Date: 201602
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Night
Aircraft: A319
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Landing
Airspace: Class B ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: FMS/FMC
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Commercial
Human factors: Confusion; Situational Awareness
Second reporter function: Pilot Not Flying; Captain
Anomaly: Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Unstabilized Approach
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Aircraft Automation Overrode Flight Crew; Flight Crew Regained Aircraft Control; Flight Crew Overcame Equipment Problem
Contributing factors: Aircraft; Human Factors
Primary problem: Ambiguous

Narrative: On approach an issue arose with the aircraft accelerating possibly due to the selection of managed speed without being activated and confirmed. I saw the Captain select activate; but can't confirm that the MCDU registered the confirm selection. Either way the plane accelerated once I selected managed speed. I had just used the speed brakes and misinterpreted the acceleration with the plane leveling off and the speed brakes deployed. I reached to confirm that the speed brakes were stowed. The Captain correctly diagnosed the issue and assumed control of the aircraft. The Captain returned the aircraft to a stabilized condition. At one point though we did dip below GS and received a low altitude alert from tower. The Captain corrected and we landed without further incident.Possible failure to 'confirm' once activating the approach. Distraction from the acceleration led to the unstabilized approach. Mental task saturation with approaching weather; changing alternates; receiving new data; etc. possibly led to a lapse in confirmation of Pilot Monitoring (PM) duties.


Second narrative: We were preparing for a flaps 3 landing. We did the Preliminary Landing Checklist and I 'Activated & Confirmed' the approach data passing 10;000 feet. We were on Final approach; flaps2; [airspeed] 180 kts; gear down. I was the monitoring pilot at the time. When my Copilot pushed for 'managed' airspeed; the thrust went to Takeoff Go Around (TOGA) and green dot speed! My copilot wasn't sure what/why that had happened because we had activated and confirmed already. It caught me by surprise also; but had seen that happen before over the years. Since we were vastly approaching the flaps2 speed limit (200kts) I took over the flying duties; disconnected the auto thrust levers and autopilot to slow the airspeed below 200 kts. I believe we got to 220-230 kts in our descent. I leveled off slightly to help slow the aircraft. My copilot set 135 in the airspeed window. We lowered the flaps 3; and finished the landing checklist. We were high; so I lowered the nose to get back down to the glide slope. Obviously; I over corrected and went below the glide path. The weather was scattered clouds and we had the runway in sight. Tower called us during final to say they had an altitude alert on us. We responded that we were aware and had the field in sight. I leveled off at 600-700 feet until we captured the glide slope. We landed normally.The situation caught both my Copilot and I off guard during final approach after 4 plus hours of flying.  When 'Managed' speed was selected; the auto thrust system did something that only happens when you fail to 'activate & confirm'; but we both verified that we had accomplished that which is why it surprised us both. Usually at that point in the approach you just lower the flaps to the desired position and land. Last night was different. Looking back; the First Officer 'suggested' that it might be a good to go around at 500 feet. To be honest; I'm not exactly sure how we got low. Obviously; trying to slow the [aircraft] down; and stay on Glide Path was a handful. I had the [runway] in sight. We were now in a position to safely land; so I told him that we were OK and would land. There was a strong line of weather behind us; but that wasn't the reason I continued the approach. I felt very comfortable that we would land safely.


Synopsis: An A319 flight crew experienced a flap overspeed during approach when managed speed is selected by the flying First Officer. The Captain takes control and disconnects autothrust allowing the approach to be continued to landing. The approach had been activated and confirmed but apparently was not accepted by the FMGC.