What type of main bearings are used in gas turbine engines?

• A. Ball bearings
• B. Roller bearings
• C. Ball or roller anti-friction types
• D. Magnetic bearings

Answer: (C)

Gas turbine main bearings must support high radial loads at very high speeds while minimizing friction and handling heat through lubrication. Rolling-contact bearings, specifically ball and roller types, provide the low friction of rolling contact, high load-carrying capacity, and good stiffness needed for the demanding rotor dynamics. This makes them ideal for the main bearing position in most gas turbines. Magnetic bearings do exist in some niche, experimental, or highly specialized setups, but they are not the standard choice for conventional main bearings due to their complexity and reliance on active control systems. Therefore, the best answer is ball or roller anti-friction types.