A B767-300ER AFTER TKOF AT 15000 FT DIVERTED DUE TO EXPERIENCING A BUMP THEN A CONSTANT VIBRATION. CAUSED BY THE APU COWLING DEPARTING ACFT.

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WHILE PERFORMING PREDEPARTURE CHK OF THE APU EVERYTHING APPEARED TO BE IN GOOD CONDITION. THE TECHNICIAN ASSISTING ME THEN CLOSED THE APU DOORS AND THE ACFT WAS RELEASED FOR SVC. THE ACFT DEPARTED AND APPROX 40 MILES OUT THE DOORS CAME OFF AND DAMAGED THE ELEVATORS. THE ACFT DID AN AIR TURNBACK AND RETURNED TO ZZZ WITHOUT INCIDENT. I AM NOT SURE WHAT CAUSED THIS BUT I SUSPECT LATCHES WERE FAULTY OR SOMEHOW DID NOT GET LATCHED PROPERLY AS THERE IS NO WAY TO PHYSICALLY CHK LATCH FOR GO OR NO GO CONDITION EXCEPT IF DOOR STAYS CLOSED. I BELIEVE A SIGHT GLASS AT EACH LATCH OR A FLORESCENT NO GO INDICATOR ON THE SIDE OF THE LATCHES COULD HAVE POSSIBLY PREVENTED THIS OR LATCH THAT LATCHES INTO THE FORWARD BULKHEAD LIKE ON THE L1011'S APU DOORS WOULD HAVE BEEN A POSITIVE LATCH TO THE FUSELAGE AND DOORS WOULD NOT HAVE BEEN ABLE TO OPEN INTO THE AIRSTREAM. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE APU COWLING WAS OPENED BY THE GATE TECH WITH THE HELP OF THE RPTR TO SVC THE UNIT. THE RPTR SAID THE COWLING WAS CLOSED AND LATCHED BY THE GATE TECHNICIAN AND WAS OBSERVED BY THE RPTR AS BEING FAIRED WITH THE FUSELAGE. THE RPTR STATED IN LATCHING AND LOCKING THIS COWLING EVERYONE HAS THEIR OWN METHOD OF CLOSURE TO AVOID FALSE LATCHING. THE RPTR SAID THE RPTRS TECHNIQUE IS LATCHING THE MOST FORWARD LATCH FIRST AND OBSERVING IT FAIRING WITH THE FUSELAGE SKIN THEN CONTINUE AFT LATCHING THE COWLING AND CHECKING THE TABS FOR POSITIVE LOCKING. THE RPTR SAID THE LOCKING TAB IS .50 INCH WIDE X .250 INCH LONG AND PROTRUDES OUT OF THE COWLING .250 INCH AND IS THE SAME MATERIAL AND COLOR AS THE LATCH MECHANISM. THE RPTR SUGGESTS COLORING THE TABS MAY ASSIST IN OBSERVING THE TABS FROM THE GND. THE RPTR SAID THE TABS ARE APPROXIMATELY 15 TO 17 FT FROM GND LEVEL DEPENDING ON STRUT EXTENSION AND TOUGH TO SEE ON A WALK AROUND CHK. CALLBACK FROM ACN 543624: THE RPTR STATED CLBING THROUGH 15000 FT THE FLT CREW FELT A 'BUMP' AND THEN AN AIRFRAME VIBRATION WHICH DECREASED WITH LOWER SPEED. THE RPTR SAID THE APU WAS NOT OPERATING AT THIS TIME. THE RPTR STATED THE FLT WAS DIVERTED AND ON THE GND THE APU COWLING WAS FOUND MISSING AND A HOLE WAS DISCOVERED IN EACH ELEVATOR. THE RPTR SAID THE COWLING WAS RECOVERED FROM A PRIVATE RESIDENCE BACKYARD.