Narrative:

I was the pilot monitoring on this leg. The aircraft had a deferred IRU #2 which we had been flying with for the last two legs. On takeoff; at approximately 100 AGL; we got an ECAM message for a navigation adr (air data reference) (2+) fault. This was basically a failure of adr #3; so coupled with the previously deferred IRU #2; were now had multiple failures of redundant systems and were down to a single adiru (air date inertial reference unit) (#1). The captain was the pilot flying; so he continued to fly the aircraft since the pfds and information on the first officer side were inop. The captain also handled the ATC radios and coordinated for a climb to and level off at 10;000 feet; while flying delay vectors. As pm; I handed the ECAM and then completed the clean-up items in the QRH to include calculating the landing distance for our impending flaps 3 landing. After the ECAM and QRH were complete; the captain directed me to start the coordination process. I spoke with the flight attendants and advised them that we would be returning to ZZZ. I then used the 'dispatch call me' function of the ACARS and got a frequency to talk to dispatch. The captain had his hands full flying the aircraft as there was moderate turbulence in the ZZZ area from 10K-16K and he had lost autopilot; autothrust; and was in alternate law. Once I spoke with dispatch; I explained our situation and was then passed to [commercial] radio for a connection to maintenance control. Maintenance said they were seeing the software download of the event from the aircraft and started estimating what might have caused it. At this point; we were content we had done everything we needed to do; so then I explained to the conference call our intentions were to [advise ATC] and land back at ZZZ. There was some discussion as to if we were overweight for landing and I shared that we were not (approximately 130K) and that I had already calculated our landing distance out of the QRH table. Terminated the call at this point; rejoined the captain in prepping for the approach; captain [advised] ATC and we got vectors to the visual.ATC was excellent! Fire trucks were standing by. We executed an uneventful flaps 3 approach and landing in accordance with the QRH.

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Original NASA ASRS Text

Title: A319 flight crew reported being dispatched with one IRU deferred. On initial climbout; the aircraft lost a second navigation system. With only one system remaining; the crew elected to return to the departure airport.

Narrative: I was the Pilot Monitoring on this leg. The aircraft had a deferred IRU #2 which we had been flying with for the last two legs. On takeoff; at approximately 100 AGL; we got an ECAM message for a NAV ADR (Air Data Reference) (2+) Fault. This was basically a failure of ADR #3; so coupled with the previously deferred IRU #2; were now had multiple failures of redundant systems and were down to a single ADIRU (Air Date Inertial Reference Unit) (#1). The Captain was the pilot flying; so he continued to fly the aircraft since the PFDs and information on the First Officer side were inop. The Captain also handled the ATC radios and coordinated for a climb to and level off at 10;000 feet; while flying delay vectors. As PM; I handed the ECAM and then completed the clean-up items in the QRH to include calculating the landing distance for our impending Flaps 3 landing. After the ECAM and QRH were complete; the Captain directed me to start the coordination process. I spoke with the flight attendants and advised them that we would be returning to ZZZ. I then used the 'Dispatch Call Me' function of the ACARS and got a frequency to talk to dispatch. The Captain had his hands full flying the aircraft as there was moderate turbulence in the ZZZ area from 10K-16K and he had lost autopilot; autothrust; and was in Alternate Law. Once I spoke with dispatch; I explained our situation and was then passed to [commercial] Radio for a connection to Maintenance Control. Maintenance said they were seeing the software download of the event from the aircraft and started estimating what might have caused it. At this point; we were content we had done everything we needed to do; so then I explained to the conference call our intentions were to [advise ATC] and land back at ZZZ. There was some discussion as to if we were overweight for landing and I shared that we were not (approximately 130K) and that I had already calculated our landing distance out of the QRH table. Terminated the call at this point; rejoined the Captain in prepping for the approach; Captain [advised] ATC and we got vectors to the visual.ATC was excellent! Fire trucks were standing by. We executed an uneventful Flaps 3 approach and landing in accordance with the QRH.

Data retrieved from NASA's ASRS site 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.