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A B737-300 flight crew rejected their takeoff upon observing uncommanded changes in the stabilizer trim.
| Attributes | |
| ACN | 926021 |
| Time | |
| Date | 201012 |
| Local Time Of Day | 1801-2400 |
| Place | |
| Locale Reference | ZZZ.Airport |
| State Reference | US |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Make Model Name | B737-300 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Takeoff |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Horizontal Stabilizer Control |
| Person 1 | |
| Function | First Officer Pilot Flying |
| Experience | Flight Crew Last 90 Days 217 Flight Crew Type 3600 |
| Events | |
| Anomaly | Aircraft Equipment Problem Critical |
Narrative:
I initiated the takeoff using standard procedures; not doing anything out of the ordinary. Shortly after starting the roll; I felt a click of the [stabilizer] trim and didn't think anything of it; assuming one of us unintentionally hit a trim switch. After the 80 KTS call; I noticed another click of trim; and then another. I confirmed that neither one of my hands was touching the trim and looked at the captain to ensure he was not inputting anything. The captain and I confirmed what we were both seeing. He immediately took the controls and rejected the takeoff. I ensured the rejected takeoff procedures were followed; notified the tower; and we taxied clear. The trim at that time was 0. We estimated the rejected takeoff speed to be approximately 110 KTS so we ran the brake temperature calculations; notified maintenance; and returned to the gate. I heard rumors that this may have been caused by autopilot engagement; but I can ensure anyone that neither the captain nor I reached up and physically moved the autopilot switches. I can't think of anything we did out of the norm to cause this.the only thing I can think of is perhaps practicing rejected takeoffs using other malfunctions than the usual ones; particularly at high speeds. I'm very self-critical and am sincerely open to suggestions as to what we did wrong or could have done better.
Original NASA ASRS Text
Title: A B737-300 flight crew rejected their takeoff upon observing uncommanded changes in the stabilizer trim.
Narrative: I initiated the takeoff using standard procedures; not doing anything out of the ordinary. Shortly after starting the roll; I felt a click of the [stabilizer] trim and didn't think anything of it; assuming one of us unintentionally hit a trim switch. After the 80 KTS call; I noticed another click of trim; and then another. I confirmed that neither one of my hands was touching the trim and looked at the Captain to ensure he was not inputting anything. The Captain and I confirmed what we were both seeing. He immediately took the controls and rejected the takeoff. I ensured the rejected takeoff procedures were followed; notified the Tower; and we taxied clear. The trim at that time was 0. We estimated the rejected takeoff speed to be approximately 110 KTS so we ran the brake temperature calculations; notified Maintenance; and returned to the gate. I heard rumors that this may have been caused by autopilot engagement; but I can ensure anyone that neither the Captain nor I reached up and physically moved the autopilot switches. I can't think of anything we did out of the norm to cause this.The only thing I can think of is perhaps practicing rejected takeoffs using other malfunctions than the usual ones; particularly at high speeds. I'm very self-critical and am sincerely open to suggestions as to what we did wrong or could have done better.
Data retrieved from NASA's ASRS site as of April 2012 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.