For a dual axial compressor forward fan engine, the fan rotational speed is the same as which compressor speed?

For a dual axial compressor forward fan engine, the fan rotational speed is the same as which compressor speed?

• A. High-pressure compressor, designated as N2
• B. Low-pressure compressor, designated as N1
• C. Turbine speed, designated as N3
• D. Overall engine RPM

Answer: (B)

In a two-spool turbofan with a forward fan and dual axial compressors, the fan and the low-pressure compressor are mounted on the same drive shaft. That means they spin together at the same speed, which is labeled N1. The high-pressure compressor sits on a separate shaft driven by the high-pressure turbine, so its speed is N2, not equal to the fan speed. The turbine speeds similarly tie to their respective spools, not to a single shared rate like the fan. So the fan rotates at the same speed as the low-pressure compressor, making N1 the correct match.

In a two-spool turbofan with a forward fan and dual axial compressors, the fan and the low-pressure compressor are mounted on the same drive shaft. That means they spin together at the same speed, which is labeled N1. The high-pressure compressor sits on a separate shaft driven by the high-pressure turbine, so its speed is N2, not equal to the fan speed. The turbine speeds similarly tie to their respective spools, not to a single shared rate like the fan. So the fan rotates at the same speed as the low-pressure compressor, making N1 the correct match.