I have tried the high vibration failure with High Vibration Alert selected and deselected and I can't spot the difference. In both cases if the lower DU is not on the secondary engine display it will automatically switch to that page and the vibration number box will go to inverted video and I get a cyan "ENGINE" annunciation on the upper DU. Other than that I don't notice anything else. The description in the manual doesn't really clarify it for me. What does it change by having High Vibration Alert selected?

I have tried the high vibration failure with High Vibration Alert selected and deselected and I can't spot the difference. In both cases if the lower DU is not on the secondary engine display it will automatically switch to that page and the vibration number box will go to inverted video and I get a cyan "ENGINE" annunciation on the upper DU. Other than that I don't notice anything else. The description in the manual doesn't really clarify it for me. What does it change by having High Vibration Alert selected?

I decided to try this malfunction out to see what happened.  There isn't a procedure I could find for it, and the ECL doesn't really tell you what you should do.  The malfunction simulates a high vibration level in the engine, but there is no indication of how you should manage it.  In reality it could be a something like a bearing breaking up or an unbalance due to a blade breaking off. You might do a precautionary shutdown, or it might be a simple case of limiting engine thrust to a lower level.  So, having got the vibration indication I decided to try an in flight shutdown and relight, which worked really well, then continued with the flight.  Then without any warning the engine seized, presumably as a result of the vibration malfunction, so I had to continue on one engine.  In fact the first thing I noticed was the engine shutdown checklist appearing and wondering why as I had restarted the thing, not realising it had stopped again. 

 

I assume that if you don't follow the correct actions in response to vibration caution message the engine is programmed to seize after a period of time.  The problem is there doesn't seem to be any definition of what the correct actions are.  It would be really nice if PMDG provided a malfunction definition for each failure, describing the cause, what any secondary effects are and what the corrective action should be.

The key thing I'm trying to learn is what does changing the high vibration alert on the on Display Options page 6 in the FMC. I just can't find the difference between having it on or off when I set a high vibration failure.