Narrative:

While departing esgg via the laban 1C SID, first officer was hand flying aircraft. Navigation and speed modes selected for flight director. First officer using FMS to navigation. I was backing up navigation with VOR and DME plus ADF. We heard a tone in our headsets (dash DOT dash DOT dash DOT). The navigation and speed modes disengaged and the flight director command bars were removed. Both FMS and short range navigation system gave erroneous indications. We continued on previous heading and system were regained in 10 seconds. The first officer had previously flown test flts for nokia and recognized the tone as that of a nokia mobile telephone. The testing had shown outgoing and incoming calls and incoming pages would cause the problem we experienced. If the aircraft speed was less than 200 KIAS, the nokia phone searching for a ground station would also cause the problems. The cabin attendants advised that shortly after departing esgg they noticed a passenger take a mobile phone out of his carry-on luggage, look at it for a few seconds, and then put it back into the luggage. Callback conversation with reporter revealed the following information: reporter states that he was very fortunate to have the particular first officer aboard since he was immediately aware of the tone from his testing experience. Once above 200 KTS, the cell phone cannot search fast enough to lock on so there was no problem. Apparently the passenger who took out his phone had received a call and he was checking it. Reporter was flying the EMB145 and doing some training for a company and afterwards he had some time to do his own testing. He took his cell phone on the aircraft and used it. There was then no doubt in his mind of the cause of the FMS problem. He had heard of passenger electronic device equipment causing problems with navigation instruments but was quite surprised that the flight director was tripped off. It went all the way to the roll mode, the lowest possible position. Apparently the frequency of the cell phone is close enough to that which they were using to cause the interference.

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Original NASA ASRS Text

Title: FLC OF AN EMB 145 ON DEP HAS A TONE IN THE HEADSETS AT THE SAME TIME AS THE NAV AND SPD MODES OF THE FLT DIRECTOR DISENGAGE AND THE COMMAND BARS REMOVED. THE TONE IS KNOWN TO BE RELATED TO A CELL PHONE BY THE FO. THE INSTS RETURNED TO NORMAL IN ABOUT 10 SECONDS.

Narrative: WHILE DEPARTING ESGG VIA THE LABAN 1C SID, FO WAS HAND FLYING ACFT. NAV AND SPD MODES SELECTED FOR FLT DIRECTOR. FO USING FMS TO NAV. I WAS BACKING UP NAV WITH VOR AND DME PLUS ADF. WE HEARD A TONE IN OUR HEADSETS (DASH DOT DASH DOT DASH DOT). THE NAV AND SPD MODES DISENGAGED AND THE FLT DIRECTOR COMMAND BARS WERE REMOVED. BOTH FMS AND SHORT RANGE NAV SYS GAVE ERRONEOUS INDICATIONS. WE CONTINUED ON PREVIOUS HDG AND SYS WERE REGAINED IN 10 SECONDS. THE FO HAD PREVIOUSLY FLOWN TEST FLTS FOR NOKIA AND RECOGNIZED THE TONE AS THAT OF A NOKIA MOBILE TELEPHONE. THE TESTING HAD SHOWN OUTGOING AND INCOMING CALLS AND INCOMING PAGES WOULD CAUSE THE PROB WE EXPERIENCED. IF THE ACFT SPD WAS LESS THAN 200 KIAS, THE NOKIA PHONE SEARCHING FOR A GND STATION WOULD ALSO CAUSE THE PROBS. THE CABIN ATTENDANTS ADVISED THAT SHORTLY AFTER DEPARTING ESGG THEY NOTICED A PAX TAKE A MOBILE PHONE OUT OF HIS CARRY-ON LUGGAGE, LOOK AT IT FOR A FEW SECONDS, AND THEN PUT IT BACK INTO THE LUGGAGE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THAT HE WAS VERY FORTUNATE TO HAVE THE PARTICULAR FO ABOARD SINCE HE WAS IMMEDIATELY AWARE OF THE TONE FROM HIS TESTING EXPERIENCE. ONCE ABOVE 200 KTS, THE CELL PHONE CANNOT SEARCH FAST ENOUGH TO LOCK ON SO THERE WAS NO PROB. APPARENTLY THE PAX WHO TOOK OUT HIS PHONE HAD RECEIVED A CALL AND HE WAS CHKING IT. RPTR WAS FLYING THE EMB145 AND DOING SOME TRAINING FOR A COMPANY AND AFTERWARDS HE HAD SOME TIME TO DO HIS OWN TESTING. HE TOOK HIS CELL PHONE ON THE ACFT AND USED IT. THERE WAS THEN NO DOUBT IN HIS MIND OF THE CAUSE OF THE FMS PROB. HE HAD HEARD OF PAX ELECTRONIC DEVICE EQUIP CAUSING PROBS WITH NAV INSTS BUT WAS QUITE SURPRISED THAT THE FLT DIRECTOR WAS TRIPPED OFF. IT WENT ALL THE WAY TO THE ROLL MODE, THE LOWEST POSSIBLE POS. APPARENTLY THE FREQ OF THE CELL PHONE IS CLOSE ENOUGH TO THAT WHICH THEY WERE USING TO CAUSE THE 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.