Originally Posted by Vilas
Flying the approach conventionally without the FMS, at DME fixes you sometimes land up high or low and then correct the descent for the next DME. In this procedure the DME fixes are hard safety altitudes you cannot go below. So you will have treat them as minimums and that cannot be progressively done all the way to the lowest minimum of 2.8DME. so if the fixes are not coded in the FMS then the highest minimum will apply whether you use the FMS or fly with manual vertical guidance.
Only if that is what your SOP says. Surely you are not suggesting you step down fix in the altitude selector and treat each as an MDA until you are past it?
In any case, that is what the dist/altitude table is for. Follow that, either using FMS VNAV if approved, or manually, and you will miss all the steps.
Which brings us back to the original question. Why are there 3 MDAs and when would you use each one?