Narrative:

RA after takeoff out of phl. Tower had cleared us for takeoff from runway 9L while simultaneously departing a commuter aircraft off of runway 8; conditions IFR. We took off and at 400 ft selected departure heading of 085 degrees. At approximately 1100 ft; we received a TA warning from an aircraft off our left; which progressed to an RA. I called out 'descend' as the PF (my first officer) simultaneously commenced following the TCAS guidance (as the pilot monitoring; I noted the guidance showing the green arc at 100-200 FPM descent). I remember looking out to the left to try and gain a visual; but no joy as we were IFR. The RA was momentary; lasting 3-4 seconds; then vanished. We continued our climb out and turned to a 180 degree heading per departure control after switching over. Afterward; en route to atlanta; my copilot and I reviewed possible contributing factors: 1) the phl 7 departure page and the phl detailed airport page page both show the following: runway 9L is slightly south of runway 8. The departure procedure heading for runway 9L is 085 degrees. The departure heading for runway 8 is 086 degrees. Both of these headings are converging. Worse; the magnetic orientation of runway 9L is 087 degrees; runway 8 is 088 degrees. This further exacerbated the convergence. 2) I don't know why tower would clear 2 aircraft for takeoff in IFR conditions given this convergence without a heading to turn away. 3) the conflict occurred (naturally) during one of the busier phases of flight when we were accelerating; accomplishing confign changes; navigation; accomplishing the after takeoff checklist; and switching to departure control. I feel we had a lot of factors coming together in just the wrong way to set us up for a problem. Perhaps; examples like this are on the rise due to the increased tempo of flight operations in an overcrowded airspace.

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Original NASA ASRS Text

Title: B737 DEP FROM PHL RWY 9L EXPERIENCED TCAS RA WITH DEP TFC FROM RWY 8.

Narrative: RA AFTER TKOF OUT OF PHL. TWR HAD CLRED US FOR TKOF FROM RWY 9L WHILE SIMULTANEOUSLY DEPARTING A COMMUTER ACFT OFF OF RWY 8; CONDITIONS IFR. WE TOOK OFF AND AT 400 FT SELECTED DEP HDG OF 085 DEGS. AT APPROX 1100 FT; WE RECEIVED A TA WARNING FROM AN ACFT OFF OUR L; WHICH PROGRESSED TO AN RA. I CALLED OUT 'DSND' AS THE PF (MY FO) SIMULTANEOUSLY COMMENCED FOLLOWING THE TCAS GUIDANCE (AS THE PLT MONITORING; I NOTED THE GUIDANCE SHOWING THE GREEN ARC AT 100-200 FPM DSCNT). I REMEMBER LOOKING OUT TO THE L TO TRY AND GAIN A VISUAL; BUT NO JOY AS WE WERE IFR. THE RA WAS MOMENTARY; LASTING 3-4 SECONDS; THEN VANISHED. WE CONTINUED OUR CLBOUT AND TURNED TO A 180 DEG HDG PER DEP CTL AFTER SWITCHING OVER. AFTERWARD; ENRTE TO ATLANTA; MY COPLT AND I REVIEWED POSSIBLE CONTRIBUTING FACTORS: 1) THE PHL 7 DEP PAGE AND THE PHL DETAILED ARPT PAGE PAGE BOTH SHOW THE FOLLOWING: RWY 9L IS SLIGHTLY S OF RWY 8. THE DEP PROC HDG FOR RWY 9L IS 085 DEGS. THE DEP HDG FOR RWY 8 IS 086 DEGS. BOTH OF THESE HDGS ARE CONVERGING. WORSE; THE MAGNETIC ORIENTATION OF RWY 9L IS 087 DEGS; RWY 8 IS 088 DEGS. THIS FURTHER EXACERBATED THE CONVERGENCE. 2) I DON'T KNOW WHY TWR WOULD CLR 2 ACFT FOR TKOF IN IFR CONDITIONS GIVEN THIS CONVERGENCE WITHOUT A HDG TO TURN AWAY. 3) THE CONFLICT OCCURRED (NATURALLY) DURING ONE OF THE BUSIER PHASES OF FLT WHEN WE WERE ACCELERATING; ACCOMPLISHING CONFIGN CHANGES; NAV; ACCOMPLISHING THE AFTER TKOF CHKLIST; AND SWITCHING TO DEP CTL. I FEEL WE HAD A LOT OF FACTORS COMING TOGETHER IN JUST THE WRONG WAY TO SET US UP FOR A PROB. PERHAPS; EXAMPLES LIKE THIS ARE ON THE RISE DUE TO THE INCREASED TEMPO OF FLT OPS IN AN OVERCROWDED AIRSPACE.

Data retrieved from NASA's ASRS site as of January 2009 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.