Narrative:

While flying level in cruise at FL410; roughly 100 NM west of ZZZ; one of the passengers came forward to advise there was a beeping noise in the cabin. I had noticed the noise just prior to the passenger stepping forward; and was not sure whether it was the flight phone or an electronic device one of the passengers may have had. When he stepped forward; I advised him it was the flight phone. The captain took the radios and I picked up my flight phone on the flight deck to see if there was an inbound call even though my phone was not ringing. Immediately thereafter; while I was looking at my phone; I heard the captain take a frequency change. As he changed the frequency; the aircraft started into a bank; which I initially thought was a waypoint passage. It quickly became apparent that was not the case as I started to notice a pitch change with peripheral vision and kinesthetic sense. When I looked up at the pfd it confirmed we were descending and in a right bank of 40 to 45 degrees. At that point I noticed that the captain was already taking corrective action by smoothly rolling the airplane level and then returning to assigned altitude and course. We were flying in straight and level cruise 5 knots below mmo when the excursion began and we never exceeded mmo. (I remember being silently impressed with how calmly and smoothly he recovered the airplane considering the angle of bank and high altitude.) he then advised ATC that he was checking on and correcting to flight level 410; to which ATC responded something similar to; 'what?' by that time we were back on course and altitude and the captain told them he was level at FL410. No mention of altitude deviation was ever made by ATC. I then pulled out the checklist and reviewed it for autopilot malfunction; but there were really no appropriate checklists to accomplish. I neither heard nor saw any annunciation that the autopilot had disconnected. One of the passengers came forward and asked if everything was alright. I informed him that the autopilot had disconnected without annunciating a disconnection and what had occurred was a direct result of that. After the flight; while discussing the event with the passengers; the one seated in the seat next to the flight phone said that the plane started to roll when he pushed the 'end call' button on the flight phone to get it to stop ringing. The passenger seated immediately to his left; who had identified himself as a pilot; said that he was watching the other passenger and that it did start to roll when he pushed the 'end call' button. It seems bizarre that the flight phone could in any way affect autopilot function; but it also seems bizarre that the autopilot would turn off without annunciating at the exact same time that my attention was diverted to the phone and the captain was in the middle of a frequency change; and the passenger was pressing the 'end call' button. Contributing factors: the diversion of the passenger and the ringing flight phone for me and the frequency change for the captain caused us both to miss the initial roll. Corrective actions and perceptions: I thought the captain did an excellent job recovering from what essentially became a high altitude unusual attitude. (I would stop short of calling it a high altitude upset.) I feel that we were actually well prepared to handle the problem as a crew even though I had very little to do with the recovery because I had noticed the attitude change at approximately the same time and didn't say anything only because of the captain's immediate and correct corrective action.

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Original NASA ASRS Text

Title: A CE560XL FLT CREW CRUISING AT 41000 FT EXPERIENCED AN UNANNUNCIATED AUTOPILOT DISCONNECT AND SUBSEQUENT ALT AND COURSE DEVIATIONS INCLUDING A 45 DEG BANK. THE REPORTER LINKS THE DISCONNECT TO THE FLIGHT PHONE SYSTEM.

Narrative: WHILE FLYING LEVEL IN CRUISE AT FL410; ROUGHLY 100 NM WEST OF ZZZ; ONE OF THE PASSENGERS CAME FORWARD TO ADVISE THERE WAS A BEEPING NOISE IN THE CABIN. I HAD NOTICED THE NOISE JUST PRIOR TO THE PASSENGER STEPPING FORWARD; AND WAS NOT SURE WHETHER IT WAS THE FLIGHT PHONE OR AN ELECTRONIC DEVICE ONE OF THE PASSENGERS MAY HAVE HAD. WHEN HE STEPPED FORWARD; I ADVISED HIM IT WAS THE FLIGHT PHONE. THE CAPTAIN TOOK THE RADIOS AND I PICKED UP MY FLIGHT PHONE ON THE FLIGHT DECK TO SEE IF THERE WAS AN INBOUND CALL EVEN THOUGH MY PHONE WAS NOT RINGING. IMMEDIATELY THEREAFTER; WHILE I WAS LOOKING AT MY PHONE; I HEARD THE CAPTAIN TAKE A FREQUENCY CHANGE. AS HE CHANGED THE FREQUENCY; THE AIRCRAFT STARTED INTO A BANK; WHICH I INITIALLY THOUGHT WAS A WAYPOINT PASSAGE. IT QUICKLY BECAME APPARENT THAT WAS NOT THE CASE AS I STARTED TO NOTICE A PITCH CHANGE WITH PERIPHERAL VISION AND KINESTHETIC SENSE. WHEN I LOOKED UP AT THE PFD IT CONFIRMED WE WERE DESCENDING AND IN A RIGHT BANK OF 40 TO 45 DEGREES. AT THAT POINT I NOTICED THAT THE CAPTAIN WAS ALREADY TAKING CORRECTIVE ACTION BY SMOOTHLY ROLLING THE AIRPLANE LEVEL AND THEN RETURNING TO ASSIGNED ALTITUDE AND COURSE. WE WERE FLYING IN STRAIGHT AND LEVEL CRUISE 5 KNOTS BELOW MMO WHEN THE EXCURSION BEGAN AND WE NEVER EXCEEDED MMO. (I REMEMBER BEING SILENTLY IMPRESSED WITH HOW CALMLY AND SMOOTHLY HE RECOVERED THE AIRPLANE CONSIDERING THE ANGLE OF BANK AND HIGH ALTITUDE.) HE THEN ADVISED ATC THAT HE WAS CHECKING ON AND CORRECTING TO FLIGHT LEVEL 410; TO WHICH ATC RESPONDED SOMETHING SIMILAR TO; 'WHAT?' BY THAT TIME WE WERE BACK ON COURSE AND ALTITUDE AND THE CAPTAIN TOLD THEM HE WAS LEVEL AT FL410. NO MENTION OF ALTITUDE DEVIATION WAS EVER MADE BY ATC. I THEN PULLED OUT THE CHECKLIST AND REVIEWED IT FOR AUTOPILOT MALFUNCTION; BUT THERE WERE REALLY NO APPROPRIATE CHECKLISTS TO ACCOMPLISH. I NEITHER HEARD NOR SAW ANY ANNUNCIATION THAT THE AUTOPILOT HAD DISCONNECTED. ONE OF THE PASSENGERS CAME FORWARD AND ASKED IF EVERYTHING WAS ALRIGHT. I INFORMED HIM THAT THE AUTOPILOT HAD DISCONNECTED WITHOUT ANNUNCIATING A DISCONNECTION AND WHAT HAD OCCURRED WAS A DIRECT RESULT OF THAT. AFTER THE FLIGHT; WHILE DISCUSSING THE EVENT WITH THE PASSENGERS; THE ONE SEATED IN THE SEAT NEXT TO THE FLIGHT PHONE SAID THAT THE PLANE STARTED TO ROLL WHEN HE PUSHED THE 'END CALL' BUTTON ON THE FLIGHT PHONE TO GET IT TO STOP RINGING. THE PASSENGER SEATED IMMEDIATELY TO HIS LEFT; WHO HAD IDENTIFIED HIMSELF AS A PILOT; SAID THAT HE WAS WATCHING THE OTHER PASSENGER AND THAT IT DID START TO ROLL WHEN HE PUSHED THE 'END CALL' BUTTON. IT SEEMS BIZARRE THAT THE FLIGHT PHONE COULD IN ANY WAY AFFECT AUTOPILOT FUNCTION; BUT IT ALSO SEEMS BIZARRE THAT THE AUTOPILOT WOULD TURN OFF WITHOUT ANNUNCIATING AT THE EXACT SAME TIME THAT MY ATTENTION WAS DIVERTED TO THE PHONE AND THE CAPTAIN WAS IN THE MIDDLE OF A FREQUENCY CHANGE; AND THE PASSENGER WAS PRESSING THE 'END CALL' BUTTON. CONTRIBUTING FACTORS: THE DIVERSION OF THE PASSENGER AND THE RINGING FLIGHT PHONE FOR ME AND THE FREQUENCY CHANGE FOR THE CAPTAIN CAUSED US BOTH TO MISS THE INITIAL ROLL. CORRECTIVE ACTIONS AND PERCEPTIONS: I THOUGHT THE CAPTAIN DID AN EXCELLENT JOB RECOVERING FROM WHAT ESSENTIALLY BECAME A HIGH ALTITUDE UNUSUAL ATTITUDE. (I WOULD STOP SHORT OF CALLING IT A HIGH ALTITUDE UPSET.) I FEEL THAT WE WERE ACTUALLY WELL PREPARED TO HANDLE THE PROBLEM AS A CREW EVEN THOUGH I HAD VERY LITTLE TO DO WITH THE RECOVERY BECAUSE I HAD NOTICED THE ATTITUDE CHANGE AT APPROXIMATELY THE SAME TIME AND DIDN'T SAY ANYTHING ONLY BECAUSE OF THE CAPTAIN'S IMMEDIATE AND CORRECT CORRECTIVE ACTION.

Data retrieved from NASA's ASRS site as of May 2009 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.