Hi Boyington,
It appears to be related with resolution of cockpit display and range accuracy of on board DME. Provided the cockpit display resolution is 0.2 or less, lowest of published minima may be accessed if the range accuracy so permits. Wherever the measured distance affects its accuracy (e.g. +/- 3% of DME measured range), inherent errors must be factored along side display resolution capabilities for check altitudes. It's possibly for this reason that difference MDAs are stated with/without D2.8 or D3.8 or both. For e.g a display resolution of D0.5 would not show D2.8 or D3.8. A range accuracy of 0.2nm at 4nm with display resolution of 0.2 or less gives access to MDA of 780' (755') with D3.8. Unless, the range accuracy or display capability at shorter ranges changes, MDA of 650' should also be accessible in this case.
The crew may therefore check accuracy range and cockpit display resolution of DME to determine applicable minima on this approach plate.
That's the best I could think.
Cheers
Last edited by peeush; 10th Apr 2022 at 09:10.
Reason: Typo