Originally Posted by
chris lz
But clearly they did not have this certainty yet.
What makes you say that? The let-down was performed in the patchy cloud north of Ross Island, where it was possible to make out visual landmarks. The overcast affected only Ross Island itself. Regarding your post #196 - the manual keying in of the data was covered by a redundancy check. One pilot read the values, the other keyed them in and read them back for cross-check purposes. This was enough to ensure that mis-keying at the gate should not be a problem.
AFAIK the only accident relating to mis-keying a nav computer (AA965) was in part caused because this protocol was not followed.
@framer - The myriad circumstances and lessons to learn surrounding this landmark accident in aviation unfortunately don't lend themselves to quick or easy summary. The best I can do is:
"Any safety-critical system is inevitably more complicated than the human brain will initially think it is - always assume that your best may not be good enough and make sure every contingency is covered".