912S - Carb Heat or Not??

[chefwarthog]

Well I don't get it, we are in 2011 and Rotax it is still useing 1930's technology. The first warplane engine were build with carduretors fuel distibution in the first worldwar. My quad use injection, my pick-up, the cars, the skidoo and they don't ice up or stop working for nothing, the only thing that remain carb feeded it is my lawn mower, ah a get it, it got a kind of propeller underneath!

Carbs have to be sychronize, clean up, set up in the right way and it work well, but it is still 1930's technology, and Rotax sell that ''hot tech'' for a reasonable 24 000.00$. I think the engine monopoly on aviation from Rotax served them well but not us.

Apologize for that thread, but I stell don't get it.

Eric

[brjohnso]

I don't know why anyone would remove a carb heat system. Carb ice happens. It happens on Kitfoxes, I happens with the 912, and it has killed people in Kitfoxes before. https://aviation-safety.net/wikibase/wiki.php?id=138373

Rotax also has a fuel circulation feature to prevent vapor lock, but for some reason, not everybody connects that up either.

[brjohnso]

There is nothing special about the 912 or the Kitfox when it comes to carb ice. It is as vulnerable as anything else. Ice is uncommon but not rare, and it's also unpredictable. It can form as fast as a minute or two. https://aviation-safety.net/wikibase/wiki.php?id=138373

I had it happen to me once in a Cessna. It took less than a minute to form and my engine stalled during my takeoff roll.

[jiott]

Sorry to totally disagree, but the Rotax Bing carb is different than other aircraft carbs in that it is a constant depression altitude compensating carb whose throat design is NOT as susceptible to icing. I will not try to describe the design reasons this is true because its been quite a while since I read up on it. Go do a search yourself and read about it. Also the position the carbs are mounted in the Kitfox tight cowl gives it an icing advantage compared to many other aircraft.

Mind you I am certainly not saying that the 912 in a Kitfox will never ice up, but I am disagreeing withe your blanket statement that "there is nothing special about the 912 or Kitfox when it comes to carb ice". There are probably thousands of us who have been flying 912 Kitfoxes without carb heat for hundreds of hours without a single icing incident.

[jrevens]

... https://aviation-safety.net/wikibase/wiki.php?id=138373
...

Hi Bruce,
It seems as though you are presenting this link/accident as a sure example of Rotax carb ice, on this and another thread. While I suppose it's possible, to my knowledge that has never been proven one way or the other. If I'm wrong about that, someone please correct me. I was there at that Kitfox fly-in, along with others on this forum. I remember the airplane having some kind of problem during it's initial takeoff from Homedale, and returning to the field. The wonderful couple from California had that airplane really loaded-up, and I remember them taking things out and removing the seats, I assume to possibly check something on the fuel system. I don't know if anything was found or not. They put things back together and took off (uneventfully as far as I could see) to get fuel at Caldwell before heading home. So if this accident report is accurate they had a problem of some kind again during the first takeoff attempt from there, aborted, and then attempted yet another takeoff that ended in tragedy. It seems like it's very possible that the problem(s) was something other than carb ice - maybe a fuel pump, or who knows what. There are others here who surely have a lot more knowledge about this accident than I do, but unless you know something I don't, I think it's wrong to present this as a certain carb ice accident. There were a lot of Kitfoxes of all models and engine types there, even a Rotec radial, and as far as I know no one else was experiencing carb ice - I might be wrong. I certainly noticed none with my O-320 powered T-18 that day, and I have had carb ice with that engine before.

[HighWing]

I posted a response on the old 2011 comment series on this thread. My feelings are exactly the same as they were then. I started my first Model IV in 1993. A year or two later a couple of guys were at the factory fly-in with info on the first Kitfox ever forum. It was of the email variety and I read every one - unlike today where things are topic related with some topics of little interest to me. In the early discussions, the consensus was just as it is today and the carb-heat box that came with my kit was never installed. A neighbor who was on the Alaska trip mentioned in my previous comment in this thread was the one who had the burps during a flight segment and with nearly 2500 hours has no carb-heat box on his Model IV to this day. He mentioned the experience in a hangar flying session last week. I don't remember everything, but in the 23 or 4 years I have been actively participating in the lists or forums, there have never been any comments from owner pilots about incidents that have suggested carb-icing issues in our airplanes that has even tempted me to rethink my original decision.

[atosrider]

there were two occasions when I thought the engine was running rough because of carb ice, out of 600 hrs with a 912ULS in a Rans S6, with the water heated carb sockets .... both times it was flying into a wetter air mass, that forced a descent ... suddenly I wished I could divert more hot water into that system ... but in the model III with round cowl, there might not be room against the firewall ....
I find all this talk of pre-heated air under the cowling rather hard to believe, sure we are getting some engine cooling, but the air flow has to be very variable with changes in airspeed, angle of attack, and power setting ...
my project came with the 1992 air box, so I read with interest that it might cause as many problems as it is supposed to prevent ..
the norm for aircraft is having a carb heat system, and I dare say the norm for pilots is not knowing they had carb icing ...

[Ronin]

This was my replies in a different thread;


I have experienced carb ice in two different 912s powered planes, A Europa XS and a Rans S-6.

This was the kit I had mounted in the Europa I flew

http://skydrive.co.uk/proddetail.asp?prod=CH-912-3

Left it on at all times and it didn't hurt performance in a measurable way.

[Esser]

My buddy in his Model IV had suspected carb ice less than 4 weeks ago. I don't know why everyone is so averse to cross of a potential safety issue off a list.

[jiott]

Those of us without carb heat and speaking for myself are certainly not averse to it at all. We are only disagreeing with the comments that imply we are idiots and that there is no difference between a 912 Kitfox and other Lyc/Cont aircraft that all require carb heat. Even though many of us have never found the need for it, I would be the last person to discourage someone from installing it if they feel a need for it. After all, it has no down side other than a little cost and complexity.

If I lived in Canada, especially the northern parts, I think I would install it. Correct me if I am wrong, but I believe it is required by the equivalent to the FAA to be on all aircraft in Canada and most European countries.