Narrative:

In cruise flight at FL310 25 NM west of the dfw VOR, the #1 compass suddenly precessed 10 degrees to the right. I asked the first flight attendant if any passenger operated electronic devices were in operation in the cabin. She said that a passenger in seat X had just turned on his laptop computer. I asked that the passenger turn off his laptop computer for a period of 10 mins, which he did. I slaved the #1 compass, and it returned to normal operation for the 10 min period. I then asked that the passenger turn on his computer once again. The #1 compass immediately precessed 8 degrees to the right. The computer was then turned off for a 30 min period during which the #1 compass operation was verified as normal. It was very evident to all on the flight deck that the laptop computer operation was adversely affecting the operation of the #1 compass. I believe that the operation of all passenger operated electronic devices should be prohibited on airlines until the safe operation of all of these devices can be verified. Callback conversation with reporter revealed the following information: reporter reiterated the incident and added that he has sent in another report on a similar incident. He is a safety committee member and claims that many cases have been reported and that he is convinced that many laptop computers do affect heading and navigation instruments. He is extremely concerned with the possible future affects on fly-by-wire aircraft. Computer was an imported pc clone.

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Original NASA ASRS Text

Title: PAX USE OF A LAPTOP COMPUTER CAUSED CAPT'S COMPASS TO PRECESS ABOUT 10 DEGS.

Narrative: IN CRUISE FLT AT FL310 25 NM W OF THE DFW VOR, THE #1 COMPASS SUDDENLY PRECESSED 10 DEGS TO THE R. I ASKED THE FIRST FLT ATTENDANT IF ANY PAX OPERATED ELECTRONIC DEVICES WERE IN OP IN THE CABIN. SHE SAID THAT A PAX IN SEAT X HAD JUST TURNED ON HIS LAPTOP COMPUTER. I ASKED THAT THE PAX TURN OFF HIS LAPTOP COMPUTER FOR A PERIOD OF 10 MINS, WHICH HE DID. I SLAVED THE #1 COMPASS, AND IT RETURNED TO NORMAL OP FOR THE 10 MIN PERIOD. I THEN ASKED THAT THE PAX TURN ON HIS COMPUTER ONCE AGAIN. THE #1 COMPASS IMMEDIATELY PRECESSED 8 DEGS TO THE R. THE COMPUTER WAS THEN TURNED OFF FOR A 30 MIN PERIOD DURING WHICH THE #1 COMPASS OP WAS VERIFIED AS NORMAL. IT WAS VERY EVIDENT TO ALL ON THE FLT DECK THAT THE LAPTOP COMPUTER OP WAS ADVERSELY AFFECTING THE OP OF THE #1 COMPASS. I BELIEVE THAT THE OP OF ALL PAX OPERATED ELECTRONIC DEVICES SHOULD BE PROHIBITED ON AIRLINES UNTIL THE SAFE OP OF ALL OF THESE DEVICES CAN BE VERIFIED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR REITERATED THE INCIDENT AND ADDED THAT HE HAS SENT IN ANOTHER RPT ON A SIMILAR INCIDENT. HE IS A SAFETY COMMITTEE MEMBER AND CLAIMS THAT MANY CASES HAVE BEEN RPTED AND THAT HE IS CONVINCED THAT MANY LAPTOP COMPUTERS DO AFFECT HDG AND NAV INSTS. HE IS EXTREMELY CONCERNED WITH THE POSSIBLE FUTURE AFFECTS ON FLY-BY-WIRE ACFT. COMPUTER WAS AN IMPORTED PC CLONE.

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.