Originally Posted by
Auster
Just to make the point once again, the point that John Evens was making. The big difference between needing or not needing a carburettor heat system on a Kitfox with a Rotax is usually determined by whether you are drawing intake air from the front of the cowl or from the rear, underneath the cowl with the carbs facing the firewall. Accumulated experience with both Rotax and the Kitfox would (I think) lead to the conclusion that a system drawing intake air from the front (outside) of the cowl requires a carburettor heat system while one drawing warm air from the rear inside of the cowl does not.
I am flying with the latter system, i.e. no carburettor heat device or system because I am using a smooth cowl and the Rotax 912 ULS carburettors draw warm air from the rear, that is they face the firewall. The one concern I have is that in winter the motor runs rather cool and I have worried that it might be too cool under that cowling to provide the necessary warm (temperature differential) air. To address this, in winter I partially cover both the oil cooler and radiator with aluminium tape and bring the temperatures closer to those I would see in summer. I hasten to add that I have never experienced carburettor ice despite flying in low temps and moist conditions. Ground testing with cowls removed in ideal icing conditions also failed to produce a problem. However keeping those engine temps up to normal gives me a warm feeling in winter so that I fly without worrying about carburettor icing.