Narrative:

During inclement WX (thunderstorms surrounding cvg from the southeast to west to north) aircraft X departed runway 18L. Given an initial heading of 090 degrees to miss WX, talking to departure south. Aircraft Y departed runway 18L after aircraft X, given an initial heading of 110 degrees to miss WX and diverge from aircraft X and talking to me at departure north. It appeared to me that aircraft X did a reduced power takeoff and a slow turn to 090 degrees and aircraft Y did a normal takeoff and standard turn to 110 degrees. The end result was when I first actively observed the aircraft, they were less than a mi apart on very nearly the same ground track and about 500 ft vertical. I checked to see if aircraft Y was on frequency (he was, but hadn't checked on yet). I then issued a traffic alert to aircraft Y and turned him to 180 degrees to avoid the traffic. I believe aircraft X's reduced power takeoff was a major factor.

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Original NASA ASRS Text

Title: DEP CTLR HANDLING TFC OFF THE SAME RWY RECOGNIZED LOSS OF SEPARATION AT CVG WITH FAILED SPACING BTWN A B737 DEPARTING BEHIND A D328 JET.

Narrative: DURING INCLEMENT WX (TSTMS SURROUNDING CVG FROM THE SE TO W TO N) ACFT X DEPARTED RWY 18L. GIVEN AN INITIAL HDG OF 090 DEGS TO MISS WX, TALKING TO DEP S. ACFT Y DEPARTED RWY 18L AFTER ACFT X, GIVEN AN INITIAL HDG OF 110 DEGS TO MISS WX AND DIVERGE FROM ACFT X AND TALKING TO ME AT DEP N. IT APPEARED TO ME THAT ACFT X DID A REDUCED PWR TKOF AND A SLOW TURN TO 090 DEGS AND ACFT Y DID A NORMAL TKOF AND STANDARD TURN TO 110 DEGS. THE END RESULT WAS WHEN I FIRST ACTIVELY OBSERVED THE ACFT, THEY WERE LESS THAN A MI APART ON VERY NEARLY THE SAME GND TRACK AND ABOUT 500 FT VERT. I CHKED TO SEE IF ACFT Y WAS ON FREQ (HE WAS, BUT HADN'T CHKED ON YET). I THEN ISSUED A TFC ALERT TO ACFT Y AND TURNED HIM TO 180 DEGS TO AVOID THE TFC. I BELIEVE ACFT X'S REDUCED PWR TKOF WAS A MAJOR FACTOR.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.