David Megginson wrote:

Alex Perry wrote:

That's a point.  Once the engine stutters/quits due to carb ice,
you have to make it take a while for the ice to go away again.
... and it takes quite a while ...

Once the engine quits, it's too late for carb heat, isn't it? If it's only a partial blockage, we can simulate the effect of water moving through the fuel system as the ice melts.

Not necessarily too late. The extent of the ice would decide if it would/could be melted before a _safe_ restart was impossible. It only needs to reduce enough for the engine to run long enough to add the heat properly and accelerate the melting process - obviously it needs to produce enough power to maintain height at a safe speed. Whereupon hopefully the ice would start to melt! I've heard stories of large chunks of carb ice and impact ice on the inner cowl coming off and getting jammed in the venturi stopping the engine dead with no possibility of a restart.

I had my engine run rough once and suspected carb ice, but it smoothed out the second I put on carb heat, so it obviously wasn't ice -- I was probably just a little too lean.

Are you sure? :-)

There was a paper published here recently that contraversially recommended that carb heat be applied constantly and systems re-engineered to remove the issues due to the air filter being bypassed on lots of engines with the heat applied. I'm not quite qualified yet, so obviously I have nowhere near the experience of you guys, but I'll _always_ use carb heat when descending, landing and for 10-15 secs every five minutes or so in the cruise on every aircraft I _ever_ fly if it has one. I can't see the harm of a temporary and slight decrease in power compared to what could go wrong if I didn't use it...

It would be useful for FG to catch us out once in a while. Stay frosty (pun intended!).

All the best,


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