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AerodynamicsQuestion 412 of 934

Why does thin air reduce the thrust of a propeller?

  1. The engine burns more fuel in thin air
  2. The propeller turns faster in thin air
  3. The propeller is less efficient in thin air
  4. The propeller blades change their pitch in thin air
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Correct answer: The propeller is less efficient in thin air

As air becomes less dense, thrust is reduced because a propeller is less efficient in thin air.

Source: Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C), Chapter 4: Principles of Flight — Density Altitude, page 91

Practice aerodynamics

Questions last reviewed: 18 October 2026