Aircraft systems and instrumentsQuestion 607 of 934

A pilot climbs to a high altitude and does not adjust the mixture control. What happens to the mixture?

  1. It becomes progressively leaner
  2. It stays the same
  3. It becomes too lean only above 10,000 feet
  4. It becomes progressively richer
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Correct answer: It becomes progressively richer

Air density decreases with altitude, but fuel density stays the same. The result is a richer mixture.

Source: Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C), Chapter 7: Aircraft Systems — Induction Systems — Mixture Control, page 169

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Questions last reviewed: 18 October 2026