I’m speculating. But, based on the inflight data, I’d bet this will be related to ice accumulation inflight. ATR aircraft have had a troublesome history with ice.
Of course, a contributing factor will be pilot error. When in severe icing you should get out of it asap. Generally a quick descent into warm air will solve all your problems. This option was available to this crew.
>ATR aircraft have had a troublesome history with ice.<
The operative word is “had”. Following an accident in Roselawn Indiana 25 years ago, they flight tested the crap out of the airplane, in icing conditions, and slightly modified the wing deice boots and icing detection system. I doubt any other aircraft type was put through that rigorous type of testing.
I have several thousand hours in the ATR42 and ATR72. During that testing we transposed our fleet sending all of the ATRs to do Texas flying and the rest of the fleet to Newark. It was dubbed Ice Tour 94 and I remember it dearly. Oh the stories.
My unofficial (non CNN credentialed) opinion is the Roselawn plane flew into severe icing. Planes were never designed for that.
Regarding Sao Paolo, I’m withholding speculation until there is more data. A flat spin is not normal unless one prop went to full reverse. A flat spin is not normal unless the rudder falls off. A flat spin is not normal unless the CG abruptly moves way aft.
The authorities have the flight recorder and should be able to make a determination fairly quickly. If our press doesn’t get distracted by some other shiny object, maybe they will stick with this story long enough to learn something.
EC
If the de-ice boots are the inflatable and not heated, then it is very easy to ice up the wings.
I hated flying the King Air anywhere near ice. It had the inflatable boots-way too easy to create an extended leading edge if you left the boots inflated (the ice just formed over the inflated boot-therefore giving you no way to break off the ice). That is why they taught you to wait until some ice builds up ~ 1 inch, then hit the de-ice and turn off once the ice breaks away. The first step was to obviously try to avoid, then get out of it.