A B767-300 IN FLT IS DIVERTED WHEN ADVISED BY A PAX THAT R ENG PYLON ACCESS PANEL; INBOARD SIDE; WAS SHAKING AND VIBRATING. PANEL DEPARTED ACFT PRIOR TO LNDG.

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UPON COMPLETION OF ROUTINE MAINT ON B767 #2 ENG; I INSTALLED A PYLON PANEL CONSISTING OF TWO SLIDE ON FWD HOOKS AND TWO REAR HOOK LATCHES. THE PANEL WAS FIRM AND THE REAR LATCHES WERE FLUSH WITH THE SKIN. IT WAS CHECKED BY TWO OTHER MECHS BY PRYING WITH SCREWDRIVERS. THE FIRST FLT AFTER THE PREFLT; THE PANEL WAS SEEN SHAKING BY A PAX AND THE CREW DECIDED TO DIVERT THE FLT TO ANOTHER ARPT. UPON APCH TO THE OTHER ARPT; THE PANEL DEPARTED THE PYLON; DAMAGING A SPOILER BY DENTING IT. UPON NOTIFICATION OF THE INCIDENT; MYSELF AND OTHER MECHS EXPERIMENTED WITH ANOTHER ACFT PYLON OF THE SAME TYPE. IT WAS DISCOVERED THAT THE PANEL COULD BE INSTALLED WITHOUT THE REAR LATCHES BEING LATCHED PROPERLY AND STILL BE FLUSH WITH THE SKIN. THE ROUTINE PAPERWORK DOESN'T GIVE ANY SPECIAL CAUTION; OR EVEN AN INSPECTION AFTER INSTALLATION. THE MANUAL GIVES ONLY TWO STEPS: 1) ENGAGE HOOKS. 2) CLOSE LATCHES. I BELIEVE THE ONLY WAY TO POSITIVELY PREVENT A REOCCURRENCE IS TO MODIFY THE PANEL TO PROVIDE A MEANS OF INSPECTING THE SECURITY OF THE REAR LATCHES. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACCESS PANEL WAS CHKED TWICE AND HAD NO GIVE OR APPARENT LOOSENESS AND WAS FLUSH WITH THE PYLON SKIN. THE RPTR SAID; AFTER BEING TOLD OF THE PANEL DEPARTING THE ACFT; THE RPTR AND OTHER TECHNICIANS BEGAN CHKING THE LATCHES OF THIS PANEL AND FOUND A DISCREPANCY. THE RPTR STATED THE PANEL HAS TWO FORWARD SLIDE IN HOOKS AND TWO REAR HOOK LATCHES ACTIVATED BY A BLADE SCREWDRIVER. THE RPTR SAID WITH THE FORWARD HOOKS ENGAGED AND THE PANEL FLUSH IN THE PYLON CUTOUT AND ACTIVATING THE TWO REAR LATCHES; IT IS POSSIBLE TO FALSE LATCH THE REAR LATCHES. THE RPTR STATED THE METHOD THAT WILL AVOID FALSE LATCHING IS TO ENGAGE THE FRONT HOOKS AND HOLD THE REAR OF THE PANEL OFF THE PYLON CUTOFF SURFACE AND ACTIVATE ONE REAR LATCH AND ALLOW THE LATCH TO PULL THE PANEL INWARD. THE RPTR SAID WHEN THE LATCH PULLS THE PANEL INTO THE PYLON CUTOUT; IT IS VERIFIED ENGAGED. THE RPTR SAID WHEN CLOSING THE SECOND REAR LATCH; IT IS ALSO ENGAGED BECAUSE THE FIRST LATCH IS POSITIVELY ALIGNED AND LATCHED. THE RPTR SAID A DEMONSTRATION WAS GIVEN FOR A GROUP OF TECHNICIANS WHO NORMALLY WORK B767 ACFT AND EXPERIENCED PYLON PANEL LATCH PROBS. THE RPTR STATED THE CARRIER HAS EXPERIENCED LOSS OF THESE PANELS BUT IS UNAWARE OF THE NUMBER. THE RPTR SAID NO CHANGE HAS BEEN MADE TO THE MAINT MANUAL CHAPTER 54 OR ANY RELATED JOB CARDS REQUIRING REMOVAL AND INSTALLATION OF THE PYLON PANELS.