What is the function of turbine case cooling passages and what issues are checked during overhaul?

• A. Provide fuel to the combustor.
• B. Support rotor shafts.
• C. Remove heat from the hot section; check for blockages, cracks, leaks, corrosion; verify cooling flow geometry.
• D. House instrumentation.

Answer: (C)

The purpose of turbine case cooling passages is to remove heat from the hot section by routing cooling air through channels in the turbine case, carrying heat away from critical areas and helping protect bearings, casings, and surrounding structures. Overhaul checks focus on ensuring this cooling works as designed: look for blockages that reduce flow, cracks or corrosion that weaken passage walls, leaks that waste cooling air or allow hot gas intrusion, and verify the geometry of the passages so the cooling flow is distributed correctly. If cooling is restricted or misdirected, temperatures rise, causing distortion, bearing damage, and reduced engine life. The other options describe functions that aren’t provided by these passages—fuel supply, structural support, or housing instrumentation.