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Formula for Icing.. Below 60deg if the dew point is within 7deg of the temp your
in iceing conditions.
TED

Les Wilson wrote:

> Scrapp,
>
> Youre right, it would be pretty hard to ice up a side draft slide type
> carb - at full throttle. But, icing occurs when you throttle back if the
> temp and humidity are right. As the slide opening gets smaller, the
> velocity of the air increases and the pressure drops. The higher speed,
> lower pressure cools the air just like the the air/paint/hairspray etc. is
> cold coming out of a spray can - even in the summer. An outside air temp of
> 45 - 50 degrees F and high humidity are right in the range to create carb
> icing. The most likely result would be a lagging or stumbling - which
> should clear up as you throttle up. Of course, if youre not careful, this
> could also set you up for a cold seizure. Its something to keep in mind if
> youre flying on those conditions - which a lot of people are in the winter.
>
> Les
> "Scrappman" wrote in message
> news:3A53B75C.E7C9E08F@microassist.com...
> > Sounds more like fuel contamination with water. To close the opening
> of a
> > side draft would be tough. Not saying its not possible, just not likely.
> > Scrappman
> >
> > Ken Kennedy wrote:
> >
> > > Mark Smith wrote:
> > >
> > > > I have heard of it but never seen it and I still believe that our
> carbs,
> > > > slide types, are not prone to internal icing, especially with the oily
> > > > mess we call fuel mix.
> > >
> > > Might other factors also be vibration and heat from engine (via
> proximity
> > > and/or blowback?)?
> > >
> > > > Also, most people think it occurs when it is cold.
> > >
> > > Conventional aviation engines are certainly prone to carb ice in warm
> humid
> > > conditions, but I am convinced it never happens to our Rotaxes in
> similar
> > > conditions.
> > > >
> > > > Ill bet all manner of two stroke ills have been missed and the
> > > > problem attributed to carb ice.
> > >
> > > No doubt this is so. However, I am also sure I have witnessed it.
> > >
> > > The conditions were just above freezing, with about a mile or two
> > > visibility in fog. After maybe twenty minutes of flight, there was a
> > > gradual loss of power. Limped back to base where engine barely ran.
> > > Shutdown. Then frost appeared on outside of carbs. Removing the air
> cleaner
> > > showed ice inside the carbs. Let it sit, then ice disappeared. Dropped
> > > bowls and found a little water (melted in carb, then drained down thru
> the
> > > jet?). Drained water and went again. (This was foolish, of course, > was
> > > the initial flight>, but he had to go out and look for several trumpeter
> > > swans that had buggered off from his wing, and whom he couldnt chase
> down
> > > when the engine misbehaved). Twice more in the next hour, he had to make
> > > precautionary landings with the same results. For several months before
> > > these occurrences, the 503 had operated perfectly. During the next month
> on
> > > the actual migration, the engine also worked perfectly, altho we never
> > > flew in the same meteorological conditions again.
> > >
> > > Given the above, I am totally convinced that the 503 can experience carb
> > > icing in moist conditions near freezing. (Conditions in which, Rotax
> pilots
> > > rarely operate). Maybe Mark could do some research by making a few
> flights
> > > in similar conditions and reporting the results. This is an area where
> we
> > > could all benefit from a little research.
> > >
> > > BTW, we found the swans late that night in a nearby river, having been
> > > tipped off by a hiker who had seen them, then later heard our plea on
> the
> > > local radio station.
> > > kk
> >

--
----------
Ted Colburn 209-358-2949
Email: mailto:colburn@jps.net
URL: http://www.jps.net/colburn

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