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After landing, unable to repos stabilizer. Failure of shear rivets on drive train allowed sprocket to detach and stabilizer went to 10 degrees nose up. Was not detected until after landing when trying to repos stabilizer. Aircraft equipment problem. Runaway stabilizer.
| Attributes | |
| ACN | 331678 |
| Time | |
| Date | 199602 |
| Day | Thu |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : sfo |
| State Reference | CA |
| Altitude | agl bound lower : 0 agl bound upper : 0 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | DC-8F |
| Operating Under FAR Part | Part 121 |
| Flight Phase | ground other : taxi |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 35 flight time total : 5000 flight time type : 400 |
| ASRS Report | 331678 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Events | |
| Anomaly | aircraft equipment problem : critical other anomaly other |
| Independent Detector | other flight crewa |
| Resolutory Action | none taken : detected after the fact |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | other |
Narrative:
During after landing flows, the first officer was unable to repos the stabilizer of a DC8-73, as required, from the last selected position during final approach to 2 degrees nose up by any means available in the cockpit. The crew were later unable to agree whether a runaway had occurred but maintenance confirmed that the indication that the stabilizer was immobilized in the full (10 degrees) nose up position was correct. The failure of shear rivets on both sides of the drive train at one point in the drive train mounting/retention system had allowed the small sprocket of the drive train to become free and detached from the rest of the drive train. Simply put, at some point on final approach perhaps just prior to landing and even as late as the flare, the stabilizer which may have runaway was ultimately failed full nose up.
Original NASA ASRS Text
Title: AFTER LNDG, UNABLE TO REPOS STABILIZER. FAILURE OF SHEAR RIVETS ON DRIVE TRAIN ALLOWED SPROCKET TO DETACH AND STABILIZER WENT TO 10 DEGS NOSE UP. WAS NOT DETECTED UNTIL AFTER LNDG WHEN TRYING TO REPOS STABILIZER. ACFT EQUIP PROB. RUNAWAY STABILIZER.
Narrative: DURING AFTER LNDG FLOWS, THE FO WAS UNABLE TO REPOS THE STABILIZER OF A DC8-73, AS REQUIRED, FROM THE LAST SELECTED POS DURING FINAL APCH TO 2 DEGS NOSE UP BY ANY MEANS AVAILABLE IN THE COCKPIT. THE CREW WERE LATER UNABLE TO AGREE WHETHER A RUNAWAY HAD OCCURRED BUT MAINT CONFIRMED THAT THE INDICATION THAT THE STABILIZER WAS IMMOBILIZED IN THE FULL (10 DEGS) NOSE UP POS WAS CORRECT. THE FAILURE OF SHEAR RIVETS ON BOTH SIDES OF THE DRIVE TRAIN AT ONE POINT IN THE DRIVE TRAIN MOUNTING/RETENTION SYS HAD ALLOWED THE SMALL SPROCKET OF THE DRIVE TRAIN TO BECOME FREE AND DETACHED FROM THE REST OF THE DRIVE TRAIN. SIMPLY PUT, AT SOME POINT ON FINAL APCH PERHAPS JUST PRIOR TO LNDG AND EVEN AS LATE AS THE FLARE, THE STABILIZER WHICH MAY HAVE RUNAWAY WAS ULTIMATELY FAILED FULL NOSE UP.
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.