A B767-300 TECHNICIAN REPORTS OF AN ETOPS FLIGHT CREW LOG ENTRY THAT CABIN SEAT XXF LUMBAR PUSHBUTTON CONTROL UNIT ON THE ARMREST CONSOLE BEGAN TO SMOKE IN-FLIGHT. B777-200'S ARE ALSO AFFECTED.

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CREW RPT VIA LOG ENTRY THAT SEAT XXF LUMBAR CTL PANEL WAS DEFECTIVE AND NEEDED TO BE REPLACED. THE MECH DEBRIEFED THE CREW AND FOUND DURING FLT THE CTL STARTED TO SMOKE. ONE OF THE FLT CREW USED A SWISS TOOL TO REMOVE THE FAILED PART. THE FLT CONTINUED TO ZZZ FROM ZZZZ. THIS PART HAS FAILED IN THE PAST AND IS ONLY BEING UPGRADED THROUGH ATTRITION. UPGRADED LUMBAR CTLS SHOULD BE INSTALLED IMMEDIATELY. SUPPLEMENTAL INFO FROM ACN 776594: UPGRADE ALL LUMBAR CTLS WITH UNIT THAT DOES NOT OVERHEAT AND POSSIBLY CAUSE A FIRE INFLT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED THE LUMBAR SEAT CONTROL UNIT ON THE ARMREST HAS A MEMBRANE COVERING OVER THE PUSHBUTTON DOME SPRING SWITCHES. THESE SPRING SWITCHES BECOME LOOSE AND SLIDE ACROSS THE CONTACTS; ARCING; SHORTING AND THEN MELTING THIS MEMBRANE; CAUSING HEAT; SMOKE AND FIRE AT THE ARMREST. REPORTER ALSO STATED A RECENT CABIN INCIDENT OF SMOKE AND FIRE REQUIRED THE USE OF PORTABLE HALON FIRE BOTTLE TO EXTINGUISH THE FIRE IN THE SEAT CONTROL UNIT. THIS CONTROL UNIT ON THE ARMREST CAN BE REMOVED BY UNLOCKING THE UNIT USING A SMALL ALLEN-TYPE WRENCH; LIFTING THE UNIT OUT OF THE ARMREST CONSOLE AND DISCONNECTING THE CLIP TYPE ELECTRICAL CONNECTOR FROM THE BOTTOM OF THE CONTROLLER. THE CABIN CREW DID NOT HAVE THIS TYPE OF WRENCH ON BOARD. REPORTER FURTHER ADDED; HIS COMPANY'S QUALITY ASSURANCE AND ENGINEERING KNOW OF THE PROBLEMS; BUT HAVE DONE LITTLE TO EXPEDITE THE REMOVAL OF THE OLDER MODEL CONTROL UNITS STILL ON-BOARD THEIR ACFT. REPORTER ALSO BELIEVES THIS IS AN INDUSTRY ISSUE AFFECTING NOT ONLY HIS CARRIER'S FLEET OF B-777 AND B-767; BUT OTHER CARRIERS' AS WELL. OVERWATER ETOPS FLIGHTS ARE MOST VULNERABLE.