Regarding those instruments with analog backup, e.g. N1/N2 on the 737NG. The analog signal is fed to the DEUs directly. Would the DEU be smart enough to recognise a missing N1/N2 sensors as a failure rather than zero rpms (and therefore show blank indications)?

The N1/N2 and accelerometor sensors also feed directly into the Airborne Vibration Monitoring Unit (AVM). I wonder how this reacts to open circuit sensors?

How catastropic is catastrophic? Both rotors locked? EEC power wiring destroyed? EGT harnesses damaged? Engine oil tank ruptured? Engine oil quantity wiring damaged?

Engine oil tank quantity goes directly to the DEUs. Again, is the DEU smart enough to recognise open circuit wiring Vs empty tank (and show blank for open circuit wiring)?

Perhaps we could have some Maintenance Engineer input here? With the cannon plug removed from an oil quantity sensor, what are the cockpit indications? The Maintenance Manual and FIM don't seem to offer any clues.

I was taught told since day one,if both N1/N2 are down to a 0, all other parameters(oil/FF) inop AND fire det FAULT is illuminated then to treat it as separation.
Now,the severe damage and separatin are in the same checklist and require the same memory items.
Never hurt anyone to check with the cabin and get a photo shot of it;-)

You mean the whole EEC would be gone now, wouldnt it?:p

Pan Am had one back in the 90's where it really did seize just after rotation. They cleaned up the aircraft and made an uneventful ATB

The third guy in the cockpit went back to take a look over a womans shoulder and related that he saw a big gaping hole in the aft section of the engine. The woman remarked that she saw flame out of the engine and was concerned. He told her it was nothing to worry about an went back to the cockpit and said to the pilot wholly ch***t there' a whopping hole in the side of that engine you can fit your head in!!

I heard this from the guy himself who flew the next day's aircraft back to JFK

I thought we were trying to distinguish between catastrophic engine failure and separation? Catastrophic might include total destruction of EEC wiring which would, in some ways, mimic separation.