A HARD LNDG IS EXPERIENCED BY A B747-200 CARGO FLT CREW; BUT WAS NOT CONSIDERED AS SUCH UNTIL AFTER A POSTFLT INSPECTION REVEALED DAMAGE TO THE ACFT'S FLAP JACKSCREW AND RELATED CANOES; AT JFK; NY.

Narrative

ON APCH TO JFK VIA THE VOR RWY 13L; WE WERE NEARLY THE LAST ACFT TO LAND ON RWY 13L. WINDS OF 240 DEGS AT 10 KTS BROUGHT ABOUT A CHANGE TO ILS RWY 31R. THE TAILWIND ON BASE WAS STRONGER THAN 10 KTS AS IT PUSHED US THROUGH FINAL JUST A BIT. THE CAPT EASILY REESTABLISHED THE ACFT ON FINAL APCH LEG. WE CALLED OUT TO HIM 'TFC STILL ON THE RWY.' WE WERE JUST ABOVE GLIDE PATH AND ON SPD. OUR LNDG WT WAS 213 TONS AND A TARGET SPD OF 139 KTS AT FLAPS 25 DEGS. HE INCREASED THE RATE OF DSCNT TO CAPTURE THE GLIDE PATH AND QUICKLY REJOINED IT. WE WERE ON SPD AND OUR SINK RATE WAS A LITTLE HIGHER THAN NORMAL. WE CALLED THE TFC CLRING AND WERE JUST 1/2 MI FROM TOUCHDOWN. OVER THE NUMBERS; THE CRAB WAS REMOVED AND THE SINK RATE WAS STILL A LITTLE HIGHER THAN NORMAL; BUT NOT SO MUCH SO THAT I FELT INCLINED TO REVIEW THE VSI. THE ACFT CALLED '50;' '40;' '30;' '20;' ONLY SLIGHTLY FASTER THAN NORMAL AND I THOUGHT THE TOUCHDOWN WOULD BE SMOOTH WITH A MORE AGGRESSIVE FLARE. THE FLARE WAS MADE; BUT THE TOUCHDOWN WAS VERY HARD -- SURPRISINGLY SO. WE EXITED THE RWY AND TAXIED TO THE RAMP. I ASKED IF A HARD LNDG WOULD BE ADDED TO THE LOGBOOK AND WAS TOLD BY BOTH THE CAPT AND THE FE THAT IT WAS NOT A HARD LNDG AND THAT A LIGHT ACFT FEELS LIKE IT LANDS HARDER. UPON POSTFLT; WE FOUND THE 2ND CANOE FOR THE R INBOARD FLAP JACK SCREW BROKEN; BUT STILL ATTACHED. UPON OUR FLAP RETRACTION AFTER LNDG; THE DAMAGED FLAP DAMAGED THE 1ST CANOE AND WEDGED ITSELF ABOVE THE INBOARD AILERON. OUR VISION HAD ADEQUATE TIME TO ADJUST TO THE EVENING AND FATIGUE WAS NOT A FACTOR AT ALL. SO CLOSE TO TOUCHDOWN; EVERY INDICATION WAS FOR A NORMAL TOUCHDOWN. AS OUR EYES HAD XFERRED TO THE RWY EARLIER; NO WIND SHIFT OR SHEAR WOULD HAVE BEEN SEEN ON THE AIRSPD INDICATOR. IN LIGHT OF THE ABSENCE OF ANY GPWS ALERT TO 'SINK RATE;' I DO NOT BELIEVE OUR APCH TO BE CONSIDERED UNSTABLE; ONLY SLIGHTLY HIGH. I DO SUBMIT THAT A SCAN OF THE VSI MAY HAVE GIVEN HIM INFO THAT COULD HAVE HELPED HIM JUDGE HIS PROGRESS BETTER. HE WAS NOT LOW ON AIRSPD OR ENERGY AND NOT DIVING FOR THE RWY; SO I CANNOT FIND AN ANSWER AS TO WHY WE HIT SO HARD OTHER THAN PERHAPS HE JUST DIDN'T FLARE ENOUGH.