B747-200 CREW LANDED BEFORE THE THRESHOLD OF RWY 26L AT ONT.

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WITH 3 SM HAZE VISIBILITY AND APPROX XA00 TIME OF THE APCH; ELECTED TO DO AN AUTO-COUPLED ILS RWY 26L APCH FOR LNDG; DUE TO LIMITED VISIBILITY INTO THE HAZE AT LOW SUNSET ANGLE. APCH SPD WAS 147 KTS; BY USING THE 520000 LBS DATA CARD. CAPTURED LOC AND GS NORMALLY. CROSSED FONTA; ALT CHKED AT 1000 FT INSTS XCHKED; NO FLAGS. AT 500 FT; FO CALLED BUG -4 KTS; SINK 8 (FPM X 100). CAPT STATED ON SPD ON MY SIDE; CAPT CORRECTED AND ADDED PWR. FO CALLED SHOWING 142 KTS; CAPT SHOWED COMMAND SPD (BUG -1 (148 KTS). CAPT CORRECTED AND ADDED A LITTLE MORE PWR. FO CALLED APCHING MINIMUMS; FIELD IN SIGHT (PRIOR SIGHTING OF FIELD HAD OCCURRED 2 1/2 - 3 MI OUT ON FINAL; BUT CONTINUED FLYING AUTO COUPLED FOR PROFICIENCY). CAPT DISCONNECTED AUTOPLT AT APPROX 200 FT ACFT MANUAL FLYING SEEMED NORMAL. AT APPROX 100 FT; CAPT DETECTED A SINK AND HELD PWR ON. CAPT LET ACFT FLY ONTO RWY INSTEAD OF TRYING TO STOP SINK RATE WITH EXCESSIVE FLARE; SO TAIL WOULD NOT STRIKE RWY. ACFT LANDED FIRMLY; WITH MAIN GEAR 45 FT SHORT OF THRESHOLD ON THE OVERRUN. AS NOSEWHEEL WAS BEING LOWERED TO RWY; IT DROPPED FIRMLY. REST OF LNDG ROLLOUT WAS NORMAL AND TAXI TO BLOCKS WAS NORMAL. WITH A 6 KT AIRSPD ERROR DISCOVERED BTWN 500 FT TO 200 FT AGL AND A SINK RATE INCREASE DETECTED APPROX 100 FT AGL; THIS RESULTED IN SHORT LNDG. WITH THE AUTOPLT COUPLED VERSUS MANUAL FLYING; THIS MIGHT HAVE DELAYED IDENTING THE ACFT FLYING 'BEHIND THE PWR CURVE' AND ADDING 'MORE' PWR 'SOONER.' MAYBE AN AIRSPD CHK SOONER (1000 FT AGL) DURING AUTO COUPLED APCHS WOULD HELP PREVENT THIS SIT. SUPPLEMENTAL INFO FROM ACN 563064: ILS APCH TO RWY 26L AT ONT ARPT; CAPT FLYING COUPLED ILS WITH AUTOPLT. VISIBILITY APPROX 3 MI WITH -X HAZE AT OR NEAR MINIMUMS; CAPT DISCONNECTED AUTOPLT AND FLEW ACFT MANUAL TO TOUCHDOWN. DEVELOPED SINK RATE WITHOUT CORRECTION. TOUCHED DOWN 45 FT INTO OVERRUN. AIRSPD INDICATORS OFF BY APPROX 6 KTS. FO'S AIRSPD BEING THE LOWER ONE AS PNF DID NOT RECOGNIZE LOW APCH TILL LAST MIN DUE TO AIRSPD INDICATORS OFF AND VISIBILITY LOOKING INTO SUN WITH GLARE OFF OF GLARE SHIELD.