Aircraft systems and instrumentsQuestion 648 of 934

A pilot does not lock the fuel primer in place. What can happen in flight?

  1. The primer can freeze open and cause carburetor ice
  2. The primer can vibrate out and richen the mixture
  3. The primer can lean the mixture at high power
  4. The primer can block the fuel flow to the pump
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Correct answer: The primer can vibrate out and richen the mixture

It is important to lock the primer when it is not in use.

Source: Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C), Chapter 7: Aircraft Systems — Fuel Systems — Fuel Primer, page 185

Practice aircraft systems and instruments

Questions last reviewed: 18 October 2026