PHX CTLR ALLOWED A B737 TO DEP FROM PARALLEL RWY AND LOST SEPARATION WITH PRECEDING B757.

Narrative

WHILE WORKING THE LCL N POS; I CLRED A B737 FOR TKOF TOO SOON BEHIND A B757 OFF A PARALLEL RWY SEPARATED BY 3565 FT. I WAS ADVISED BY ANOTHER POS OF THE B757 DEPARTING AND MY SEQUENCE WAS TO FOLLOW. SINCE I HAD AN ARR I WAS NOT ABLE TO TAXI MY ACFT INTO POS AND HOLD. I OBSERVED THE B757 IN POS ON RWY 7L WHILE WAITING FOR THE ARR ON RWY 8 TO LAND. AFTER THE ARR LANDED; I PUT MY B737 INTO POS. I ALSO HAD AN AIRBUS ON A 4 MI FINAL FOR RWY 8. ONCE THE LNDG ACFT EXITED THE RWY; I CLRED ACFT X FOR AN IMMEDIATE TKOF TO ENSURE APPROPRIATE ARR/DEP SEPARATION. AS ACFT X BEGAN TKOF ROLL; I SCANNED UPWIND AND OBSERVED THE B757 UPWIND OFF RWY 7L. THE INITIAL DEP ROUTING OF THE 2 ACFT INITIALLY WERE TO CONVERGE SO I GAVE ACFT X A RWY HDG VECTOR TO AVOID A PATH THAT WOULD NOT PUT IT DIRECTLY BEHIND THE B757. I ALSO RESTR THE CLBOUT SPD TO 210 KTS TO TRY AND MEET THE 4 MI SEPARATION STANDARD. I ISSUED THE B757 TFC TO ACFT X. ACFT X RPTED THE B757 IN SIGHT. I ASKED ACFT X IF THEY COULD MAINTAIN VISUAL AND THEY REPLIED AFFIRMATIVE. AT APPROX 4 MI E OF THE ARPT; ACFT X WAS ON A CONVERGING COURSE LESS THAN 4 MI BEHIND A B757 WITH VISUAL SEPARATION. AT THIS POINT; THE ACFT WAS SWITCHED TO DEP CTL.