Narrative:

While at cruise at FL320 with automation guiding aircraft we experienced a left IRS (inertial reference system) fault. I was pilot flying. The first two indications were an audible tone; and the word 'pitch' appear at the top of my eadi (electronic attitude direction indicator). I then observed my V bars pitch from a -5 degree pitch attitude to -10 degrees. Soon after we observed a pitch disagree EICAS message. We also heard a 'bank angle' chime. I immediately disconnected the autopilot; flight director and auto throttles; and began hand flying. My initial reaction was to apply back pressure to the control yoke to adjust pitch. My vsi (vertical speed indicator) began showing a descent of -1000 ft/min; and altimeter indicated a descent. My first officer vocalized what he was seeing on his instruments. I confirmed what he was saying by cross checking his instruments. His indications were exact opposite of what mine were showing. His instruments were showing a climb of +1000 ft/min; with matching trend on his altimeter. First officer (first officer) quickly called ATC to advise them of our instrumentation problem and that we were in a climb. At this point I referenced the standby attitude indicator while selecting altn IRS (alternate inertial reference system). Immediately my eadi matched the standby and first officer attitude indication. I leveled off. Our indicated altitude was now FL330. I then began descent back down to FL320 and called for left IRS fault checklist (as this is what was indicated now on EICAS). Checklist called for the altn IRS be selected on faulty side. End of checklist. We reported the fault to flight control; sent a maintenance report with proper frm (fault reporting manual) code; and performed the logbook write up. We continued to destination uneventfully. After analyzing this event; I should have taken a few more moments to analyze the situation before taking action. The extra few seconds would have allowed me to cross check all 3 sets of primary flight instruments. Taking that extra time would have eliminated us climbing away from our assigned altitude.

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Original NASA ASRS Text

Title: At cruise during a night oceanic flight with the Captain flying; the left IRS (Inertial Reference System) failed. An audible tone and EADI PITCH (Electronic Attitude Directional Indicator) alert along with a flight director pitch down were indicated. Countering the pitch down indication; the Captain gained 1;000 ft before selecting ALTN (Alternate) IRS and descending.

Narrative: While at cruise at FL320 with automation guiding aircraft we experienced a Left IRS (Inertial Reference System) fault. I was pilot flying. The first two indications were an audible tone; and the word 'pitch' appear at the top of my EADI (Electronic Attitude Direction Indicator). I then observed my V bars pitch from a -5 degree pitch attitude to -10 degrees. Soon after we observed a pitch disagree EICAS message. We also heard a 'bank angle' chime. I immediately disconnected the autopilot; flight director and auto throttles; and began hand flying. My initial reaction was to apply back pressure to the control yoke to adjust pitch. My VSI (Vertical Speed Indicator) began showing a descent of -1000 ft/min; and altimeter indicated a descent. My First Officer vocalized what he was seeing on his instruments. I confirmed what he was saying by cross checking his instruments. His indications were exact opposite of what mine were showing. His instruments were showing a climb of +1000 ft/min; with matching trend on his altimeter. FO (First Officer) quickly called ATC to advise them of our instrumentation problem and that we were in a climb. At this point I referenced the standby attitude indicator while selecting ALTN IRS (Alternate Inertial Reference System). Immediately my EADI matched the standby and FO attitude indication. I leveled off. Our indicated altitude was now FL330. I then began descent back down to FL320 and called for Left IRS Fault checklist (as this is what was indicated now on EICAS). Checklist called for the ALTN IRS be selected on faulty side. End of checklist. We reported the fault to flight control; sent a maintenance report with proper FRM (Fault Reporting Manual) code; and performed the logbook write up. We continued to destination uneventfully. After analyzing this event; I should have taken a few more moments to analyze the situation before taking action. The extra few seconds would have allowed me to cross check all 3 sets of primary flight instruments. Taking that extra time would have eliminated us climbing away from our assigned altitude.

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.