French investigators have detailed an incident involving an Air France Airbus A320 on which the stall-protection system activated on approach to Bordeaux.
The aircraft (F-HBNI) entered a hailstorm at a height of 3,000ft as it descended towards the airport following a service from Paris Orly on 2 August.
French investigation authority BEA says the first officer's windshield cracked.
As the A320 passed through 2,800ft, with its autopilot engaged, the aircraft pitched up to an attitude of 25°. The crew set the thrust levers to go-around power.
The A320's normal flight-control law provides angle-of-attack protection - known as "alpha floor" - above a certain threshold.
BEA says this protection activated and engaged the "TOGA LOCK" mode, which maintains go-around power after the immediate stall threat has been averted. The pilots subsequently disengaged this mode and landed at Bordeaux.
Meteorological data from Bordeaux airport around the time of the incident shows the presence of thunderstorms and heavy rain.