What drives the N1 fan?

• A. Low pressure turbine
• B. High pressure turbine
• C. FADEC
• D. N2 compressor

Answer: (A)

In a turbofan engine, the fan is mounted on the low-pressure spool, and the energy that turns that spool comes from the low-pressure turbine. The low-pressure turbine extracts energy from the hot exhaust gases and uses it to spin the low-pressure shaft, which directly drives the fan and other components on that same spool. That speed is what we refer to as N1. The high-pressure turbine, on the other hand, drives the high-pressure compressor on the separate high-pressure spool (N2). FADEC is an electronic control system that manages fuel and other settings, not the mechanical drive of the fan. The N2 compressor isn’t responsible for turning the fan; it’s driven by the high-pressure turbine. So the driver of the N1 fan is the low-pressure turbine.