In the event that that anyone doubts that the AINS was not to be used as Captain Collins used it, note the following:
"Like any good pilot, Collins would certainly have made up his mind that unless visual conditions were good, there was no way he would take the aircraft below Minimum Safe Altitude of 16000 feet. MSA constitutes a platform for pilots. Once below it they leave behind the self-sufficiency of the inertial navigation system and commit themselves once more to guidance from aids on mother earth, and to visual flying - 'eyeballing' it in pilot jargon."
That's from p119 of Impact Erebus by Gordon Vette. (He then goes no to suggest that the captain did not know about sector white-out, conveniently ignoring the CVR, Collins years in the RNZAF at Wigram, and the visit he and Lucas made to Operation Deep Freeze a few weeks before the flight.)