This is not the final report yet, but it confirms that there was an issue with the icing conditions, and it was acknowledged by the crew. It also suggests a potential issue with the de-icing system? But maybe I just read it wrongly:
15:15:42 - a single chime was heard in the cockpit. Subsequently, the crew commented on the occurrence of an AIRFRAME DE-ICING Fault;
Some other excerpts from the sequence of events:
16:19:28 - at a speed of 184 kt., the DEGRADED PERFORMANCE alert was triggered, together with a single chime. The alert was triggered concomitantly with the exchange of messages between APP-SP and the crew;
16:20:00 - the Second in Command (SIC) commented, “a lot of icing”;
16:20:57 – during the turn, at a speed of 169 kt., the INCREASE SPEED alert was triggered, in conjunction with a single chime. Immediately afterwards, vibration noise was heard in the aircraft, simultaneously with the activation of the stall alert;
16:21:09 - control of the aircraft was lost, and it entered an abnormal flight attitude until colliding with the ground. The aircraft rolled to the left to a bank-angle of 52 degrees, and then rolled to the right to a bank-angle of 94 degrees, performing a 180-degree turn in a clockwise direction. Subsequently, the turn was reversed to an anticlockwise direction, with the aircraft completing five full rotations in a flat spin before crashing into the ground.
About those alerts:
If the aircraft’s drag increased due to ice accumulation and performance was degraded, resulting in loss of cruise speed, alerts in three levels were triggered and presented to the pilots on both alert panels of the APM, as follows:
1st Level - CRUISE SPEED LOW.
The blue-colored message would indicate performance degradation of around 10%, with reduction of the Indicated Air Speed (IAS) during the cruise phase by at least 10 kt. below the speed computed by the APM. This alert would be triggered only during the cruise phase.
2nd Level - DEGRADED PERFORMANCE.
The amber-colored message would be followed by a single chime and a master caution alert, indicating a significant performance degradation in the range between 22% and 28%, induced by a significant increase in aerodynamic drag, causing a drop in cruise IAS of around 15 to 20 knots below the speed computed by the APM. This alert could be triggered during climb, cruise, or descent.
3rd Level - INCREASE SPEED.
The amber-colored message would appear flashing, followed by a single chime and a master caution alert, indicating that the degraded performance condition had worsened , reaching an IAS value below the ICING BUG + 10 kt. This alert could be triggered during climb, cruise, or descent.
