Aircraft systems and instrumentsQuestion 603 of 934

A pilot suspects carburetor icing and plans to close the throttle for a descent. What is recommended?

  1. Apply partial carburetor heat after closing the throttle
  2. Keep the carburetor heat off to save engine power
  3. Apply carburetor heat only after the engine runs rough
  4. Apply full carburetor heat before closing the throttle
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Correct answer: Apply full carburetor heat before closing the throttle

The heat aids fuel vaporization. The pilot should leave it on during closed-throttle operation.

Source: Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C), Chapter 7: Aircraft Systems — Induction Systems — Carburetor Heat, page 170

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Questions last reviewed: 18 October 2026