Originally Posted by
Flight_Idle
@ post 1362 I don't know anything about Trent engines, but judging by the size of the fan (It seems to be twice the height of a man by looking at some photos) I don't see how it can be direct drive.
If the LP turbines are running at 3,000 rpm (as mentioned earlier in the thread) there must be reduction gears for the fan (Unless the fan blade tips are well supersonic)
Trent 900 fan is about 3m diameter, so twice the height of a fairly short man.
It is not geared, and the fan blade tips are indeed "well supersonic".
Geared turbo fans do exist, allowing more flexibility to optimise LP turbine and fan speeds, but I am not aware of RR making anything of that type.