Similar issue during start up with ground power and CATM-9. After engine start using external air supply, the AIM9 tone kicks in. I have to cycle A/A mode button to make it stop.
My procedure:
1. BATT > ON
2. Fire test > A and B
3. Request ground power
4. Ground power switch > RESET
5. Ground power switch 1 and 2 > B
6. DDI's, HUD, AMPCD > ON
7. Air supply > Connect, than apply
8. ENG crank > Right
9. Right throttle > IDLE
When engine stabilizes on idle rpm-s the AIM9 tone kicks in.
I will try to make a short track later on.