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Aircraft systems and instrumentsQuestion 617 of 934

Why should a pilot let a turbocharger cool before engine shutdown?

  1. The turbine could freeze in the cold exhaust flow
  2. The turbine shaft could warp from uneven cooling
  3. Oil in the bearing housing can boil and form carbon
  4. The fuel in the lines would boil at shutdown
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Correct answer: Oil in the bearing housing can boil and form carbon

Carbon deposits on the bearings and shaft rapidly reduce the efficiency and life of the turbocharger.

Source: Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C), Chapter 7: Aircraft Systems — Superchargers and Turbosuperchargers — System Operation, page 174

Practice aircraft systems and instruments

Questions last reviewed: 18 October 2026