Editing Turbofan (section)

===Geared fan===
{{main|Geared turbofan}}
[[File:Geared Turbofan NT.PNG|thumb|Geared turbofan. The gearbox is labeled 2.]]

As bypass ratio increases, the fan blade tip speed increases relative to the LPT blade speed. This will reduce the LPT blade speed, requiring more turbine stages to extract enough energy to drive the fan. Introducing a [[epicyclic gearing|(planetary) reduction gearbox]], with a suitable gear ratio, between the LP shaft and the fan enables both the fan and LP turbine to operate at their optimum speeds. Examples of this configuration are the long-established [[Garrett TFE731]], the [[Honeywell ALF 502]]/507, and the recent [[Pratt & Whitney PW1000G]].