Narrative:

Approximately 3 hours into our flight, level at FL320 with autoplt #1 engaged, the FMA pitch window annunciation began to cycle between altitude hold and vertical speed. Shortly thereafter, vertical speed remained annunciated and the aircraft began a 100 FPM climb. The captain corrected for the deviation, but found that the autoplt would not enter the altitude hold mode -- either with the altitude capture feature, or by manually selecting altitude hold with the vertical speed thumbwheel. The captain elected to switch to autoplt #2 and was able to engage the altitude hold mode, leading us to believe that the problem was with autoplt #1. During descent, with both autoplts disconnected, the flight mode annunciators again would not annunciate altitude hold, and instead would switch from altitude capture to vertical speed during the leveloff. We did not believe any altdevs occurred. My concern is that this malfunction had been written up in the log 4 times prior to our flight. Each time a different component was removed and replaced -- over an 11 day period -- yet the problem persisted.

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Original NASA ASRS Text

Title: A DC10-10 IS RPTED AS HAVING A CHRONIC PITCH CHANNEL FLT MODE ANNUNCIATOR MALFUNCTION WITH 5 RPTS IN 11 DAYS AND NUMEROUS UNITS REPLACED.

Narrative: APPROX 3 HRS INTO OUR FLT, LEVEL AT FL320 WITH AUTOPLT #1 ENGAGED, THE FMA PITCH WINDOW ANNUNCIATION BEGAN TO CYCLE BTWN ALT HOLD AND VERT SPD. SHORTLY THEREAFTER, VERT SPD REMAINED ANNUNCIATED AND THE ACFT BEGAN A 100 FPM CLB. THE CAPT CORRECTED FOR THE DEV, BUT FOUND THAT THE AUTOPLT WOULD NOT ENTER THE ALT HOLD MODE -- EITHER WITH THE ALT CAPTURE FEATURE, OR BY MANUALLY SELECTING ALT HOLD WITH THE VERT SPD THUMBWHEEL. THE CAPT ELECTED TO SWITCH TO AUTOPLT #2 AND WAS ABLE TO ENGAGE THE ALT HOLD MODE, LEADING US TO BELIEVE THAT THE PROB WAS WITH AUTOPLT #1. DURING DSCNT, WITH BOTH AUTOPLTS DISCONNECTED, THE FLT MODE ANNUNCIATORS AGAIN WOULD NOT ANNUNCIATE ALT HOLD, AND INSTEAD WOULD SWITCH FROM ALT CAPTURE TO VERT SPD DURING THE LEVELOFF. WE DID NOT BELIEVE ANY ALTDEVS OCCURRED. MY CONCERN IS THAT THIS MALFUNCTION HAD BEEN WRITTEN UP IN THE LOG 4 TIMES PRIOR TO OUR FLT. EACH TIME A DIFFERENT COMPONENT WAS REMOVED AND REPLACED -- OVER AN 11 DAY PERIOD -- YET THE PROB PERSISTED.

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.