skiingman,
Thanks! I've found similar, but that's one more.
So far, things point to the "5 ATI" referring to the size of the cutout in the panel being a nominal 5.000".
Same as the 4 ATI cutout being 4.000". and the 6 ATI cutout being 6.000".
To help the confusion, 2 ATI corresponds to 2.200" and 3 ATI corresponds to 3.200", but let's not quibble over that...
I do start wondering if ARINC 408 does go beyond defining the case cross-section, or does it leave bezel dimensions, mounting (front-face screws, clamp, etc.) and hence the front panel "footprint" to the instrument and aircraft manufacturers.... ?
Does anybody else have more info?
CJ