Originally Posted by
tdracer
For some reason Rolls hasn't used the 'clashing blades' to slow the turbine in the event of a shaft separation. I always figured it had something to do with the 3 spool architecture on the RB211 and Trent, but that wouldn't explain the Spey...
The Trent series uses an electronic Turbine OverSpeed protection system on both the LP and IP shafts that instantly shuts off fuel if a shaft separation is sensed.
That's because an electronic system is too slow on a small fan engine and red-line/rotor burst would be exceeded in the event of a shaft break, on RR BR series fuel flow is reduced to flameout via a centrifugally activated "bog chain" system connected to a dedicated mechanical Overspeed Unit in <17ms.