Carb Heat

Is the need for carb heat affected by ambient humidity? In low
humidity conditions, and also at very low temperatures, is the
propensity for carb ice reduced thus 'eliminating' the need for carb
heat?
Just curious what the discussion might bring.
Thx.

Is the need for carb heat affected by ambient humidity?

It sure is. I tried to take off once in Shenandoah on a humid day, and
the engine failed its runup - when I pulled the power back, it quit
entirely. I did this a few times and called the mechanic over. We
couldn't find anything - the final theory was that carb ice had built up
while I was taxiing and during the runup. This had never happend to me
before, in this aircraft, or any other.

I preflit and took off with carb heat, and had no problem.

Jose
--
He who laughs, lasts.
for Email, make the obvious change in the address.

vlado wrote:
Is the need for carb heat affected by ambient humidity? In low
humidity conditions, and also at very low temperatures, is the
propensity for carb ice reduced thus 'eliminating' the need for carb
heat?
Just curious what the discussion might bring.

You may want to hang out behind the back of your local ground school
and grab one of the old Private Pilot manuals they are throwing out.

-Robert

Robert M. Gary wrote:
vlado wrote:
Is the need for carb heat affected by ambient humidity? In low
humidity conditions, and also at very low temperatures, is the
propensity for carb ice reduced thus 'eliminating' the need for carb
heat?
Just curious what the discussion might bring.

You may want to hang out behind the back of your local ground school
and grab one of the old Private Pilot manuals they are throwing out.

-Robert

OK OK. Here's the deal, Outside the weather is "frightful" with no
visible moisture, 30% humidity & -12 centrigrate. Any chance of carb
ice in this condition?
(The manuals are gone; they've gone to CDs if not on their iPods.)
Thx

AOPA has an excellent chart showing the likelyhood (sp?) of carb ice at

http://flighttraining.aopa.org/membe...rticles/58.cfm

I'm surprised it isn't more widely published.

"nrp" wrote:
AOPA has an excellent chart showing the likelyhood (sp?) of carb ice
at

http://flighttraining.aopa.org/membe...lo/articles/58.
cfm

I'm surprised it isn't more widely published.

I clicked through and got:
"The section that you're trying to access requires membership in AOPA."

Does this AOPA public link have the same chart you intended to
reference?:

http://www.aopa.org/asf/epilot_acc/nyc02fa025_1.html

The chart (if it is the same one you mean) also appears on these pages:

http://www.faa.gov/ats/afss/newyork/ENROUTE.htm

http://www.tc.gc.ca/CivilAviation/pu...71/AIR/2-1.htm

vlado wrote:




OK OK. Here's the deal, Outside the weather is "frightful" with no
visible moisture, 30% humidity & -12 centrigrate. Any chance of carb
ice in this condition?




Nope, way too cold.

Newps wrote:
vlado wrote:




OK OK. Here's the deal, Outside the weather is "frightful" with no
visible moisture, 30% humidity & -12 centrigrate. Any chance of carb
ice in this condition?




Nope, way too cold.

Newps.....Thanks for the quick answer.
The AOPA chart shows that as well. It is true, a good chart with not
enough distribution.
Thx again.

Yes they appear to be similar charts. The AOPA chart actually shpws a
strange anomaly for pressure carbs that limits the severe icing to
about 80% humidity. I'm not sure why that is so, and it may only be an
artist's mistake.

At any rate the general trend for when to expect icing from those
charts is clear.

nrp wrote:
Yes they appear to be similar charts. The AOPA chart actually shpws a
strange anomaly for pressure carbs that limits the severe icing to
about 80% humidity. I'm not sure why that is so, and it may only be an
artist's mistake.

At any rate the general trend for when to expect icing from those
charts is clear.
\
The OP's post indicates the increasing trend to ignore
training about carb ice. There have been several accidents in the last
few years around our part of the country involving carb ice, and in my
teaching i find that pilots don't know the mechanism of carb ice, nor
do they know how to recognize and manage it.

Dan