Mt. Saint Helens

in article fT27d.3595$mS1.2578@fed1read05, BTIZ at
wrote on 9/30/04 7:00 PM:

that would be one heck of a thermal ride... if it weren't for the rocks...
and "cough cough" the ash..

BT

I was thinking about this recently, and I was trying to determine exactly
what the effects would be on a small plane flying into an ash cloud. How
long would it take for the air filter to become completely clogged? And at
that point, assuming the plane had a carburetor, what would be the effect on
the engine? Would the plugs become fouled? Would they fire at all?

I'm a new pilot and relatively ignorant of engine operations, so I'm curious
to hear the answers.

In article ,
Philip Sondericker wrote:

in article fT27d.3595$mS1.2578@fed1read05, BTIZ at
wrote on 9/30/04 7:00 PM:

that would be one heck of a thermal ride... if it weren't for the rocks...
and "cough cough" the ash..

BT

I was thinking about this recently, and I was trying to determine exactly
what the effects would be on a small plane flying into an ash cloud. How
long would it take for the air filter to become completely clogged? And at
that point, assuming the plane had a carburetor, what would be the effect on
the engine? Would the plugs become fouled? Would they fire at all?

I'm a new pilot and relatively ignorant of engine operations, so I'm curious
to hear the answers.



You can count on an early overhaul, at best. During the 1980s, several
turbine aircraft, including a B747, encountered ash clouds in flight.
The ash is so abrasive that it eroded the compressors to the point of
flameout. The B747 descended to ~10000 ft before they got three engines
relit. A C130 had similar problems.

In a piston engine, the alternate air door would probably open, allowing
unfiltered air into the engine. I p-robably wouldn't atop, but the
compression test would be pretty grim.

Orval Fairbairn wrote:

You can count on an early overhaul, at best. During the 1980s, several
turbine aircraft, including a B747, encountered ash clouds in flight.
The ash is so abrasive that it eroded the compressors to the point of
flameout. The B747 descended to ~10000 ft before they got three engines
relit.


June 24, 1982, a British Airways 747 over Java.

The ash cloud also sandblasted the windshield nearly opague.
The flight crew had great difficulty making out the approach and
runway lights to land the aircraft. If the incident had occurred
during daylight hours, they probably would not have been able
to see out at all.

"Orval Fairbairn" wrote in message
news
In article ,
Philip Sondericker wrote:

in article fT27d.3595$mS1.2578@fed1read05, BTIZ at

wrote on 9/30/04 7:00 PM:

that would be one heck of a thermal ride... if it weren't for the
rocks...
and "cough cough" the ash..

BT

I was thinking about this recently, and I was trying to determine
exactly
what the effects would be on a small plane flying into an ash cloud. How
long would it take for the air filter to become completely clogged? And
at
that point, assuming the plane had a carburetor, what would be the
effect on
the engine? Would the plugs become fouled? Would they fire at all?

I'm a new pilot and relatively ignorant of engine operations, so I'm
curious
to hear the answers.



You can count on an early overhaul, at best. During the 1980s, several
turbine aircraft, including a B747, encountered ash clouds in flight.
The ash is so abrasive that it eroded the compressors to the point of
flameout. The B747 descended to ~10000 ft before they got three engines
relit. A C130 had similar problems.

New Zealand-based pilots , especially those close to the central range on N
Island, have to deal with ash from time to time. When I visited in 1997, our
747 was sent from Auckland airport an hour early because Ruapehu was acting
up. Any Kiwis here can comment?

-- David Brooks

"Philip Sondericker" wrote in message
...
I was thinking about this recently, and I was trying to determine exactly
what the effects would be on a small plane flying into an ash cloud. How
long would it take for the air filter to become completely clogged? And at
that point, assuming the plane had a carburetor, what would be the effect
on
the engine? Would the plugs become fouled? Would they fire at all?

The Northwest Mountain Division has rearranged things, and I can't find
their article anymore. But sometime back in the 90's, I read a description
on their web site about some consequences of the St. Helens eruption in
1980. The description included a jet that suffered the failure of all
engines, and a lightplane that barely survived.

Here are some articles that address the turbine side of things:
http://www.boeing.com/commercial/aer...nic_story.html
http://www.nw.faa.gov/releases/volash.html
I found them looking for the other article I remember.

Anyway, I don't know how long it would take for the air filter to become
clogged, but probably not too terribly long if you flew through the meat of
an ash cloud. Obviously, it depends on how close you get to the densest
part; just skim a side of the cloud, and you might not notice a problem at
all. Go through the middle, and you might clog the filter in a matter of
minutes.

Of course, the next step at that point would be to use the alternate air;
carb heat for carbureted engines, and whatever alternate air source for
fuel-injected (often is an automatically deployed, spring-loaded door that
bypasses the filter when it's clogged). One ingested, the ash would start
eating up the engine, but I would guess that you'd at least have enough time
to get on the ground to make an emergency landing. I think that the plugs
getting fouled would be the least of your worries, but who knows? Maybe the
heat of the spark would cause a nice, insulating glass barrier to form at
the sparkplug gap.

That is assuming, of course, you can still see out of the windows, since
they'll have been sandblasted the whole time. And that you find an area of
visibility high enough to make a landing. If the engine fails before you
can land, then you obviously will be forced to land wherever you happen to
be, regardless of whatever visibility you have.

I gather that generally speaking, other than trashing the airplane, pilots
usually make it out of ash clouds alive. But not all do, and it's certainly
not something I'd want to try, given the option.

Pete

Philip Sondericker wrote in message ...
in article fT27d.3595$mS1.2578@fed1read05, BTIZ at
wrote on 9/30/04 7:00 PM:

that would be one heck of a thermal ride... if it weren't for the rocks...
and "cough cough" the ash..

BT

I was thinking about this recently, and I was trying to determine exactly
what the effects would be on a small plane flying into an ash cloud. How
long would it take for the air filter to become completely clogged? And at
that point, assuming the plane had a carburetor, what would be the effect on
the engine? Would the plugs become fouled? Would they fire at all?

I'm a new pilot and relatively ignorant of engine operations, so I'm curious
to hear the answers.

The engine is about the last part I would worry about when flying
through a vulcanic ash cloud.
Probably you get burned to death or at least get a bit charred,
together with your plane.

To answer your quistion about the engine.
It will end up ruined, either by crashing or by inhaling to much dust
and then crashing. Or maybe you are lucky and you end up with a nice
sandblasted aircraft.

Some jets have flown through such clouds(they fly much higher, the
cloud is cooler that high), they needed a repaint and have their
engines replaced.


-Kees

Philip Sondericker wrote:

in article fT27d.3595$mS1.2578@fed1read05, BTIZ at
wrote on 9/30/04 7:00 PM:


that would be one heck of a thermal ride... if it weren't for the rocks...
and "cough cough" the ash..

BT


I was thinking about this recently, and I was trying to determine exactly
what the effects would be on a small plane flying into an ash cloud. How
long would it take for the air filter to become completely clogged? And at
that point, assuming the plane had a carburetor, what would be the effect on
the engine? Would the plugs become fouled? Would they fire at all?

Considering that a volcano almost brought down a 747 once, I don't
think a small plane is going to last long at all. Of course, the pilot
is going to have been broiled long before he has to worry about his
engine.

Rich Lemert

"Rich Lemert" wrote in message
k.net...
Philip Sondericker wrote:

in article fT27d.3595$mS1.2578@fed1read05, BTIZ at

wrote on 9/30/04 7:00 PM:


that would be one heck of a thermal ride... if it weren't for the
rocks...
and "cough cough" the ash..

BT


I was thinking about this recently, and I was trying to determine
exactly
what the effects would be on a small plane flying into an ash cloud. How
long would it take for the air filter to become completely clogged? And
at
that point, assuming the plane had a carburetor, what would be the
effect on
the engine? Would the plugs become fouled? Would they fire at all?

Considering that a volcano almost brought down a 747 once, I don't
think a small plane is going to last long at all. Of course, the pilot
is going to have been broiled long before he has to worry about his
engine.

Depends on how close you are to the volcano. If you are more than a couple
miles away it won't be that hot inside the ash cloud.

"Philip Sondericker" wrote in message
...
in article fT27d.3595$mS1.2578@fed1read05, BTIZ at

wrote on 9/30/04 7:00 PM:

that would be one heck of a thermal ride... if it weren't for the
rocks...
and "cough cough" the ash..

BT

I was thinking about this recently, and I was trying to determine exactly
what the effects would be on a small plane flying into an ash cloud. How
long would it take for the air filter to become completely clogged? And at
that point, assuming the plane had a carburetor, what would be the effect
on
the engine? Would the plugs become fouled? Would they fire at all?

Volcanic ash is very fine, like talcum powder. It is the same abrasive stuff
that they sell in pumice soap that removes anything, including your skin,
from your hands. It gets into everything. Worst case scenario if you flew
into a cloud of it your air filter would become clogged almost instantly. A
lot of the ash might work its way through the filter and into the engine,
where it is going to start abrading all the moving parts very quickly. Using
unfiltered air will just suck huge quantities of ash into the engine. The
cylinders will quickly overheat and the engine will quit. Odds are, though,
it would not be that bad. There are plenty of films of people driving around
in the ash cloud. It isn't smart and most of them suffered engine damage,
but their cars kept running. You might be able to keep a piston airplane
engine running long enough to make it to a safe landing area, but it will
probably suffer some damage.

Perversely, just when you would like to enrichen the mixture in order to
cool the engine and maybe wash some ash out of it, the ash is displacing air
and causing the mixture to be too rich already. As you set up for approach
and landing, you will find brakes, flaps, landing gear, propellers, and
every other moving part clogged with ash, even if you are no longer inside
the cloud. Your alternator may be ground to a pulp and your battery dead, so
you will not have any electrical system anyway. Your prop governor will also
be damaged, as will the oil cooler and anything else that moves. Control
surfaces and cables will be coated with abrasive, sticky ash.

The ash will also simultaneously reduce lift and increase drag. Stall speed
will increase as significant amounts of ash accumulate on and in the
airplane.

You also will be IMC and the cabin will also fill with ash to the point that
you will have difficulty breathing. All surfaces will be sand blasted and
you won't be able to see out the windows once you leave the cloud. It is
very dark inside a volcanic cloud, even darker than night. You cannot see
your hand in front of your face. The whole effect is one of driving around
at night in a very heavy snowstorm and dense fog.

Did I mention the poisonous gases? They aren't concentrated enough to hurt
most people, but asthmatics and others with impaired breathing can be
killed. There will be unhealthy concentrations of CO2, various sulfur
compounds, and acids. They can also damage the airplane. Fortunately they
are pretty well dispersed except in the immediate vicinity of the volcano.

There are plenty of films of people driving around
in the ash cloud.


They are likely driving at ten percent power.

Jose

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