HYD 'B' SYS FAILED AFTER TKOF DUE TO FAILED 'O' RING IN THE FLT SPOILER CTLR. THE SPOILER REMAINED EXTENDED AND CREATED ACFT CTL PROB; GETTING WORSE AND MORE EXAGGERATED WITH FLAP EXTENSION BEYOND 15 DEGS. FULL PWR WAS REQUIRED TO KEEP ACFT ON GS FOR LNDG.

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SHORTLY AFTER TKOF; AFTER GEAR RETRACTION; THE B-SYS HYDS (THE SECONDARY SYS) FAILED. WE WENT THROUGH THE APPROPRIATE CHKLISTS AND RETURNED FOR WHAT SHOULD HAVE BEEN A RELATIVELY NORMAL LNDG. ON DOWNWIND WE NOTICED THAT THE AIRPLANE WAS STARTING A GENTLE ROLL TO THE R. IT WAS ALMOST UNNOTICEABLE; AT FIRST. BUT AS WE CONTINUED TO LNDG THE ROLL BECAME MORE PRONOUNCED. BY THE TIME WE LANDED WE NEEDED FULL L AILERON AND EXCESSIVE PWR. (WE HAD TO HOLD THE SAME AMOUNT OF PWR TO STAY ON THE GS THAT WE WOULD USUALLY USE FOR TKOF.) WE DID LAND UNEVENTFULLY. AFTER LNDG IT WAS DETERMINED THAT THE CAUSE OF THE FAILURE WAS A LEAK IN A SPOILER MECHANISM THAT HOLDS THE FLT SPOILERS DOWN. SO; THE CAUSE OF THE ADVERSE ROLL WAS A LOCKED-'UP' SPOILER. MY REASON FOR FILING THIS RPT IS MAKE KNOWN ONE MORE VARIATION OF OUTCOMES OF A HYD FAILURE; IN THE HOPES THAT THE INFO CAN BE APPROPRIATELY PASSED ALONG TO PROTECT OTHER PLTS IN THE FUTURE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: ACFT WAS B737-200. AFTER TKOF AND GEAR RETRACTION; 'B' SYS HYDS FAILED. POST-FLT INSPECTION REVEALED THAT THE CAUSE OF THE FAILURE WAS A LEAK IN ONE OF THE SPOILER MECHANISMS; AN 'O' RING IN THE FLT SPOILER CTLR. WHEN THE FAILURE OCCURRED; THOUGH NOT KNOWN AT THE TIME; ONE OF THE SPOILERS REMAINED IN THE UP; EXTENDED POS. BECAUSE OF THE SPOILER DEFLECTION THE FLC NOTICED THE ACFT ROLL SLOWLY AND GENTLY AT FIRST. BECAUSE THE PROC FOR A 'B' SYS HYD FAILURE DIRECTS USE OF FULL FLAPS FOR LNDG; THAT IS WHAT THE FLC USED. HOWEVER; RPTR CAPT NOTICED THAT; AS THE FLAPS WERE PROGRESSIVELY LOWERED; THE ROLLING MOVEMENT INCREASED AND BECAME ALMOST UNCONTROLLABLE. RPTR HAD TO USE ALMOST MAX PWR TO COUNTERACT THE DEGRADED PERFORMANCE OF THE ACFT. RPTR WAS ASKED ABOUT THE SPOILER BEING; AS RPTED; 'LOCKED UP' AND WAS TOLD BY THE MECHS THAT THE SPOILER WAS VERY STIFF AND HAD TO BE FORCEFULLY PUSHED DOWN. IT WAS NOT KNOWN WHY THE SPOILER HAD PRESSURE BEHIND IT.