They are in the Eurw/scenery folder and they are the BGL flies that start with AP and FL. (example AP951170.bgl and FL951170.bgl)I installed two of these type of files from a add on scenery I have but I don't see any difference.

I believe it's the terrain mesh or possibly a flatten for the scenery.Was it LIRN?

Yes it's LIRN.I looked at the scenery before and after I put the two BGL files in and I did not see any difference.

they are the BGL flies that start with AP and FLhttp://library.avsim.net/esearch.php?CatID...util&DLID=44634AP files are default airport data - AP951170.bgl holds the default airport data, the approaches and the terminal navaids and many default scenery objects for the airports:LIRHLIRMLIRGLIRLLIRNLIRELIRALIRFLIRULIRIFL files are the airport flattens/ polygons.