carb ice experience

I got carb ice almost every time I flew the cub. On cold 6am flights,
the Cub just loved to suck up the ice. I learned to leave the carb heat
in during touch-n-go operations until climbing out because I lost the
engine once after shutting off the carb ice as I was moving the
throttle forward. The engine ran far enough to get me 300 feet up then
started to die. Luckily, turning around at 300 feet is very easy in a
Cub, not so easy in a Mooney. I kept a timer for cruise and ran 15
minutes heat off then 15 minutes heat on. I would also often get ice in
the time it takes to taxi to runup. I learned to clear out with heat
first. For some reason, the cub got ice much more than the Aeronca with
the same engine, I think it has something to do with how heat moves
around in the cowl.

-Robert

On 23 Oct 2005 04:23:46 -0700, "Tony" wrote:

The drop in RPM does not mean you have
carb ice, it means the carb heat is working.

If the RPMs went up right away you probably melted away exisitng carb
ice.

Yes, that's indeed how I understood it to happen, as I had seen it
happen on many occasions. But what happened when the rpms surged?


-- all the best, Dan Ford

email: usenet AT danford DOT net

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On Sun, 23 Oct 2005 11:59:37 GMT, Larry Dighera
wrote:

Did the mag check.
Pulled carb heat on. Whoom! Rpms went up to 1700.

What was the temperature/dew point spread at the time? Was the air
mass wet?

Hm. There was heavy frost on the grass and frost on the wings and tail
feathers, condensation inside the plexiglass windscreen. I'm sure it
was above freezing by that time, 8:15am. I melted the frost off by
turning the planes into the sun while I did the preflight check.



-- all the best, Dan Ford

email: usenet AT danford DOT net

Warbird's Forum: www.warbirdforum.com
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On Sun, 23 Oct 2005 12:24:23 GMT, "A. Smith"
wrote:

Check the idle mixture. When you pull carb heat on you are putting hot,
less dense, air through the carbuerator. If you were initially running lean
applying carb heat will improve the fuel/air mixture. Cold day, dense air,
more fuel required.

No mixture control in the Cub!

Could ice in the carb cause the fuel mix to be lean?


-- all the best, Dan Ford

email: usenet AT danford DOT net

Warbird's Forum: www.warbirdforum.com
Piper Cub Forum: www.pipercubforum.com
the blog: www.danford.net
In Search of Lost Time: www.readingproust.com

On 23 Oct 2005 08:27:50 -0700, wrote:

Another trick to stick in your pilots bag of magic is to use the primer
knob if your engine gets starved for carb ice and stops.

Ah, but that's on the instrument panel, and I fly from the back seat!

(A time or two, I've not noticed until I'm in the air that the field
altitude wasn't set, and I've had to add/subtract a hundred feet to
TPA etc. One time I was heading off on a crosscountry, and I landed in
a private field so I could set it correctly, which entails getting out
of the harness so as to reach forward across the front seat.)



-- all the best, Dan Ford

email: usenet AT danford DOT net

Warbird's Forum: www.warbirdforum.com
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the blog: www.danford.net
In Search of Lost Time: www.readingproust.com

Cub Driver wrote:

But the other day, first cold day, I had quite a different experience.
The engine may have been running rough when I taxied--hard to know
with earphones, but I had a feel it was rough. Did the mag check.
Pulled carb heat on. Whoom! Rpms went up to 1700.


The reason it zooms back to 1700 is that the ice melted and you were
giving it enough gas for 1700. The engine running rough on taxi is a
good indication of that, too. The rpms may have dropped momentarily,
but the ice release was apparently very sudden and it appeared to have
just gone up. Did the rpms increase again when you turned carb heat
off? They should have.

On Sun, 23 Oct 2005 15:54:42 GMT, George Patterson
wrote:

Now what was the difference between that experience and the ordinary
one where the rpms drop, then rise back to 1500?

The Selway Kid just mentioned that carb heat application also bypasses the air
filter in most aircraft. IMO, the most likely problem here is a clogged filter.

Yes, it bypasses the filter on the Cub.

Now you scare me. Clogged filter? Got unclogged?

(Must be more to carb heat than that. Bypassing the filter ought to
increase performance in every instance, or at least never decrease it.
But pulling carb heat on, in the Cub, does definitely cause a decrease
in power. In a go-around, the climb picks up as soon as I kick the
carb heat in.)



-- all the best, Dan Ford

email: usenet AT danford DOT net

Warbird's Forum: www.warbirdforum.com
Piper Cub Forum: www.pipercubforum.com
the blog: www.danford.net
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On 23 Oct 2005 10:51:39 -0700, wrote:

On cold mornings, using summer mogas (which will have a lower vapor
pressure), the fuel doesn't vaporize as easily in the manifold.
Applying carb heat can sometimes improve this and the RPM will rise a
bit. I use the heat on my A-65 on such mornings.

It was 100LL. There is mogas at the airport, but the sample smelled
sweet and clean, and the mogas is foul smelling. Indeed, that's a
major reason we switched back to 100LL -- the instructors didn't like
to smell the mogas in the front seat.


-- all the best, Dan Ford

email: usenet AT danford DOT net

Warbird's Forum: www.warbirdforum.com
Piper Cub Forum: www.pipercubforum.com
the blog: www.danford.net
In Search of Lost Time: www.readingproust.com

"Cub Driver" usenet AT danford DOT net wrote in message
On 23 Oct 2005 04:23:46 -0700, "Tony" wrote:

The drop in RPM does not mean you have
carb ice, it means the carb heat is working.

If the RPMs went up right away you probably melted away exisitng carb
ice.

Yes, that's indeed how I understood it to happen, as I had seen it
happen on many occasions. But what happened when the rpms surged?

What happened when you turned the carb heat off?

moo

"Cub Driver" usenet AT danford DOT net wrote in message
...
On Sun, 23 Oct 2005 12:24:23 GMT, "A. Smith"
wrote:

Check the idle mixture. When you pull carb heat on you are putting hot,
less dense, air through the carbuerator. If you were initially running
lean
applying carb heat will improve the fuel/air mixture. Cold day, dense
air,
more fuel required.

No mixture control in the Cub!

There is no ground adjustable idle mixture screw on a Cub? I am not
familiar enough with the model to suggest more, sorry.

Allen


Could ice in the carb cause the fuel mix to be lean?


-- all the best, Dan Ford

email: usenet AT danford DOT net

Warbird's Forum: www.warbirdforum.com
Piper Cub Forum: www.pipercubforum.com
the blog: www.danford.net
In Search of Lost Time: www.readingproust.com