MD83 flight crew experiences failure of the autopilot to capture the localizer during approach; caus...

Narrative:

Approach control gave us a 330 heading to intercept the localizer and cleared us for the approach. We were then turned over to tower. As we converged with the localizer the FMA annunciated localizer cap and my flight director indicated a turn; but the #2 autopilot did not turn the airplane to join. I stated that we needed to turn right as the airplane continued on the 330 heading. The first officer disengaged the autopilot and made the correction to the right. His flight director; however; was giving incorrect inputs; thus making bracketing back to the localizer very difficult. In the final approach the FMA annunciated 'heading' and 'no autoland' for about a minute then went out. The first officer did a fine job of flying the airplane down to the runway and made an uneventful landing in 400 ft ovc and 7 miles visibility weather. I did not query ATC if they were having problems with the ILS and we wrote up the #2 autopilot and flight director. In retrospect; I should have alerted the tower controller of our difficulties; but we were quite involved in the flying of the airplane.

Original NASA ASRS Text

Title: MD83 flight crew experiences failure of the autopilot to capture the LOC during approach; causing an overshoot. The First Officer takes over manually and continues the approach to landing.

Narrative: Approach Control gave us a 330 heading to intercept the localizer and cleared us for the approach. We were then turned over to Tower. As we converged with the localizer the FMA annunciated LOC CAP and my flight director indicated a turn; but the #2 autopilot did not turn the airplane to join. I stated that we needed to turn right as the airplane continued on the 330 heading. The First Officer disengaged the autopilot and made the correction to the right. His flight director; however; was giving incorrect inputs; thus making bracketing back to the localizer very difficult. In the final approach the FMA annunciated 'heading' and 'no autoland' for about a minute then went out. The First Officer did a fine job of flying the airplane down to the runway and made an uneventful landing in 400 FT OVC and 7 miles visibility weather. I did not query ATC if they were having problems with the ILS and we wrote up the #2 autopilot and flight director. In retrospect; I should have alerted the Tower Controller of our difficulties; but we were quite involved in the flying of the airplane.

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.

Attributes
ACN	974399
Time
Date	201110
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Daylight
Aircraft 1
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Flight Plan	IFR
Component
Aircraft Component	Approach Coupler
Person 1
Function	Pilot Not Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Pilot Flying First Officer
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Track / Heading All Types

MD83 flight crew experiences failure of the autopilot to capture the localizer during approach; causing an overshoot. The first officer takes over manually and continues the approach to landing.