Narrative:

We were on a vector to intercept the localizer. I armed the localizer; which would have allowed everything to work out just fine. But; since we were 25 NM out; I thought it would have been better to capture the course in navigation mode. After I did that; the FMGC showed no navigation intercept. Then; I attempted to correct the problem by selecting direct to a fix on the approach. Finally; I just rearmed the localizer and turned in with the heading bug to intercept the course. By then we were flying through the localizer. I clicked off the autopilot and turned in manually toward the course. The captain grabbed his control side-stick to turn in more aggressively to re-intercept the localizer because we had gone far enough through that we approached the center line for [a parallel runway]. The whole time this was going on; I never looked outside to get a better situational awareness. We finally got back on the localizer for a stabilized approach. I have not been sleeping well. That is why I was tired prior to the start of the duty period. Furthermore; my marriage has not been going well. That is why I froze up for a couple of seconds and did not take the right action when it needed to be taken. If I had only armed the localized and left it alone and used heading on the FCU to turn inward a mile before intercept; then none of this would have happened. This was due to a combination of over-thinking something and then being to slow to react when it went wrong.

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Original NASA ASRS Text

Title: A320 First Officer reported a course deviation on ILS arrival that was caused at least in part by fatigue and personal problems.

Narrative: We were on a vector to intercept the localizer. I armed the localizer; which would have allowed everything to work out just fine. But; since we were 25 NM out; I thought it would have been better to capture the course in NAV mode. After I did that; the FMGC showed no NAV intercept. Then; I attempted to correct the problem by selecting Direct to a fix on the approach. Finally; I just rearmed the localizer and turned in with the heading bug to intercept the course. By then we were flying through the localizer. I clicked off the autopilot and turned in manually toward the course. The Captain grabbed his control side-stick to turn in more aggressively to re-intercept the localizer because we had gone far enough through that we approached the center line for [a parallel runway]. The whole time this was going on; I never looked outside to get a better situational awareness. We finally got back on the localizer for a stabilized approach. I have not been sleeping well. That is why I was tired prior to the start of the duty period. Furthermore; my marriage has not been going well. That is why I froze up for a couple of seconds and did not take the right action when it needed to be taken. If I had only armed the localized and left it alone and used heading on the FCU to turn inward a mile before intercept; then none of this would have happened. This was due to a combination of over-thinking something and then being to slow to react when it went wrong.

Data retrieved from NASA's ASRS site as of July 2013 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.