Avionics
Charting a new course for IFR approaches
The GPS approach is out, and the Rnav approach is in.

The GPS approach is out, and the Rnav approach is in. That’s because many pilots tend to think of GPS as a land-based navaid like a VOR, NDB or as a part of an ILS, and experts believe that thinking is misleading. More precisely, it’s the FMS in the airplane that allows the actual instrument approach to be flown. GPS provides only the precise positioning information needed to carry it all off by listening in to some of the 24 GPS satellites orbiting nearly 11,000 miles above the Earth.

Under the best conditions, a pure GPS-Rnav approach can provide an MDA as low as 250 feet agl and visibility minimums down to one mile without the use of ground-based navaids and without the line-of-sight restrictions of earlier Rnav systems, if an airport has a certified approach, that is.