How many stages of compression are in the engine's N1 section?

• A. One
• B. Three
• C. Two
• D. Four

Answer: (C)

The N1 section is the low‑pressure compressor driven by the N1 shaft. Air entering N1 is compressed in stages as it passes through the fan and the next low‑pressure compressor stage. In this engine model, there are two stages of compression within N1: the fan acts as the first stage, and one additional low‑pressure compressor stage adds the second stage before the air moves on to the high‑pressure compressor. That’s why two is the correct count. Other numbers would imply a different compressor setup than what this engine is described to have.