Confirmation about tip speeds:
"To optimize the cycle the
bypass flow has to be raised to a pressure of approximately 1.6 times the
inlet pressure. This is achieved in the fan by utilizing very high tip
speeds (1500 ft. per sec.) and airflow such that the bypass section of the
blades operate with a supersonic inlet air velocity of up to Mach 1.5 at the
tip" Quoted from "The Jet Engine" by Rolls Royce plc 5th edition 1996 page
26.