Narrative:

Shortly after localizer capture/localizer track, the heading cursor on the first officer's HSI drifted off selected heading by approximately 30-45 degrees to the right. The heading select knob would not drive the heading cursor on the first officer's HSI. First officer disconnected the autoplt and the approach was flown manually. These events occurred a couple of mi outside of tapps OM. ATC had assigned an airspeed of 180 KTS or better to the marker. Given our situation I thought it prudent to slow to final approach speed and configure as we rejoined the localizer/GS. Unfortunately for the aircraft in trail they were instructed to go around by the tower. After clearing the runway tower gave us a local phone number for ord TRACON. (Never a good sign.) I spoke with a controller who wanted to know why we slowed early and were not able to maintain our assigned airspeed. I explained we experienced a system malfunction and in the process of flying the airplane, limited troubleshooting, checklist completion and frequency congestion I was not able to give them a call. He understood. I asked him if he would pursue this matter further and he said no.

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Original NASA ASRS Text

Title: DISTR BY MALFUNCTIONING FLT MGMNT GUIDANCE SYS, FLT CREW OF MD80 ELECTS TO SLOW ACFT BELOW ASSIGNED AIRSPD TO MITIGATE WORKLOAD. FOLLOWING ACFT TOLD TO GO AROUND DUE TO INADEQUATE SPACING.

Narrative: SHORTLY AFTER LOC CAPTURE/LOC TRACK, THE HEADING CURSOR ON THE FO'S HSI DRIFTED OFF SELECTED HEADING BY APPROX 30-45 DEGS TO THE R. THE HEADING SELECT KNOB WOULD NOT DRIVE THE HEADING CURSOR ON THE FO'S HSI. FO DISCONNECTED THE AUTOPLT AND THE APCH WAS FLOWN MANUALLY. THESE EVENTS OCCURRED A COUPLE OF MI OUTSIDE OF TAPPS OM. ATC HAD ASSIGNED AN AIRSPD OF 180 KTS OR BETTER TO THE MARKER. GIVEN OUR SIT I THOUGHT IT PRUDENT TO SLOW TO FINAL APCH SPD AND CONFIGURE AS WE REJOINED THE LOC/GS. UNFORTUNATELY FOR THE ACFT IN TRAIL THEY WERE INSTRUCTED TO GO AROUND BY THE TWR. AFTER CLRING THE RWY TWR GAVE US A LCL PHONE NUMBER FOR ORD TRACON. (NEVER A GOOD SIGN.) I SPOKE WITH A CTLR WHO WANTED TO KNOW WHY WE SLOWED EARLY AND WERE NOT ABLE TO MAINTAIN OUR ASSIGNED AIRSPD. I EXPLAINED WE EXPERIENCED A SYS MALFUNCTION AND IN THE PROCESS OF FLYING THE AIRPLANE, LIMITED TROUBLESHOOTING, CHKLIST COMPLETION AND FREQ CONGESTION I WAS NOT ABLE TO GIVE THEM A CALL. HE UNDERSTOOD. I ASKED HIM IF HE WOULD PURSUE THIS MATTER FURTHER AND HE SAID NO.

Data retrieved from NASA's ASRS site as of July 2007 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.