When one looks at the an air crash or the miraculous avoidance of one you can sometimes pick out a key factor or rather combination of factors that was the determinant. Of course, as usual, had many other factors been different it would not have happened.
For instance, in the case of the 737 MAX crashes it seems to be–as the NTSB and Sully Sullenberger (in a letter to to the New York Times Magazine) just pointed out–it was the confusing cascade of alarms and strange behavior of the aircraft with virtually no time to work out a solution that was the determinant.
Take the case of AF447, the Air France A330 that crashed into the South Atlantic after the captain (who had only had an hour’s sleep the night before) left two first officers in the cockpit when he went for his routine rest–seemingly not in his bunk next to the cockpit but in the cabin where his female companion was sitting.
The aircraft then flew into a storm. The computer could not make sense of the airspeed data because the pitot tubes had iced up. The autopilot disengaged with the systems passing into alternate law meaning the computer would not stop the pilots doing something stupid.
Manual control had passed to the most inexperienced of the first officers, who for some reason put the aircraft into a steep climb causing it to eventually stall and “drop like a brick”.
The captain did eventually return but only realized too late what was happening when the junior copilot said he had been “pulling back all the time”.
Our book Air Crashes and Miracle Landings details all the contributing factors, both technical and human. However, the determining factor seems to be that the pilot in command (the most junior) believed they could not be stalling because as he said on the CVR, “We are in TOGA (TakeOff Go-Around, aren’t we?”. However, TOGA only gets one out of a stall at low altitude not high up in thin air.
Had the engines situated low under the wings not been at a such a high TOGA setting, the nose of the aircraft would have dropped and in a dive with plenty of height they would have regained enough speed for the aircraft to begin flying again rather than mulching downwards.
Nowadays, all pilots will know how to recover from a high-altitude stall.
To sum up, in the case of AF447, TOGA made the pilot wrongly believe they could not be stalling despite 50 warnings, and TOGA stopped them recovering.