Several years ago, I saw a talk by Captain David Cronin. If you don't know the name, you might remember the story. In 1989, Cronin and his crew were climbing through 22,000 feet en route from Honolulu, Hawaii to Sydney, Australia, when the forward cargo door blew off their Boeing 747-100. The entire cabin depressurized fast enough to fill it with mist and the right two engines were taken offline. (Nine passengers were also blown out or killed by the resulting damage).
Cronin said the first thing they did was grab the backup oxygen masks. Unfortunately, Boeing put the O2 tanks for the crew by the cargo door for easy maintenance and they were no longer on board the airplane. Clearly the next action was an emergency decent, which Cronin initiated from memory, but then called for by checklist from his first officer. On the checklist is, GEAR DOWN. The FO read the item and looked to Cronin before lowering the gear. Cronin chose to leave the gear up, because the plane was already passing through 10,000 feet by then, and he saw no need to make it descend faster. He said (and I'm paraphrasing here), "Someone taught me that you run the checklist only until the task is completed. And then you stop there."
They landed safely, despite extensive aircraft damage and best guesses by the flight engineer on landing speeds with so much stuff broken (the FE's paperwork was blown all over first class during the decompression). What's fascinating about this, however, is that when simulator runs of this scenario were done to see how different crews would react, every crew that put the gear down early went swimming. It seems that, even dumping fuel as fast as possible, the 747 with that much damage and weight and only two engines running is too heavy and draggy to get back over dry land if the wheels are down.
So, the captain broke from protocol and saved the day.
Now there's an indication the captain of Flight 3407 pulled back on the yoke right after the aircraft warned the crew of an impending stall with a stick shaker. and then tried to fix the situation with a nose-down action. The captain's pull-up may have put the aircraft into a stall/spin and crash. What would make a well-trained aviator do such a thing?
I don't know. But here's how the randomness of reality could make the right thing the wrong thing. Suppose the crew is worried about icing. The captain is thinking about his icing training and the reading he's done on his own. He knows deploying flaps and gear have the potential to cause a problem, so he's spring-loaded. There is ice on the airplanenot more than the Dash 8 can handle, but enough to cause a dangerously-low airspeed at the current power setting. The stick-shaker activates and the plane pitches down to recover from the immanent stall.
What are two indications of a tailplane stall? Tailplane vibration and nose-down pitch. What's the correct recovery action? Full aft elevator.
I'm not saying this is what happened outside of Buffalo that day. It seems an unlikely chain of events, in fact, since tailplane vibration being felt in the yoke applies to aircraft without mechanical controls, not hydraulic ones. The captain should have known that. But it's not impossible that stimulus-response mentally developed in earlier flying led to the wrong action in a different airplane, and that's more the point. An old habit or reaction applied in a new scenario might save the day, or end it.
No matter how long we try to regulate, train or procedure away the winds of chaos, there will still always exist just the right constellation of events where right becomes wrong, wrong becomes right and survival is a matter of a split-second, lucky guess.