Narrative:

I cleared the B733 for takeoff. My aircraft was following the WW24 off the parallel runway. The WW24 was climbing out at 200 KTS and the B733 was climbing out at 180 KTS. I shipped the B733 to departure control. I looked at my d-brite radar and felt I had 3 mi of departure separation (later investigation showed my departure spacing was 2.94 mi). Subsequently, 5-6 mi east of the airport the B733 was climbing out at 240 KTS and the WW24 was climbing at 200 KTS. Eventually the departure controller's separation decreased to 1.66 mi and 500 ft. Several casual factors came to play. Both aircraft were not flying departure procedure (dp) correctly and the departure controller did not recognize the deteriorating condition. The departure procedures initial heading is 080 degrees, the WW24 was 12 degrees south of the departure procedure (dp), the B733 was climbing out faster than company requirements, the WW24 was given 020 degrees to resume the departure procedure (dp), that's where the separation decreased to 1.66 mi and 500 ft. I believe had both aircraft behaved properly on initial climb out, my 2.94 mi would've continued to increase to 3+ mi. Although, I told the B733, that he'd be following a WW24 off the south runway, I did not go back and apply visual separation, because I felt I had the minimum 3 mi of radar departure separation. The lesson learned, if you're going to use minimum separation also apply visual separation on the trailing aircraft to the one out front.

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Original NASA ASRS Text

Title: ATCT LCL CTLR AT PHX LOST SEPARATION BTWN 2 IFR DEPS OFF PARALLEL RWYS.

Narrative: I CLRED THE B733 FOR TKOF. MY ACFT WAS FOLLOWING THE WW24 OFF THE PARALLEL RWY. THE WW24 WAS CLBING OUT AT 200 KTS AND THE B733 WAS CLBING OUT AT 180 KTS. I SHIPPED THE B733 TO DEP CTL. I LOOKED AT MY D-BRITE RADAR AND FELT I HAD 3 MI OF DEP SEPARATION (LATER INVESTIGATION SHOWED MY DEP SPACING WAS 2.94 MI). SUBSEQUENTLY, 5-6 MI E OF THE ARPT THE B733 WAS CLBING OUT AT 240 KTS AND THE WW24 WAS CLBING AT 200 KTS. EVENTUALLY THE DEP CTLR'S SEPARATION DECREASED TO 1.66 MI AND 500 FT. SEVERAL CASUAL FACTORS CAME TO PLAY. BOTH ACFT WERE NOT FLYING DEP PROC (DP) CORRECTLY AND THE DEP CTLR DID NOT RECOGNIZE THE DETERIORATING CONDITION. THE DEP PROCS INITIAL HEADING IS 080 DEGS, THE WW24 WAS 12 DEGS S OF THE DEP PROC (DP), THE B733 WAS CLBING OUT FASTER THAN COMPANY REQUIREMENTS, THE WW24 WAS GIVEN 020 DEGS TO RESUME THE DEP PROC (DP), THAT'S WHERE THE SEPARATION DECREASED TO 1.66 MI AND 500 FT. I BELIEVE HAD BOTH ACFT BEHAVED PROPERLY ON INITIAL CLBOUT, MY 2.94 MI WOULD'VE CONTINUED TO INCREASE TO 3+ MI. ALTHOUGH, I TOLD THE B733, THAT HE'D BE FOLLOWING A WW24 OFF THE S RWY, I DID NOT GO BACK AND APPLY VISUAL SEPARATION, BECAUSE I FELT I HAD THE MINIMUM 3 MI OF RADAR DEP SEPARATION. THE LESSON LEARNED, IF YOU'RE GOING TO USE MINIMUM SEPARATION ALSO APPLY VISUAL SEPARATION ON THE TRAILING ACFT TO THE ONE OUT FRONT.

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.