Build it per planes is my motto (kind of)
Hi All,
I have heard bad comments about the efficiency of the standard carb heat muff and carb heat connector assembly.
Can you please let me know about your experience, any alternative solution ?
Thanks in advance
If you are talking about CARB heat specifically, yes its not a flame thrower that will melt your carb in to a pile of molten metal. Will it melt ice? yes it will. Is it up to the certification standards for factory planes? I doubt it.
GOOD NEWS, RV's rarely (not never) have carb ice issues partly because they are so tightly cowled and the exhaust runs down and around near the carb. So the carb it self is cooking. Also its a HOT sump Lycoming, which is already resistant to carb ice more than say some Continentals where the induction is cold. Some continentals have carb ice constantly.
If you where to have a CAT (carb air temp) gauge you will find in normally flying year round in moderate temps your carb air temp is above 32F or freezing. If the air is warmer 0C (32F) or warmer it will not freeze. NOTE: BEFORE you correct me, I am talking about CAT not ambient temp. You can get carb ice in warm air as high as +35c, the worst being from about 0C (32F) to 20C (70F). The air temp in the carb of course can drop as much as 20C-30C, therefore you can get carb ice in warm ambient temps. It takes freezing temps to get ice. It takes mosture. You need both. But if temp (in carb) is warmer than freezing or air is too dry than no ice. No mystery.
WITH THAT SAID, Carb ice is not a trivial thing to be discounted. We all have to be aware of the condition's and the situation that leads to ice (lower power with partially or fully closed throttle). If you descend from high altitude at low power (idle or near idle) for a long time with out carb heat on, you are asking for trouble.
Again Van's aircraft and carb ice are pretty rare, but if you look at the archives or NSTB reports you will see a few. One guy at 9,000 ft went to idle and descended all the way down to 1000 ft at idle. Well he went to add power and the engine did not run. He crashed and was OK. This was like the South in the summer so high humidity was a given and probable cause along with pilot error.
So it is possible at very low power (low engine heat) and extream condition that carb ice might form even with the carb heat? The solution is not to fly around at idle. A little idle time on short final will not hurt sense carb ice takes some time to form. With constant speed prop I always have power on final. That is why carb ice is insidious, it happens real slow, your RPM slowly drops (fixed prop) or MAP slowly drops (c/s prop).
Install VANS set up per planes and be happy. There are better heat muffs that make more heat, but that is more for the cabin. The carb is already sucking a lot of warm air from the cowl area. The CARB HEAT blocks the wet air from outside. The air in the lower cowl should be dryer. So even if the temp increase from the Van's carb heat is not great, it should be much dryer air. Again either increase temp above freezing or lower water content, no ice.
The big thing is cabin heat, staying warm in the winter with one small heat muff is a challange for those northern RV'ers. I have welded studs on my pipes that the heat muff goes over. The studs are the type done on factory planes; it makes the pipe look like a porcupine. The heat muff shell wraps have the studs. This gives more surface area for heat transfer.
