Carburetor icing at Rotax 912 ?
Andrius D. Diksaitis
Has anybody observed carburetor icing at Rotax 912 engine ?
I wonder why so many builder don't install a carburetor heating.
Even the manufacturer don't give any clear suggestions for this topic.
The basic question is:
Must I install a carburetor heating at a 912 or is it really unnecessary
?
Any comments, please !!!
Andrius Diksaitis
Germany
John R. Johnson
Andrius,
If it were me, I would make up some kind of carb heat box for ANY
engine with a carb. Carb ice is a function of the nature of gasoline,
the nature of the atmosphere, and the construction of carburetors.
It is the same for all engines.
Lycomings need less carb heat because they run the induction system
through the oil pan and use it to cool the oil. The oil provides some
carb heat ALL of the time. As a result they do not need ADDITIONAL
heat often. Other engines do not do that, and do need carb heat.
It is easy to do, and could save your life. I would do it. Just my
opinion.
John
Rick
> > After compliance with the one piece venturi on the
> > Marvelous-Sniveler carb on my LYCOMING O-235 C1 I
> > found that at 40 degrees F out over Puget Sound
> > I now experience carb ice at all times under these conditions.
> > This was NEVER a problem with the old 2 piece venturi.
> > So I think that the above statement about Lyc's and carb
> > heat used to be true. But now that the Fed's with their
> > twisted logic have decided that I need a referigator
> > in my carbureter it is not.
> > RICK
Reinerh
Has anybody observed carburetor icing at Rotax 912 engine ?
I wonder why so many builder don't install a carburetor heating.
we use the same type carb on our engines.
in most cv type carbs there is no venturi to speak of. therefore there is very
little pressure drop across the carb=no ice.
reiner
Howard Wilkinson
Andrius:
Carburetor icing is caused by the temperature drop resulting from the
increased velocity in the venturi of your carb. At high relative humidity
the drop in temperature results in condensation of moisture on the inside of
the carb. If the air temp is just above freezing the temperature drop also
results in the build up of ice on the inside of the carb. Below freezing
OAT carb icing does not occur as the condensate is in the form of ice
particles which do not adhere to the inside of the carb. I have seen carb
icing mostly in the temperature range of about 33 - 40 degrees. It is quite
common on automobiles under certian weather conditions. Fuel injected
engines tend not to be subject to carb ice nor are diesels. Carb heat is a
must in all aircraft as far as I'm concerned. H.W.
Andrius D. Diksaitis wrote in message <6domul$ufb$1...@news02.btx.dtag.de>...
>Has anybody observed carburetor icing at Rotax 912 engine ?
>
>I wonder why so many builder don't install a carburetor heating.
Nigel Field
Andrius D. Diksaitis wrote:
>
> Has anybody observed carburetor icing at Rotax 912 engine ?
>
> I wonder why so many builder don't install a carburetor heating.
> Even the manufacturer don't give any clear suggestions for this topic.
>
> The basic question is:
> Must I install a carburetor heating at a 912 or is it really unnecessary
> ?
>
> Any comments, please !!!
>
> Andrius Diksaitis
> Germany
The majority of the cooling comes from the latent heat of vapourization
of the fuel, the same principle your freezer works on only with freon or
whatever refrigerant they now use. The Bing and Mikuni carbs are
constant velocity employing a diaphram driven slide which becomes a
variable venturi. So at reduced power (mass flow) it does have a
venturi.
Please install carb heat with any carb, it is mandatory here in Canada
and may someday save your life.
Nigel Field
Graham E Laucht
In article <6domul$ufb$1...@news02.btx.dtag.de>, Andrius D. Diksaitis
<Ma...@t-online.de> writes
>The basic question is:
>Must I install a carburetor heating at a 912 or is it really unnecessary
>?
In an article entitled "Fitting an Alternative Engine" appearing in
March/April 98 "Popular Flying" and written by Francis Donaldsen the
PFA's Chief Engineer he says:
"On the Rotax 912, the carburettors are mounted behind the engine in an
area where the carb bodies receive plenty of heat from the nearby
exhaust pipes. Consequently if the intke air is taken from within an
enclosed cowling, induction icing does not seem to occur and no special
carb system need be provided."
He goes on to point out the importance of flame trapping internally
sourced intakes to reduce the risk of engine bay fires from backfiring
through the inlet system.
The experience is based on a growing 912/914 population in the UK in a
meterological environment which is conducive to icing at least 75% of
the time. It is probably conditioned to some extent by a majority of the
engines being tractor installed in tightly cowled Europas etc.
As to whether the Bing CD carb is itself less liable to icing is
uncertain as for instance Jabiru installations with a single Bing CD
neatly tucked in under the oil sump and close by the muffler provide a
carb heat ducting and heat exchanger kit as standard. Their own kitplane
employs the same equipment as I suspect the Australian CAA insisted on
carb heat for engine certification.
You might do well to contact the OUV or the Luftfahrt-Bundesampt for
guidance as it may affect local certification/approval as what may be
acceptable practise in the US or the UK may not be the case in the
Germany.
--
Graham E Laucht
Joe Hovel
Andrius D. Diksaitis wrote:
> Has anybody observed carburetor icing at Rotax 912 engine ?
> The basic question is:
> Must I install a carburetor heating at a 912 or is it really unnecessary?
I've had carby ice in a 912 running in a Skyfox Gazelle - on a 28 deg C
day at 4500', just under an inversion layer. But I was running at only
around 50% power to stay with a friend in a slower open Ultralight....
It needed more and more throttle until I realised what was going on and
"jiggled" the throttle - it then coughed a couple of times and ran clean
again. This plane HAS carby heat and I put it on and left it on for 30
seconds every two or three minutes - just to make sure......
nick norman
It depends on where your air inlets are positioned! In our Europa, with
tightly fitting cowls, the air was taken in just aft of the engine in a
very warm environment and we never got carb icing. However this was
causing a loss of power during climbs etc and Europa brought out a mod
to take the intake air direct from outside via a scoop in the top of the
cowling. The result of that is that we now have had carb icing causing
rough running (though fortunately no stoppages) several times in just a
few winter flights (not suprising really!). Now we are working on our
own mod to allow selection of warm intake air from the engine bay, or
cold from outside.
The moral - to get good performance you need cold intake air normally,
but this will give you carb icing on bad days so selectable hot air is
essential!
Nick Norman, Scotland
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