lucille...
OzExp..From memory, Rwy 14 at POM had a noticeable false GP at 6 degrees, a point missed by the advocates of the higher-is-safer school of Instrument approach flying!
Yes, I believe that was true of the old installation. It may even be true of the new one but I never saw the commissioning data on it.
False GP's and Erroneous GP's, I think are not necessarily the same thing. False GP's are a fact of life and are an unfortunate side effect of GP design
Very true, they are not the same at all. Let me quote the following excerpt from the June 2002 (I think) issue of of the New Zealand CAA’s magazine “Vector", in which they reported on the Erroneous ILS Indications at Faleolo...
"
A false glideslope is a normal byproduct of the glide path. If it is intercepted, and if it can be followed, it will guide the aircraft to the source of the glide path.
An erroneous glideslope, on the other hand, is not well known. It is the result of a faulty or partial signal being transmitted. It will indicate to the aircraft that it is ‘on slope’ irrespective of where the aircraft is in space, and it will not lead the aircraft to the source of the glide path. Erroneous glideslope signals are occasionally transmitted for maintenance purposes."
This is a pretty general description of the differences, but should provide enough information so that everyone understands the difference. The information on the "false GS" is necessarily brief in the article, but it can be inferred that although it can guide the aircraft to the source of the GP, the descent rate will usually be very much steeper, as you say.
The "erroneous GS" situation is almost always the result of maintenance work, or lack of proper work practices by the navaid technicians. It will bite the unwary pilot very hard indeed but the same simple integrity checks that you describe will help to detect both problems.
In a past life, I have observed that monitors have been disabled by the techies because of spurious warnings.
Or they simply wind the monitor settings in until the LLZ or GP is so tight that it is impossible to fly. I've been caught by that one at POM... I ripped a new a-hole in the responsible person and, as far as I know, the problem hasn't recurred.