I can't speak for the airline types, but us corporate types have been able to use R-Nav and GPS approaches on a regular basis for many years now. We use our FMSes to fly these approaches.
The are several different manufacturers of FMSes, the ones that I'm personally most familiar with are the UNS-1Cs and the Global GNS-XLS. Depending upon the specific aircraft installation and interface and the particular software version being employed, the UNS-1s provide pseudo-ILS capability in conjunction with VOR, LOC, LOC-BC
, GPS, and NDB non-precision approaches. The long and short of it is that every instrument approach that we make is, for all intents and purposes, just another ILS - its cockpit presentation is identical to an ILS and it's flown identical to an ILS. We even have the capability to create and fly (fully coupled if we wanted to) "VFR" approaches to any runway (or for that matter, to any set of lat/long coordinates) in the world.
As to how they work, the FMSes simply use GPS and some magic to calculate a glidepath that will meet all of the minimum crossing restrictions published for the approach. From a safety point of view, they are excellent. You are able to set up a stabilized approach from the point that you are turned onto the final approach course. There is none of the "dive and drive" that can be so destabilizing. The only time we have to fly the various approaches the "old" way is during recurrent training and checkrides, but even then they're starting to ease up a bit.
The main difference between a conventional ILS and a non-precision approach employing a "pseudo-glideslope" is at the "bottom" of the approach - you end up with a "DH" situation rather than a "MDA". The FMS brings you down a 3 degree (more or less, depending upon the particular approach) and you'll hit the minimum altitude before you arrive at the published missed approach point - which is typically at the runway threshold. You end up with a VDP that corresponds quite nicely to the standard 3 degree descent path. It's just like an ILS - when you get to the DH
you look for the runway. If you see the runway you land, if you don't you go somewhere else. (In practice I guess you could level off and continue on to the MAP, but why? We're not in a helicopter or a Super Cub and we'd have a difficult time landing and getting a jet stopped from that point.) These pseudo-ILS approaches aren't always available. There are a few where they won't work and the box won't let you do them. The one place that comes readily to mind is Aspen, Colorado. However, I've been flying with this equipment for 15 years and hundreds of actual approaches and I can count on one hand the number of places where the box won't give you a glideslope.
Additionally, the FMS's will also also fly holding patterns and DME
arcs. On a typical non-precision approach in a non-radar environment, the "box" will intercept and fly the arc, then fly the entire approach approach (complete with pseudo-glideslope). In the event of a miss, it will fly the entire missed approach procedure, including entering the hold. All we have to do is relax and monitor the approach and make sure that the gear and flaps were down. Pretty amazing stuff when you think about it. Its neat to watch it fly the arc. It flys it by varying the bank angle rather than with a series of straight legs. It will stay within .1 NM
of the arc at all times - even interception.
As always, there is always "good news" and "bad news". The good news is that pilot work load is greatly reduced. There is little or no need to perform the "dive and drive" vertical profiles that are inherent in many of the non-precision approaches. This makes for a much more stabilized approach. Situational awareness can also be greatly enhanced. (It's pretty neat to be able to watch yourself being vectored onto the final approach course! It's fully displayed on your EFIS.) Now for the bad news. It's easy to allow yourself to become too complacent - you still need to pay close attention to what's going on around you. And finally, FMSes are wonderful tools, but like any other computer it's garbage in, garbage out. In other words, you had better know how use the equipment and program them correctly. It's not difficult, but you do have to do it right.