Last fall I was flying my C-172 on a short flight to a neighboring runway when I noticed the the carb heat indicator showed the needle slowley dropping into the yellow caution range. It was a cool day (68 degF ) with low humidity. Being that I flying 2000' over the forest I decided to add in a little carb heat to bring the needle out of the caution range. Prior to adding the carb heat, the engine showed no sign of roughness and no sign of a drop in RPM. As I slowely pulled out the carb heat, the engine started to cough and sputter as I watched my prop come to a complete standstill in front of my eyes.
As you can imagine, after this experience, I have re-added the carb heat indicator to the top of the list to monitor while flying. I am well aware of the causes of carb icing and the conditions that are to exist for carb icing to occure. I am also aware of the "text book " checklist required during an indication of carb ice.
Flying the Hiller I have never seen an indication of requiring carb heat during a hover. At times I will add a bit of carb heat during flight to keep the needle out of the caution range. Last week during a local flight( 68 deg low humidity) I watched the needle drop rather rapidley during my flight. I had to add 100 percent carb heat to get the needle moving in the right direction.
After studying a number of helo pilots I have noticed that many fly with the needle in the caution range. I would like to receive some input from other Hiller pilots on their take on the use of carb heat and when it is required. I would also like to here any stories regarding problems with carb icing. I would always rather learn from other pilots experiences in lieu of my own.. lol