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SESK: Stuff Everyone Should Know · sesk.info/pilot-carb-heat-rpm-response

With carburetor ice present, what happens to RPM when full carburetor heat is applied?

RPM drops, then gradually rises as the ice melts.

  1. RPM rises right away and stays up
  2. RPM drops, then gradually rises as ice melts ✔
  3. RPM stays exactly the same

Why: Heated air is less dense, so power drops at first. As the ice melts, RPM gradually climbs back and the engine runs smoother. With no ice, RPM just drops and stays lower until heat is removed.

Huh, didn't know that: Carburetor heat can cost up to 15 percent of engine power because heated air is less dense, which also enriches the mixture.

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Sources

  1. FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C), Chapter 7 https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/faa-h-8083-25c.pdf

Test yourself in the game

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