WU-660/WU-880 Antenna stabilization
 

Reading through the Embraer AOM during these days locked in the house and I've come across a question I've failed to get a sourced answer to.

The antenna stabilization function description in the AOM reads as following:
"The antenna is stabilized in pitch and roll using attitude information from the IRU. Momentarily selecting STAB OFF... etc etc"

The problem is I can't find if the reference is to pitch attitude, direction of flight or horizontal. There was an old thread on this and the question remains largely unanswered. I'm tempted to say that logically it should be at the horizon. Disclaimer: I'm fresh out of a type rating and haven't even had base training yet. Thanks for the help.

With stabilization ON, the radar antenna should be stabilized to align with the local horizon. With STAB off, should be bore sighted along the fuselage.

How they come up with that idea to turn "STAB OFF"?

With STAB off, you can use the radar as a back up horizon source.