CAPT OF AN LGT ACR ACFT TOOK OVER CTL OF THE ACFT AFTER THE FO HAD OVERSHOT FINAL RESULTING IN A CONFLICT WITH ANOTHER ACFT ON FINAL TO THE ADJACENT RWY.

Narrative

WE WERE CLRED FOR THE VISUAL APCH TO RWY 26 AT IAH; FROM A DOWNWIND ON THE N SIDE; TO FOLLOW AN ACFT ON FINAL AT OUR 3 O'CLOCK POS. CONDITIONS WERE NIGHT VMC; THERE WAS ANOTHER ACFT AT OUR 1 O'CLOCK POS ON FINAL FOR RWY 27; AND THERE WAS CONFUSION ABOUT WHICH ACFT WE WERE FOLLOWING. THIS LED TO A SHALLOWER TURN TO FINAL THAN WE NEEDED AS WE CONCENTRATED MORE ON THE TFC THAN THE APCH; RESULTING IN AN OVERSHOOT OF THE RWY CTRLINE AND A TCASII 'DSND' WARNING. WE INCREASED THE BANK ANGLE TO ABOUT 45 DEGS AND INCREASED THE DSCNT RATE TO AVOID THE TFC CONFLICT. THE ROOT OF OUR PROB WAS POOR AIRMANSHIP BY THE FO; WHO WAS FLYING THE VISUAL APCH. A GOOD 30 DEG BANK TURN TO FINAL WOULD HAVE AVOIDED ANY TFC CONFLICT. INSTEAD; HE FIXATED ON THE TFC AND LOST TRACK OF THE RWY. I; AS CAPT; TWICE TOLD HIM TO TURN HARD R; THEN TOOK CTL OF THE PLANE MYSELF; INITIATING THE HARD TURN. I WAS MOST IMPRESSED WITH HOW QUICKLY OUR SIT DETERIORATED TO A SERIOUS TFC CONFLICT IN THE VERY SHORT TIME IT TOOK ME TO WATCH FOR THE FO TO REACT; DIRECT HIM TO ACT; AND FINALLY; TAKE CTL OF THE ACFT MYSELF.