Narrative:

Climbing through FL344 for FL370 in smooth air, the aircraft experienced a loud momentary thump jolt followed by a momentary vibration. It was a hard sudden thump jolt that displaced the aircraft and had an audible thump noise. Simultaneously with this hard jolt, the left aft overwing emergency exit open ECAM warning illuminated and remained on. We immediately leveled off and noted the cabin pressure was normal and remaining normal. The hard jolt was significant enough to ask the 'a' flight attendant to come to the flight deck and confirm there were no injuries and verify the cabin was secure. The 'a' flight attendant verified no injuries and advised the white slide inflation light adjacent to the left overwing emergency exits was illuminated. As a precaution, we descended to the MEA, declared an emergency and returned to sea. Approximately 1/2 way back to sea, the ECAM warning extinguished. Flight attendants advised that is approximately the same time the white slide inflation light extinguished as well. Overweight landing accomplished at sea. Landing weight was 143400 pounds. Landing was normal. Callback conversation with reporter revealed the following information: the reporter states that the climb up to the time of the incident was smooth and that the jolt experienced was much like crossing wake turbulence with perpendicular motion. He states that the crew wondered whether they had impacted something or some part had separated from the aircraft and discussed the possibility of loss of pressurization and donning of oxygen masks. The FAA controller made no mention of other traffic in the vicinity of the involved aircraft. On checking with maintenance at a later date, the reporter learned that nothing was found to be out of the ordinary on ground inspection. The aircraft was flown the next day, and that flight crew experienced the same malfunction of ECAM warning lights during an encounter with moderate chop. As a result, a sensor or switch at the left aft emergency overwing exit was replaced and the reporter knows of no further action or difficulties with the aircraft. He states also that he is unaware of this type of occurrence with this aircraft or any other of the A320 fleet.

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Original NASA ASRS Text

Title: A320 CREW EXPERIENCES JOLT VIBRATION ACCOMPANIED BY ECAM MESSAGE WARNING FOR L OVERWING EXIT. FLC ELECTS TO RETURN TO SEA.

Narrative: CLBING THROUGH FL344 FOR FL370 IN SMOOTH AIR, THE ACFT EXPERIENCED A LOUD MOMENTARY THUMP JOLT FOLLOWED BY A MOMENTARY VIBRATION. IT WAS A HARD SUDDEN THUMP JOLT THAT DISPLACED THE ACFT AND HAD AN AUDIBLE THUMP NOISE. SIMULTANEOUSLY WITH THIS HARD JOLT, THE L AFT OVERWING EMER EXIT OPEN ECAM WARNING ILLUMINATED AND REMAINED ON. WE IMMEDIATELY LEVELED OFF AND NOTED THE CABIN PRESSURE WAS NORMAL AND REMAINING NORMAL. THE HARD JOLT WAS SIGNIFICANT ENOUGH TO ASK THE 'A' FLT ATTENDANT TO COME TO THE FLT DECK AND CONFIRM THERE WERE NO INJURIES AND VERIFY THE CABIN WAS SECURE. THE 'A' FLT ATTENDANT VERIFIED NO INJURIES AND ADVISED THE WHITE SLIDE INFLATION LIGHT ADJACENT TO THE L OVERWING EMER EXITS WAS ILLUMINATED. AS A PRECAUTION, WE DSNDED TO THE MEA, DECLARED AN EMER AND RETURNED TO SEA. APPROX 1/2 WAY BACK TO SEA, THE ECAM WARNING EXTINGUISHED. FLT ATTENDANTS ADVISED THAT IS APPROX THE SAME TIME THE WHITE SLIDE INFLATION LIGHT EXTINGUISHED AS WELL. OVERWT LNDG ACCOMPLISHED AT SEA. LNDG WT WAS 143400 LBS. LNDG WAS NORMAL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATES THAT THE CLB UP TO THE TIME OF THE INCIDENT WAS SMOOTH AND THAT THE JOLT EXPERIENCED WAS MUCH LIKE XING WAKE TURB WITH PERPENDICULAR MOTION. HE STATES THAT THE CREW WONDERED WHETHER THEY HAD IMPACTED SOMETHING OR SOME PART HAD SEPARATED FROM THE ACFT AND DISCUSSED THE POSSIBILITY OF LOSS OF PRESSURIZATION AND DONNING OF OXYGEN MASKS. THE FAA CTLR MADE NO MENTION OF OTHER TFC IN THE VICINITY OF THE INVOLVED ACFT. ON CHKING WITH MAINT AT A LATER DATE, THE RPTR LEARNED THAT NOTHING WAS FOUND TO BE OUT OF THE ORDINARY ON GND INSPECTION. THE ACFT WAS FLOWN THE NEXT DAY, AND THAT FLC EXPERIENCED THE SAME MALFUNCTION OF ECAM WARNING LIGHTS DURING AN ENCOUNTER WITH MODERATE CHOP. AS A RESULT, A SENSOR OR SWITCH AT THE L AFT EMER OVERWING EXIT WAS REPLACED AND THE RPTR KNOWS OF NO FURTHER ACTION OR DIFFICULTIES WITH THE ACFT. HE STATES ALSO THAT HE IS UNAWARE OF THIS TYPE OF OCCURRENCE WITH THIS ACFT OR ANY OTHER OF THE A320 FLEET.

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.