Narrative:

Weather was reported 150BKN in ord. We briefed visual backed up by RW28 localizer in ord. 22 mile downwind. I added all points on the approach including rocse and bluto to the approach and took out ppos. Bluto was the from at 1L. We were assigned 360 heading at 5000 feet for base leg. Approx 4 miles prior to localizer; we were assigned a 290 heading to intercept 28 localizer. Autopilot was on. I turned heading to 290. Once we were heading 290 I pushed for navigation. I usually try to intercept in navigation if I am far from the field so I don't get spurious localizer inputs. It was a 22 mile final. When I pushed navigation; the aircraft started to turn back to the right. I pulled the heading knob and selected 290 again and aircraft turned back left. As soon as established in left turn again I pushed for navigation. The only traffic on TCAS was +2300 at our right 3 o'clock and about 5 miles; presumably on final for south complex at ord. At about .5 miles from course as identified on screen; aircraft seemed to get that it was supposed to intercept and started slow left turn. I should have disconnected at this point and turned it myself. I didn't and don't really have a good reason why. I didn't feel concerned that it wouldn't intercept I guess. Navigation was displayed as a FMA. By the time we were actually headed toward ord; we had overshot by .6 miles as identified on the nd and ord was asking us if we had started the turn. Ord asked again if we were turning to intercept when we were about .3 back to final. I noticed at that time that the traffic for south complex was now +1.1 at our right 5 o'clock on TCAS at about 2 miles. I don't feel like we had a separation issue but I am wondering what I did wrong so the aircraft wouldn't intercept navigation line in navigation. We were outside the from point but that shouldn't matter if my from point is in 1L? I've been on the aircraft for approx 7 years and have used this technique for a long time and have never seen the airplane so unaggressive to capture a navigation line. SOP says I can intercept a localizer final in navigation or localizer and I usually use localizer if I am inside 15 miles. If I had to do it over again I would have used localizer but I still don't know what I did wrong. After we got back on localizer; ord quickly handed us off to tower and there was no further discussion of it until we had shut down and neither the cap nor I could explain why the a/c did not aggressively turn to intercept the navigation line. I understand there are things I could have changed to keep this from happening. Notably; turn off the autopilot when I see such a situation developing. On the other hand; I'd like to know why the a/c didn't act like I'm used to. Any info in this regard would be appreciated.

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Original NASA ASRS Text

Title: A320 First Officer reports attempting to use NAV to follow the LOC course during intercept at 22 miles. Aircraft did not intercept and overshot the LOC.

Narrative: Weather was reported 150BKN in ORD. We briefed visual backed up by RW28 LOC in ORD. 22 mile downwind. I added all points on the approach including ROCSE and BLUTO to the approach and took out PPOS. BLUTO was the FROM at 1L. We were assigned 360 heading at 5000 feet for base leg. Approx 4 miles prior to LOC; we were assigned a 290 heading to intercept 28 LOC. Autopilot was on. I turned heading to 290. Once we were heading 290 I pushed for NAV. I usually try to intercept in NAV if I am far from the field so I don't get spurious LOC inputs. It was a 22 mile final. When I pushed NAV; the aircraft started to turn back to the right. I pulled the heading knob and selected 290 again and aircraft turned back left. As soon as established in left turn again I pushed for NAV. The only traffic on TCAS was +2300 at our right 3 o'clock and about 5 miles; presumably on final for south complex at ORD. At about .5 miles from course as identified on screen; aircraft seemed to get that it was supposed to intercept and started slow left turn. I should have disconnected at this point and turned it myself. I didn't and don't really have a good reason why. I didn't feel concerned that it wouldn't intercept I guess. NAV was displayed as a FMA. By the time we were actually headed toward ORD; we had overshot by .6 miles as identified on the ND and ORD was asking us if we had started the turn. ORD asked again if we were turning to intercept when we were about .3 back to final. I noticed at that time that the traffic for south complex was now +1.1 at our right 5 o'clock on TCAS at about 2 miles. I don't feel like we had a separation issue but I am wondering what I did wrong so the aircraft wouldn't intercept NAV line in NAV. We were outside the FROM point but that shouldn't matter if my FROM point is in 1L? I've been on the aircraft for approx 7 years and have used this technique for a long time and have never seen the airplane so unaggressive to capture a NAV line. SOP says I can intercept a LOC final in NAV or LOC and I usually use LOC if I am inside 15 miles. If I had to do it over again I would have used LOC but I still don't know what I did wrong. After we got back on LOC; ORD quickly handed us off to tower and there was no further discussion of it until we had shut down and neither the CAP nor I could explain why the a/c did not aggressively turn to intercept the NAV line. I understand there are things I could have changed to keep this from happening. Notably; turn off the autopilot when I see such a situation developing. On the other hand; I'd like to know why the a/c didn't act like I'm used to. Any info in this regard would be appreciated.

Data retrieved from NASA's ASRS site as of April 2012 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.