I added
[newgrf]
AV*.........grf
(I'm at work and forgot the exact entry)
to the bottom of the cfg file and put the gfx file in /data folder.
The set shows up in the newgfx window in the game but I don't notice any difference in the planes behavior.

Any idea what I am doing wrong?
Also does the change (if working) affect saved games I download or only new games I create.
THX.......great game after all these years.
Edit by spiff: changed topic title