B757 FREIGHTER TKOF ABORTED WHEN UNKNOWN CARGO; BALLAST; SHIFTS AND SLIDES TO REAR OF ACFT.

Narrative

THE PROB WAS DISCOVERED ON TKOF ROLL JUST AFTER TKOF THRUST WAS SET. THE COCKPIT INDICATIONS WERE A LARGE AIRFRAME VIBRATION AND NOISE. THE CAPT DECIDED TO REJECT THE TKOF AND THE NOISE AND VIBRATION STOPPED. AT FIRST WE THOUGHT IT WAS A TIRE PROB; BUT THE TAXI BACK TO THE RAMP WAS A SMOOTH RIDE. NEXT WE SURMISED THAT THERE WAS A CARGO CANISTER IN THE CARGO AREA AND IT HAD COME LOOSE EVEN THOUGH THE LOAD MANIFEST SHOWED THE ACFT WAS EMPTY OF CARGO. THE PROB AROSE BECAUSE MAINT WAS PERFORMED ON THE ACFT THAT NEEDED A BALLAST PALLET TO BE PLACED IN THE MAIN CARGO HOLD ON ONE OF THE FORWARD STATIONS; AND SUBSEQUENTLY THE BALLAST PALLET WAS NOT REMOVED BEFORE FLT. THE PALLET IS A FLAT PIECE OF METAL THAT WAS PLACED ON THE CARGO DECK FLOOR WITH A SLAB OF CONCRETE ON IT. I WAS TOLD THE CONCRETE SLAB WEIGHED ABOUT 7400 LBS. ON TKOF ROLL; THE CONCRETE SLAB SLID OFF THE METAL PALLET; ROLLED THE LENGTH OF THE CARGO DECK AND WEDGED ITSELF INTO THE TAIL SECTION OF THE AIRPLANE. IT PUNCHED A HOLE IN THE FUSELAGE AND PROBABLY CAUSED OTHER INTERNAL DAMAGE THAT I COULDN'T SEE UPON POST FLT. ONE OF THE CONTRIBUTING FACTORS TO THIS INCIDENT ARE MAINT PROCS NOT BEING FULLY COMPLETED AND THE DOCUMENTATION SAYING THAT IT WAS. IF THE MAINT PROC WAS PROPERLY COMPLETED; THEN THE BALLAST PALLET WOULD HAVE BEEN REMOVED. IF THE DOCUMENTATION WAS DONE PROPERLY; THEN THE ACFT WOULD NOT HAVE BEEN DISPATCHED FOR FLT AS IT STILL HAD AN UNSECURED BALLAST PALLET INSIDE OF IT. ANOTHER CONTRIBUTING FACTOR IS THE LOAD MANIFEST. THE LOAD MANIFEST SHOWED THAT ALL CARGO STATIONS OF THE MAIN CARGO DECK WERE EMPTY; WHEN IN FACT THERE WAS A PALLET WITH A CONCRETE SLAB IN ONE OF THE FORWARD MAIN CARGO POS. THIS SIT COULD POSSIBLY HAVE BEEN A LOT WORSE. WHAT IF THE BALLAST PALLET HAD STARTED ROLLING DOWN THE CARGO HOLD AT TKOF ROTATION? WOULD IT HAVE GONE ALL THE WAY THROUGH THE AIRPLANE TAKING OUT THE CTL LINES; HYD LINES; AND OTHER IMPORTANT PARTS OF THE AIRPLANE? EVEN IF IT WOULD NOT HAVE; WOULD THIS RADICAL AFT SHIFT IN CTR OF GRAVITY STILL HAVE ALLOWED THE ACFT TO BE CONTROLLABLE? ONE OTHER PLAUSIBLE CONSIDERATION IS IF THE ACFT HAD GOTTEN AIRBORNE THE SLAB OF CONCRETE COULD ALSO HAVE ROLLED FORWARD IN LNDG ROLL DURING BRAKING; COMPROMISING THE CREW CABIN; POSSIBLY INJURING OR KILLING THE CREW. AS FOR CORRECTIVE ACTION; WE SHOULD ENSURE MAINT IS PROPERLY COMPLETED BEFORE IT IS DOCUMENTED COMPLETE; AND THE LOAD MANIFEST SHOULD ALSO BE VISUALLY VERIFIED CORRECT BY THE LOAD-MASTER BEFORE FLT. SUPPLEMENTAL INFO FROM ACN 344022: WT AND BAL INDICATED A VOID ACFT AND DOORS WERE CLOSED WHEN CREW ARRIVED. MAINT HAD THE WT IN PLACE WHILE PERFORMING AN ENG CHANGE AND FORGOT IT AFTER WORK WAS COMPLETE. NO LOGBOOK ENTRY HAD BEEN MADE FOR THE BALLAST.