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37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
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Aircraft position roll yaw a concern until first officer realizes that the rudder trim was still activated after having released the rudder trim switch.
| Attributes | |
| ACN | 262802 |
| Time | |
| Date | 199401 |
| Day | Thu |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : bna |
| State Reference | TN |
| Altitude | msl bound lower : 37000 msl bound upper : 37000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zme |
| Operator | common carrier : air carrier |
| Make Model Name | B737-400 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | cruise other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : flight engineer pilot : atp pilot : instrument |
| Experience | flight time last 90 days : 125 flight time total : 14000 flight time type : 3000 |
| ASRS Report | 262802 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : commercial |
| Events | |
| Anomaly | aircraft equipment problem : critical |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | flight crew : overcame equipment problem |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | Pilot Deviation |
Narrative:
The first officer was flying the aircraft on autoplt at 37000 ft, when he introduced a small amount of right rudder trim. Very shortly, (3-4 seconds), the aircraft started a smooth yaw to the left and a roll to the right. Bank angle approached 20 degrees. The autoplt remained engaged until the first officer disconnected it and started the trim back to the left. The trim reached at least 9 units of right trim before being rectred. The aircraft was retrimmed and autoplt was re-engaged with no further incident. Callback conversation with reporter revealed the following information: reporter called back to state that the aircraft was a B-737-400. The first officer had only 'tweaked' the rudder trim a bit to center the ball and it might be surmised that the trim switch had some form of internal problem that allowed the rudder trim to go to the near 9 degrees position after the switch was released. The item was written up in the logbook but the post-flight findings are not known.
Original NASA ASRS Text
Title: ACFT POS ROLL YAW A CONCERN UNTIL FO REALIZES THAT THE RUDDER TRIM WAS STILL ACTIVATED AFTER HAVING RELEASED THE RUDDER TRIM SWITCH.
Narrative: THE FO WAS FLYING THE ACFT ON AUTOPLT AT 37000 FT, WHEN HE INTRODUCED A SMALL AMOUNT OF R RUDDER TRIM. VERY SHORTLY, (3-4 SECONDS), THE ACFT STARTED A SMOOTH YAW TO THE L AND A ROLL TO THE R. BANK ANGLE APCHED 20 DEGS. THE AUTOPLT REMAINED ENGAGED UNTIL THE FO DISCONNECTED IT AND STARTED THE TRIM BACK TO THE L. THE TRIM REACHED AT LEAST 9 UNITS OF R TRIM BEFORE BEING RECTRED. THE ACFT WAS RETRIMMED AND AUTOPLT WAS RE-ENGAGED WITH NO FURTHER INCIDENT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR CALLED BACK TO STATE THAT THE ACFT WAS A B-737-400. THE FO HAD ONLY 'TWEAKED' THE RUDDER TRIM A BIT TO CTR THE BALL AND IT MIGHT BE SURMISED THAT THE TRIM SWITCH HAD SOME FORM OF INTERNAL PROB THAT ALLOWED THE RUDDER TRIM TO GO TO THE NEAR 9 DEGS POS AFTER THE SWITCH WAS RELEASED. THE ITEM WAS WRITTEN UP IN THE LOGBOOK BUT THE POST-FLT FINDINGS ARE NOT KNOWN.
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.