Jim Carter wrote:

I had a question today that I’ve never considered, and need the
experience of the group.



Are there airports with ILS approaches such that if the Glide Slope
component failed or went OTS, the entire approach would be un-executable
by regulation? I’ve always assumed that with the GS OTS I’d just revert
to the LOC, but are there approaches were the full ILS is approved but
the LOC only isn’t? In other words, are there precision approaches where
vertical guidance is required and there is no non-precision alternative?



Quite a few, such as Boeing Field, Arcata,California Reno, Butte,
Montana. All of those have a separate LOC procedure, which cannot be
switched to midsstream. Missula, Montana was an ILS that does not have
a separate LOC IAP.

It's all about being able to place stepdown fixes in accordance with
TERPs criteria (facility accuracy, fix displacement factor) rather than
with the continous, and varying with distance, electronic glide-path
obstacle clearance plane.