 |
37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
|
Medium large transport aircraft after pushback flight crew attempting to resolve trim problem. Told ground crew that they would have them tow them back to gate and when the brakes were released the towbar was cocked and shear bolts broke on towbar due to the bar being misaligned.
| Attributes | |
| ACN | 371867 |
| Time | |
| Date | 199706 |
| Day | Sun |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : pdx |
| State Reference | OR |
| 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 | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Flight Phase | ground : preflight ground : parked |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 240 flight time total : 17000 |
| ASRS Report | 371867 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : commercial pilot : instrument |
| Events | |
| Anomaly | aircraft equipment problem : less severe non adherence : published procedure |
| Independent Detector | other flight crewa |
| Resolutory Action | none taken : detected after the fact |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | other |
Narrative:
After our pushback from the gate, brakes set, engines running, we discovered our main stabilizer trim was inoperative. We troubleshoot it for a few mins, conferred with maintenance over radio and decided to return to gate. The push crew was still hooked up, and I told them I'd have them pull us back into gate. I believed the towbar to be aligned straight with aircraft, but when I released brakes, the towbar slid sideways, shearing 2 shear bolts on fork of towbar. No damage to aircraft or tug, or injuries resulted. Aircraft rolled 3-5 ft before I stopped it. Towbar was disconnected and we taxied into gate. Cause: preoccupation with stabilizer trim problem. Didn't fully assess situation before releasing brakes. Engage brain before action.
Original NASA ASRS Text
Title: MLG ACFT AFTER PUSHBACK FLC ATTEMPTING TO RESOLVE TRIM PROB. TOLD GND CREW THAT THEY WOULD HAVE THEM TOW THEM BACK TO GATE AND WHEN THE BRAKES WERE RELEASED THE TOWBAR WAS COCKED AND SHEAR BOLTS BROKE ON TOWBAR DUE TO THE BAR BEING MISALIGNED.
Narrative: AFTER OUR PUSHBACK FROM THE GATE, BRAKES SET, ENGS RUNNING, WE DISCOVERED OUR MAIN STABILIZER TRIM WAS INOP. WE TROUBLESHOOT IT FOR A FEW MINS, CONFERRED WITH MAINT OVER RADIO AND DECIDED TO RETURN TO GATE. THE PUSH CREW WAS STILL HOOKED UP, AND I TOLD THEM I'D HAVE THEM PULL US BACK INTO GATE. I BELIEVED THE TOWBAR TO BE ALIGNED STRAIGHT WITH ACFT, BUT WHEN I RELEASED BRAKES, THE TOWBAR SLID SIDEWAYS, SHEARING 2 SHEAR BOLTS ON FORK OF TOWBAR. NO DAMAGE TO ACFT OR TUG, OR INJURIES RESULTED. ACFT ROLLED 3-5 FT BEFORE I STOPPED IT. TOWBAR WAS DISCONNECTED AND WE TAXIED INTO GATE. CAUSE: PREOCCUPATION WITH STABILIZER TRIM PROB. DIDN'T FULLY ASSESS SIT BEFORE RELEASING BRAKES. ENGAGE BRAIN BEFORE ACTION.
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.