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DC9-50 flight crew experienced an involuntary turn by the autoplt during cruise. Autoplt reacted normally after the captain asked passenger to turn off any ped's. However, later learned that a cell phone in overhead bin was heard during the time of the autoplt problem.
| Attributes | |
| ACN | 504194 |
| Time | |
| Date | 200103 |
| Day | Sun |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | airport : grr.airport |
| State Reference | MI |
| Altitude | msl single value : 31000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | artcc : zau.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | DC-9 50 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other vortac |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp pilot : cfi pilot : commercial pilot : flight engineer |
| Experience | flight time last 90 days : 200 flight time total : 18000 flight time type : 9000 |
| ASRS Report | 504194 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : commercial pilot : multi engine |
| Events | |
| Anomaly | aircraft equipment problem : less severe inflight encounter other non adherence : clearance other spatial deviation |
| Independent Detector | aircraft equipment other aircraft equipment : autoplt reaction other other : 3 |
| Resolutory Action | aircraft : equipment problem dissipated flight crew : returned to intended or assigned course |
| Consequence | Other |
| Supplementary | |
| Problem Areas | Passenger Human Performance Aircraft |
| Primary Problem | Passenger Human Performance |
Narrative:
While at cruise at FL310, the autoplt made an uncommanded turn of 15 degrees at 1/2 standard rate, autoplt in turn rate mode. Heading select switch off, VOR/localizer track not engaged with both RMI's agreeing before and after the turn. The autoplt continued to function normally for the rest of the flight. I asked the lead flight attendant at the time to do a ped walk. She returned to say that several usual type of ped's were in use. I made a PA asking that ped's be depwred and we completed the flight uneventfully. I subsequently learned from the lead flight attendant that her husband (who was a passenger on this flight) reported to her that he heard a cell phone ringing in an overhead bin at about this time. Since I only learned about this later, it was not included in my logbook write-up on the autoplt.
Original NASA ASRS Text
Title: DC9-50 FLC EXPERIENCED AN INVOLUNTARY TURN BY THE AUTOPLT DURING CRUISE. AUTOPLT REACTED NORMALLY AFTER THE CAPT ASKED PAX TO TURN OFF ANY PED'S. HOWEVER, LATER LEARNED THAT A CELL PHONE IN OVERHEAD BIN WAS HEARD DURING THE TIME OF THE AUTOPLT PROB.
Narrative: WHILE AT CRUISE AT FL310, THE AUTOPLT MADE AN UNCOMMANDED TURN OF 15 DEGS AT 1/2 STANDARD RATE, AUTOPLT IN TURN RATE MODE. HDG SELECT SWITCH OFF, VOR/LOC TRACK NOT ENGAGED WITH BOTH RMI'S AGREEING BEFORE AND AFTER THE TURN. THE AUTOPLT CONTINUED TO FUNCTION NORMALLY FOR THE REST OF THE FLT. I ASKED THE LEAD FLT ATTENDANT AT THE TIME TO DO A PED WALK. SHE RETURNED TO SAY THAT SEVERAL USUAL TYPE OF PED'S WERE IN USE. I MADE A PA ASKING THAT PED'S BE DEPWRED AND WE COMPLETED THE FLT UNEVENTFULLY. I SUBSEQUENTLY LEARNED FROM THE LEAD FLT ATTENDANT THAT HER HUSBAND (WHO WAS A PAX ON THIS FLT) RPTED TO HER THAT HE HEARD A CELL PHONE RINGING IN AN OVERHEAD BIN AT ABOUT THIS TIME. SINCE I ONLY LEARNED ABOUT THIS LATER, IT WAS NOT INCLUDED IN MY LOGBOOK WRITE-UP ON THE AUTOPLT.
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.