When starting an aircraft engine equipped with a float carburetor, in what position should the carburetor heat control be placed?

• A. Off
• B. Cold
• C. Warm
• D. Hot

Answer: (B)

Carburetor heat is used to introduce warmed air into the carburetor to melt or prevent icing. When starting a cold engine, you want the intake air to be as dense as possible for a better mixture and reliable ignition. Introducing heat during start would reduce air density and can alter the fuel–air ratio unfavorably, making the engine harder to start. Therefore, the cold position is used during starting to avoid heating the intake air. Once the engine is running and icing becomes a possibility (in moist conditions or at higher power settings), you would apply heat as needed to prevent or clear carburetor icing.