Would it be possible to enter an incorrect value for the MDA @IMTOY, e.g. typo 1-2-0 or 2-0-0 instead of 1-2-0-0, and the autopilot would try to fly that profile? What are the typical safeguards or controls to prevent an incorrect data entry?
one would think the constraint at IMTOY would have been in the database....many airlines SOPs prohibit modifying any portion of the final approach if it is to be flown managed...
The altitude constraint at IMTOY is actually 1380 feet and if you can identify IMTOY you can go down the path past IMTOY to an MDA of 1200 feet. Add 50 feet to get a D-DA of 1250 feet which I believe is what most 'authorized' U.S. carriers would use on this approach.
The FMS database I have access to does not have IMTOY depicted, you would have to identify it with 3.3 DME off IBXO to go down to the 1250 feet D-DA.
With IMTOY missing from the FMS procedure you would never manually insert it inside the FAF at any place I've ever worked, as IB57 has said. However, if for some unknown reason you did, with say, a D-DA of 1250 instead of the published crossing altitude of 1380, I do believe you would get a new path that leads to touchdown well short of the runway. And the path would not just be lower, but steeper as well with the altitude constraints at BASKN and IMTOY. I would hope you would get some sort of error message since the path angle has changed with the erroneous entry, but perhaps not.
As pointed out previously, the IBXO DME reads 1.3 at the runway threshold, not zero so this might confuse the cross check when things don't look exactly right.
It is an absolute alphabet soup but I read the 'Only authorized operators may use VNAV DA (H) in lieu of MDA (H)' to mean that you can use the D-DA on the 3.28 degree path, if like presumably UPS, you are authorized.
The additional question of whether an incorrect entry of minimums on the approach page of the FMS would cause the autopilot to stay on lower than it should is a good one. Data entry on these legacy FMS boxes is arcane and archaic, sometimes you need a leading zero, a decimal point or a slant, sometimes you don't. And, subtle differences exist between similar looking FMS's on Boeings, Airbuses and MD's from what I've seen.