Can someone explain to me how RNAV approaches actually work?

[HalberQuacky]

@anon50268670

So basically if MDA is 300 ft, we would use 350 ft as DA. We decide to go-around at 350 ft before we achieve positive climb we would have descended to 300 ft and then climb away. Thats why it is possible sometimes to have a lower LNAV minima on the approach chart compared to LNAV / VNAV. That sounds weird, but if you think about it the LNAV / VNAV minima on the charts are DA’s while the LNAV minima are MDA’s. (it is exceptional though to have lower LNAV minima).

The RNAV(GPS) 24 approach at my home airport KELM is that way. The LNAV/VNAV DA is 1807 feet with 2 1/2 mile visibility, while the LNAV MDA is 1740 feet, with 2400 RVR (Category A), 4000 RVR (Category B) or 1 3/4 miles (Category C and D).

The LPV DA is the same as the ILS MDA at 1155 / 2400 (all categories).

The LNAV/VNAV DA for the opposite end (runway 6) is even higher at 2234 feet, 3 miles, while the LNAV MDA is 2040 feet and 3/4.