Which statement is true about the two-shaft gas turbine architecture?

• A. It uses two shafts that are geared together
• B. It uses two shafts with a direct drive on a single turbine
• C. It uses three shafts
• D. It uses no shafts

Answer: (A)

Two-shaft gas turbine architecture uses two separate rotating assemblies, each on its own shaft, that are linked by a gearbox. The gas generator side (compressor driven by its own high-speed turbine) runs at a different speed from the power-turbine side, which drives the output through a reduction gear. This setup lets the gas generator run at its optimal high speed for efficient compression while the power output shaft operates at a lower, suitable speed for the load. That gear connection between the two shafts is what makes this arrangement work.

Other options don’t fit: direct drive on a single turbine would tie both parts to the same speed (a single-shaft arrangement), having three shafts is a different configuration, and having no shafts would make turning the load impossible.