Narrative:

While in cruise, we experienced multiple occasions of spontaneous disengagement of the left, center, and right autoplts over several hours of flight while in cruise. (Portable electronic devices authority/authorized.) after due consideration of the sequence of disengagements starting immediately after I had authority/authorized portable electronic devices, I checked with my 'a' line flight attendant. I asked if anyone had turned on any portable electronic devices that might have corresponded with the disconnects. We could not find an immediate link. I then made a PA asking that all portable electronic devices be secured and explained that we were experiencing random disconnects of the aircraft's autoflt system. All passenger complied. The anomaly continued. I asked the 'a' flight attendant to make a more rigorous check of the cabin, looking for any electronic device that might cause this random performance. She reported that there was a passenger in seat XXX that had a significant hearing impairment requiring that he use a hearing aid with headphones. The microprocessor was carried in his shirt pocket. Without it, he could not hear at all. Recalling that interference from portable electronic devices is normally associated with wired devices not contained within the microprocessor case, and further that portable electronic device interference is normally very site specific, I asked the 'a' flight attendant to move the passenger forward not less than 3 rows, but preferably 6 rows. This was accomplished and no further interference occurred for the balance of the trip. The only reason that I did not have the passenger turn off his device was my concern with his being able to hear and follow instructions from the flight attendants in the event of an emergency. In consideration of this, and since we had no further instance of disengagement, were looking at good WX in cvg, and retained the option of securing the device since we knew what the culprit was, I was very comfortable with this course of action. Callback conversation with reporter revealed the following information: the crew was flying a B757- 200 aircraft from sea to cvg. The captain stated the autoflt disconnects began about the time they reached cruise, at FL370. Problems lasted for the next 3-4 hours. The captain further said, during this time the cockpit routine was disrupted excessively, that with 3 autoplts he has never had to operate without at least 1 functioning autoflt system. The captain made a PA announcement, explained the problem to the passenger and requested that all passenger operated electronic devices be turned off. The passenger willingly complied with the captain's request. The problems continued. During a second cabin sweep a flight attendant observed a passenger seated in seat XXX wearing headphones. The passenger told the flight attendant that it was a hearing aid, and that the passenger was quite deaf without it. The captain directed that the passenger be moved. He was reseated to row yy on the right. As soon as the passenger was reseated, the autoflt problems stopped. The crew wrote up the autoflt system and maintenance did an extensive check. No problems were found. The captain has had previous experience with interference caused with passenger operated games which were interconnected with a wiring harness. He states wiring acts as an antenna capable of radiating an RF signal, which is capable of interfering with the aircraft electronics. The captain wonders why the aircraft manufacturer does not properly shield the aircraft electronics to prevent such interference.

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Original NASA ASRS Text

Title: B757 CREW HAD MULTIPLE AUTOPLT DISCONNECTS OF ALL 3 AUTOFLT SYS.

Narrative: WHILE IN CRUISE, WE EXPERIENCED MULTIPLE OCCASIONS OF SPONTANEOUS DISENGAGEMENT OF THE L, CENTER, AND R AUTOPLTS OVER SEVERAL HRS OF FLT WHILE IN CRUISE. (PORTABLE ELECTRONIC DEVICES AUTH.) AFTER DUE CONSIDERATION OF THE SEQUENCE OF DISENGAGEMENTS STARTING IMMEDIATELY AFTER I HAD AUTH PORTABLE ELECTRONIC DEVICES, I CHKED WITH MY 'A' LINE FLT ATTENDANT. I ASKED IF ANYONE HAD TURNED ON ANY PORTABLE ELECTRONIC DEVICES THAT MIGHT HAVE CORRESPONDED WITH THE DISCONNECTS. WE COULD NOT FIND AN IMMEDIATE LINK. I THEN MADE A PA ASKING THAT ALL PORTABLE ELECTRONIC DEVICES BE SECURED AND EXPLAINED THAT WE WERE EXPERIENCING RANDOM DISCONNECTS OF THE ACFT'S AUTOFLT SYS. ALL PAX COMPLIED. THE ANOMALY CONTINUED. I ASKED THE 'A' FLT ATTENDANT TO MAKE A MORE RIGOROUS CHK OF THE CABIN, LOOKING FOR ANY ELECTRONIC DEVICE THAT MIGHT CAUSE THIS RANDOM PERFORMANCE. SHE RPTED THAT THERE WAS A PAX IN SEAT XXX THAT HAD A SIGNIFICANT HEARING IMPAIRMENT REQUIRING THAT HE USE A HEARING AID WITH HEADPHONES. THE MICROPROCESSOR WAS CARRIED IN HIS SHIRT POCKET. WITHOUT IT, HE COULD NOT HEAR AT ALL. RECALLING THAT INTERFERENCE FROM PORTABLE ELECTRONIC DEVICES IS NORMALLY ASSOCIATED WITH WIRED DEVICES NOT CONTAINED WITHIN THE MICROPROCESSOR CASE, AND FURTHER THAT PORTABLE ELECTRONIC DEVICE INTERFERENCE IS NORMALLY VERY SITE SPECIFIC, I ASKED THE 'A' FLT ATTENDANT TO MOVE THE PAX FORWARD NOT LESS THAN 3 ROWS, BUT PREFERABLY 6 ROWS. THIS WAS ACCOMPLISHED AND NO FURTHER INTERFERENCE OCCURRED FOR THE BAL OF THE TRIP. THE ONLY REASON THAT I DID NOT HAVE THE PAX TURN OFF HIS DEVICE WAS MY CONCERN WITH HIS BEING ABLE TO HEAR AND FOLLOW INSTRUCTIONS FROM THE FLT ATTENDANTS IN THE EVENT OF AN EMER. IN CONSIDERATION OF THIS, AND SINCE WE HAD NO FURTHER INSTANCE OF DISENGAGEMENT, WERE LOOKING AT GOOD WX IN CVG, AND RETAINED THE OPTION OF SECURING THE DEVICE SINCE WE KNEW WHAT THE CULPRIT WAS, I WAS VERY COMFORTABLE WITH THIS COURSE OF ACTION. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE CREW WAS FLYING A B757- 200 ACFT FROM SEA TO CVG. THE CAPT STATED THE AUTOFLT DISCONNECTS BEGAN ABOUT THE TIME THEY REACHED CRUISE, AT FL370. PROBS LASTED FOR THE NEXT 3-4 HRS. THE CAPT FURTHER SAID, DURING THIS TIME THE COCKPIT ROUTINE WAS DISRUPTED EXCESSIVELY, THAT WITH 3 AUTOPLTS HE HAS NEVER HAD TO OPERATE WITHOUT AT LEAST 1 FUNCTIONING AUTOFLT SYS. THE CAPT MADE A PA ANNOUNCEMENT, EXPLAINED THE PROB TO THE PAX AND REQUESTED THAT ALL PAX OPERATED ELECTRONIC DEVICES BE TURNED OFF. THE PAX WILLINGLY COMPLIED WITH THE CAPT'S REQUEST. THE PROBS CONTINUED. DURING A SECOND CABIN SWEEP A FLT ATTENDANT OBSERVED A PAX SEATED IN SEAT XXX WEARING HEADPHONES. THE PAX TOLD THE FLT ATTENDANT THAT IT WAS A HEARING AID, AND THAT THE PAX WAS QUITE DEAF WITHOUT IT. THE CAPT DIRECTED THAT THE PAX BE MOVED. HE WAS RESEATED TO ROW YY ON THE R. AS SOON AS THE PAX WAS RESEATED, THE AUTOFLT PROBS STOPPED. THE CREW WROTE UP THE AUTOFLT SYS AND MAINT DID AN EXTENSIVE CHK. NO PROBS WERE FOUND. THE CAPT HAS HAD PREVIOUS EXPERIENCE WITH INTERFERENCE CAUSED WITH PAX OPERATED GAMES WHICH WERE INTERCONNECTED WITH A WIRING HARNESS. HE STATES WIRING ACTS AS AN ANTENNA CAPABLE OF RADIATING AN RF SIGNAL, WHICH IS CAPABLE OF INTERFERING WITH THE ACFT ELECTRONICS. THE CAPT WONDERS WHY THE ACFT MANUFACTURER DOES NOT PROPERLY SHIELD THE ACFT ELECTRONICS TO PREVENT SUCH INTERFERENCE.

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.