[neurotech1]

The Asiana pilots were not able to fly a coupled (automatic) landing due to the ILS glideslope being out of service.

The pilots were under the misguided impression that the aircraft would automatically spool-up the engines if the aircraft became to slow. This was a safety feature that didn't engage for a obscure technical reason. Even with a manual visual approach the pilot can still use the autothrust for landing.

A more rigorously trained pilot (eg. Capt. Sully) would have aborted the approach and performed an immediate go-around if he got below the glidepath (or too slow) below a certain altitude (eg. 400ft Above Ground Level).

The rules requiring a go-around (or missed approach) apply for a fully automated approach and landing, just as much as manually flown approach and landing.