Date: 202107
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Daylight
Aircraft: A320
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Air Data Computer
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Human-Machine Interface; Distraction; Confusion; Communication Breakdown; Situational Awareness; Troubleshooting; Training / Qualification
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural FAR; Inflight Event / Encounter Loss Of Aircraft Control
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Became Reoriented; Flight Crew Overcame Equipment Problem; Flight Crew Regained Aircraft Control; General Flight Cancelled / Delayed
Contributing factors: Procedure; Software and Automation; Human Factors; Aircraft
Primary problem: Human Factors

Narrative: Inadvertent switching off of IR1 mode selector which deactivated that associated ADIRU. ADR and IR data not available. This occurred during flight one of day two of an initial Captain upgrade. The trainee came off the B777. He has been with our company for many years. The three legs of day one was extraordinarily busy. It was immediately clear to me during those three legs he had studied hard during training and had mastered much of the material. On the first two legs of day one I had a LCA (Line Check Airman) in-training watching me conduct the line check as part of that LCA's upgrade training. I commented to the new LCA not all trainees will be so well prepared as this one.This flight was leg four of the IOE and the first flight of day two. Our transportation to the airport was 15 minutes late and there was a detour so we arrived at the aircraft about 30 minutes prior to departure. Normally; I introduce myself to all the FAs (Flight Attendant). However; because we were on IOE; [we] were somewhat late to the aircraft and on Release 6. I only introduced myself to the FM. I felt I did not have time go to the back to introduce myself to the FAs assigned to the rear of the aircraft.We had been in the seat for approximately 3 hours. The upgrade Captain requested I ask the FM to prepare the meals and that we would then take a restroom break when the meals were ready. I did so. The FM called us about 25 minutes later to state the meals were ready. The upgrade Captain offered me the opportunity to use the Lav first. I declined and said he should go first and I would then go. The door chime rang and then I heard a knock. That knock is not standard. However; it occurs occasionally with legacy Company 2 flight attendants. We put on our masks. I saw the upgrade Captain move to get out of his seat; stand up; and let the FA in while he then left the cockpit. I noticed nothing odd about his movement out of the seat and to the rear of the cockpit. I saw out of the corner of my eye the FA was standing near the rear of the cockpit just behind and to the right of the Captain's seat; a normal position for a relief FA.My concentration then focused on something else. I think it was because we were getting ready to enter a large area of convective activity. I might have been looking at WSI and comparing that to what I was seeing on the weather radar. Why my gaze was generally focused forward and right I am not sure; but it was. I planned to brief the relief FA about this weather and its possible effect on their service in a few minutes. It was at that point; maybe 30-45 seconds after the upgrade Captain had left the cockpit; that for lack of a better description; 'all hell broke loose.' The cockpit went from a completely benign environment to one of confusion. The startle effect was in full force. The first warning was a continuous repetitive chime and the warning lights flashing. I immediately looked at the E/WD (Engine/Warning Display) and noted about 4-5 ECAMs listed; primary secondary and independent failures in both red and amber. I silenced the CRC (Continuous Repetitive Chime) by pushing [the] master warning light. That silenced the CRC. However; there still was an aural alert going off that I could not silence; which created a fair bit of consternation on my part. I look at my PFD and saw the FMAs were wrong. I then saw the AP (Autopilot) was off and that there was nothing where I expected to see the AT (Autothrottle) condition. I noted the aircraft climbing slightly and corrected that. I knew the AP disengaged for some reason but didn't know why. I thought about engaging AP 2 but then thought that may create new problems; so I elected to hand-fly until the ECAMs were sorted out. I saw we were no longer in NAV but again; wasn't sure why. I did see that the aircraft didn't diverge much from the 'green line' so lateral stick inputs weren't necessary. At this point ATC called to ask us something about recycling the transponder. We wereon speaker at that time; I responded we had a problem and to standby.I then noted the airspeed increasing and pulled the TLs (Thrust Lever) back; I didn't want to add an over-speed to our problems. This silenced another aural sound. I do not recall seeing a Thrust Locked ECAM or FMA which I thought would have been the source of the alert I couldn't silence. I glanced at the Captain PFD (Primary Flight Display) and ND (Navigation Display) and saw they didn't look right.The aircraft was reasonably stabilized now but; in my mind; because the ECAMs were displayed; the situation wasn't. I then told the FA to recall the trainee Captain to the cockpit. He opened the door; looked and then closed it; and said he was in the bathroom. I told the FA I knew that and I wanted him back in the cockpit now. He then had the FM knock on the Lav door. The trainee Captain returned to the cockpit and the relief FA left. The trainee Captain was incredulous when he looked at the E/WD. I told him I was hand-flying; had the aircraft and radios; and that he was to handle the ECAMs. It was at this point I noted we were about 20 knot slow; well within flying speed but slow for planned speed. I had overcompensated for my worry of overspending the aircraft. I pushed the power back up. Airspeed had fallen out of my cross-check. The trainee Captain methodically and correctly went through the ECAMs. As I recall the first several ECAMs had no action items; one ECAM had us switch the air data switch to three. At some point during this; ATC stated they now had data on us and asked if we needed assistance. We told him we were completing a procedure and to standby. Once the status messages were read and the ECAM procedure completed; I reached up to engage AP two. It did so. I armed the AT and then moved the TLs to the climb detent to engage it. Our ATC clearance was to proceed direct to a fix so we reinserted that. I don't recall having to pull or push to capture our assigned altitude but I can't be sure.It was now maybe 4-5 minutes after the initial event where I could take a breath. I recalled the ECAM and saw the ADR 1 fault. I then looked over to the ADIRS panel and saw IR mode selector one was in the OFF position. It; of course; was on for the flight up until some point in [the] last few minutes. I asked the trainee Captain if he recalls hitting the switch with his head or back as he left his seat. He said no. I then thought perhaps the switch was defective. This aircraft came to us as a through flight. We did not have to turn them on so we had no knowledge of how that switch felt by turning it on. We again discussed it and he stated he didn't recall even touching the overhead panel while leaving the seat.Because I didn't introduce myself to the FAs at the rear of the aircraft prior to the flight; I wasn't sure which FA came to the cockpit during our break. I asked the FM to ask the FA who came to the cockpit to call us on the interphone. That FA did and I asked him if he recalled touching anything on the overhead panel; he stated he did not. What I found unusual was that during the event; the FA seemed very nonplussed by the cacophony of sounds in the cockpit. I would have expected a FA to at least ask what was going on; but maybe he was somewhat shocked by what he saw and heard during his short time in the cockpit.The trainee Captain and I discussed that I would write up the ECAM and then conference Dispatch and Technical Support Maintenance Control to provide further details of what we thought may have occurred. I wanted the switch looked at but also didn't want Maintenance to search for a problem which might not exist. I ACARS'd Dispatch with the request and he set up the conference call. The communications with Technical Support Maintenance Control were reasonably good and he captured exactly what I wanted him to know and he appended it to our write-up. Since the Captain's displays were significantly degraded; we switched PF/PM roles. Fromthat point we continually deviated for weather; were put in holding; and changed our alternate three times. We over-burned by almost 5500 lb on this flight; more than on any flight I have been on in [an] Airbus. It was an understatement to say this was a busy flight. I don't know how this happened. The final flight of the day was a termination. As the trainee ran that checklist and turned off the IRUs; he stated he couldn't believe how he accidentally managed to switch that style of switch - pull and turn - off by getting out of the cockpit.I am disappointed in myself for not more thoroughly reviewing the flight manual for ADR 1 fault after things had settled down. We did not have a GPWS TERR FAULT light and no ECAM direction to switch it off so it remained on. We discussed that threat in that we were now the aircraft's GPWS system and to be cognizant of the terrain. We also discussed changing the transponder to position 2 but did not do so because there was no ECAM direction to [do] so and ATC noted no anomalies in our reporting. Also; once I saw the IR mode selector switch in the off position; I should have considered reviewing the NAV IR fault non-normal even though we didn't have that ECAM. I did not do a word search in the flight manual for ADR. Had I done so; I would have seen that there may be RVSM limitations associated with its failure and should have gone to the FOM for further information. I recall many years ago; our Line Manager at the time; wrote up in his weekly update a similar event. As I recall he wrote the trainee somehow managed to hook the window shade into that same switch and turned it off. That of course didn't happen here.




Synopsis: A320 Captain reported that a component was inadvertently switched off after the other pilot left the cockpit for a lavatory break and a multitude of warnings and ECAM messages went off as a result.