Oh dear, I said I wasn't going to come back on this thread but since the subject has changed, can I change my mind? Wow - was Nick pointing out that old proven reliable technology was actually a good thing safety-wise. Perhaps that's because the CT7-8 fitted to the 92 is an even older engine than the Makila!
The Makila 2A (as fitted to the 225) has turbine blade shedding to cope with otherwise unresolved overspeed - ie an overspeed that is not contained by the normal electronic overspeed shutdown at 120% N2 (as happened in the Norwegian accident Nick refers to). At 140% (from memory) the turbine blades are designed to all detach simultaneously and are contained within the engine. No more blades = no more turbine disc acceleration so the disc won't burst. Now what would you rather have, a turbine disc bursting and hoping that all that airframe reinforcement doesn't allow bits to hit the flight controls, rotor blades etc, or a system that intrinsically guarantees that the turbing can't overspeed to the point of disc destruction?
I have to say that I am not sure exactly what JAR FAR 29 says on this subject. Can anyone point to a web location that has the publications as I can never find them? However I am pretty sure that the Makila 2A is compliant. Some EC/TM person could confirm that?
If you don't change anything, you can fall back on grandfather rights, but once you change something, it has to be re-certified and hence meet the current requirements. If Sikorsky can get their FAA to grant certification to the 92's gearbox, I am sure that Turbomeca can do the same with the DGAC/EASA and their 2A (sorry, couldn't resist
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