AIM Block 13 Practice Test 2026 – Your All-In-One Guide to Exam Success!

In a dual axial-flow (two-spool) compressor, there are two concentric shafts: an outer low-pressure spool and an inner high-pressure spool. Each spool has its own turbine driving its respective compressor. The first stage of the turbine that feeds the inner (high-pressure) shaft powers the high-pressure compressor, so the high-pressure compressor ends up being driven by the first stage turbine. That’s why the correct choice is the high-pressure compressor (N2). The outer, low-pressure turbine drives the low-pressure compressor (N1), and there isn’t a separate “N3” or a general “main” compressor in this setup.