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Good post, and good reminder. One comment. As I understand it, carb ice
is most common on warm (70 degree or so), humid, days. As the
temperature drops, so does the moisture in the air.
veeduber@isp.com wrote:
> VW-powered plane goes down in the Frozen North, which to me is
> anywhere other than Southern California. Pilot walks away from it,
> having just bought one airplane's-worth of education. Now he wants to
> know why he lost power.
>
> I do not know & tell him so. (Kinda hard to do an accident
> investigation via email). But he keeps pinging on me as the Guru of
> Last Resort, so powerful my name has been slipped to him under the
> table after swearing not to reveal his Source. (Eh? Are these people
> serious?)
>
> So I ask him a few questions and based on his answers tell him:
> 'Sounds like carb ice.'
>
> But that's the one thing he's sure it's NOT. No way. Can't be.
> EVERYONE says so. In fact, his particular engine is (or was) totally
> ice-proof; didn't even need a carb heat system. Has one of them slide-
> valve carbs -- no venturi therefore no possibility of icing. And
> besides, he always uses a 'dryer' in his gas, just like he does in all
> of his vehicles and he has NEVER had any problems with ice, yada-yada-
> yada...
>
> By now it's obvious I am dealing with an idiot. I offer the fellow a
> whiff of reality, pointing out that the 'dryer' was probably a
> contributing factor since it not only diluted the energy content of
> his fuel, it contained methanol (ie, wood alcohol) which happens to
> have an endotherm of about 300 degrees -- twice that of ethyl ethanol
> (ie, regular alcohol). The probability that ice was a contributing
> factor to his 'unexplained' loss of power is now about 99% and rising.
>
> His response? "That cannot be right." And the world's largest kill-file
> gains another entry.
>
> --------------------------------------------------------
>
> Carb and manifold icing is simple physics, clearly spelled out in all
> the manuals. Even so, you can find messages to this Group from guys
> BRAGGING about their ice-proof engines, as if the laws of physics
> do not apply to them. (Which is really kinda scary when you think about
> it. I mean, these people are allowed to breed and vote and share air-
> space with normal people... )
>
> Your life is worth something. (Yes, even to me :-) Don't allow
> yourself to be murdered by all those goods friends with their swell
> advice. Think for YOURSELF.
>
> Reality may be a bitch but so is ignorance. And denial.
>
> -R.S.Hoover
>
> PS - Gasoline is 'endothermic.' That means it absorbs heat from its
> surroundings when it changes its state from a liquid to a gas.
> Straight-run gasoline (ie, without additives) has an endotherm of
> about 40F, meaning your carb can produce ice cubes on a balmy 72F day.
> Or even warmer, if the gasoline contains certain additives. Cooler
> day? Guaranteed ice-generator.
>
> Ethanol, that lovely stuff the politicians are pushing, thanks to
> ADM's lobbyests, has an endotherm of 150F. Mix that with your gas and
> you have to start thinking ice even here in the desert southwest.
>
> But of course, that cannot be right :-)
>
> - - - - - - - - - - - - - - - - - - - - - - - -
>
> I posted the above to Yahoo's AirVW Group about six months and
> continue to get mail from idiots insisting slide-valve carbs cannot ice-
> up since they do not have a butterfly valve. I have reposted it here in
> the interest of safety. If you know of someone running a slide-valve
> carb without any provision for carb heat please give them a nudge
> toward reality. -RSH
>
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Re: Ice
