Outer Marker substitute UK?
On our KLM-approachplates, on all of our UK-destinations, there is a dotted line always at 4 NM from the threshold.
Most of my collegues say this is an outermarker substitute. I don't thinks so, because I cannot recall on any ILS that I have flown in the UK, there is an outermarker, so a substitute is not possible. Also if this is the OM-substitute, it would be the point to continue the approach, if the visibility is at or above the minima's, but in the UK there is always an approachban at 1000' HAT.
So my question to all of the UK-pilots is:
1. Are there any ILS-es in the UK with markerbeacons.
2. Why aren't there any markerbeacons in the UK (if answer 1 is no).
3. What is the purpose of this 4 nm before the threshold.
Personally I think this 4 nm has to do with the borderline for obstacleclearance in the final approach segment. It is a changeoverpoint for the intermediate segment to the final approach segment.