I was working on the ramp at Bahrain in the early 70's when a Qantas B707 (I can't remember the variant) landed after a major upset on route. We disembarked the passengers, all very subdued and shaken, and got them off to the hotels we had organised.
In the cabin, we found evidence that something had gone wrong, including soap still stuck to the toilet ceilings. One of the passengers had told how her baby had "flown" a considerable distance from her seat row to another, without injury. We reckoned that this was in negative "G".
As I recall,, the flight crew said that Captain's Flight Director had indicated a increasing bank which the AP did not correct. The action of disengaging it and applying a manual incremental correction put the aircraft out of control, because the Director was wrong in the first place. I'm sure that someone knows what really happened; that story is very probably wrong.
The point of the post is that the Captain told us that he had eventually brought the aircraft under control again at 6,000 ft, by simply going back to his basic single-engine training using the basic panel, yoke, rudder and engine controls and taking the action he had been taught for "recovery from unusual attitudes". That would have been a laconic over-simplification, of course.
I have found one short record of this incident describing it as a "steep dive and recovery", but I'm sure it was a lot more than that. The aircraft was, according to the same record, written off due to structural damage. My memory was that a Boeing team spent 2 - 3 weeks crawling over the aircraft and found little damage, after which it was ferried away. That would have been consistent with the way Boeings were built, but I guess the record is right and it was finally written off.
I think about that incident occasionally, usually as I get on board an Airbus.