ACR Y ISSUED GAR HAD LTSS FROM ACR X TKOF. SYS ERROR.

Narrative

ACR X CLRED FOR TKOF; (ISSUED 140 DEG TURN TO R); FROM RWY INTXN. ACR Y 3 PLUS MI FINAL. ACR Y OBSERVED BRAKING OUT OF CLOUDS. ACR X NOT AIRBORNE. ACR Y ISSUED GAR WITH 40 DEG L TURN. IN MY JUDGEMENT; THE GAR WAS ISSUED AT OR PRIOR TO THE THRESHOLD. THE PLT SAYS HE WAS AT APPROX 50 FT. AS THE ACR Y BEGAN THE GAR I OBSERVED ACR X AIRBORNE. I HAD BOTH ACFT IN SIGHT AT ALL TIMES AND ISSUED BOTH DIVERGING HDG. I ADVISED THE ACR X OF THE GAR AND REITERATED TO START THE R TURN ASAP. THE ACR Y DID NOT TURN AS QUICKLY AS I EXPECTED. WE LEARNED LATER THAT IT WAS OPERATING ON ONLY 3 ENGS AND WAS LOW ON FUEL. I WAS CHARGED WITH AN OPERROR ON 2 COUNTS. ACFT BEGINNING TKOF ROLL PRIOR TO ACFT ON 2 MI FINAL SO THAT DISTANCE COULD INCREASE TO 3 MI WITHIN 1 MIN. I BELIEVE THE TKOF ACTION BEGAN CORRECTLY TO FULFILL THIS. I APPLIED VISUAL SEPARATION WHEN ACR Y WAS IN SIGHT. LNDG ACFT XING THRESHOLD PRIOR TO DEP AIRBORNE AND 1000 FROM THRESHOLD. I BELIEVE THE OP WOULD BE IN COMPLIANCE; WHEN I OBSERVED ACR Y APCHING THE THRESHOLD; I HAD DOUBTS THAT I WOULD RETAIN SEPARATION AND INITIATED THE GAR. AT NO TIME DURING THIS OP DID I FEAR A COLLISION. NEEDLESS TO SAY; IF I HAD KNOWN OF ACR Y SITUATION; THIS SITUATION WOULD NEVER HAVE OCCURRED. EVERY TIME WE SQUEEZE A DEP OUT PRIOR TO AN ARR WE TAKE THE RISK OF A GAR SITUATION. EXPEDITIOUS MOVEMENT OF TFC INVOLVES SOME RISK AT ALL TIMES. MY USUAL ROUTINE IS TO ADVISE THE ARR ABOUT THE DEP AND VICE VERSA. ALTHOUGH NOT REQUIRED; I FEEL THAT GIVING THE PLTS A FULL PICTURE HELPS THEM AND ME TO COMPLETE A SUCCESSFUL OP. ACR X WAS ADVISED OF THE ACR Y BUT FOR SOME REASON I DID NOT ADVISE ACR Y OF THE DEP. PERHAPS HE WOULD HAVE TOLD ME OF HIS ENG PROBLEM AND THE SITUATION WOULD NOT HAVE OCCURRED. WHY I DIDN'T TELL ACR Y I DON'T KNOW. THAT IS A VERY RARE CASE FOR ME AND I INSTRUCT ALL TRAINEES OF THE SAME JUST TO AVOID SITUATIONS LIKE THIS. BECAUSE OF THIS; MY GAR RATIO IS VERY LOW.