Hello pilots! I recently swiped and bought Mrs Virginia and wee willy II from the Reno air race pack, I noticed the p51 wee willy 2 had no carb heat in the cockpit, how does it work? It would therefore have a hot air intake under the engine hood? System that is found on certain aircraft, in particular light aircraft? And if not what do you think of the p51 of the Reno pack?
I don’t know about the P-51, but the P-38 doesn’t have a carb heat control in the cockpit on the grace that the turbocharger heats the air due to compression and the remedy for carb icing is to push the throttle far enough to engage the turbos.
If the P-51 has an automatic second-stage boost control, this could explain the lack of a carb heat switch-- you just have to kick in the second-stage supercharger to get carb heat.
Two possibilities when you encounter a piston-engined plane with no carb heat: It’s boosted, or it’s fuel-injected. One of these comes built-in with carb heat, the other doesn’t have a carb in the first place.
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In this case it has pressure type carburettor as well which are not given to icing, beyond having a two stage supercharger (I don’t think it’s a turbosupercharger though, just a mechanical one).
(Another general possibility, encountered on Rotax engines, is that the intake air is vented around the engine to heat it, hence no need for carb heat)
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Moved to #self-service:aircraft-systems
Pressure carbs allow you to run the engine while inverted or under negative g loads-- has nothing to do with icing. The carburetor still has a throat venturi that creates a partial vacuum and ends up cooling the air (and any water vapor within it).
As I understand it it’s a question of fuel nozzle placement. In regular carb the nozzle is in the venturi and the delivery of fuel there is one of the factors that contributes to the cooling and hence icing there. With pressure carb the nozzle can be placed outside the venturi, which takes that specific cooling element away. This considerably reduces the band where icing can happen:
(Picture from www.aopa.org)
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Thank you for your answer, we learn every day!