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Carb Heat
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kerrjohna(at)comcast.net
Guest

Posted: Sun Dec 02, 2007 6:19 am Post subject: Carb Heat

John Oakley raises a point that has been hashed over before.  The carb heat box out in the cold brings in cold air.  Operating without the carb heat box the carburetors are always in a "carb heat condition", high up in the motor compartment out of direct air flow, just like on the RV line, pulling heated air from the engine compartment.  It has been suggested that the only 912 flyers that have experienced carb ice are sucking in cold air.  Has anyone experienced carb ice on a 912 pulling air from the engine compartment? 

  

John Kerr   

 [quote]  

  

 [quote]-------------- Original message -------------- 

From: "john oakley" <john(at)leptron.com> 



[quote] --> Kitfox-List message posted by: "john oakley" 

 

 Darin, 

 I have the carb box that was a stock system on the model 4. I have had ice 

 twice, both times in a bad place. I have several friends that fly rans and 

 they have had ice also. On the 914 you get the air after the turbo if I 

 remember right and it will take care of any problems. 

 

 john 

 

 

 

 --

rdmac(at)swbell.net
Guest

Posted: Sun Dec 02, 2007 6:38 am Post subject: Carb Heat

Vic,

	I have the same set up as you. The alternate intake is probable for

carb heat but in yours and my setup it is not needed and here's my take on

that. That induction plenum is located in an area of the engine compartment

where engine heat is going to be at its highest. It's my belief that plenum

chamber will warm the incoming air sufficiently to prevent any icing

problems. Heck the carbs them selves are right behind the cylinders where

air is blown across the cooling fins. I'm not saying it's impossible but it

would be highly unlikely for carb icing to form. Now that being said, if I

did a lot of flying in a climate at or below freezing I would tend toward

the cautious side and install some sort of carb heat and cabin heat sense I

don't have neither. For the most part I'm a fair weather flyer and won't

even roll my plane out of the hanger if it is colder than 50 degrees. I

think everyone has to decide for themselves if carb heat is needed based on

under what conditions they plan to fly in.

Roger McConnell, Duncan, OK

Model 7 Trigear, Rotax 912uls 

Flying sense Jan. 06



--

MichaelGibbs(at)cox.net
Guest

Posted: Sun Dec 02, 2007 9:16 am Post subject: Carb Heat

Roger sez:



 	  Quote: 	
		  For the most part I'm a fair weather flyer and won't even roll my 

plane out of the hanger if it is colder than 50 degrees.


	


Keep in mind that carb ice can form in ambient temperatures as high 

as 70 degrees Fahrenheit.



Mike G.

N728KF

Phoenix, AZ

MichaelGibbs(at)cox.net
Guest

Posted: Sun Dec 02, 2007 9:16 am Post subject: Carb Heat

Noel sez:



 	  Quote: 	
		  Dave, exactly where are you?...What I'm getting at is if you are 

high up in the mountains than you probably also have a very dry 

climate and you may not get ice...


	


It seems to me that you build for where you plan to go, not where you are now.



Mike G.

N728KF

Phoenix, AZ

clemwehner(at)sbcglobal.n
Guest

Posted: Sun Dec 02, 2007 10:00 am Post subject: Carb Heat

I can confirm Mike's comment. I have a LOT of experience with carb

ice--in my old Dodge van. I had a 1986 Dodge Caravan that was plaqued

with carb ice every spring and fall, when temps were in the 50's and low

60's.  The carb would ice up so bad that the van would slow down to 20

MPH max. 



The solution was during those seasons, to remove the air ducting from

the carb to the front of the vehicle, and let the carb suck air through

the air filter from inside the engine compartment. This is just like

we've been talking about the 912 getting carb ice when a de-ice duct is

pulling air from the front and less (or no) carb ice when the air is

sucked through the air filters inside the engine compartment. 



My old van never got carb ice when it was really cold outside like down

in the 30's or less. 



Clem Wehner

Lawton, OK

KF-IV-912

--

Sbennett3(at)aol.com
Guest

Posted: Sun Dec 02, 2007 3:27 pm Post subject: Carb Heat

I flew 2 hrs today. Complete overcast. Rain and  drizzle the entire flight. Ceiling at 2000 to 2500.  Outside air temp at  take off was 43f. I have breathers on the firewall, no carb heat. Good solid  flight. Location NC, take off airport 351 msl. Destination airport 126  msl.  Steve Bennett



hottest products and top money wasters of 2007.

clemwehner(at)sbcglobal.n
Guest

Posted: Sun Dec 02, 2007 3:50 pm Post subject: Carb Heat

I can confirm Mike's comment. I have a LOT of experience with carb

ice--in my old Dodge van. I had a 1986 Dodge Caravan that was plaqued

with carb ice every spring and fall, when temps were in the 50's and low

60's.  The carb would ice up so bad that the van would slow down to 20

MPH max. 



The solution was during those seasons, to remove the air ducting from

the carb to the front of the vehicle, and let the carb suck air through

the air filter from inside the engine compartment. This is just like

we've been talking about the 912 getting carb ice when a de-ice duct is

pulling air from the front and less (or no) carb ice when the air is

sucked through the air filters inside the engine compartment. 



My old van never got carb ice when it was really cold outside like down

in the 30's or less. 



Clem Wehner

Lawton, OK

KF-IV-912

--

kitfoxmike

Joined: 05 Dec 2006
Posts: 373

Posted: Sun Dec 02, 2007 4:08 pm Post subject: Re: Carb Heat

I flew yesterday for 30min.  The weather was bad.  Ceiling was about 4000 with field elevation at 2000.  Temp was 24.   15 minutes later the ceiling was down to 3000 vis. was getting close to 7 miles.  did a few more touches and then noticed that everything went to heck, with snow flurries hitting the window.  Landed and looked around and felt the ceiling was down to about 900 off the ground.  About 5 minutes later it was snowing big time.   way below mins.  I don't have carb heat.



Was I taking a change with vis.  no way, that's why I was in close traffic and doing touch and go's.  I also kept an eye on the weather.  



I feel carb heat is a bigger issue if you let it idle too much, so keep the speed up.  Plus with the Rotax you have higher rpm's with slower blade speed, that helps also.

occom

Joined: 26 Aug 2006
Posts: 404

Posted: Sun Dec 02, 2007 4:13 pm Post subject: Carb Heat

I live in Halifax Average humidity ~70-80% average temp for much of the year 

10-20 deg C.

Here's a handy carb icing chart 

http://ibis.experimentals.de/images/carbicingfromcaassl14.gif



The U.S. Navy tested their Osprey here quite a bit but I don't think carb 

icing was what they were looking for. It's an impressive device in any case, 

but I wonder how useful.



Dave Goddard- Mod IV 1050/582

do not archive



 	  Quote: 	
		  >>Dave, exactly where are you?...


	


 	  Quote: 	
		   It seems to me that you build for where you plan to go, not where you are 

 now.

lcfitt(at)sbcglobal.net
Guest

Posted: Sun Dec 02, 2007 6:59 pm Post subject: Carb Heat

John,  Never here.  Last Summer's flight to the north country was to the 

coastal area of Oregon mostly between Waldport and Tillamook with several 

trips up and down the coast as we were trying to penetrate the marine layer 

lying against the inland hills to get to McMinnville for the Antique fly in 

and to see the Spruce Goose.  Lots of fog (low ceilings) and rain but 

nothing resembling carb ice.  There were six of us on this flight.  Also 

lots of flying over the past nine years with no evidence of carb ice.



Lowell



---

kitfoxjunky(at)decisionla
Guest

Posted: Mon Dec 03, 2007 5:44 am Post subject: Carb Heat

I had a situation where I was taking the plane from my hanger to another hanger for an EAA event.  It was cold, with light rain.  The engine rpm was below 2500 most of the way and it started loading up after about 5 minutes. It was fine after sitting in the heated hanger overnight.  I am pretty sure it was carb ice.  Then again..the engine was not up to full operating temp yet. 

 

Gary Walsh

 KF IV  Anphib 912S

 C-GOOT

 www.decisionlabs.com/kitfox

 

 do not archive

  [quote][b]

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Mon Dec 03, 2007 6:42 am Post subject: Carb Heat

Alternate intake is for fuel injection in case of blockage of the normal

screened (filtered) air.  Such a blockage can be caused by impact ice

forming on the front of the air intake.  Alternate a9ir should only be used

as necessary because it is not filtered in any way.



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Mon Dec 03, 2007 6:38 pm Post subject: Re: Carb Heat

Any carbeurated engine can get carb ice or carb icing.



In Canada for amatuer  builts it is mandatory to have it installed.



I have experienced it before on many engines and latest today was a gasoline tractor I installd a snow blower on .



Just because it has not happened to some, i could be that they have never flown in conditions where carb ice "could " happen.    If you have Carb heat  then you have one less thing to worry about not  having If  you need it .

_________________
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Sbennett3(at)aol.com
Guest

Posted: Mon Dec 03, 2007 6:47 pm Post subject: Carb Heat

In a message dated 12/3/2007 9:41:12 PM Eastern Standard Time,  dave(at)cfisher.com writes:

  	  Quote: 	
		  Any    carbeurated engine can get carb ice or carb icing 	


 

 True, but we dont all fly in Canada.  

  

  If you have Carb heat  then you have one less thing to worry  about not  having If  you need it .



 If you have carb heat, you better be prepared to use it cause  you are always intaking colder air. Here we go again re hashing this... If I  lived where I grew up near Chicago, i'd have it. Down where I live now... A  different story.   Steve Bennett    NC





  [quote][b]

MichaelGibbs(at)cox.net
Guest

Posted: Mon Dec 03, 2007 7:10 pm Post subject: Carb Heat

Steve sez:



 	  Quote: 	
		  ...If I lived where I grew up near Chicago, i'd have it. Down where 

I live now... A different story.   Steve Bennett   NC


	


As I mentioned before, Steve, if you live someplace it can get below 

70 degrees F outside, you live where it is cold enough to get carb 

ice.  And don't forget that it gets 3-1/2 degrees cooler every 

thousand feet you climb.



I don't want to get into the debate about whether or not carb heat is 

needed on 912s, but don't kid yourself that living in the south makes 

you safe.



Mike G.

N728KF

Phoenix, AZ

(where it seldom gets below 70...except at night...in the winter)

wingnut

Joined: 11 Jan 2006
Posts: 356

Posted: Mon Dec 03, 2007 8:04 pm Post subject: Re: Carb Heat

I agree that anecdotal evidence is useless. A few people saying that they've never had carb ice doesn't prove much at all no matter how many hours they have flown. However, if we can say that no one on this list who is running without carb heat has ever had carb ice; That's a whole different ball game. 



 	  Quote: 	
		  Just because it has not happened to some, i could be that they have never flown in conditions where carb ice "could " happen. If you have Carb heat then you have one less thing to worry about not having If you need it .

_________________
Luis Rodriguez
Model IV 1200
Rotax 912UL
Flying Weekly
Laurens, SC (34A)

Sbennett3(at)aol.com
Guest

Posted: Mon Dec 03, 2007 8:08 pm Post subject: Carb Heat

Mike, I understand lapse rate. It's been  mentioned here that the 912's that breath air from the back of the firewall are  less prone to freezing. I'm not playing word games and neither are you. You  could fly my plane here and feel confidant not having icing with my  configuration. pick your region and configuration wisely. I know of many planes  here running the 912 without carb heat.  SBennett



Check out AOL Money & Finance's list of the hottest products and top money wasters of 2007.

  [quote][b]

MichaelGibbs(at)cox.net
Guest

Posted: Mon Dec 03, 2007 8:26 pm Post subject: Carb Heat

Steve sez:



 	  Quote: 	
		  ...You could fly my plane here and feel confidant not having icing 

with my configuration. pick your region and configuration wisely. I 

know of many planes here running the 912 without carb heat. SBennett


	


I don't think I worded my last message very well.  There are those 

that feel carb heat is mandatory and those that feel that removing 

the hardware works best.  I am not qualified to comment on the 

issue--I really don't know which is better.  As with most areas of 

disagreement, there are probably elements of truth to both sides.



I was simply trying to say that you should satisfy yourself that your 

airplane can operate safely in the expected ambient conditions. 

Anyone in the mid-latitudes (continental U.S., Europe, central 

Australia, etc.) can experience temperatures and humidity conducive 

to carb icing.  In fact, temperate climates are more susceptible than 

arctic ones because in the arctic it gets too cold for ice to form in 

the carb.



In other words, it has everything to do with the design and 

construction of the engine installation and nothing to do with where 

you live.



Mike G.

N728KF

Phoenix, AZ

nail13zg(at)centurytel.ne
Guest

Posted: Mon Dec 03, 2007 8:27 pm Post subject: Carb Heat

In a typical aircraft normally aspirated  carburetor, the venturi effect can reduce the temperature inside the carburetor  by as much as 60 degrees Fahrenheit. So even at 90 degrees  outside air temperature, the inside of the carburetor can be below freezing. If  the air is moist, as measured by the dew point spread, you have the recipe for  carburetor ice. How much this applies to a Rotax 912 or other typical Kitfox  engine, I have no idea, but I suspect it isn't far off.

  

 One of the hardest charts to find is the  Carburetor Icing Probability chart. I have attached it to this  message.

  

 Trey Moran

 CFI, CFII, almost complete Model 5, Stratus  EA-81

 Polson, MT

Carburetor_Icing_Probability_Chart_C_(small)_pdf.pdf

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Carburetor_Icing_Probability_Chart_C_(small)_pdf.pdf

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john(at)leptron.com
Guest

Posted: Mon Dec 03, 2007 8:54 pm Post subject: Carb Heat

Trey,  

Thanks for the chart, I will add it to my manual.  

   

John Oakley  

         

  

From: owner-kitfox-list-server(at)matronics.com [mailto:owner-kitfox-list-server(at)matronics.com] On Behalf Of Trey Moran

 Sent: Monday, December 03, 2007 9:26 PM

 To: kitfox-list(at)matronics.com

 Subject: Fw: Re: Carb Heat  

  

     

   

    

In a typical aircraft normally aspirated carburetor, the venturi effect can reduce the temperature inside the carburetor by as much as 60 degrees Fahrenheit. So even at 90 degrees outside air temperature, the inside of the carburetor can be below freezing. If the air is moist, as measured by the dew point spread, you have the recipe for carburetor ice. How much this applies to a Rotax 912 or other typical Kitfox engine, I have no idea, but I suspect it isn't far off.  

    

   

    

One of the hardest charts to find is the Carburetor Icing Probability chart. I have attached it to this message.  

    

   

    

Trey Moran  

    

CFI, CFII, almost complete Model 5, Stratus EA-81  

    

Polson, MT  

    

   

  

        [quote][b]

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