From the ‘727 Captain’ FLIGHT MANUAL Part II – Aircraft and Systems (cs727_manual2.pdf) page 109:


Autopilot will track CIVA-INS flightplan:
- Autopilot Mode Selector should be in MAN position
- Autopilot HDG Switch should be engaged
- Autopilot Navigation Source Selector - pos AB
- Heading Bug on Captain's HSI will be controlled by CIVA-INS

Note. The manuals can be downloaded from HERE.