You seem to have more info than we do
Information from presentation:
Abnormal Valpha Prot
In-service event ( A321)
• At FL250, speed became managed at 290kt but the Autopilot (AP) was unable to reach the target speed. Airspeed remained around 250kt.
• At FL 310, during a L/H turn, the crew reported PFD showing Valpha-prot rising upward current airspeed (245kt).
The flight crew manually disconnected the AP
• Alpha protection activated with an order of pitch down
• Aft stick input maintained for 55 min to keep level flight at FL270
• ADR 2 switched off, leading to alternate law
• Remaining of flight performed in alternate law
• During climb, the following AOA values were recorded:
• AOA1 = 4.5° constant value
• AOA 2 = 4.5° constant value
• AOA 3 = normal behaviour
• The Flight Controls computers rejected the AOA n°3 (no cockpit effects)
• When the flight crew disconnected the AP, the Mach was 0.675.
Alpha prot =f(Mach= 0.675)=4.2°
Alpha prot activated with an associated pitch down
• The protection remained active until reversion to alternate law