Jet engine Question...
On a large turbofan jet engine...I always thought that the front fan was driven by the turbine shaft. BUT...i have seen MANY instances of the front fan just "freewhelling in the wind" on a parked Jet plane that as not even powered at all. If the turbine shaft was connected to the fan..HOW could simple wind make it rotate? It would seem to be WAAYYY too much mass for that. Also...I have also seen pictures of the front fan spinning MUCH slower--it appeared and sounded like--than the jet engine..Maybe 1500-2000 RPM..but jet engine spin at MANY thousands of RPM when running--even at idle--right?
So...is the front fan driven...OR does it just spin by AIR PRESSURE ?
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