There was that Air France Flight from South America. Ice had rendered all tachometer devices useless, and the autopilot tried to counter with the data it received. When the jet lost altitude it gave positive elevator control and the nose went up until stalling.
The pilots did not know what was going on and were not able to switch from automatic to manual steering. A stall, drop and circling could be a hint for a similar technical failure.
Just saying.
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>^..^<*)))>{ All generalizations are wrong.
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