A B767-300 ACFT ENCOUNTERED A MOMENTARY LIGHT 'SHUDDER' AND PRONOUNCED 'THUMP;' AS THE RIGHT OVERWING ESCAPE SLIDE DEPLOYED INFLT; RESULTING IN AN AIR TURNBACK.

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I WAS ASSIGNED TO ACFT X AND GIVEN THE TASK OF INSPECTION OF THE R OVERWING ESCAPE SLIDE DOOR LATCH MECHANISM. AN INSPECTOR AND I FOUND SEVERAL RODS; ROD ENDS; JAM NUTS; AND 1 LATCH TO BE CORRODED. OVER THE COURSE OF 4 DAYS; I HELPED REPLACE THE CORRODED PARTS WITH NEW PARTS. THE INSTRUCTION CARDS ACCOMPANY THE ROUTINE INSPECTION CARD AND MAINT MANUAL REFS WERE ADHERED TO IN THE ACCOMPLISHMENT OF THESE TASKS. EXTREME CARE WAS TAKEN TO MAINTAIN THE ORIGINAL DIMENSIONS ON ALL PARTS REPLACED. THERE WERE INSPECTION BUYBACKS FOR EACH PART REPLACED. ON DAY #1; I ALSO CLOSED AND LATCHED THE R OVERWING ESCAPE SLIDE DOOR; AGAIN FOLLOWING THE PROC SPELLED OUT IN THE ROUTINE WORK CARD. ANOTHER A&P MECH ASSISTED ME BY TUCKING IN THE SEAL ALONG THE LEADING EDGE OF THE DOOR; ASSURING THAT THE LEADING EDGE OF THE DOOR WAS NOT OVER FLUSH. THE LEADING EDGE OF THE DOOR WAS; IN FACT; SLIGHTLY UNDER FLUSH. THE CLOSING OF THE DOOR AND THE LATCHING AND LOCKING PROC WAS WITNESSED BY AN INSPECTOR. 2 DAYS LATER; DURING ITS THIRD FLT FOLLOWING THE AFOREMENTIONED MAINT ACTIONS; THE R OVERWING EMER EXIT SLIDE DEPLOYED AND WAS TORN FROM THE ACFT. THE ACFT RETURNED SAFELY TO ZZZ. AFTERWARDS; I WAS ABLE TO EXAMINE THE EMER ESCAPE SLIDE DOOR. IT IS CLR; UPON INSPECTION OF THE DOOR; THAT THE DOOR HAD BEEN SECURELY LOCKED. ALL 4 LOCK PINS BROKE WHEN THE DOOR WAS FORCED OPEN. 2 OF THE LOCK PINS WERE STILL HELD IN THE JAWS OF THE LATCHES. GIVEN THAT I HAVE NO DOUBT THAT THE LEADING EDGE OF THE OVERWING SLIDE DOOR WAS NOT OVER FLUSH; AND THAT THE 4 DOOR LATCHES WERE SECURE; I AM CERTAIN THAT THE ESCAPE SLIDE INFLATED AND BROKE THE ESCAPE SLIDE DOOR OPEN. I UNDERSTAND THAT IN THE PAST THERE HAVE BEEN INSTANCES ON OTHER ACFT WHERE SLIDE BOTTLES WITH DEFECTIVE VALVES SLOWLY LEAKED INTO THE SLIDE. THIS APPARENTLY CAUSED THE SLIDE TO EXPAND ENOUGH TO BREAK OPEN THE EMER ESCAPE SLIDE DOOR. THIS SCENARIO SEEMS TO FIT THIS INCIDENT. IF IT IS FOUND THAT THERE IS INDEED A HISTORY OF THESE VALVES LEAKING; IT SEEMS APPARENT THAT THESE SAME VALVES MUST BE REPLACED WITH SOME OTHER TYPE. SUPPLEMENTAL INFO FROM ACN 789518: AFTER SLIDE DEPLOYMENT THE DOOR LATCH PINS WERE FOUND SHEARED AND NO BOTTLE SQUIBS OR SPOILER BLOW DOWN SQUIBS HAVE BEEN FIRED WHICH INDICATES THE SLIDE INFLATED INSIDE THE COMPARTMENT ON ITS OWN. A POSSIBLE CAUSE COULD BE A LEAKY INFLATION VALVE. IF THE VALVE HAD A SMALL LEAK IT WOULD TAKE SOME TIME BEFORE THE SLIDE PRESSURIZED ENOUGH TO BREAK THE DOOR LATCH PINS OUT OF THE DOOR AND DEPLOY THE SLIDE. SUPPLEMENTAL INFO FROM ACN 790134: I WAS WORKING A NON-ROUTINE CARD TO REPLACE LINKAGE THAT WAS CORRODED ON THE R OVERWING SLIDE SYS. TO REPLACE THE LINKAGE; I USED THE MAINT MANUAL REF TO REMOVE AND INSTALL THE DOOR OPEN ACTUATOR. THE LINKAGE WAS REPLACED USING A TRAMMEL BAR TO KEEP THE REPLACEMENT LINKAGE AS CLOSE AS POSSIBLE TO THE ORIGINAL LINKAGE; IF NOT EXACT. THE R OVERWING SLIDE DEPLOYED INFLT RESULTING IN AN AIR TURN-BACK. I CAME TO WORK THE NEXT MORNING AND WAS INFORMED OF THE INCIDENT. LOOKING AT WHAT WAS LEFT OF THE SLIDE PACK AND DOOR ASSEMBLY (DOOR WAS INTACT; EXCEPT FOR LATCH HOOKS THAT WERE SHEARED OFF: 2 RECOVERED; 2 MISSING). MY CONCLUSION IS THAT THE BOTTLE FAILED INFLT RESULTING IN THE SLIDE INFLATING IN THE STORAGE AREA; WHICH IN TURN FAILED THE LATCH HOOKS AND DEPLOYED THE SLIDE PACK. AS TO HOW TO PREVENT THIS FROM HAPPENING AGAIN; AN EDUCATED GUESS WOULD BE TO REDESIGN THE BOTTLE FIRING MECHANISM CABLE AND BOTTLE CAM TO PREVENT THIS PROB. SUPPLEMENTAL INFO FROM ACN 791499: APPROX 50 NM NNE OF ZZZ; WHILE CLBING THROUGH FL200-FL210; THE ACFT ENCOUNTERED A MOMENTARY LIGHT SHUDDER FOLLOWED BY A THUMP IN THE REAR OF THE ACFT. THE FLT ATTENDANT CREW AND NUMEROUS PAX ALSO CONFIRMED THIS THUMP. IT WAS DESCRIBED AS PRONOUNCED AND OCCURRED ON THE R AFT SECTION OF THE ACFT. CONCURRENTLY; THE 'R WING SLIDE' EICAS MESSAGE ILLUMINATED. THIS LIGHT WOULD REMAIN ON FOR THE DURATION OF THE FLT. ALL FLT CHARACTERISTICS WERE NORMAL. THE FLT CREW PERFORMED A VISUAL INSPECTION AND EVERYTHING THAT COULD BE SEEN APPEARED NORMAL. THE QRH WAS REFED AND WE CONTACTED FLT CTL (DISPATCH) AND MAINT TO DISCUSS AVAILABLE OPTIONS. IT WAS UNANIMOUSLY DECIDED BY THE TEAM THAT THE BEST COURSE OF ACTION WOULD BE TO RETURN TO ZZZ. A DIVERT TO ZZZ WAS COORD WITH ATC. AN EMER WAS DECLARED FOR THE FOLLOWING REASONS: 1) THE QRH INDICATED CONSIDERING A NONSTANDARD FLAPS SETTING FOR LNDG. 2) THE SLIDE MAY HAVE DAMAGED OR WAS ENTANGLED WITH THE TAIL SECTION. (HOWEVER; THIS WAS THOUGHT TO BE HIGHLY UNLIKELY AS THERE WAS NO UNUSUAL VIBRATION OR OTHER UNUSUAL FLT CHARACTERISTICS.) AT THIS POINT; EVERYTHING APPEARED NORMAL EXCEPT FOR THE EICAS MESSAGE. 3) WE WERE GOING TO DUMP FUEL. 4) WE WERE GOING TO CONDUCT A FLY-BY BY THE ZZZ TWR FOR AN EXTERNAL INSPECTION. 5) WE WERE GOING TO BE CONDUCTING AN OVERWT LNDG. A FLY-BY BY THE TWR ON THE S SIDE OF THE FIELD WAS CONDUCTED. THE TWR AND OTHER ACFT ON THE GND RPTED NOTHING ABNORMAL. THE APCH; LNDG; AND TAXI-IN WERE ALL NORMAL. TOUCHDOWN AND LNDG WERE EXTREMELY SMOOTH. CALLBACK CONVERSATION WITH RPTR ACN 790471 REVEALED THE FOLLOWING INFO: REPORTER STATED WHEN THEY SAW THE RIGHT OVERWING SLIDE COMPARTMENT DOOR WITH THE LATCH HOOKS SHEARED OFF; THEY IMMEDIATELY REALIZED THE SLIDE PACK COMPARTMENT DOOR WAS FORCED OPEN FROM INSIDE. REPORTER ALSO STATED ANY CABLE LINKAGE ASSOCIATED WITH THE SLIDE BOTTLE VALVE; OR THE VALVE ITSELF LEAKING; COULD HAVE CONTRIBUTED TO THE SLIDE BOTTLE SLOWLY INFLATING THE SLIDE AND OVERRIDING THE LOCKING DOOR LATCHES.