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.
Synopsis
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.
Second reporter narrative
Approach gave 330 heading to intercept final for the ILS. [We] took up heading; [were] cleared for ILS approach; and switched to Tower. Armed the ILS and noted FMA annunciated LOC Capture. Autopilot failed to turn to intercept and dropped to heading hold. [We] flew through final. [I] disconnected autopilot and turned back to final intercept heading. Flight director gave a turn to left when final was clearly to right. I bracketed the final and corrected onto course by ignoring the input headings my 'fly to' wings were indicating. [We] got a 'heading' light and a 'no autoland' light as we broke out of IMC and visually flew a final to landing. Indications through rest of final were incorrect to the visual picture. Captain wrote up the navigation equipment after the flight.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.