A320 ILS Auto-land lining up incorrectly

[McFlinty 1]

Good evening, 

 

I've been working on learning the A320 autopilot functions and ILS landing, and I've had a few instances where the plane lines up left of the runway (on proper glideslope). Most of the time it's toward the taxiways but now and then it's a mile or so out. 

 

I assume it's something I've done incorrectly, anyone have any ideas?

[diajohn 169]

Could be the airport is not set up properly.  I have found this at KSFO on 28R

[Chock 17,769]

It could be for a few reasons, depends on the airport and depends on the sim too sometimes (if it is an error). Some airports in sims are not completely accurately aligned with the terrain, and occasionally this can mean a localiser beacon which is in the right place is not correctly lined up with the runway. However, this phenomenon occurs in the real world too at some airports for a number of reasons and usually if you find the paper or PDF charts for the particular runway, you will discover this is the case and why...

For example, there are approaches called SDFs (simplified directional facility) which are intended to give guidance for an approach, but not completely aligned with the runway guidance. There can be a number of reasons for this but a common one is that a straight in approach might not be possible owing to terrain or obstacles or the signal from the beacon might have suffered interference if aligned with the runway and so it is offset to avoid that. You might see some stuff labelled as an LDA approach on a chart (localiser directional aid), and then it might specify that it either has, or has not got other types of guidance such as glideslope. You might also notice that what looks like an ILS approach is referred to as an LDA approach, and that will probably be because the runway doesn't have the runway and approach lighting necessary for an ILS approach to minimums in poor weather.

If you let us know what runway it is you are experiencing problems with, we can probably figure out which of the above is the issue.