So how many spools are normally turned on a 2 spool engine?
Not sure what Davies is trying to say, but just the N2 (HP) is driven by the gearbox on a two-spool engine... & just the N3 (HP) on a 3-spool.
I would have said the RB211's were actually harder to start than, say, two-spool CF6's. The RB211 powered 767 even has extra ground cart connections because it is so difficult to start the engines. I would have also said that the CF6 accelerates quicker after light-up (fuel on).
Rgds.
NSEU.