Originally Posted by
Viperstick
KDSM rwy 31, A-320 sometime in 2015. Aborted approach, lined up on 23 and landed uneventfully.
The closest inspection before the date you give was 09/11/2014.
The next after was 03/15/2016.
There are no special inspections issued for that facility between the two periodic inspections.
In both of those inspections that clearance required to keep the needle pegged were over 50% greater than required. The last inspection was in Nov 2020 and had the same excess of clearances.
This is a CAT III/E- the highest class of ILS system performance category - and a report of false anything on this type of system would be immediately reported to the FAA's Command Center and would probably result in a priority 1A or 2 directed flight inspection.
Was there any actual investigation into this event? Again - any chance of such a thing happening with a shred of question whether the ILS was producing a False LOC indication would trigger a shut down and inspection.
The LOC service volumes between the ILSs between RWYs 23 and 31 barely overlap between the 90hz side of RWY 23 and the 150hz side of 31. Not the area that you would generally received a false .
I type all of this not to dispute that an A-320 had an aborted approach to RWY 23 when they thought they were lined up on RWY 31, but to dispute that it was because of FALSE LOC indications.
[MENTION=74834]pangolin[/MENTION] -
YES - anxiously awaiting the final report of that mishap. If it turns out to be the performance of the LOC - look to new rules for the issuance of SNOW NOTAMS.
The environment definitely affects ILS LOC and GS performance. That is why there are critical areas at some airports. That is the reason for many restrictions on some systems. Environmental interferences are some of the hardest things to try and track down find a solution to and often end of having to get engineers involved to find fixes.
But even if we count that one system, it is still far from 'countless'. That was my rebuttle to your remark - not that there can be false LOC or GS, but that there are "countless" of them - because there just aren't in the US NAS.
As for the pilots who are saying that the AP is capturing the GS before established on the LOC - well that is an AP issue or a FMS issue or usage problem - not an ILS problem. IF you are within the service volume of the LOC and the GS - the ILS system doesn't determine when your airplane starts the approach. That is a whole different problem.