Well the only protection that gives you pitch-up is high-speed protection and I have reasons to believe that the aeroplane was nowhere near its Vmo of 350 kt on DME arc. Protections are also designed to shut themselves off if there are discrepancies between all three air data or inertial reference sensors.
. All on here would be surprised by how quickly the IAS winds back to zero in the climb, once water freezes in the static lines. Similarly, how very quickly it winds UP after the aircraft descends below the height at which it freezes and blocks static pressure changes reaching the ADIRU's, In fact, does it even need to freeze? Maybe water can just quickly flow to and collect at a low-point due to the attitude change of a descent/config change inducing a flow and a blockage.
. Now I'm guessing that the A320 doesn't have independent static pressure line systems for each of its ADIRU's - so there'd be an effect upon all threeADIRU's and no shut-off of protections per:
Protections are also designed to shut themselves off if there are discrepancies between all three air data or inertial reference sensors.
So you have a rapidly increasing IAS in the approach/descent sensed by all three ADIRUs and it generates a programmed response of a rapid pitchup and power increase...... into an aerodynamic stall/spin.
. Just a theory but........ any arguments against the logic and feasibility?
. Maintenance => aircraft repaint and/or aircraft wash => water in static system......... => freezes at height (maybe during system checks on pressn system).