John,
As Richard says, the 912 has been known to suffer badly from carb icing
when installed in some microlights, the main recipient being the butterfly
valve. On trikes there is no cowling and no chance for the air temperature
to rise. One manufacturer here cured the carb icing problem with hot water
pipes wrapped around the air filter - this on a Rotax 582 trike I believe.
The problem with this solution, like direct hot air from an exhaust jacket,
is that it reduces the performance of the engine. So you either leave it
on all the time to be safe and suffer performance loss, or (like me) you
forget to apply hot air periodically in flight; sooner or later it catches
you out.
Nigel's device warms the throat of the carb itself and prevents ice build
up on the throat and butterfly without significant warming of the
air entering the engine. This means you can leave it on all the time. He
detects no speed drop with heat on.
Dave
----------
> From: John Wigney <johnwigney@worldnet.att.net>
> Subject: Carb heat for 912
> Date: 18 January 1999 01:41
>
> Dave,
>
> Your note on the Skydrive carburetor throat warmer for the 912 begs a
> question. Is it imagination or did I read/hear that the standard
> configuration 912 is not susceptible to carb icing.
>
> I know it is obviously good practice to provide carb heat since icing is
> theoretically possible in many routine situations. However, I would be
> very interested to learn of any first hand experience on the 912 where
> carb heat has proved to be necessary.
>
> P.S. A 912 carb heat system was marketed here in the US some years ago
> which consisted of a hot water spiral coil arrangement round each air
> filter. I am not sure that it is still on the market.
>
> Cheers, John Wigney, A099
>
> <<< Dave Simpson wrote:-
> Subject: Re: Carb Heat
> John,
>
> Skydrive has just developed a carb heat system for the 912 which uses
> hot
> water to warm the throat. I'm not sure if it's available yet - (Nigel's
> just finished testing it), but it won't be long. Talk to Nigel Beale
> 01926
> 612188 or e mail him on skydrive@avnet.co.uk.>>>>
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