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2 Answers

Carb Heat Off on Final after Making the Runway

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General Aviation, Private Pilot, Student Pilot

So I saw a YouTube  video the other day where a guy is flying a carb engine 172 and is on final. As he approaches the end of the runway he declares that he has "made the runway", and knocks off the carb heat. His  reasoning is that in case of a go around, he is one step ahead.

I've never seen this, and I don't plan on starting to do it either. Even when practicing go arounds, I still go throttle, carb heat, and then flaps.

Maybe I am missing something because the video did make me curious. Perhaps some of  the veteran CFI's here can comment.

 

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2 Answers



  1. Bryan on Apr 10, 2024

    First, follow the POH. I fly Piper Archers with a Lycoming 0-360 where the carburetor is bolted to the bottom of the oil pan so the POH says to only use carb heat if carb icing is suspected. But when I fly with my buddy in his Cessna 150 with the Continental 0-200A, the POH says in the landing checklist to “Apply full heat before closing throttle” and then not put it back to cold until after landing.

    Second, understand the principles involved. Carb icing is more likely a low power settings. This is why many POHs and instructors tell you to turn it on for descent and landing. In an engine prone to carb icing and conditions likely to produce it, I personally would go full throttle and then turn off the carb heat.

    Third, consistent procedures. Is the guy you saw on YouTube saving time in case of a go-around? Sure. How much time? Maybe 2 seconds. But he’s also giving more time to the chance of carb ice to develop. To me, even though the risk is pretty low (short time for carb ice to develop), those two seconds saved are not worth the increase in risk.

    My two cents…

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  2. Mark Kolber on Apr 11, 2024

    It’s a personal technique I’ve seen done. I don’t do it in a Cessna because it’s easy enough to hit throttle and carb heat together, but I don’t see anything wrong with it.

    @Bryan, I’ve heard the location of the carb explanation many times, but I go with Piper’s simpler explanation in the manual for not using it as a preventive – the concern with having inadequate power for a go-around. Unlike the Cessna, the location of the carb heat control makes it difficult to access on a go-around

    For anyone interested, years ago the NTSB recommended using carb heat as a preventative in all carbureted aircraft. http://midlifeflight.net/downloads/files/900108NtsbRecCarbHeat.pdf If I did that in a Piper, I probably would use the off-on-final technique (I use it for cowl flaps).

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