Rolls-Royce engined 727's
I recently saw a picture of a UPS 727 which had been re-engined with Rolls-Royce Tay's. This posed a couple of questions, which I hope somebody will be able to provide answers to.
(a) What advantages does the Tay have over the P+W? (if any - and I presume there must be a reason for the re-engine)
(b) The duct for the centre engine has a very characteristic bulge. Clearly this is nothing to do with the size of the engine as that is mounted well away from the intake, so what is the reason?