Narrative:

Flying an aircraft with an open write-up of autoplt will not engage, we experienced a normal ground check and altitude capture. While we were distracted with an RMI erroneous indication the aircraft climbed to FL315 with the green altitude hold light illuminated. Supplemental information from acn 403922: the autoplt tested correctly on preflight and then engaged normally in the climb out of cvg. The autoplt correctly captured the altitude at FL310, and made a normal leveloff. The altitude hold light illuminated. Approximately 5 mins after leveloff, while the crew was troubleshooting an inoperative #2 navigation needle, ZID requested us to confirm our flight level. The autoplt altitude hold had failed and the aircraft had slowly climbed to FL315. The altitude hold light was still illuminated and the autoplt did not disengage. The aircraft was then corrected to FL310 and the autoplt disengaged. Due to the late hour of the flight, fatigue may have been a contributing factor, as well as the distraction of other malfunctioning system at the time. This was the first of this type of occurrence I have observed in 10 yrs on this type aircraft. Supplemental information from acn 403925: so was making a report to company radio.

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Original NASA ASRS Text

Title: B727 ACFT IN CRUISE, FLC DISTRACTED BY RMI INDICATION, AUTOPLT DIDN'T HOLD ALT AND ACFT CLBED 500 FT BEFORE ATC CTLR CAUGHT ALT DEV.

Narrative: FLYING AN ACFT WITH AN OPEN WRITE-UP OF AUTOPLT WILL NOT ENGAGE, WE EXPERIENCED A NORMAL GND CHK AND ALT CAPTURE. WHILE WE WERE DISTRACTED WITH AN RMI ERRONEOUS INDICATION THE ACFT CLBED TO FL315 WITH THE GREEN ALT HOLD LIGHT ILLUMINATED. SUPPLEMENTAL INFO FROM ACN 403922: THE AUTOPLT TESTED CORRECTLY ON PREFLT AND THEN ENGAGED NORMALLY IN THE CLB OUT OF CVG. THE AUTOPLT CORRECTLY CAPTURED THE ALT AT FL310, AND MADE A NORMAL LEVELOFF. THE ALT HOLD LIGHT ILLUMINATED. APPROX 5 MINS AFTER LEVELOFF, WHILE THE CREW WAS TROUBLESHOOTING AN INOP #2 NAV NEEDLE, ZID REQUESTED US TO CONFIRM OUR FLT LEVEL. THE AUTOPLT ALT HOLD HAD FAILED AND THE ACFT HAD SLOWLY CLBED TO FL315. THE ALT HOLD LIGHT WAS STILL ILLUMINATED AND THE AUTOPLT DID NOT DISENGAGE. THE ACFT WAS THEN CORRECTED TO FL310 AND THE AUTOPLT DISENGAGED. DUE TO THE LATE HR OF THE FLT, FATIGUE MAY HAVE BEEN A CONTRIBUTING FACTOR, AS WELL AS THE DISTR OF OTHER MALFUNCTIONING SYS AT THE TIME. THIS WAS THE FIRST OF THIS TYPE OF OCCURRENCE I HAVE OBSERVED IN 10 YRS ON THIS TYPE ACFT. SUPPLEMENTAL INFO FROM ACN 403925: SO WAS MAKING A RPT TO COMPANY RADIO.

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.