Outside of the FAF, the safest response (although agreed not always the most efficient) is to execute a go-around and sort it out for another fully briefed approach. Continuing the approach on a "slide" to a non-precision is acceptable under some situations, but it really depends on many factors...such as how far back you are on approach, how poor the weather is, how easily the approach can "slide" (ie: no complicated step-downs), and whether or not the aircraft is configured appropriately to fly the profile.
I would say that in 80% of the situations (and always when doing a SIM ride) I would call for the go-around and try to figure out what the hell happened. As BPF stated, this is really an exercise that probably will never happen to you in the real world. It just isn't that common. Most likely (as has happened to me a few times) you either lose all navaids (power failure at the airport), aircraft equipment fails (go-around and sort that one out for sure), or the entire GS/LOC gets shut off (ATC blunder). Just losing the GS has never happened to me. It really is something drummed up by instructors or examiners of days past...sorry guys - it's been going on since I did my first IFR
.As far as the approach brief goes, having gone through the stages of IFR instructor, BE20 pilot, and now with the airlines on a Boeing - I can tell you that the approach brief has gotten more concise with each. The brain simply isn't rigged to remember a large amount of information, especially while flying an approach. How many times have you required confirmation of a landing clearance, readback of an altimeter setting, or winds?
