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carb icing in Rotax 912 ULS in an RV12

Over 1300 hours behind 912's in Kitfoxes, RV-12's, and Just Superstols with no carb ice. That includes flight in actual IMC as well.

Vic
 
In another thread titled "Air Induction Option" I wrote that the J3-Cub I owned for more than twenty years had an updraft carb on Continental A65-8 engine. You could view the entire carb through the open cowling. I would land on a hot summer day and the carb would be dripping wet (literally) from condensation - cold carb / humid air. Carb ice was always a possibility.

I have 300TT on my RV-12 with zero incidence of carb icing. Nice powerful, smooth running engine...
 
How hot is it?

So, the air around the carb filters is hot because it is at the back of the engine. I get that. But, how hot is it? Did Van's put a temp probe near the carb filters during flight testing? I think about these kind of things on wet Pacific Northwest days.
 
A lot of testing (including the use of temp sensors) was done during the early development of the RV-12.
This was more for evaluating what benefit in performance there would be if a cold air induction system were used (yes, even that was tested but found to not be worth the added cost and complexity).

This testing (and Van's is locate in the wet Pacific North West), along with the accumulated flight time of 650+ RV-12's flying many thousands of hrs around the world, in widely varied flight conditions, has provided data that indicates carb. icing is not an issue.
 
During my annual/condition inspection, my mechanic showed me how the Rotax was designed and showed me the fitting adjacent the carbs that hot coolant flows thru. So, no need for carb heat it?s built in.
 
During my annual/condition inspection, my mechanic showed me how the Rotax was designed and showed me the fitting adjacent the carbs that hot coolant flows thru. So, no need for carb heat it’s built in.

The standard 912ULS engine delivered by Van's with the RV-12 kit does not have any passages that route hot coolant through/around the carburetors (and I am not aware of any other version of the engine that does either).

There is an aftermarket kit to add this but I am not aware of any RV-12 ever having it installed, though I guess it is possible that yours has.
 
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I believe RV12JT has a Sling aircraft. Sometimes important details are left out.
 
Some important information left out.
Some people like myself look at VAF for more information than Van's aircraft. Carb heat is a good example. On the RV 12 it is common practice that carb heat is not required on the 912 series engine. But deeper research shows that airframes with a 912 installation where the engine is not enclosed in a cowl should have carb icing protection installed. I'm just finishing up on an AirCam and did not have anything in place and carb heat was one of the last items installed because I thought carb icing was not an issue on the 912ULS.
 
I believe RV12JT has a Sling aircraft. Sometimes important details are left out.

Yes, I?ve got a Sling 2, S-LSA. WOW, I would have thought that feature to be standard on all Rotax 912 UL/ULS applications, unlike air boxes or placement of radiators, which I?ve seen mounted differently in some aircraft.

I haven?t come across any Rotax powered aircraft that had manually operated carb heat in the cockpit. Are there any?
 
I have a Rotax 912 installed on an Airborne trike (weight-shift control LSA). It has the coolant-based carb heat (always on) - perhaps due to the open/uncowled installation mentioned on the AirCam.
 
Rans uses the rotax airbox that uses cockpit controlled carb heat. The airbox is expensive. I have it on my 912 powered Rans S19 using a Rans supplied neat muff on the muffler and cold air induction. That being said I have used it except during preflight runup and have never experienced carb ice.
 
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A lot of testing (including the use of temp sensors) was done during the early development of the RV-12.
This was more for evaluating what benefit in performance there would be if a cold air induction system were used (yes, even that was tested but found to not be worth the added cost and complexity).

This testing (and Van's is locate in the wet Pacific North West), along with the accumulated flight time of 650+ RV-12's flying many thousands of hrs around the world, in widely varied flight conditions, has provided data that indicates carb. icing is not an issue.

Thanks Scott. This is helpful
 
Hopefully it is apparent from this thread that the actual aircraft and engine installation will have a huge influence on the likelihood of carb. ice on a 912 Rotax.

The RV-12 is very tightly cowled and the interior cowl temps are such that carb heat was determined during the development process, to not be required

Installing a carb heat system on an RV-12 because an airplane with exposed or loosely cowl engines (think Aircam, etc.) has had carb ice, is not an apples to apples comparison.
 
I?ve got hot-water carb heaters on my RV12
http://www.skydrive.co.uk/proddetail.asp?prod=CH-912-3-BODY&cat=36

This was a recommendation from another UK-based builder and it seems very common on many 912ULS engines here even if not particularly on RV12s.

Probably me, Harry....?! It may be seen as overkill by Scott and the crew at Van's who obviously did all the testing and decided the RV-12 (ULS) wasn't prone to suffering from carb ice. I don't have a problem with that - they're the ones with the experience on type so no arguments on that score.

We decided to install the Skydrive (UK based) system that is as Harry said very common on Rotax ULS installations in the UK.

It is fit and forget, not particularly expensive and little weight penalty so what's not to like? Down side are a few more joints in the coolant system. It may not be necessary but it's a bit of extra comfort factor.

No loss of power as the air is still cold, it's just that the carb's surfaces are warm enough to prevent any ice from forming.

In my previous experience of being involved with many Rotax powered Tecnams (singles and twins), the Rotax ULS rarely suffers from carb ice when up to normal operating temperature. When the engine is cold and the conditions right, the Tecnams will ice up on the ground - cleared in the case of the certified Tecnams by applying carb heat hot air to the airbox from the muffler shroud. As Scott said - different cowlings and these used the Rotax single airbox as fitted to the certified Rotax ULS.
 
Scott,
I just installed the Silent Hitek VR and cowl. Will this impact the potential for carb ice?

No
It is a very small volume of unheated air entering the cowl. There are no indications that impacts the interior cowl temp any significant amount.
 
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