Triple Spool vs Double Spool
Hi guys,
I recently had an interview where I was asked the difference between British made Rolls Royce RB211 and American made Pratt&Whitney 4000's, now I answered by saying the Rolls is a triple spool design where as the PW is a double spool design and this was right. I was then asked if I knew why Rolls decided to go with the triple spool design and PW didn't. I wasn't sure of that answer. So....
I've done a bit of reading and found it maybe had somthing to do with allowing each spool to spin closer to its optimum speed, therefore reducing fuel burn.
Is this correct and is this the only reason or could there be something more?? If someone knows of a book or website I can look at that would be good aswell.
Thanks alot!
Andrew