kasatochi volcano erupted in Alaska. It brought to mind something that happened to me a long time ago that I have always wondered about.

In 1989 I was flying from Alaska to Seattle. Days earlier, Mt Redoubt - a volcano in the Aleutian chain - had a big eruption. Most flights out of Anchorage were canceled but I was surprised that my flight was scheduled to go.

Just minutes into the flight, the cabin was filled with airborne ash. It was so thick that it bothered everyone's eyes and if you ground your teeth together, you could feel the grit. I recall a slight sulfur smell.

It only lasted maybe 10 seconds. The flight went on without incident.

I always wondered were ever really in danger? What's the protocol for flying through a volcano plume?

 

[wolram]

No way should you fly through volcanic ash, there was a famous incident where an aircraft lost all engine power and had to glide for miles.

 

[lisab]

Yes, I figured it wasn't safe. It was actually terrifying. Can't a plume be seen on radar?

 

[Evo]

Wow, that is very scary Lisab. I wonder why the pilot would take such a risk.

 

[wolram]

Yes, I figured it wasn't safe. It was actually terrifying. Can't a plume be seen on radar?

It seems not

http://www.geo.mtu.edu/department/classes/ge404/gcmayber/intro.html

 

[Andre]

Were you flying KLM, Lisa?

Check:

http://www.alpa.org/DesktopModules/...View.aspx?itemid=1470&ModuleId=1316&Tabid=256

On Dec. 15, 1989, a KLM Boeing 747 flew into the ash plume from Alaska's Mt. Redoubt and similarly lost power from all four engines within less than a minute. The pilots were able to restart the engines, but could not obtain full power. The pilots landed the airplane safely at Anchorage despite their windshield being sandblasted so badly that they could only see out of a small portion of it.

 

[lisab]

Were you flying KLM, Lisa?

Check:

http://www.alpa.org/DesktopModules/...View.aspx?itemid=1470&ModuleId=1316&Tabid=256

That happened just a few days before my flight - it was all over the news, as you might guess. Knowing about it added to my anxiety!

 

[LURCH]

Didn't look at the link yet, but does it say anything about the ash getting inside the passenger compartment? I would think that in a pressurised cabin, the quality of the outside air could not effect people's eyes or cause grit in their teeth. Maybe what you all experienced was ash from the recent eruption that got into the cabin while the plane was on the ground, and ti settled into the ventilation system, only to get blown back out into the cabin when the system was turned on. You say it atsrted just minutes into the flight, maybe that's the time it took to get out of the vents and into your face.

 

[lisab]

Didn't look at the link yet, but does it say anything about the ash getting inside the passenger compartment? I would think that in a pressurised cabin, the quality of the outside air could not effect people's eyes or cause grit in their teeth. Maybe what you all experienced was ash from the recent eruption that got into the cabin while the plane was on the ground, and ti settled into the ventilation system, only to get blown back out into the cabin when the system was turned on. You say it atsrted just minutes into the flight, maybe that's the time it took to get out of the vents and into your face.

Hmmm...I guess that makes sense! It was odd to me, too, how it got into the cabin. I suppose it may have been in the ventillation system somehow.

 

[Astronuc]

Didn't look at the link yet, but does it say anything about the ash getting inside the passenger compartment? I would think that in a pressurised cabin, the quality of the outside air could not effect people's eyes or cause grit in their teeth. Maybe what you all experienced was ash from the recent eruption that got into the cabin while the plane was on the ground, and ti settled into the ventilation system, only to get blown back out into the cabin when the system was turned on. You say it atsrted just minutes into the flight, maybe that's the time it took to get out of the vents and into your face.

I believe commercial airliners take some of the air from the engine compressors, and that's why one will smell the fuel odor in the cabin when the doors are closed and the engines are started. The compressors obviously suck in the local air. Similarly in an ash cloud, the dust would find its way into the cabin.

Ash would certainly be detrimental to the compressor and turbine blades, and mess with the fuel/air mixing in the combustors, as well as accumulate in the hot areas of the engine.

http://volcanoes.usgs.gov/Hazards/Effects/Ash+Aircraft.html

Ash Reduces Engine Performance and May Cause Engine Failure

Ash ingested by jet engines may lead to the immediate deterioration in engine performance and engine failure. The principal cause of engine failure is the deposition of ash in the hot sections of the engine. Glass from melting volcanic ash will coat fuel nozzles, the combustor, and turbine, which reduces the efficiency of fuel mixing and restricts air passing through the engine. This causes surging, flame out, and immediate loss of engine thrust. Ash may also seriously erode moving engine parts, including the compressor and turbine blades, which reduces the efficiency of the engine.