FLC OF ACR WDB ACFT INADVERTENTLY LANDED OVER THE ACFT WT FOR THE RWY USED.

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DSNDING INTO EWR ON A FLT THAT ORIGINATED IN CGN WITH AN INTERMEDIATE STOP AT STN SPOILER PUMP PRESSURE WAS RPTED LOW BY THE FE: 2400 PSI INSTEAD OF 2800 PSI AS REQUIRED BY THE ACFT OPERATING MANUAL (AOM). AT APPROX THE SAME TIME WE EXPERIENCED A FAILURE OF THE CAPT'S AIRSPD INDICATOR AND INTERMITTENTLY THE FO'S ALTIMETER. WE ATTEMPTED TO RECTIFY THESE TWO ADDITIONAL FAILURES TO NO AVAIL. THE 'ABNORMAL SPOILER PRESSURE CHKLIST' WAS ACCOMPLISHED AND THE LNDG PROCEEDED OTHERWISE UNEVENTFULLY. ON TOUCHDOWN THE SPOILER PRESSURE REACHED THE NORMAL 3000 PSI AND THE SPOILERS OPERATED AS EXPECTED. REVIEWING THE EVENTS; IT WAS NOTICED THAT THE LNDG DATA FOR THIS ABNORMAL OPERATION WAS NOT CHKED DUE TO THE ADDITIONAL WORKLOAD. DATA FOR THIS SPECIFIC ABNORMAL SITUATION COULD NOT BE FOUND WHEN WE LOOKED FOR IT; IN REVIEW. THE PROC CALLS FOR ALTERNATE SPOILER ACTIVATION THROUGH THE MAIN HYD SYS AS WELL AS LNDG WITH FLAPS AT A MAX OF 35 DEGS. DATA COULD BE FOUND FOR ALTERNATE SPOILER DEPLOYMENT WITH FULL FLAPS AND LNDG DISTANCE FOR FLAPS 35 DEGS BUT NOT FOR BOTH ALTERNATE SPOILER DEPLOYMENT AND FLAPS 35 DEGS. THE LNDG WT FOR EWR WITH THE ALTERNATE SPOILER OPERATION WAS 197000 LBS HOWEVER; OUR LNDG WT WAS 240000 LBS. THEREFORE WE CAN ASSUME THAT THE LNDG WAS ACCOMPLISHED WITHOUT MEETING FAR FIELD LENGTH LIMITS. THIS OVERSIGHT OCCURRED FOR THE FOLLOWING REASONS: THE PROPER DATA WAS NOT AVAILABLE (THE COMPANY HAS BEEN NOTIFIED); WE HAD MULTIPLE FAILURES OCCURRING IN THE TERMINAL AREA ON AN IFR DAY WITH TYPICAL HEAVY MORNING AIR TFC IN THE NEW YORK AREA.