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Aircraft systems and instrumentsQuestion 599 of 934

An airplane has a constant-speed propeller. How is carburetor icing usually indicated?

  1. By lower rpm with no change in manifold pressure
  2. By higher manifold pressure with a drop in rpm
  3. By lower oil pressure with no drop in rpm
  4. By lower manifold pressure with no drop in rpm
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Correct answer: By lower manifold pressure with no drop in rpm

The propeller pitch changes automatically to hold the rpm, so the rpm stays constant.

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

Practice aircraft systems and instruments

Questions last reviewed: 18 October 2026