[f-AA] Carb Temp Probe Location

[Homer Keisler]

Wow! This subject brings up a lot of questions and very few definative answers. Personally, I will not attempt to try to determine the most effective area in which to install a temp probe or install one on my Champ, If there is any doubt I use carburetor heat. In these low compression engines we are not likely to cause detonation.The most lasting memory of my use of an approved carb temperature gage was in a C45 at 10000 ft in instrument conditions when we suddenly encountering freezing rain. The carburetor air temperature was being constantly monitored and kept in the green by the copilot  There was a sudden drop in manifold pressure indicating ice and the co pilot attempted to add more heat to  the intake air but he found the heat control levers frozen in position. The recommended procedure to correct this condition was to yank the power off and back on again causing a backfire through the carburetor and freeing the heat control valves. It worked, only problem, the right engine died in the process and we could not maintain altitude. The most exasperated feeling I have ever had for Air Traffic Control was when I declared an emergency an told ATC we could not maintain altitude and were descending and he asked for my bearing was off an unmonitored VHF station. I said, you should be able to confirm our position, we reported over Tri City five minutes ago.  I am here to report that we did get the right engine started again and were able to maintain level flight at a lower altitude with accumulated ice. We did not get a view of the mountains a couple of thousand feet lower. Homer Keisler

[Stephen Briggs]

I read in one of the older FAA pubs that when monitoring carb temp, you should be aware of possible ice formation at temps between -15 C and  +5 C.  So if in doubt and you have a carb temp gauge.  You're probably not flying in -15C because it tooooo cold.  So keep above 40 F on the carb air temp regardless of OAT if in doubt about possible ice forming.

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From: fast...@windstream.net
To: aer...@westmont.edu
Date: Sun, 24 Apr 2011 11:32:14 -0400
Subject: [f-AA] Carb Temp Probe Location

Wow! This subject brings up a lot of questions and very few definative answers. Personally, I will not attempt to try to determine the most effective area in which to install a temp probe or install one on my Champ, If there is any doubt I use carburetor heat. In these low compression engines we are not likely to cause detonation.The most lasting memory of my use of an approved carb temperature gage was in a C45 at 10000 ft in instrument conditions when we suddenly encountering freezing rain. The carburetor air temperature was being constantly monitored and kept in the green by the copilot  There was a sudden drop in manifold pressure indicating ice and the co pilot attempted to add more heat to  the intake air but he found the heat control levers frozen in position. The recommended procedure to correct this condition was to yank the power off and back on again causing a backfire through the carburetor and freeing the heat control valves. It worked, only problem, the right engine died in the process and we could not maintain altitude. The most exasperated feeling I have ever had for Air Traffic Control was when I declared an emergency an told ATC we could not maintain altitude and were descending and he asked for my bearing was off an unmonitored VHF station. I said, you should be able to confirm our position, we reported over Tri City five minutes ago.  I am here to report that we did get the right engine started again and were able to maintain level flight at a lower altitude with accumulated ice. We did not get a view of the mountains a couple of thousand feet lower. Homer Keisler

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[Cy Galley]

Mine has a red zone so I try to keep it above it.

[Stephen Briggs]

What kind do you have Cy, mine has a little yellow light that comes on when it's in the range?
cga...@mchsi.com
To: aer...@westmont.edu
Date: Sun, 24 Apr 2011 16:05:51 -0500

[Cy Galley]

I’ll have to go look as I have been repairing for the last 7 years and CRS has taken its tole.

[jay curtis]

Stephen and Cy, I have a question ?

 

If a person had a carb temp gauge, is it standard practice to run partial carb heat to just stay out of the freezing zone when this occurs ???  Or simply more prudent applications of carb heat frequency wise in the danger zone shown  ??   

 

I just returned from #2 Easter turkey-ham meal at the inlaws and wasn't allowed to fly today :-(  but will feel better knowing more on this topic !!!!!! 

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Aer...@westmont.edu
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From: jay curtis <jcu...@execulink.com>
To: aer...@westmont.edu
Sent: Sun, April 24, 2011 7:25:36 PM

[Ian Harvie]

I was taught not to use partial carb heat as it may bring the carb temp
up to a condition at which carb icing may more easily occur.
In other words, full heat or none at all.

Ian

On 25/04/2011 10:25 AM, jay curtis wrote:
> Stephen and Cy, I have a question ?
> If a person had a carb temp gauge, is it standard practice to run
> partial carb heat to just stay out of the freezing zone when this
> occurs ??? Or simply more prudent applications of carb heat frequency
> wise in the danger zone shown ??
> I just returned from #2 Easter turkey-ham meal at the inlaws and
> wasn't allowed to fly today :-( but will feel better knowing more on
> this topic !!!!!!
>

[Cy Galley]

I believe the only time one can run partial heat with FAA blessing is when one can monitor the carb temps. I tried to keep the temp at least 5 degrees.  If it would run more without heat, I would do it.

 

 

Cy Galley; Editor - Aeronca Aviator

Supporting Aeroncas every day

www.aeronca.org  

[Stephen Briggs]

The operating manual that came with my prob from EI suggests to run the temp just above (+9F) freezing potential (i.e. 40F)  This serves two purposes, 1 - keep you free of ice, 2 - preheats the intake air to help fuel atomization and create better combustion in the cylinder resulting in fewer lead deposits, cleaner plugs and better economy.

Steve

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From: jcu...@execulink.com
To: aer...@westmont.edu
Date: Sun, 24 Apr 2011 20:25:36 -0400

[Tony Markl]

Carb heat should be ON or OFF.  If you use partial heat you may be raising the temp right into the icing range  .Just OMO of course

Regards,
Tony Markl
www.tailwheel-and-fabric-spoken-here.com
"Fabric work done or taught at your location"

[Rob McDonald]

I'm no expert, but my understanding was that we generally use only full
heat or no heat because most of us do not have a carb air temp gauge. I
was taught that it was acceptable to use partial carb heat to keep the
temp out of the icing range *only if you have a carb air temp gauge*.

Rob

On Mon, 2011-04-25 at 06:09 -0400, Tony Markl wrote:
> Carb heat should be ON or OFF. If you use partial heat you may be
> raising the temp right into the icing range .Just OMO of course
> Regards,
> Tony Markl
> www.tailwheel-and-fabric-spoken-here.com
> "Fabric work done or taught at your location"
>
> On 4/24/11 8:25 PM, jay curtis wrote:
> > Stephen and Cy, I have a question ?
> >
> > If a person had a carb temp gauge, is it standard practice to run
> > partial carb heat to just stay out of the freezing zone when this
> > occurs ??? Or simply more prudent applications of carb heat
> > frequency wise in the danger zone shown ??
> >
> > I just returned from #2 Easter turkey-ham meal at the inlaws and
> > wasn't allowed to fly today :-( but will feel better knowing more
> > on this topic !!!!!!

_______________________________________________

[Cy Galley]

Tony is correct UNLRSS you have a carb temp gage. Then the FAA permits partial application because one can monitor the temps to stay out of the freeze range.  Even then you have to maintain at least 5°C above freezing (40°F).

[jay curtis]

Thanks for more  clarification,  my original question was meant is partial ok if running a carb temp gauge, and fully understand why only proper on -off  use of carb heat is allowed without a gauge, and also realize the importance of having to trust that gauge if installed ..     I got word back from Iceman Company and they as suspected do not have STC for probe into a Stromberg carb...   May try other brands for approval..  I do understand Tonys excellent points and at sunup this morning with a 2 deg dewpoint spread was extra vigilent in its proper use.. Its a most worthy topic to hash and rehash refresher wise. Thanks to all , will report if find an approved installation, and may very well just continue with 65 yrs history that with a keen lookout and proper use of carb heat all will be well, and not add more clutter to an already excellent machine...  The $ savings being used for more gas and even  some more  MMO  :-))

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[John Rodkey]

Interesting discussion.  My father-in-law was involved in an accident that was apparently caused by icing.  It was in Alaska and the temperature was extremely cold.  He applied carb heat prior to and during takeoff, and apparently raised the temperature in the carb just enough to allow carb ice.  As the engine lost power after lift-off and before crosswind turn, he was unable to clear trees near the end of the runway and crashed into the tree tops.  The airplane then slid its way down between several trees, stripping off branches as it fell and absorbing all of the energy fairly slowly, so that there were only very minor injuries, Lord be praised.  I certainly wouldn't have anticipated that applying carb heat would actually induce icing, but apparently so.

John

--
John (poobah) Rodkey - N9361E 11AC at Goleta

[jay curtis]

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[jay curtis]

Sorry for blank post,  This cold weather example now makes me wonder, was my flying in minus 25C really a good idea, now has me flip flopping on needing, not needing a Carb temp gauge.   First need to find a Stromberg approved method.   I see confusion without a gauge when flying in bitter cold and making possible ice as I add heat before entering down wind for example.

 

 

----- Original Message -----

[Tom Pederson]

For what it's worth, I've done most of my flying with a CAT gauge and love it.  Becomes part of one's scan and always answers the question about how close one is to carb icing;  just add heat as necessary to maintain a safe margin.   OMHO :-)

Tom