A320 flight crew reported during climb the aircraft did not respond to the airspeed selected on the FCU. They disconnected the autopilot and returned to the departure airport.
Synopsis
A320 flight crew reported during climb the aircraft did not respond to the airspeed selected on the FCU. They disconnected the autopilot and returned to the departure airport.
Narrative
Climbing through approximately 5000 ft with speed managed and auto thrust on; airspeed continued to increase past 250 kts to 320 kts. Speed did not respond to 250 selected on FCU (Flight Control Unit) either. Initially; I suspected an unreliable airspeed; accomplished memory items; and the unreliable airspeed checklist. Conditions were IMC and with ZZZ departure. We inquired our speed with them. They said 360 kts. I was cautious to manually slow speed with auto thrust off because I didn't trust the airspeed indication. CA; FO; and standby airspeed indicator all had same indication so I now wasn't for sure the problem was unreliable airspeed. There were no ECAMS. I turned AP1 back on to test the autopilot. The autopilot did not respond to selected altitude or pitch commands. So I disconnected AP1 and flew raw data the rest of the way. I did not attempt AP2 at that point. [ATC was advised] and we were vectored for visual Rwy XX in ZZZ. I requested my FO to brief the FA;s and make a PA to the passengers since I had my hands full flying the airplane on raw data. We elected to land overweight by 4000 lbs at 146;000. We stopped on the runway while emergency vehicles confirmed there were no smoking brakes or anything else appearing abnormal from overweight landing. I asked my FO to announce remain seated; remain seated" on PA to prevent any inadvertent evacuation. Once stopped and communication established with emergency vehicles; I made a PA to passengers that they would see fire trucks as a precaution and that I expected to be taxiing to gate shortly. Afterward we continued to the gate uneventful. A total of 5 writeups were submitted to maintenance to include overweight landing; landing lights extended at 320 kts; and no ECAMS associated with emergency. A brief with local maintenance; ZZZ flight ops; and Chief Pilot were subsequently accomplished."
Second reporter narrative
Departed ZZZ runway XYL on the ZZZZZ [SID]; initially in heading mode then direct ZZZZZ. I was PM for this leg. We engaged NAV and made the left turn east; climbing to 4;000 assigned. We were then cleared to climb via SID and I selected 16;000 in the FCU (Flight Control Unit). CA asked for managed speed at ~2;600 ft. I noticed we were above the SID altitudes at this point inadvertently (5;000') and then CA noticed the airspeed was running away well above 300 knots at this point with the auto thrust engaged. CA disconnected autopilot (AP); auto thrust (AT) and flight directors at this point and we executed the memory items for unreliable airspeed. The AT was not commanding the correct speed and we accelerated to 320 knots indicated airspeed at 5;000 feet. I called ATC and told them we were correcting and they noticed we were doing around 360 knots ground speed at this point. We decided it was not unreliable airspeed given all 3 airspeeds matched; but the AP and AT appeared to not be functioning properly.We [advised ATC] at this point; since there was no ECAM and we couldn't trust the automation to keep the plane safe and level. We received vectors from ATC back for runway XX; CA was flying all raw data at this point. He tried to re-engage the AP and AT but it was still not responding appropriately. CA instructed me to do a brief with the flight attendants as well as making the PA to the passengers informing them of what was going on; since CA was deeply concentrating on hand flying the airplane in IMC. Eventually we were cleared for the visual approach to XX; and landed successfully and announced Remain seated; remain seated" to mitigate an inadvertent evacuation. We did land at 146;000 pounds; roughly 4;000 pounds overweight. The ARFF (Airport Rescue and Firefighting) vehicles did an aircraft inspection on the runway. We taxied back to the gate thereafter."
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.