carb heat knob where you manually turn the carb heat on. The other,
which is more common and to which I believe you are referring, the carb
heat is ALWAYS on. Note where the carb air intake is on your engine.
It is on the back of the carbs, inside the engine cowling in the back
and on the top of the engine where the air is the most warm. You only
need a manual carb heat knob with the other set up that uses cold
external air as the default for the carburetors.
We have planes with both types of set ups, and with only one exception
to my knowledge in more than 10,000 hours we've only had carb ice on the
planes which use external air and hence have a manual carb heat knob.
(Carb ice on the "manual knob" model is fairly common in the spring.)
The one instance I mentioned where I believe I had ice on the "always
on" model was on a very wet spring day where the engine was cold soaked
and the relative humidity close to 100%. I think I had ice shortly
after starting which quickly cleared itself up as the engine and hence
carb intake air warmed up.
So the answer to your question is that you don't need to turn the heat
on because it is always on. Don't reduce engine power beause that will
reduce engine temp and hence the temperature of your "always on" heat. I
have also heard manufactures also say that if you should get carb ice in
flight, fly to a lower altitude with warmer air, but again the chances
of ice with the "always on" engine set-up are remote.
As a side note, not sure if you've ever had carb ice before, but I have
an O300 on my Cessna which is very prone to ice. Even with that the
only times I've ever had ice are are on humid spring mornings with a
cold soaked engine during taxi and flying in actual IMC. I'm not saying
ice doesn't happen at other times, but those are the most likely in my
experience. The first is a non-issue since you are on the ground. The
second won't pertain to you as a sport pilot.
Helen
On 12/25/2011 6:16 PM, circicirci wrote:
> As you know, with the exception of some of a few flying 912s in the UK and other places who have custom-installed some sort of carb heat on their Rotax, our 912's have no carb heat.
>
> Although it appears that there rarely is carb-icing, it IS possible. And anyway I believe my flight examiner may want me to state what the symptoms are (I do know those) and what the proceedure for dealing with it is.
>
> Of course in most piston aircraft engines like the Lycomasaurus, the primary response is supposed to be "turn on carb heat."
>
> But is there ANYthing one could do on a Rotax that has no carb heat if detecting symptoms of carb icing (other than pray?).
>
> Might "descend to lower warmer altitude if available" be appropriate?
> Or?
> Possibly cut back power (if practical/safe?) as that might reduce the rate of cooling due to expanding air flow in the carb intake?
>
> Or?
>
> Alex
>
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> ------------------------------------
>
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>
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>
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