How many stages are there in the low pressure and high pressure compressors, respectively?

• A. 4 low, 10 high
• B. 5 low, 9 high
• C. 6 low, 8 high
• D. 3 low, 12 high

Answer: (A)

Air is squeezed in two stages of compression in a typical two-spool turbofan: a low-pressure compressor does the initial boost, then a high-pressure compressor adds more to reach the final pressure before combustion. The LPC has fewer stages because it handles the larger volume flow from the fan and provides the initial pressure rise, while the HPC adds many more stages to achieve the high overall pressure ratio needed for efficient combustion and thrust. In this commonly tested configuration, there are four stages in the low-pressure compressor and ten stages in the high-pressure compressor. This setup balances flow, efficiency, and stability across the operating range.