AN ACR B727 FREIGHTER FLC HAS THE P1 CONTAINER BREAK LOOSE FROM ITS LOCKED POS AND SHIFT DURING INITIAL CLBOUT. THE FLC EVALUATED THE SIT AND DECIDED TO RETURN TO AKL FOR AN OVERWT LNDG.

Narrative

NORMAL START UP AND TAXI OUT AFTER LOADING CARGO INCLUDING SPECIAL CARGO (HORSES FOR SYD) WITH 4 GROOMS. SHORTLY AFTER LIFT-OFF WHICH WAS NORMAL; I HEARD AN UNMISTAKABLY LOUD NOISE (WHICH I NEVER WANT TO HEAR AGAIN) OF A CONTAINER AT P1 COMING LOOSE. NOTE B727-284 HAS 12 POS. LOCKS WERE UP AS PER OUR PROC AT ALL STATIONS. P2 LOCKS STOP APPROX 3700 LBS CONTAINER FROM GOING TO OPEN P3 POS AND ULTIMATELY TO P4 POS WHERE LOSS OF HUMAN (GROOMS) AND ANIMAL LIFE COULD HAVE OCCURRED. CAPT (PNF) IMMEDIATELY ASSESSES ACFT CTL. FO (PF) RPTS NO CTL PROBS. GROOMS RPT IMMEDIATELY EXTENT OF PROB. LEVELOFF AT 2000 FT MSL TO ASSESS SIT. EXCELLENT CRM AND LEADERSHIP BY CAPT WHO DIRECTS ME (SO) TO COMPUTE NEW CTR OF GRAVITY WITH LOAD SHIFT BEFORE DUMPING FUEL. CTR OF GRAVITY CALCULATED WITH FUEL DUMPING PER THE SCHEDULE. CONTAINER SLIDES A SECOND TIME WHILE FUEL DUMPING IS IN PROGRESS. CREW DECIDES TO LAND OVERWT DUE TO THE UNCONTROLLABLE NATURE OF CONTAINER SHIFTS. GROOMS SECURE CONTAINER WITH BROWNLINE STRAPS AND THROW CONTENTS TO P1 TO LIGHTEN CONTAINER LOAD. I CONSIDER MYSELF A 'LOAD SHIFT SURVIVOR' LUCKY AND GRATEFUL TO HAVE HAD SUCH A GREAT CREW. I WELCOME FAA/NASA INVESTIGATION TO DISCOVER HOW THIS OCCURRED.