Narrative:

During the descent our course was rerouted to approach from the north due to a large area of weather to the north-northwest. While being vectored to the approach we flew through an area with severe turbulence which caused a large airspeed and altitude deviation; and overspeed of the flaps. The captain was flying; ATC had assigned us a descent from 3500'msl to 2500'msl. We were indicating 240 KTS when ATC assigned 210 KTS. We were in light to moderate turbulence and heavy rain. Just below 3000'msl the airspeed dropped suddenly; the autopilot disconnected; and the autothrottles went into toga/lock. The airspeed was dropping through 180KTS with a trend arrow that extended off the airspeed scale. I felt that a stall could be imminent; so I advised the captain 'I'm giving you flaps 1!' and moved the flap selector to flaps 1. Before the slats could fully extend the trend arrow reversed and we were accelerating too quickly as the captain reduced the thrust. Passing 210KTS I said 'flaps coming up!' and retracted them. We exceeded 235KTS before they were retracted and an ECAM message was generated. The aircraft continued to accelerate to 280KTS and climbed to 3500 before we were clear of the weather and able to stabilize the aircraft at which point the captain returned to assigned airspeed and continued the descent to the assigned altitude. I immediately advised ATC that we had encountered severe turbulence and were returning to assigned speed and altitude. The flight was uneventful after that; and we contacted maintenance to advise them of the overspeed. The weather as depicted on the radar did not give sufficient indication of the severity of the weather encountered. The company was advised of the flap overspeed. I do realize that the aircraft's fly-by-wire software should have prevented a stall from occurring. Due to the extreme rate that the airspeed was being lost and our low altitude; I believe that adding flaps was the correct action for the situation.

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Original NASA ASRS Text

Title: Severe turbulence and a rapid loss of airspeed leads an A321 flight crew into a flap overspeed condition.

Narrative: During the descent our course was rerouted to approach from the north due to a large area of weather to the North-Northwest. While being vectored to the approach we flew through an area with severe turbulence which caused a large Airspeed and Altitude deviation; and overspeed of the Flaps. The Captain was flying; ATC had assigned us a descent from 3500'MSL to 2500'MSL. We were indicating 240 KTS when ATC assigned 210 KTS. We were in Light to Moderate Turbulence and Heavy Rain. Just below 3000'MSL the Airspeed dropped suddenly; The Autopilot Disconnected; and the autothrottles went into TOGA/Lock. The Airspeed was dropping through 180KTS with a trend Arrow that extended off the Airspeed Scale. I felt that a Stall could be imminent; so I advised the Captain 'I'M GIVING YOU FLAPS 1!' and moved the flap selector to Flaps 1. Before the slats could fully extend the trend arrow reversed and we were accelerating too quickly as the captain reduced the thrust. Passing 210KTS I said 'FLAPS COMING UP!' and retracted them. We exceeded 235KTS before they were retracted and an ECAM message was generated. The aircraft continued to accelerate to 280KTS and climbed to 3500 before we were clear of the weather and able to stabilize the aircraft at which point the Captain returned to assigned airspeed and continued the descent to the assigned altitude. I immediately advised ATC that we had encountered Severe Turbulence and were returning to Assigned Speed and Altitude. The flight was uneventful after that; and we contacted Maintenance to advise them of the overspeed. The weather as depicted on the radar did not give sufficient indication of the severity of the weather encountered. The company was advised of the flap overspeed. I do realize that the Aircraft's Fly-By-Wire software should have prevented a stall from occurring. Due to the extreme rate that the airspeed was being lost and our low altitude; I believe that adding flaps was the correct action for the situation.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.