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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" 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, > > 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 > |
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