TAIL STRIKE ON TKOF IN ACR WDB TWIN.

Narrative

SHORTLY AFTER TKOF TWR RPTED THEY HAD SEEN SPARKS FROM THE REAR OF THE ACFT. WE ASKED IF SPARKS WERE STILL VISIBLE AND TWR RESPONDED NO. FROM THE COCKPIT THE ROTATION HAD SEEMED NORMAL TO ALL 3 CREW MEMBERS AND NOTHING ABNORMAL WAS FELT BY PF. AFTER CLEANING ACFT UP; CAPT ASKED RELIEF PLT TO CALL FORWARD FLT ATTENDANTS TO SEE IF THEY HAD HEARD ANYTHING ON TKOF. FORWARD CABIN FLT ATTENDANTS REPLIED NOTHING WAS HEARD. AFT FLT ATTENDANTS WERE CALLED NEXT. THEY SAID THEY HAD HEARD SCRAPING ON TKOF. COMPANY MAINT WAS CONTACTED AND GIVEN INFO. WITH ALL SYS NORMAL AND NO OTHER ADVERSE INFO IT WAS DECIDED BY THE CAPT AND COMPANY MAINT IT WOULD BE OK TO CONTINUE TO OUR DEST. AFTER LEVELING OFF AT 25000 FT; CAPT ASKED THE RELIEF PLT TO GO TO THE BACK OF THE ACFT TO INFORM THE FLT ATTENDANTS WHAT THE NOISE HAD BEEN ON TKOF. ON RETURN TO THE COCKPIT HE INFORMED THE CAPT THAT FLT ATTENDANTS IN AFT HAD ALSO HEARD A LOUD METALLIC BANG OR CRASHING SOUND ON ROTATION. THE CAPT THEN CALLED THIS FLT ATTENDANT TO THE COCKPIT FOR MORE INFO. AFTER RECEIVING THIS NEW INFO THE CAPT FELT IT WOULD NOT BE PRUDENT TO CONTINUE OVER WATER NOT KNOWING IF THERE WAS DAMAGE TO THE AFT FUSELAGE. A REQUEST FOR RETURN TO JFK AND FUEL DUMP WAS RECEIVED. APPROX 5 MINS FROM LNDG OR AT GS INTERCEPT THE AFT FLT ATTENDANTS RPTED THE SAME LOUD METALLIC NOISE. APCH WAS CONTINUED AND A NORMAL LNDG WAS MADE. MAINT AND FLC INSPECTED THE ACFT AFTER PARKING AT THE GATE. UPON INSPECTION; PAINT WAS MISSING FROM TAILSKID. MAINT WAS ASKED TO INSPECT AFT CARGO COMPARTMENT. UPON DOING SO IT WAS FOUND THAT THE CARGO BINS HAD COME LOOSE. CARGO BINS WERE SECURED AND A NORMAL TKOF AND LNDG FOLLOWED. I BELIEVE THAT ON TKOF THE CARGO BINS SHIFTED AFT CAUSING A SLIGHT MOVEMENT OF CTR OF GRAVITY TO THE REAR CAUSING TAILSKID CONTACT. AND UPON PITCHING THE ACFT DOWN TO FOLLOW THE GS; THE BINS SLID FORWARD CAUSING THE BANGING NOISE JUST BEFORE LNDG. THIS CONTAINER MAY HAVE BEEN OPENED TO PULL BAGS FOR SOME PAX THAT DID NOT BOARD THE ACFT BUT HAD CHKED BAGS. AFTER THIS HAD BEEN DONE THE CONTAINER MAY NOT HAVE BEEN LOCKED BACK IN PLACE.