1. so it is a shaft failure or the bolts that hold the gear to the shaft and not the gear breaking up - that makes more sense.
2. However, Nick's post indicates that the problem won't happen again since the shaft and gear were redesigned - therefore not much point in teaching it in the sim.
3. On the N1 governing by the DECU - with AC talking about matching N1 or Tq - I think that is confusing the ability to beep the engines up and down to match them in the way you prefer with what the DECU is designed to do (govern N1 and load share with the other engine)
1. I think that gear is 2 separate pieces that are bolted together. As NL pointed out the failure mode in the example cited was bolts coming loose. Gears in helicopter gear boxes can certainly fail and make metal for other reasons. I know, not long after when we got C model there was an AD about the possibility of loose bolts within the MGB. Sikorsky sent a maintenance team to open all the gear boxes in the new helicopters and check the torques on the bolts. They had some pretty impressive test gear with them. It is very rare event to see inside a S76 MGB.
2. As I mentioned earlier, we do not cover this malfunction in the simulator. It is discussed in class room training, more-so to get the trainees to think about and diagnose a set of circumstances which might not be covered in the RFM. Not all malfunctions are in the ECL.
3. There is no beep available to the pilot with DECU in automatic mode. The DECU gives you 107% N2 on both engines with N1 matched. That's it. The engine trim switch on the pilot collective - of which there is only one - only functions when the engine is in manual mode (i.e. using the MFCU controlling fuel flow, DECU controlled AFCU is disabled). It will beep up/down the engine/s in manual mode. Things get a bit tricky with the single eng trim switch and both engines in manual mode, particularly if there is a TQ split between the engines. This isn't usually practiced in the simulator, but it is easily manageable if you know what you're doing.