[AT] Carb Icing / Wind Chill (was RE: oil change)

[Gene Waugh Elgin, Illinois USA]

I copied this from the FAA site.  Icing CAN occur well above freezing 
(ambient temps); as I see it, primary causes are humidity / dew point 
and lack of adequate heat, whether from a hot engine / manifold, or a 
carb heat device such as used in aircraft, and ambient temperature.  
Clearly, "wind-chill" in itself will NOT affect icing, except by the 
increased rate of the wind removing latent heat from the carb / engine, 
etc.  IOW, it might, IMHO, bring carb icing around a bit faster, but is 
NOT the direct cause.

Gene
Elgin, Illinois USA


    * *Throttle ice is formed at or near a partly closed throttle
      valve.  The water vapor in the induction air condenses and freezes
      due to the venturi effect cooling as the air passes the throttle
      valve.  Since the temperature drop is usually around 5°F, the best
      temperatures for forming throttle ice would be 32-37°F although a
      combination of fuel and throttle ice could occur at higher ambient
      temperatures.   *


        In general, carburetor ice will form in temperatures between
        32-50°F when the relative humidity is 50% or more.  If visible
        moisture is present, it will form at temperatures between
        15-32°F.  Partial throttle (cruise or letdown) is the most
        critical time for carburetor ice.  It is recommended that
        carburetor heat be applied before reducing power and that
        partial power be used during letdown to prevent icing and
        overcooling the engine.



David Rotigel wrote:
>> Carburetor icing has NOTHING WHATSOEVER to do with wind chill...  
>> not now,
>> not ever, not at the North Pole, not anywhere, or any time.
>> George
>>     
>
> Hi George, Are you sure of this George? I hear that in Canada that  
> sometimes carburetors ice up at 95 degrees because of wind chill.  
> (But ONLY if you drive your tractor REAL fast!)
> 	Dave
> PS, Books, school, eat!
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