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As the troubled Boeing 737 MAX jets are being diverted in European skies, with nations shutting airspace over the deadly crash in Ethiopia one by one, an Israeli-bound Norwegian Airlines plane was forced to return to Stockholm.
Data from tracker website Flightradar24 shows that Norwegian flight DY4545 got as far as Romania before the plane was diverted back to Stockholm Arlanda Airport.
The U-turn coincided with an announcement by Norwegian Airlines that it was suspending all Boeing 737 MAX 8 flights following the Ethiopian Airlines crash on Sunday – the second disaster involving the new Boeing jet in the last six months.
The key of the matter is that pilots fly normal 737s every day, and have internalized a mental model of how that plane operates. Pilots probably actually read manuals, and safety directives, and practice for rare events. However, I bet that what they know best is how a plane actually operates most of the time. (I am adjusting to a new car, same manufacturer and model as the last one, but the 9 years of habit are still often stronger than the manual-led actions required by the new configuration).
When they fly a 737 Max there is a bit of software in the system which detects stall conditions and corrects them automatically
The pilots should know that, they should adjust to that, they should know that they must switch off that system if it seems to be getting in the way, but all that may be steps too far, when something so important is so opaque.
What is interesting is that in emergencies people rely on their most validated mental models: residents fleeing a burning building tend to go out their usual exits, not even the nearest or safest exit.
Pilots are used to pulling the nose up and pushing it down, to adding power and to easing back on it, and when a system takes over some of those decisions, they need to know about it.