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SESK: Stuff Everyone Should Know · sesk.info/pilot-mixture-richer-with-altitude

As an airplane climbs with the mixture left at full rich, the fuel-air mixture becomes what?

Richer, because the air thins but the fuel does not.

  1. Leaner
  2. Exactly correct
  3. Richer ✔

Why: Carburetors are set up for sea-level air. As you climb, the air gets less dense but the fuel stays the same, so the mixture gets richer. Leaning restores the right ratio.

Huh, didn't know that: Coming down from altitude, the mixture must be enriched again or it may become too lean.

The dad joke
Why did the engine go hiking in the mountains? It wanted to get a little leaner.
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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

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