Originally Posted by
Big Pistons Forever
The efficiency of the carb heat system will be indicated by the magnitude of the RPM drop during the runup. I have grounded several airplanes when they did not IMO appear to be getting sufficient heated air during the runup carb heat check as indicated by a non existent or very small drop in RPM when the carb heat was selected full on. In all cases various problems were found with cracked carb air boxes, deteriorated scat hoses or improperly adjusted carb heat controls.
Originally Posted by
Big Pistons Forever
Grumman POH's have a note in the before landing checklist that says "Carb Heat: As required, leave on if icing conditions exist"
I rent a Grumman Cheetah in Dallas. Recently I flew one of their models that I had not flown before. It had been several months since my last flight and I only have a few flights total.
During the carb heat check on the run up there was barely any needle movement. I ended up calling the instructor who checked me out and he assured me that it is normal. The owner of the school who seems to be very knowledgeable later said the same. He said that the heater unit around the exhaust pipe is smaller than the Cessna's I am used to.
I have meant to ask about this on a Grumman forum but haven't done so yet. No problems encountered on that flight.